Final Report Summary - AFORE (Forest biorefineries: Added-value from chemicals and polymers by new integrated separation, fractionation and upgrading technologies)
Executive Summary:
The aim of the AFORE project has been to develop new, industrially adaptable and techno-economically viable and sustainable methods and technologies for the separation, fractionation, and primary upgrading of wood polymers and low molecular weight compounds from forest residue or process side-streams. These valuable components can then be further utilised as starting materials in chemical, material and fuel applications. The project is focusing both on utilising the side-streams of the kraft pulping process employed in paper making today and on developing new forest biorefinery technologies for the future.
During the 4 years project the research and development has been done for both novel and existing methods to separate and further up-grade the valuable wood components in side-streams. The project has strongly targeted at up-scaling and demonstration of the best technologies in current processes on a pilot or mill scale. The techno-economic modelling, environmental impact analyses and market assessments have supported and guided both research and development work in AFORE and evaluation of the exploitation potential of the project processes and products. Both research and industry partners in the multidiciplinary consortium with 19 partners have actively contributed to the success of the project.
Several separation, fractionation and up-grading technologies for both solid and liquid wood derived samples have been studied in AFORE. In total, 9 of the studied technologies were selected for up-scaling and process concept evaluation. Finally, 6 of the up-scaled concepts were demonstrated in pilot or industrial scale. Three of these, separation of xylan from kraft cooking liquor and bleached kraft pulp, and production of xylo-oligosaccharides from pulp xylan, are related to the current kraft mills. The other three, separation and fractionation of birch bark, supercritical CO2 extraction of valuable components from eucalyptus and birch bark, and catalytic pyrolysis of lignin, are self standing concepts applicable in future forest biorefineries. The primary techno-economic and LCA evaluation is available for the up-scaled concepts. Advances in novel methods for characterisation and use of wood components in chemicals and materials have been achieved. Several inventions and two patent applications based on the exploitation of wood components in chemical and material applications have been made. The results of AFORE have been disseminated in various scientific publications and conferences as well as in 4 public AFORE Workshops, 4 newsletters and an AFORE training school. The list of AFORE publications and the public materials can be found in the project net site at: www.eu-afore.fi
The work carried out in AFORE has produced both scientific, technical, environmental, and market knowledge applicable in further forest biorefinery research and development work. Both short and long term basic and applied research and development work is, however, still needed to overcome the scientific, technical, environmental and safety challenges of the interesting current process concepts and to generate new openings for the future technologies. Companies interested to start evaluating the developed separation, fractionation and up-grading technologies are now also needed to promote their commercial exploitation. Although a clear interest in the wood based components was detected in AFORE among the various industrial appliers, in most cases the solid, long term source of these components is missing. Here, the key player is apparently the forest industry currently managing the starting material. In the furture, interaction between the companies in the product value chains starting from wood derived components would be utterly important to generate new business opportunities for the forest industry through side-stream exploitation.
Project Context and Objectives:
The forest–based industry is a significant industrial sector in Europe converting wood to pulp, paper, cardboard, energy, and other wood derived products. To retain and increase its competitiveness in the increasing global competition, the pulp and paper industry is looking for to maximize the value addition of raw materials in its fibre refining processes and to find new and profitable businesses alongside the traditional product lines. Today, only part of the valuable wood biomass ends up in high-value applications (paper and cardboard), whilst a significant part is channelled into different “side-streams”, such as logging residues, debarking residues and pulping liquors. All of these side-streams contain chemically appealing and reactive constituents that could be further refined to value-added chemicals, polymers, materials, and fuels alongside with the sustainable forestry and paper fibre production. Recent developments in tailored and efficient biomass pre-treatment and fractionation technologies together with the market challenges in the pulp and paper industry and rising oil prices have awakened interest towards side-stream exploitation.
Only minor part of the wood side-streams representing of over 50 % of initial wood biomass are valorised to various by-products. The rest, about 31.5 Mt/year of kraft pulping side-streams and 6-8 Mt/year of bark is mainly burned for steam and power generation and used for land construction. Furthermore, substantial amounts of harvesting residues are left in the forests, partially due to the forest ecology reasons.
Wood consists mainly of cellulose, hemicelluloses, lignin and extractives. During kraft pulping, wood components are partly dissolved into the cooking liquor either in intact, modified, or degraded form. Many of the constituents in wood also occur in bark, but their proportions are different. Bark also contains other interesting components such as suberin consisting alterating regions of lignin-like aromatic regions and esterified hydroxy(epoxy)fatty acids. Attempts to exploit kraft lignin have been carried out especially in Sweden and recovery of lignin from kraft pulping by the LignoBoost process has recently been implemented to industrial kraft mill process. Dissolved hemicelluloses and hydroxy acids have so far remained totally unexploited as raw materials for the chemical industry.
In current kraft pulp production the solid matrix separation processes are fine-tuned for efficient production of papermaking fibres. Various alternative chemical pulping methods such as alkaline sulphite and soda cooking, different organosolv cooking and acidic cooking concepts have been developed during the past decades. More recently, fractionating pulping methods such as reactive organosolv cooking using phosphinic acid catalyst have also been developed. Certain ionic liquids (ILs) have shown to efficiently dissolve wood and enable efficient derivatization of lignocellulosic materials. These cooking and wood structure opening methods, although not competitive with kraft pulping for the paper and packaging applications, could be suitable for by-product recovery together with a cellulosic fibre product in the future forest biorefineries.
The low concentration of the valuable components in the kraft process liquid streams has hampered their exploitation and thus the challenge has been to find efficient separation methods for isolation of hemicelluloses, lignin and valuable low molecular mass components from these streams. Membrane processes form the key separation technique for liquid streams in biorefineries because of their excellent fractionation capability, low chemical consumption and low energy requirement. However, concentration polarisation and membrane fouling can be a serious problem in membrane filtration. The performance of conventional membrane filtration can be improved by the use of ultrasound or by enzymatic treatments. Supercritical fluid extraction is also a potential technology for sustainable fractionation of both liquid and solid wood streams.
Valuable wood components, called primary products in the AFORE project, present in the wood side streams have various potential applications. Hemicelluloses, i.e. xylan and glucomannan, are currently not industrially isolated from wood streams but when available would be suitable as a starting material for various material and chemical applications. Lignin currently used mainly as an energy source in pulp mills has a number of attractive properties making it suitable for advanced material applications. The foliage, needles in softwoods and leaves in hardwoods, and bark contain up to 30-40 % of different extractives, waxes and phenols that can be applicable in e.g. pharma, functional material or chemical applications.
The objective of the AFORE project is to develop new, industrially adaptable and techno-economically viable and sustainable methods and technologies for the separation, fractionation, and primary upgrading of wood polymers and low molecular weight compounds from forest residue or process side-streams. These valuable components can then be further utilised as starting materials in chemical, material and fuel applications. The project is focusing both on utilising the side-streams of the kraft pulping process employed in paper making today and on developing new forest biorefinery technologies for the future.
AFORE is focused on two approaches:
A) Upgrading the current kraft pulping process into a multi-product biorefinery concept without compromising the process energy balance or the fibre properties, and
B) Development of entirely new wood-based biorefinery concepts, in which the wood cellulose is exploited in value-added applications with simultaneous production of a multitude of novel non-cellulosic products.
The success of the technological developments is evaluated in AFORE using different modelling and assessment tools and pilot or mill scale demonstrations. The techno-economical evaluations will also include a thorough investigation of how the new side-stream based value chains will affect the current end uses (mainly energy generation) as well as the environmental footprint of the process.
The overall goals of the AFORE project have been 1) to increase the product portfolio and thereby the economic value of the pulp and paper industry through the development of mild and selective technologies for separation and primary upgrading of components that can be applied in novel high-value applications without compromising the current fibre and energy production; 2) to generate future forest-based biorefineries by developing and applying novel separation and fractionation methods for wood components with special emphasis on bio-technologies; and 3) to demonstrate that the current kraft pulping process can be upgraded into an integrated wood-based biorefinery in a sustainable, flexible and techno-economical way. The project will thus combine a short-term (improved kraft pulping) and a long-term (future wood-based biorefinery concepts) development path as shown in Figure 1.
It was expected that the AFORE project results in i) 1-2 demonstrated, technically feasible processes for separation of potential components from the side-streams of current kraft pulp mills and the wood materials in novel biorefinery concepts, ii) novel, innovative technologies for wood matrix opening and further separation, fractionation and upgrading of valuable wood components to be used as a basis of future wood biorefineries and iii) business concepts for techno-economically and environmentally sustainable products and applications based on the valuable wood components.
Efficient separation of components from solid materials and process liquors would enable more specific isolation of targeted fractions from wood side-streams. Thus, novel separation, fractionation and primary up-grading methods and technologies to be developed in the project promote the the exploitation of all valuable wood-derived components in current or future wood biorefineries. Information on the technical and economic potential as well as the environmental impact of the most promising technologies to be developed in the project will also offer a solid basis for further business considerations and scientific and technological development. Overall, it is expected that the results of AFORE project will help in tackling the important challenge of transferring forest industry into an efficient and sustainable lignocellulosic biorefinery, in which the unique chemical composition of all wood fractions is fully exploited.
Project Results:
The AFORE project have had 21 partners of which 19 has been active till the end of the project. The partners represent the whole forest biorefinery value-chain (Table 1). The partners, both academic and industrial, had expertise, equipment and complementary knowledge in
• raw material processing by physical, chemical and biotechnical methods both in laboratory and industrial scale
• up-scaling of disassembly, separation, fractionation technologies for forest biomass and its fractions
• techno-economic and environmental modelling, simulation and impact assessment needed in evaluation of the applicability of novel technologies and biorefinery concepts
• modern chemical and physical analytics of wood raw materials and wood chemical components
• physical, chemical, and enzymatic modification of primary products originating from wood
• applications of wood-derived components, especially hemicellulose, lignin, and extractives and solid cellulosic materials
Table 1. List of AFORE participants
The project approach is summarized in Figure 1. AFORE focused on two paths, A) upgrading the current kraft pulping process into a multi-product biorefinery concept without compromising the process energy balance or the fibre properties, and B) development of entirely new wood-based biorefinery concepts, in which the wood cellulose is exploited in value-added applications with simultaneous production of a multitude of novel non-cellulosic products. The strong focus at demonstrating in pilot or industrial scale the most promising separation, fractionation and up-grading technologies resulted in total 6 demonstrated concepts with techno-economic and LCA analysis. The main AFORE results of the development of separation and fractionation methods for wood and process side streams and the up-grading of resulting primary products project are presented below.
Figure 1 The approach of the AFORE project. A indicates a conventional kraft pulp mill and B a novel wood biorefinery concept
KRAFT PULP MILL BASED CONCEPTS
Both current kraft pulping process liquors and kraft pulps have been shown to be good sources for wood-derived polymeric xylan. Three kraft mill related process concepts for xylan separation and up-grading that is, i) separation of xylan from early cooking liquor, ii) extraction of xylan from bleached birch kraft pulp, and iii) production of xylo-oligosaccharides from xylan alkali extracted from pulp, have been up-scaled and demonstrated in pilot scale. Enzymes have been shown to be exploitable both in enhancing alkaline xylan extraction from pulps, tailoring the molecular weight distribution of extracted polymers and producing hemicellulose-poor pulps. The efficiency of membrane separation of lignin in LignoBoost process has been enhanced. Advanced membrane separation processes have also been shown to be applicable in the separation of hemicellulose from the LignoBoost filtrate process filtrate. On the contrary, distillation is not a suitable method for separation and fractionation of hydroxyl acids from kraft black liquor.
Alkaline extraction of xylan from wood chips and bleached kraft pulp
A lab scale method to extract xylan from hardwood kraft pulp with alkali was improved, up-scaled and successfully demonstrated in 1600 kg scale by VTT in collaboration of Södra. The xylan obtained from bleached birch kraft pulp from Södra Cell had very high purity (monosaccharide purity >99%). The technical and economic feasibility and the LCA evaluation of the process concept shown in Figure 2 was made. The process concept is economically feasible in all the cases calculated. The quality and price of the extracted xylan poor pulp has the highest effect on the production cost of xylan and the economic outcome of this concept. The production cost of xylan was calculated to be 600-1000 EUR/t of pure xylan depending on the quality of the hemi-poor pulp. The lower production costs represents a case in which pulp has been up-graded to dissolving grade pulp with two stage extraction. In this case a high ROI (Return on Investment) could be obtained. The higher production cost is obtained with one stage extraction and resulting pulp classified as market pulp. More research needs to be put both on the technical solutions for the large scale extraction and xylan separation and the further process the pulp to meet the requirements of dissolving grade pulp.
Figure 2. Simplified process model of alkaline extraction of xylan from bleached birch kraft pulp
Enzymes were shown to be applicable in enhancing the alkaline extraction of polymeric xylan or xylo-oligosaccharieds from the kraft pulp. Depending on the target, enzyme treatment can be carried out either before, after or in between two alkaline extraction steps (Fig. 3). When xylanase treatment was carried out by VTT before alkaline extraction both xylo-oligosaccharides (~10% of original xylan) and xylan (~50% of original xylan) were obtained from the pulp. As a comparison, from the reference pulp 60% of xylan could be extracted. Xylanase treatment decreased the molecular weight of the extracted xylan. To obtain xylan with un-altered molecular weight as well as xylo-oligosaccharides, xylanase treatment can be carried out after alkaline extraction. By this combination up to about 4 % of xylo-oligosaccharides can be obtained and the xylan content of the remaining pulp is further decreased.
Figure 3 Verified options of feasible enzyme-aided alkaline extraction of birch kraft pulp for xylan or xylo-oligosaccharide production
Alkaline extraction of hardwood chips was shown to result in the hemicellulose extract rich in water soluble xylan. The alkaline extraction procedure was more suitable for birch than for eucalyptus in terms of yield and extraction specificity. Extraction of xylan from wood chips could be improved by ultrasound irradiation. Alkaline extraction of wood chips with or without ultrasound enhancement can be combined with various subsequent matrix opening technologies including kraft pulping. The alkaline pre-extraction might provide an additional fraction to be obtained from the raw material without compromising the yield and efficiency of the subsequent process.
Separation of xylan from kraft pulp mill liquors
Membrane separation techniques for xylan from early-phase and final-phase/partially evaporated alkaline pulping liquors as well as LignoBoost filtrates from birch and eucalyptus were developed by Innventia. The main separation technique used was ultrafiltration using both ceramic and polymeric membranes followed by precipitation of the xylan.
A method to separate xylan from early cooking liquor was improved, up-scaled and successfully demonstrated in kg scale with both birch and eucalyptus kraft black liquor. The demonstration was carried out at LignoBoost demo facilities in Bäckhammar, Sweden. Birch black liquor was sampled at Södra’s mill in Mönsterås. Eucalyptus black liquor was sampled at CELBI mill in Leirosa, Figueira da Foz, Portugal. In the demo scale trials about 67 % of the kraft cooking liquor xylan was withdrawn for the xylan separation. In total 5 kg of birch xylan and 9 kg of eucalyptus xylan was isolated. The xylan obtained was relatively pure, containing 70-80% of xylan with average molecular mass of 10 600 g/mole and about 20-30% of lignin, other hemicelluloses and inorganics. The technical and economic feasibility and the LCA evaluation of the process concept shown in Figure 4 was made based on birch black liquor. The estimation of the investment cost for the concept is very rough but gives an indication of the production cost, 880 EUR/t of pure xylan in the case with no precipitation and 1060 EUR/ton of pure xylan in the case of precipitation included. The main contributors to the ROI of this concept were the price of resulting xylan and the price of the bark bark purchased due to the steam deficit (less raw xylan to recovery boiler and increased load on evaporation). Further development work to optimize process parameters and efficiency would be beneficial for the implementation of the process to the industry. The results from this study show that xylan isolated according to this concept can provide a renewable and green product to meet the demands of the future generations.
Figure 4. A model of the process for separation of xylan from hardwood cooking liquor and its implementation to the kraft process
Xylan separation from LignoBoost filtrate of eucalypt and birch comparing different ultrafiltration membranes was also evaluated by Innventia. To separate xylan from black-liquor after withdrawing of the main part of the lignin with the LignoBoost process is investigated since there is a large potential of xylan in hardwood black liquors and today, the filtrate is evaporated and burnt; the only value used is hence the energy of the dissolved xylan. With the process set up used it was found that the ceramic membranes produced more pure xylan than the polymeric membranes and the best xylan retention was 84%. After further ultrafiltration and precipitation LignoBoost filtrate seemed comparable to the early cooking liquor as a source of polymeric xylan in terms of xylan purity. Thus, filtrate from the LignoBoost process is an interesting raw material for xylan production.
NATEX in collaboration with Innventia carried out precipitation and extraction of xylan from hardwood kraft black liquor using supercritical carbon dioxide, scCO2, and co-solvents. A separation scheme consisting of lignin separation, followed by hydroxy acid separation and finally separation by anti-solvent precipitation of hemicellulose was proposed. Precipitation of xylan from the kraft hardwood liquor using scCO2 was performed in a view-cell, designed for pressures up to 300 bar and temperatures up to 250 °C.
Production of xylo-oligosaccharides from wood based xylan
Danisco developed and demonstrated in semi-pilot scale a membrane assisted enzymatic process to produced xylo-oligosaccharides. Hydrolysis of birch xylan, alkaline extracted from bleached birch cellulose by VTT and about 10 kg DS of oligomers were collected from the permeate. It was shown that it is possible to produce xylo-oligomers with this method by avoiding the hydrolysis of oligomers to monomeric xylose.
Separation of lignin from black liquors
Innventia developed methods for isolating more homogenous lignin fractions with interesting properties from black liquors based on the LignoBoost process. Lignin fractions obtained in the laboratory trials were characterized. An interesting observation was made; the pre-hydrolysis resulted in higher content of acid insoluble lignin in the fractions separated from both hardwood kraft and hardwood soda black liquors.
Separation technologies of hydroxy acids from black liquor
Isolation of commercially interesting hydroxy acids from kraft cooking black liquor was aimed at by VTT using distillation and reactive scCO2 extraction together with NATEX. Over 20 different, chromatographically separated hydroxy acid mixtures were subjected to vacuum distillation (typical pressure 1–2 mbar). The acid mixtures were derived from commercial or synthetic model compounds, from alkaline degradation of starch or xylo-oligosaccharides (XOS), and from birch black liquor. Some compounds (such as simple 2-hydroxyalkanoic acids) were isolated as technically pure chemicals from black liquors (Figure 5). It is thus evident that many hydroxy acids can well be separated by distillation from synthetic (lignin-free) black liquors, although inevitable condensation reactions form a challenge. It appears that the distillation of hydroxy acids from real black liquors is strongly inhibited by various impurities (even in low concentrations). It is also evident although not yet well understood that the condensation reactions and other impurity problems are hard to control, making it very challenging to up-scale this type of process to real industrial operations. Further experiments to esterify the hydroxy acids into more volatile form were carried out with limited success.
Figure 5 Isolation of 92% pure 2-hydroxybutanoic acid from a birch black liquor fraction by distillation (crystallised before entering the receiving flask).
SELF-STANDING SEPARATION AND FRACTIONATION CONCEPTS
In AFORE detailed characterization of forest residues and industrial by-products (needles, branches, barks tops, and stumps), using the most recent spectroscopic techniques, has allowed to identify some of them as sources of bioactive compounds (triterpenic acids and other triterpenoids, terpenes, phenolic compounds among others) with potential nutraceutical and pharmacological properties. Bark from both eucalyptus and birch has been found to be an interesting source of valuable low molecular weight components. Raw material collection, primary fractionation and extraction technologies for the exploitation of these components have been studied and developed by the consortium.
Advanced and novel matrix opening methods including soda and soda-anthraquinone cooking, LignoFibre (LGF) organosolv cooking, various oxidative cooking methods and ionic liquid (IL) treatment have been applied for project solid wood materials with promising results. Furthermore, the effect of hot-water pre-extraction on novel cooking methods and the primary products obtained has been elucidated. Various extraction and separation methods have been studied to further separate and fractionate the target primary products from wood processing liquors. Both supercritical carbon dioxide technique (scCO2) and Accelerated Solvent Extraction (ASE) has showed promise in extraction of high-value low molecular mass compounds from different solid and liquid wood fractions.
Three self-standing process concepts aimed to the novel forest biorefinery concepts that is, i) Separation and fractionation of birch bark, ii) Supercritical CO2 extraction of triterpenic acids from outer eucalypt bark, and iii) Catalytic pyrolysis of lignin, have been up-scaled and successfully demonstrated in pilot or industrial scale.
Eucalypt bark as a source of valuable components
Physical (densimetric) fractionation processes, were developed by UTL for the separation of birch and eucalyptus barks, allowing the exploitation of their most valuable components. UAVR characterized the lipophilic extracts of the outer and inner barks of E. globulus, E. urograndis, E. grandis, E. maidenni, E. grandis x globulus and E. nitens, with particular emphasis on the triterpenic acids. It was demonstrated that all eucalyptus species are promising sources of triterpenic acids, which are particularly abundant in outer barks (Table 2), ranging from ~5g/kg of extract up to 20-25 g/kg of extract. In addition, UAVR characterized the phenolic components from eucalyptus barks and for example, 29 phenolic compounds were identified in E. globulus bark, of which 18 reported in this species for the first time. The phenolic content of the extracts showed a positive correlation with their antioxidant activities. These results confirm the high potential of eucalyptus bark as source of biologically active compounds.
Table 2. Main triterpenic acids in Eucalyptus ssp. outer barks (g/kg of extract). * including the 3-acetyl derivative
UAVR together with NATEX up-scaled and successfully demonstrated in industrial scale the scCO2 extraction of triterpenic acids from Eucalyptus globulus external outer bark (Fig. 6). Two extraction approaches (Approach 1: higher pressure and no co-solvent and Approach 2: lower pressure and co-solvent addition) were both demonstrated in 80L/550bar plant of NATEX (Fig. 6). The overall yield achieved was about 1wt% of triterpenic acids from the bark. The concentration of triterpenic acids in the extracts was up to 41wt%. The process of SFE of TTAs can thus be successfully exploited in industrial level. The techno-economical evaluation of this case showed promising economic performance with the assumptions made. The concept is, however, highly sensitive to the price obtainable from the end product. Thus, further research and development activities in the separation and purification of the triterpenic acids from the extracts already were already started in AFORE by UAVR.
Figure 6 Example of the extraction yields in scaling up the scCO2 extraction of triterpenic acids (TTAs) from eucalyptus outer bark and 80L/550bar pilot plant in NATEX laboratory
Hardwood bark as a source of valuable components
Birch outer bark, a source of betulin, can be recovered in pure form from birch bark by proper comminution and a two stage flotation technique in high yield using methodology developed by SepRes (Fig. 7). The processes were up-scaled and demonstrated with several hundred kilograms of birch bark from a Finnish plywood mill and a Finnish kraft pulp mill. The scCO2 extraction of betulin from pure birch outer bark recovered by SepRes was further carried out by NATEX. The extraction of birch outer bark works well and there is serious interest of triterpenoids from the cosmetics industry. Extracts, which contain more than 97w% of triterpenoids (Figure 8) were produced. After AFORE, the industrial production is expected to be executable at low technical risk.
Figure 7 Principle of the birch bark fractionation processes
Figure 8 Birch outer bark extracts
Debarked branch wood from pine and spruce were studied as potential sources of valuable components and their extraction technologies were studied by SepRes. Phenolic and lipophilic components from spruce and pine branch extracts were separated by hexane and ethanol. Birch outer bark was depolymerised by alkaline and acid hydrolysis to yield hydroxy fatty acids. The extract from spruce branch wood 15 cm segment closest to the stem was found to be of potential commercial interest. Specifically, the concentration of lignans, particularly hydroxymatairesinol, reached concentrations typical of spruce knotwood. The extract produced is of high purity and comparable to a knotwood extract. The hexane extract of pine branch wood contained the bulk of the resin and fatty acids and a small portion of the pinosylvin monomethyl ether. The ethanol extract contained the stilbenes pinosylvin and pinosylvin monomethyl ether as well as the lignan nortrachelogenin with some traces of resin and fatty acids.
Novel pulping and matrix opening technologies
Catalytic matrix opening reactions, catalytic alkaline oxidation, CatOx, and alkaline oxidation, AlkOx, to pine (wood, needles) and alkaline matrix opening reactions for eucalyptus (leaves), birch (bark, leaves) and pine (wood, bark, needles) were studied by UH. All wood material fractions tested were easily oxidized in catalytic and alkaline oxidations in lab scale. In these treatments lignin is solubilised and if preferred can be collected with filtration after precipitation with acid. When extractive-free lignin is wanted, the starting material can be extracted before CatOx and AlkOx with hexane or heptane for two days following one day extraction with acetone. The fibre length distribution analysis indicated that the length of the AlkOx birch fibres is comparable to kraft pulp whereas the length of AlkOx eucalyptus and pine fibres is slightly shorter than average kraft pulp fibres.
UH also studied the fibrillation of hardwoods by ionic liquids (ILs). For hardwood (birch), a high number of different imidazole derivatives was screened, but only N-ethyl,N-methyl imidazolium acetate [EMIM][OAc] promotes wood fibrillation. Based on the composition analysis it was concluded that the fibrillation might be due to removal of pectins. In addition to the characterization work of IL fibrillated wood, further delignification of the IL fibrillated birch chips with another IL, Amim-Cl, or kraft cooking was conducted. The results revealed that Amim-Cl is able to dissolve the birch fibres essentially completely. Regeneration of the dissolved fibres showed that it is possible to partially fractionate birch components by precipitation in organic solvents and their water mixtures.
Two separate existing sulphur and chlorine free matrix opening technologies, pre-hydrolysis soda cooking with oxygen delignification and WoodOx, were further developed by Innventia. The pre-hydrolysis soda cooking of Eucalyptus globulus together with a harsh oxygen delignification step (Fig. 9) resulted in a high purity cellulose pulp (cellulose content >98%) at 37% yield after only three – totally sulphur and chlorine free – process steps. The pulp is well suited for special applications after triacetylation.
Figure 9 Pre-hydrolysis soda cooking followed by harsh oxygen delignification - only three process stages; results in high purity cellulose pulp (>98% cellulose) at 37% yield when using Eucalyptus globulus pulp wood
A low-temperature oxidative delignification method, WoodOx (Fig. 10), has earlier proven to produce a bright, low lignin containing pulps at approx. 70% yield in one step from softwood. In this project WoodOx was successfully applied to eucalypt wood reject (0-2 mm thick) which in the pulping industry mainly is used for burning. Although further optimization of both delignification methods is needed they are promising concepts for production of specialty cellulose pulps. The pre-hydrolysis soda is considered more advantageous than WoodOx even though the yield is lower.
Figure 10 WoodOx process, low-temperature oxidative delignification combined with alkaline extraction, produces cellulose pulp at high yield from wood reject, 0-2 mm thick. PAA= peracetic acid
The existing Lignofibre (LGF) organosolv cooking process characteristic of its phosphinic acid chemical additive was further developed by VTT. In AFORE the LGF process with acetic acid as a cooking chemical was made industrially more feasible by shortening the cooking time, recycling the cooking chemical and enhancing the recovery of the wood-based components (Fig. 11). Furthermore, LGF cooking was successfully performed at pilot-scale for birch chips and positive economics were shown when combined with subsequent triacetylation. In the lab scale cooking experiments with eucalyptus and birch wood chips fibre yield between 55-59% was obtained. The lignin-containing pulps had high cellulose (70-80%) and very low xylan (eucalyptus 1-2%, birch 2-5%) content. Xylan dissolved during the LGF cooking was converted promarily to furfural. The delignification of pine was less efficient in the LGF cooking than that of birch and eucalyptus. Interestingly, the birch LGF pulp was very prone for further delignification and high final brightness (>88.7% ISO) and low lignin content (kappa below 0.5) pulp suitable for subsequent triacetylation was obtained by the chosen chlorine free bleaching sequence. After various process considerations it can be concluded that the LGF organosolv cooking should be limited to kappa level 20-30, corresponding to cooking times 3-4 h with alkaline extraction
Figure 11 The LGF organosolv cooking process for fractionation of wood chips to added value components
UP-GRADING AND PERFORMANCE OF PRIMARY PRODUCTS
Further purification, characterisation and up-grading of the primary products separated from various wood residues and process side streams has been carried out. Interesting properties and performance in respect to applications have been identified for hemicellulose, lignin and several component groups of the extractives as well as cellulose residues. Advanced analytical techniques have been developed both for the lignin composition analysis, the molecular mass determination of polymeric hemicelluloses, and the structural characterisation of oligosaccharides. All advanced techniques have been used in AFORE and recently, the latter was successfully exploited in applied for the characterisation of acidic xylo-oligosaccharides.
Hemicellulose in applications
New type of adhesive components was developed from wood derived xylan by VTT. Current polymers in hot melt adhesives are most commonly synthetic polymers. However, the market for bio-based adhesives is increasing and here non-food components such as hemicelluloses are attractive as raw material. Simple derivatization of xylan by hydroxypropylation was utilized for production of an adhesive component in AFORE. The glass transition temperature of the modified xylans was with 60 °C lower than that of pure xylan (171°C). The modified xylan was blended successfully in the compounder with oxidized cellulose acetate and a plasticizer to produce a tacky blend. This hot melt adhesive formulation showed good adhesion in cardboard gluing (Fig. 12). Slow tearing showed a tacky seam and no fiber damages were observed whereas fast tearing resulted in fiber rupture. It was thus demonstrated, that the hydroxypropylated xylans have potential as adhesive components. Patent applications of this new method to produce xylan based hot melt adhesives are pending.
Figure 12 Xylan hot melt glue samples in testing
Chemically functionalized xylans were successfully synthesized and tested as paper strength additives by Innventia. Birch and eucalyptus black liquor xylans and kraft pulp xylans were derivatized by carboxymethylation using sodium monochloroacetate under aqueous alkaline condition. The functionalized xylans synthesized demonstrated high and low degree of substitution with anionic CM-groups, respectively. The chemically functionalized black liquor xylans differed with respect to molar size and distribution. The carboxymethylated xylans adsorbed onto the fibres and thereby increased the frequency of anionic functional groups on the surface. The paper strength properties of sheets prepared from CMX activated pulps were improved, e.g. the z-strength increased. Carboxymethylated xylans synthesized from birch and eucalyptus xylans can thus be employed to activate bleached softwood pulps and improve their dry strength properties.
Carboxymethylated birch and eucalyptus xylans produced by GreenValue were shown to be effective additives to improve concrete fluidity. These products can therefore be considered novel renewable non-sulfonated dispersants that are also expected to be highly biodegradable.
Lignin in applications
The performance of various lignins in selected material applications was clarified by Green Value. Kraft lignin was shown to be applicable after modification for both novolac- and resole-type thermoset applications. For concrete additive (to improve fluidisation) the modified kraft lignins performed as well as commercial references. Kraft lignin plasticized by GreenValue also performed well in the biopolymer composites developed by PPIMC, significantly improving strength parameters after accelerated weathering.
Thermal treatment of kraft lignin is a promising method to convert the lignin into an efficient adsorbents, in particular for gas applications, if modified prior to carbonization as shown by Innventia. Activation of the lignin-derived carbon adsorbent may further improve the quality.
The catalytic pyrolysis of lignin together with biomass was found to be applicable. In the lab scale co-pyrolysis of LignoBoost kraft lignin and vegetable oils PPIMC showed that the distribution of compounds in co-pyrolysis oils is strongly affected by both the lignin and the catalysts. The heterogeneous catalytic pyrolysis of LignoBoost kraft lignin to bio-oil using a novel catalyst developed by SINTEF in AFORE and a commercially available catalyst was demonstrated in pilot scale in CERTH. The preparation of the 5 kg pilot plant batch of the novel catalyst was performed using a SINTEF recipe. Formulation of this batch was performed successfully. Both catalysts (novel and commercial) were tested for lignin catalytic pyrolysis in the circulating fluid bed pilot scale reactor in CERTH (Fig. 13). For the demonstration of the technology a new system for lignin feeding and a new lignin/biomass pre-treatment procedure were developed. It was concluded that lignin can be catalytically pyrolyzed with both catalysts by co-feeding the lignin with biomass up to 25%wt content. The oil produced from this process has low oxygen content and it can be used as fuel after further upgrading or as source for chemicals and phenols.
Figure 13. The process of heterologous catalytic pyrolysis of kraft lignin to bio-oil
Added-value extracts from wood
Various extractives including triterpenic acids, polyphenols, and stilbene glucosides were observed to have bioactivity and/or other application value. An interesting new birch extract based material for surface hydrophobisation was invented by SepRes.
The antioxidant activity of both methanol and methanol:water extracts of E. globulus bark was measured by UAVR to be in the same level than that measured for ascorbic acid (Table 3). These results are in agreement with the total phenolic content of the extracts suggesting that the phenolic compounds are the main responsible for the antioxidant activity in these extracts.
Table 3 Antioxidant activity of ascorbic acid and eucalyptus bark extracts (values expressed as mean ± standard deviation (n=3))
Ursolic (UA), oleanolic (OA), butilinic (BA) and betulonic acids (BOA), as well as total and fractionated Eucalyptus ssp bark extracts have been tested in order to better characterized their anti-tumor activity on human breast and colorectal cancer cells. The content of triterpenic acids, especially BOA, in the bark extracts correlated with the inhibition of cell proliferation and induction of cell death in the case of colorectal cancer cells. Among the bark extracts studied E. nitens extracts were more active than E. globulus extracts apparently due to its specific composition of triterpenic acids. E. nitens extracts concentrated with triterpenic acids is about two times more effective than the crude extract in inducing the inhibition of cell proliferation. Regarding human breast cancer cells, pure triterpenic acids also presented a strong anti-proliferative capacity, which was proved by significant alterations in cell cycle progression. Thus, to fully exploit the anti-tumor potential of eucalyptus bark extracts purification and concentration of triterpenic acids already started in AFORE needs to be further developed.
Wood material-polymer composites
The applicability of cellulosic materials origin from different AFORE matrix opening processes for polymer composites was studied by PPIMC. Wood-polymer composites comprising polypropylene (PP), MAPP (3%) and 60% CARBOCEL residue were first designed. Their behavior in accelerated weathering indicated that for applications such outdoor decking only extracted CARBOCEL material should be used.
Composites comprising 15% unbleached LGF organosolv pulp as such or after hydrophobication by chemical modification, 15% PLA, 3% MAPP and PP were prepared and tested before and after weathering. Weathering incresed substantially the dynamic water sorption capacity of the composite samples. The moisture absorption was much lower for samples comprising modified pulp fibres as compared to samples with untreated fibres. The composites prepared were concluded to be a good alternative for wood plastic composites that need to be subjected to damp places, such as the interior of bathrooms, wood decks, food packaging, etc, since the water absorption of these materials was considerably lower.
Polymer composites consisting lignin and PLA were prepared. Lignins used were hardwood LignoBoost kraft lignin as such or after plasticization by Green Value, and LGF organosolv lignin from beech. A good adhesion between the lignin and PLA matrix was observed. Use of plasticized lignin resulted into the best mechanical and thermal properties. Also, it recorded the lowest water sorption capacity. The blends containing lignins exhibited decreased melt viscosity compared to the matrix, the reason being related to the fact that they act as plastifiers, reducing the resistance of the matrix to the external forces and thus determining an improvement of flow for PLA-lignin systems. After weathering due to the fact that lignin contains chromophoric groups that are more susceptible to degradation, but also the degradation products could form hydrogen bonds that strengthen the material structure, the thermal and mechanical properties were not highly affected.
POTENTIAL MARKETS FOR WOOD COMPONENTS
The comprehensive market assessments made by WoodKPlus have evaluated the potential markets of the AFORE primary products. Ten business to business surveys with more than 400 companies contacted and two consumer surveys were made to clarify the market potential and product value, barriers and incentives, consumer acceptance and perceptions related to the wood based components in end products. Table 4 summarises the different market analysis and shows the market potential in terms of market volume and market value with the barriers and incentives for the different applications.
Table 4. Summary of the market potential of possible AFORE concept products
ENVIRONMENTAL CONSIDERATIONS
In addition to the LCA evaluation carried out by VTT for the most potential separation and fractionation technologies of AFORE, the existing regional environment simulator SIMPLOT allowing the estimation of harvested biomass by tree components and thus the availability of raw material for the bio-refineries have been further developed by UTL. The SIMPLOT designed for Portuguese forest management was updated to obtain a first prototype that can provide annual estimations of the amount of forest residues that can be extracted from the forest if using different harvesting methods with a same known scenario of wood and biomass demand, fire occurrence, rate of planting and deforestation, and forest management approaches. Based on the updated information around 1-2 million tons of forest residues per year can be extracted in Portugal depending principally on the harvesting method and on the fire episodes. From these forest residues, around 25% is eucalyptus bark that could be used as raw material for the new bio-refinery concepts developed in the project. The total biomass available represented by the eucalyptus stands, was found to decrease along the simulated period with expected increase in demand of woody biomass. This can have important consequences, not only on an economic aspect, as the wood available and demand may not be met in the future, but also from an environmental point of view if there will be a significant reduction of the carbon stocked by eucalyptus plantations. The reduction of carbon stocked in the eucalyptus stands has already been and can in future be more pronouncedly compensated by an increase of the carbon sequestered by the forest products from the highly material efficient forest biorefineries.
SELECTED REFERENCES
Brebu, M. and Spiridon, I. 2012. Co-pyrolysis of LignoBoost® lignin with synthetic polymers, Polymer Degradation and Stability, 97(11), 2104-2109.
Brebu, M., Tamminen, T. and Spiridon, I. 2013. Thermal degradation of various lignins by TG-MS/FTIR and Py-GC-MS, Journal of Analytical and Applied Pyrolysis, in press
Domingues, R.M.A. de Melo, M.M.R. Oliveira, E.L.G. Neto, C.P. Silvestre, A.J.D. and Silva, C.M. 2013. Optimization of the supercritical fluid ectraction of triterpenic acids from Eucalyptus globulus bark using experimental design. J. Supercritical Fluids,74, 105-114.
Domingues, R.M.A. Oliveira, E. L.G. Simões, P.C. Neto, P.C. Silvestre, A.J.D. and Silva C. M. 2012. Supercritical fluid extraction of Eucalyptus Globulus bark – A promising approach for triterpenoids production. Int. J. Mol. Sci, 13, 7648-7662.
Gominho J., Lourenço A., Miranda I. and Pereira H. 2012. Chemical and fuel properties of stumps biomass from Eucalyptus globulus plantations for bioenergy purposes. Ind. Crops Prod. 39, 12-16.
Hakala, T.K. Liitiä T. and Suurnäkki A. 2012. Enzyme-aided alkaline extraction of oligosaccharides and polymeric xylan from hardwood kraft pulp. Carbohydr. Polymers, 93, 102-108. 10.1016/j.carbpol.2012.05.013
Mikkelson, Atte, Maaeimo, H. and Hakala, T. 2013. Hydrolysis of konjac glucomannan by Trichoderma reesei mannanase and endoglucanases Cel7B and Cel5A for the production of glucomannooligosaccharides. Carbohydrate research 372, 60-68.
Miranda, I., Gominho, J. and Pereira, H. 2012. Incorporation of bark and tops in Eucalyptus globulus wood pulping, Bioresources, 7(3) 4350-4361
Santos, S.A.O. Villaverde, J.J. Freire, C.S.R. Domingues, M.R. Silvestre, A.J.D. and Pascoal Neto, C. 2012. Phenolic composition and antioxidant activity of Eucalyptus grandis, E. urograndis (E. grandis x E. urophylla) and E. maidenii bark extracts. Ind. Crops Prod. 39, 120-127
Sousa, A.F. Gandini, A., Silvestre, A.J.D. Pascoal Neto, C., Cruz Pinto, J. J. C., Eckerman, C., Holmbom, B. 2011. Novel suberin-based biopolyesters: from synthesis to properties. Journal of Polymer Science Part A – Polymer Chemistry 49(10), 2281-2291. http://onlinelibrary.wiley.com/doi/10.1002/pola.24661/full
Spiridon, I., Darie, R.N. Bodirlau, R., Teaca C-A and Doroftei, F. 2013. Polypropylene based composites reinforced by toluene diisocyanate modified wood, Journal of Composite Materials, online 4.12.2012 15 pages. doi:10.1177/0021998312466906
Stern, T., Heil, G., Ledl, C. and Schwarzbauer, P. 2012. Identifying Innovation Barriers using a Delphi Method Approach: The Case of Technical Lignin in the Wood-based Panel Industry, International Wood Products Journal, 3/2, 116-123. ISSN 2042-6445
Patent application FI20135840, Hydrophobisation extract, method for hydrophobisation and substrate.
Patent application US61/729,377, Novel uses of hemicellulose derivatives
Potential Impact:
Socio-economic impact
This project contributed towards the overall RTD needs and objectives defined in the European Forest Technology Platform, FTP, SusChem Technology Platform strategic research agendas and the 7th FP Work Programme 2008 by promoting the transformation of European forest industry by creating additional sectoral and cross-sectoral product applications. In particular, Theme 4: Nanosciences, nanotechnologies, materials and new production technologies, NMP, was well addressed in the project. The AFORE project brought together interdisciplinary scientific groups and the representatives of forest based industry and wood component refining industry, especially SMEs, to exploit new and emerging research opportunities in the area of forest biorefineries. The project addressed economic, social and environmental challenges in forest based industries. More specifically, the need to renew forest industries, to generate new revenue sources for the industry in a sustainable manner based on the use of all wood components to added value products and thus to keep the European industry vital employer also in the future was addressed. Particularly, the project focused on the call FP7-NMP-2008-LARGE-2 and its topic NMP-2008-4.0-6: “Sustainable new products and markets through bioproduction of green forest-based chemicals and materials with the special target on developing novel, industrially adaptable and techno-economically viable and sustainable methods and technologies for the separation, fractionation, and primary upgrading of wood polymers and low molecular weight compounds from forest residue or process side-streams.”
The project contributed to the above mentioned goals by providing the following major outcomes:
• In total 6 separation, fractionation and up-grading processes for forest residues or process side-streams demonstrated in pilot scale. Three of the processes are related to current kraft pulp mills and three are self-standing concepts for future forest biorefineries. The primary techno-economic feasibility and LCA evaluation of the concepts is available as a basis of further exploitation
• Valuable knowledge and expertise of the other novel, innovative technologies for wood matrix opening and further separation, fractionation and upgrading of valuable wood components to be used as a basis of future wood biorefineries.
• New methods and tools including two new inventions to up-grade and exploit the wood components for material and chemical applications
• Information of the performance of wood components in selected material and chemical applications
• Information of the markets of materials and chemicals for which valuable wood components could be applied and the product requirements to be met by the wood components
• Information of the environmental, economic and social effects of exploitation of forest residues in Portugal as a regional European case
• Business concepts for techno-economically and environmentally sustainable products and applications based on the valuable wood components
The impact of these results is following. They
• promote the use of wood side streams for added-value products instead of burning/energy source
• promote the novel business opportunities for existing wood refining and pulp industry through up-grading of side stream components
• generate novel business opportunities for fractionation machinery, equipment and process companies
• promote the generation of new product value chain opportunities based on wood components
• support thus restoring or even generating employment in existing European forest based industries
• promote science based SME industries by integrating advanced technologies for the development of new, high value, products and processes and even leading to new industries
• promote sustainable production of chemicals which does not originate from petrochemical by providing alternative wood based sources
• in Portugal, assist the sustainable management of forests together with the promotion of efficient and profitable forest based biorefinery business in short, middle and long term
The project supported European forest based industry, especially pulp industry represented by Södra, Södra Cell and CELBI in AFORE. Europe has traditionally been very strong in pulp and paper production with the largest pulp companies worldwide. As the bulk production of paper pulp is gradually shifting to southern hemisphere, the efficient use of all wood components to added value products along with the current main products that is, pulp and paper, has identified as means to enhance the competitiveness of the European companies. Separation and up-grading of added-value components of wood and process side streams to be used in value chains novel to forest based industries opens up new revenue opportunities. There is, however, a gap between the forest based industry and the value chains new to the industry. It is thus essential to introduce and support new companies, especially SMEs like Separation Research, NATEX and hte, to the area of separating, fractionating and up-grading the added value components from the wood and process side streams. Furthermore, the project supported the companies such as Green Value and Danisco/DuPont, interested in exploiting the wood based components. The interaction of the industrial players from the different sites of the wood component based value chains was one of the main strengths of the AFORE project. It is clear that the means to further promote the collaboration within the wood component based value chains from the raw material owner and producer to converter to end product producer in the defined cases should be further generated in the future to push forward the exploitation of AFORE result and business generation throughout the value chain.
Combined efforts and European level collaboration with scientists and the industry are needed for developing future wood based biorefineries for economical and sustainable production of novel product openings along with the main products pulp and paper. The project aimed at new, industrially adaptable and techno-economically viable and sustainable methods and technologies for the separation, fractionation, and primary upgrading of wood polymers and low molecular weight compounds from forest residue or process side-streams. This aim was well achieved by bringing together research-oriented and technology-oriented partners from different countries. The project successfully combined various expertises, including
• raw material processing by physical, chemical and biotechnical methods both in laboratory and industrial scale
• up-scaling of disassembly, separation, fractionation technologies for forest biomass and its fractions
• modern chemical and physical analytics of wood raw materials and wood chemical components
• physical, chemical, and enzymatic modification of primary products originating from wood
• applications of wood-derived components, especially hemicellulose, lignin, and extractives and solid cellulosic materials
• techno-economic and environmental modelling, simulation and impact assessment needed in evaluation of the applicability of novel technologies and biorefinery concepts
• product and market knowledge and the methods to assess these
Collaboration among the partners was excellent. This can be seen by various co-publications and visits between the members. Without the shared knowledge, resources and facilities the goals would not have been possible to obtain.
Education and training of PhD students and other academic personnel was also carried out within AFORE. Due to the multidisciplinary nature of the project, the project offered great opportunities for the students. Altogether twelve Master’s theses and four PhD theses were completed in the project. In addition one Master’s theses is in progress. Project and project results have been disseminated in many scientific and technical meetings. In addition, one training school and four open AFORE workshops have been organized.
Dissemination activities
Net pages for the AFORE project can be found at: http://www.eu-afore.fi. The pages contain both a public and restricted site, latter available only for the AFORE consortium members. Four leaflets presenting the AFORE progress have been published. One press release has been published. AFORE has also been presented in the Portuguese Pasta el Papier and in the national radio interview by UAVR.
Altogether 33 peer reviewed scientific papers have been published so far in the AFORE project, six papers have been submitted and five will be submitted in the near future. In addition, several other manuscripts are in preparation by partners. The results from the project have been disseminated in various scientific meetings.
Exploitation of the results
The expoitation issues within the project have been constantly reviewed and discussed in Expoitation Committee, twice a year. Stephan Kallus (hte) was nominated and has been acting as the exploitation manager for the AFORE project. The companies Södra, Södra Cell, CELBI, SepRes, NATEX, hte, Green Value and Danisco/DuPont are in first hand responsible for the exploitation of the obtained results and discoveries. The project has generated a lot of data, methods and information which will be exploited after the AFORE project by partners. The main exploitable results in AFORE can be summarized as:
• A novel method for preparation of hemicellulose based tacky glue (patent pending)
• A novel method for hydrophobisation based on birch bark extracts (patent pending)
• A novel process for lignin catalytic pyrolysis including a novel catalyst
• Protocols for scaling up of following processes/methods: xylan separation from kraft process liquors, xylan extraction from bleached birch kraft pulp, production of xylo-oligosaccharides from wood based xylan, hardwood bark fractionation, scCO2 extraction of triterpenic acids from eucalypt outer bark, and lignin catalytic pyrolysis
• Novel physical and chemical wood separation and fractionation methods
• Improved sulphur free methods, pre-hydrolysis soda cooking, LGF organosolv cooking, and catalytic and alkaline oxidation of wood, to open up the wood structure
• Information of the composition and end use performance of the hemicellulose, lignin, added value low molecular mass components and cellulose fractions produced by novel separation and fractionation and upgrading methods
List of Websites:
http://www.eu-afore.fi
Project coordinator:
Dr. Anna Suurnäkki, VTT Technical Research Centre of Finland
Tel: +358 20 722 7178
Fax: +358 20 722 7071
E-mail: anna.suurnakki@vtt.fi
The aim of the AFORE project has been to develop new, industrially adaptable and techno-economically viable and sustainable methods and technologies for the separation, fractionation, and primary upgrading of wood polymers and low molecular weight compounds from forest residue or process side-streams. These valuable components can then be further utilised as starting materials in chemical, material and fuel applications. The project is focusing both on utilising the side-streams of the kraft pulping process employed in paper making today and on developing new forest biorefinery technologies for the future.
During the 4 years project the research and development has been done for both novel and existing methods to separate and further up-grade the valuable wood components in side-streams. The project has strongly targeted at up-scaling and demonstration of the best technologies in current processes on a pilot or mill scale. The techno-economic modelling, environmental impact analyses and market assessments have supported and guided both research and development work in AFORE and evaluation of the exploitation potential of the project processes and products. Both research and industry partners in the multidiciplinary consortium with 19 partners have actively contributed to the success of the project.
Several separation, fractionation and up-grading technologies for both solid and liquid wood derived samples have been studied in AFORE. In total, 9 of the studied technologies were selected for up-scaling and process concept evaluation. Finally, 6 of the up-scaled concepts were demonstrated in pilot or industrial scale. Three of these, separation of xylan from kraft cooking liquor and bleached kraft pulp, and production of xylo-oligosaccharides from pulp xylan, are related to the current kraft mills. The other three, separation and fractionation of birch bark, supercritical CO2 extraction of valuable components from eucalyptus and birch bark, and catalytic pyrolysis of lignin, are self standing concepts applicable in future forest biorefineries. The primary techno-economic and LCA evaluation is available for the up-scaled concepts. Advances in novel methods for characterisation and use of wood components in chemicals and materials have been achieved. Several inventions and two patent applications based on the exploitation of wood components in chemical and material applications have been made. The results of AFORE have been disseminated in various scientific publications and conferences as well as in 4 public AFORE Workshops, 4 newsletters and an AFORE training school. The list of AFORE publications and the public materials can be found in the project net site at: www.eu-afore.fi
The work carried out in AFORE has produced both scientific, technical, environmental, and market knowledge applicable in further forest biorefinery research and development work. Both short and long term basic and applied research and development work is, however, still needed to overcome the scientific, technical, environmental and safety challenges of the interesting current process concepts and to generate new openings for the future technologies. Companies interested to start evaluating the developed separation, fractionation and up-grading technologies are now also needed to promote their commercial exploitation. Although a clear interest in the wood based components was detected in AFORE among the various industrial appliers, in most cases the solid, long term source of these components is missing. Here, the key player is apparently the forest industry currently managing the starting material. In the furture, interaction between the companies in the product value chains starting from wood derived components would be utterly important to generate new business opportunities for the forest industry through side-stream exploitation.
Project Context and Objectives:
The forest–based industry is a significant industrial sector in Europe converting wood to pulp, paper, cardboard, energy, and other wood derived products. To retain and increase its competitiveness in the increasing global competition, the pulp and paper industry is looking for to maximize the value addition of raw materials in its fibre refining processes and to find new and profitable businesses alongside the traditional product lines. Today, only part of the valuable wood biomass ends up in high-value applications (paper and cardboard), whilst a significant part is channelled into different “side-streams”, such as logging residues, debarking residues and pulping liquors. All of these side-streams contain chemically appealing and reactive constituents that could be further refined to value-added chemicals, polymers, materials, and fuels alongside with the sustainable forestry and paper fibre production. Recent developments in tailored and efficient biomass pre-treatment and fractionation technologies together with the market challenges in the pulp and paper industry and rising oil prices have awakened interest towards side-stream exploitation.
Only minor part of the wood side-streams representing of over 50 % of initial wood biomass are valorised to various by-products. The rest, about 31.5 Mt/year of kraft pulping side-streams and 6-8 Mt/year of bark is mainly burned for steam and power generation and used for land construction. Furthermore, substantial amounts of harvesting residues are left in the forests, partially due to the forest ecology reasons.
Wood consists mainly of cellulose, hemicelluloses, lignin and extractives. During kraft pulping, wood components are partly dissolved into the cooking liquor either in intact, modified, or degraded form. Many of the constituents in wood also occur in bark, but their proportions are different. Bark also contains other interesting components such as suberin consisting alterating regions of lignin-like aromatic regions and esterified hydroxy(epoxy)fatty acids. Attempts to exploit kraft lignin have been carried out especially in Sweden and recovery of lignin from kraft pulping by the LignoBoost process has recently been implemented to industrial kraft mill process. Dissolved hemicelluloses and hydroxy acids have so far remained totally unexploited as raw materials for the chemical industry.
In current kraft pulp production the solid matrix separation processes are fine-tuned for efficient production of papermaking fibres. Various alternative chemical pulping methods such as alkaline sulphite and soda cooking, different organosolv cooking and acidic cooking concepts have been developed during the past decades. More recently, fractionating pulping methods such as reactive organosolv cooking using phosphinic acid catalyst have also been developed. Certain ionic liquids (ILs) have shown to efficiently dissolve wood and enable efficient derivatization of lignocellulosic materials. These cooking and wood structure opening methods, although not competitive with kraft pulping for the paper and packaging applications, could be suitable for by-product recovery together with a cellulosic fibre product in the future forest biorefineries.
The low concentration of the valuable components in the kraft process liquid streams has hampered their exploitation and thus the challenge has been to find efficient separation methods for isolation of hemicelluloses, lignin and valuable low molecular mass components from these streams. Membrane processes form the key separation technique for liquid streams in biorefineries because of their excellent fractionation capability, low chemical consumption and low energy requirement. However, concentration polarisation and membrane fouling can be a serious problem in membrane filtration. The performance of conventional membrane filtration can be improved by the use of ultrasound or by enzymatic treatments. Supercritical fluid extraction is also a potential technology for sustainable fractionation of both liquid and solid wood streams.
Valuable wood components, called primary products in the AFORE project, present in the wood side streams have various potential applications. Hemicelluloses, i.e. xylan and glucomannan, are currently not industrially isolated from wood streams but when available would be suitable as a starting material for various material and chemical applications. Lignin currently used mainly as an energy source in pulp mills has a number of attractive properties making it suitable for advanced material applications. The foliage, needles in softwoods and leaves in hardwoods, and bark contain up to 30-40 % of different extractives, waxes and phenols that can be applicable in e.g. pharma, functional material or chemical applications.
The objective of the AFORE project is to develop new, industrially adaptable and techno-economically viable and sustainable methods and technologies for the separation, fractionation, and primary upgrading of wood polymers and low molecular weight compounds from forest residue or process side-streams. These valuable components can then be further utilised as starting materials in chemical, material and fuel applications. The project is focusing both on utilising the side-streams of the kraft pulping process employed in paper making today and on developing new forest biorefinery technologies for the future.
AFORE is focused on two approaches:
A) Upgrading the current kraft pulping process into a multi-product biorefinery concept without compromising the process energy balance or the fibre properties, and
B) Development of entirely new wood-based biorefinery concepts, in which the wood cellulose is exploited in value-added applications with simultaneous production of a multitude of novel non-cellulosic products.
The success of the technological developments is evaluated in AFORE using different modelling and assessment tools and pilot or mill scale demonstrations. The techno-economical evaluations will also include a thorough investigation of how the new side-stream based value chains will affect the current end uses (mainly energy generation) as well as the environmental footprint of the process.
The overall goals of the AFORE project have been 1) to increase the product portfolio and thereby the economic value of the pulp and paper industry through the development of mild and selective technologies for separation and primary upgrading of components that can be applied in novel high-value applications without compromising the current fibre and energy production; 2) to generate future forest-based biorefineries by developing and applying novel separation and fractionation methods for wood components with special emphasis on bio-technologies; and 3) to demonstrate that the current kraft pulping process can be upgraded into an integrated wood-based biorefinery in a sustainable, flexible and techno-economical way. The project will thus combine a short-term (improved kraft pulping) and a long-term (future wood-based biorefinery concepts) development path as shown in Figure 1.
It was expected that the AFORE project results in i) 1-2 demonstrated, technically feasible processes for separation of potential components from the side-streams of current kraft pulp mills and the wood materials in novel biorefinery concepts, ii) novel, innovative technologies for wood matrix opening and further separation, fractionation and upgrading of valuable wood components to be used as a basis of future wood biorefineries and iii) business concepts for techno-economically and environmentally sustainable products and applications based on the valuable wood components.
Efficient separation of components from solid materials and process liquors would enable more specific isolation of targeted fractions from wood side-streams. Thus, novel separation, fractionation and primary up-grading methods and technologies to be developed in the project promote the the exploitation of all valuable wood-derived components in current or future wood biorefineries. Information on the technical and economic potential as well as the environmental impact of the most promising technologies to be developed in the project will also offer a solid basis for further business considerations and scientific and technological development. Overall, it is expected that the results of AFORE project will help in tackling the important challenge of transferring forest industry into an efficient and sustainable lignocellulosic biorefinery, in which the unique chemical composition of all wood fractions is fully exploited.
Project Results:
The AFORE project have had 21 partners of which 19 has been active till the end of the project. The partners represent the whole forest biorefinery value-chain (Table 1). The partners, both academic and industrial, had expertise, equipment and complementary knowledge in
• raw material processing by physical, chemical and biotechnical methods both in laboratory and industrial scale
• up-scaling of disassembly, separation, fractionation technologies for forest biomass and its fractions
• techno-economic and environmental modelling, simulation and impact assessment needed in evaluation of the applicability of novel technologies and biorefinery concepts
• modern chemical and physical analytics of wood raw materials and wood chemical components
• physical, chemical, and enzymatic modification of primary products originating from wood
• applications of wood-derived components, especially hemicellulose, lignin, and extractives and solid cellulosic materials
Table 1. List of AFORE participants
The project approach is summarized in Figure 1. AFORE focused on two paths, A) upgrading the current kraft pulping process into a multi-product biorefinery concept without compromising the process energy balance or the fibre properties, and B) development of entirely new wood-based biorefinery concepts, in which the wood cellulose is exploited in value-added applications with simultaneous production of a multitude of novel non-cellulosic products. The strong focus at demonstrating in pilot or industrial scale the most promising separation, fractionation and up-grading technologies resulted in total 6 demonstrated concepts with techno-economic and LCA analysis. The main AFORE results of the development of separation and fractionation methods for wood and process side streams and the up-grading of resulting primary products project are presented below.
Figure 1 The approach of the AFORE project. A indicates a conventional kraft pulp mill and B a novel wood biorefinery concept
KRAFT PULP MILL BASED CONCEPTS
Both current kraft pulping process liquors and kraft pulps have been shown to be good sources for wood-derived polymeric xylan. Three kraft mill related process concepts for xylan separation and up-grading that is, i) separation of xylan from early cooking liquor, ii) extraction of xylan from bleached birch kraft pulp, and iii) production of xylo-oligosaccharides from xylan alkali extracted from pulp, have been up-scaled and demonstrated in pilot scale. Enzymes have been shown to be exploitable both in enhancing alkaline xylan extraction from pulps, tailoring the molecular weight distribution of extracted polymers and producing hemicellulose-poor pulps. The efficiency of membrane separation of lignin in LignoBoost process has been enhanced. Advanced membrane separation processes have also been shown to be applicable in the separation of hemicellulose from the LignoBoost filtrate process filtrate. On the contrary, distillation is not a suitable method for separation and fractionation of hydroxyl acids from kraft black liquor.
Alkaline extraction of xylan from wood chips and bleached kraft pulp
A lab scale method to extract xylan from hardwood kraft pulp with alkali was improved, up-scaled and successfully demonstrated in 1600 kg scale by VTT in collaboration of Södra. The xylan obtained from bleached birch kraft pulp from Södra Cell had very high purity (monosaccharide purity >99%). The technical and economic feasibility and the LCA evaluation of the process concept shown in Figure 2 was made. The process concept is economically feasible in all the cases calculated. The quality and price of the extracted xylan poor pulp has the highest effect on the production cost of xylan and the economic outcome of this concept. The production cost of xylan was calculated to be 600-1000 EUR/t of pure xylan depending on the quality of the hemi-poor pulp. The lower production costs represents a case in which pulp has been up-graded to dissolving grade pulp with two stage extraction. In this case a high ROI (Return on Investment) could be obtained. The higher production cost is obtained with one stage extraction and resulting pulp classified as market pulp. More research needs to be put both on the technical solutions for the large scale extraction and xylan separation and the further process the pulp to meet the requirements of dissolving grade pulp.
Figure 2. Simplified process model of alkaline extraction of xylan from bleached birch kraft pulp
Enzymes were shown to be applicable in enhancing the alkaline extraction of polymeric xylan or xylo-oligosaccharieds from the kraft pulp. Depending on the target, enzyme treatment can be carried out either before, after or in between two alkaline extraction steps (Fig. 3). When xylanase treatment was carried out by VTT before alkaline extraction both xylo-oligosaccharides (~10% of original xylan) and xylan (~50% of original xylan) were obtained from the pulp. As a comparison, from the reference pulp 60% of xylan could be extracted. Xylanase treatment decreased the molecular weight of the extracted xylan. To obtain xylan with un-altered molecular weight as well as xylo-oligosaccharides, xylanase treatment can be carried out after alkaline extraction. By this combination up to about 4 % of xylo-oligosaccharides can be obtained and the xylan content of the remaining pulp is further decreased.
Figure 3 Verified options of feasible enzyme-aided alkaline extraction of birch kraft pulp for xylan or xylo-oligosaccharide production
Alkaline extraction of hardwood chips was shown to result in the hemicellulose extract rich in water soluble xylan. The alkaline extraction procedure was more suitable for birch than for eucalyptus in terms of yield and extraction specificity. Extraction of xylan from wood chips could be improved by ultrasound irradiation. Alkaline extraction of wood chips with or without ultrasound enhancement can be combined with various subsequent matrix opening technologies including kraft pulping. The alkaline pre-extraction might provide an additional fraction to be obtained from the raw material without compromising the yield and efficiency of the subsequent process.
Separation of xylan from kraft pulp mill liquors
Membrane separation techniques for xylan from early-phase and final-phase/partially evaporated alkaline pulping liquors as well as LignoBoost filtrates from birch and eucalyptus were developed by Innventia. The main separation technique used was ultrafiltration using both ceramic and polymeric membranes followed by precipitation of the xylan.
A method to separate xylan from early cooking liquor was improved, up-scaled and successfully demonstrated in kg scale with both birch and eucalyptus kraft black liquor. The demonstration was carried out at LignoBoost demo facilities in Bäckhammar, Sweden. Birch black liquor was sampled at Södra’s mill in Mönsterås. Eucalyptus black liquor was sampled at CELBI mill in Leirosa, Figueira da Foz, Portugal. In the demo scale trials about 67 % of the kraft cooking liquor xylan was withdrawn for the xylan separation. In total 5 kg of birch xylan and 9 kg of eucalyptus xylan was isolated. The xylan obtained was relatively pure, containing 70-80% of xylan with average molecular mass of 10 600 g/mole and about 20-30% of lignin, other hemicelluloses and inorganics. The technical and economic feasibility and the LCA evaluation of the process concept shown in Figure 4 was made based on birch black liquor. The estimation of the investment cost for the concept is very rough but gives an indication of the production cost, 880 EUR/t of pure xylan in the case with no precipitation and 1060 EUR/ton of pure xylan in the case of precipitation included. The main contributors to the ROI of this concept were the price of resulting xylan and the price of the bark bark purchased due to the steam deficit (less raw xylan to recovery boiler and increased load on evaporation). Further development work to optimize process parameters and efficiency would be beneficial for the implementation of the process to the industry. The results from this study show that xylan isolated according to this concept can provide a renewable and green product to meet the demands of the future generations.
Figure 4. A model of the process for separation of xylan from hardwood cooking liquor and its implementation to the kraft process
Xylan separation from LignoBoost filtrate of eucalypt and birch comparing different ultrafiltration membranes was also evaluated by Innventia. To separate xylan from black-liquor after withdrawing of the main part of the lignin with the LignoBoost process is investigated since there is a large potential of xylan in hardwood black liquors and today, the filtrate is evaporated and burnt; the only value used is hence the energy of the dissolved xylan. With the process set up used it was found that the ceramic membranes produced more pure xylan than the polymeric membranes and the best xylan retention was 84%. After further ultrafiltration and precipitation LignoBoost filtrate seemed comparable to the early cooking liquor as a source of polymeric xylan in terms of xylan purity. Thus, filtrate from the LignoBoost process is an interesting raw material for xylan production.
NATEX in collaboration with Innventia carried out precipitation and extraction of xylan from hardwood kraft black liquor using supercritical carbon dioxide, scCO2, and co-solvents. A separation scheme consisting of lignin separation, followed by hydroxy acid separation and finally separation by anti-solvent precipitation of hemicellulose was proposed. Precipitation of xylan from the kraft hardwood liquor using scCO2 was performed in a view-cell, designed for pressures up to 300 bar and temperatures up to 250 °C.
Production of xylo-oligosaccharides from wood based xylan
Danisco developed and demonstrated in semi-pilot scale a membrane assisted enzymatic process to produced xylo-oligosaccharides. Hydrolysis of birch xylan, alkaline extracted from bleached birch cellulose by VTT and about 10 kg DS of oligomers were collected from the permeate. It was shown that it is possible to produce xylo-oligomers with this method by avoiding the hydrolysis of oligomers to monomeric xylose.
Separation of lignin from black liquors
Innventia developed methods for isolating more homogenous lignin fractions with interesting properties from black liquors based on the LignoBoost process. Lignin fractions obtained in the laboratory trials were characterized. An interesting observation was made; the pre-hydrolysis resulted in higher content of acid insoluble lignin in the fractions separated from both hardwood kraft and hardwood soda black liquors.
Separation technologies of hydroxy acids from black liquor
Isolation of commercially interesting hydroxy acids from kraft cooking black liquor was aimed at by VTT using distillation and reactive scCO2 extraction together with NATEX. Over 20 different, chromatographically separated hydroxy acid mixtures were subjected to vacuum distillation (typical pressure 1–2 mbar). The acid mixtures were derived from commercial or synthetic model compounds, from alkaline degradation of starch or xylo-oligosaccharides (XOS), and from birch black liquor. Some compounds (such as simple 2-hydroxyalkanoic acids) were isolated as technically pure chemicals from black liquors (Figure 5). It is thus evident that many hydroxy acids can well be separated by distillation from synthetic (lignin-free) black liquors, although inevitable condensation reactions form a challenge. It appears that the distillation of hydroxy acids from real black liquors is strongly inhibited by various impurities (even in low concentrations). It is also evident although not yet well understood that the condensation reactions and other impurity problems are hard to control, making it very challenging to up-scale this type of process to real industrial operations. Further experiments to esterify the hydroxy acids into more volatile form were carried out with limited success.
Figure 5 Isolation of 92% pure 2-hydroxybutanoic acid from a birch black liquor fraction by distillation (crystallised before entering the receiving flask).
SELF-STANDING SEPARATION AND FRACTIONATION CONCEPTS
In AFORE detailed characterization of forest residues and industrial by-products (needles, branches, barks tops, and stumps), using the most recent spectroscopic techniques, has allowed to identify some of them as sources of bioactive compounds (triterpenic acids and other triterpenoids, terpenes, phenolic compounds among others) with potential nutraceutical and pharmacological properties. Bark from both eucalyptus and birch has been found to be an interesting source of valuable low molecular weight components. Raw material collection, primary fractionation and extraction technologies for the exploitation of these components have been studied and developed by the consortium.
Advanced and novel matrix opening methods including soda and soda-anthraquinone cooking, LignoFibre (LGF) organosolv cooking, various oxidative cooking methods and ionic liquid (IL) treatment have been applied for project solid wood materials with promising results. Furthermore, the effect of hot-water pre-extraction on novel cooking methods and the primary products obtained has been elucidated. Various extraction and separation methods have been studied to further separate and fractionate the target primary products from wood processing liquors. Both supercritical carbon dioxide technique (scCO2) and Accelerated Solvent Extraction (ASE) has showed promise in extraction of high-value low molecular mass compounds from different solid and liquid wood fractions.
Three self-standing process concepts aimed to the novel forest biorefinery concepts that is, i) Separation and fractionation of birch bark, ii) Supercritical CO2 extraction of triterpenic acids from outer eucalypt bark, and iii) Catalytic pyrolysis of lignin, have been up-scaled and successfully demonstrated in pilot or industrial scale.
Eucalypt bark as a source of valuable components
Physical (densimetric) fractionation processes, were developed by UTL for the separation of birch and eucalyptus barks, allowing the exploitation of their most valuable components. UAVR characterized the lipophilic extracts of the outer and inner barks of E. globulus, E. urograndis, E. grandis, E. maidenni, E. grandis x globulus and E. nitens, with particular emphasis on the triterpenic acids. It was demonstrated that all eucalyptus species are promising sources of triterpenic acids, which are particularly abundant in outer barks (Table 2), ranging from ~5g/kg of extract up to 20-25 g/kg of extract. In addition, UAVR characterized the phenolic components from eucalyptus barks and for example, 29 phenolic compounds were identified in E. globulus bark, of which 18 reported in this species for the first time. The phenolic content of the extracts showed a positive correlation with their antioxidant activities. These results confirm the high potential of eucalyptus bark as source of biologically active compounds.
Table 2. Main triterpenic acids in Eucalyptus ssp. outer barks (g/kg of extract). * including the 3-acetyl derivative
UAVR together with NATEX up-scaled and successfully demonstrated in industrial scale the scCO2 extraction of triterpenic acids from Eucalyptus globulus external outer bark (Fig. 6). Two extraction approaches (Approach 1: higher pressure and no co-solvent and Approach 2: lower pressure and co-solvent addition) were both demonstrated in 80L/550bar plant of NATEX (Fig. 6). The overall yield achieved was about 1wt% of triterpenic acids from the bark. The concentration of triterpenic acids in the extracts was up to 41wt%. The process of SFE of TTAs can thus be successfully exploited in industrial level. The techno-economical evaluation of this case showed promising economic performance with the assumptions made. The concept is, however, highly sensitive to the price obtainable from the end product. Thus, further research and development activities in the separation and purification of the triterpenic acids from the extracts already were already started in AFORE by UAVR.
Figure 6 Example of the extraction yields in scaling up the scCO2 extraction of triterpenic acids (TTAs) from eucalyptus outer bark and 80L/550bar pilot plant in NATEX laboratory
Hardwood bark as a source of valuable components
Birch outer bark, a source of betulin, can be recovered in pure form from birch bark by proper comminution and a two stage flotation technique in high yield using methodology developed by SepRes (Fig. 7). The processes were up-scaled and demonstrated with several hundred kilograms of birch bark from a Finnish plywood mill and a Finnish kraft pulp mill. The scCO2 extraction of betulin from pure birch outer bark recovered by SepRes was further carried out by NATEX. The extraction of birch outer bark works well and there is serious interest of triterpenoids from the cosmetics industry. Extracts, which contain more than 97w% of triterpenoids (Figure 8) were produced. After AFORE, the industrial production is expected to be executable at low technical risk.
Figure 7 Principle of the birch bark fractionation processes
Figure 8 Birch outer bark extracts
Debarked branch wood from pine and spruce were studied as potential sources of valuable components and their extraction technologies were studied by SepRes. Phenolic and lipophilic components from spruce and pine branch extracts were separated by hexane and ethanol. Birch outer bark was depolymerised by alkaline and acid hydrolysis to yield hydroxy fatty acids. The extract from spruce branch wood 15 cm segment closest to the stem was found to be of potential commercial interest. Specifically, the concentration of lignans, particularly hydroxymatairesinol, reached concentrations typical of spruce knotwood. The extract produced is of high purity and comparable to a knotwood extract. The hexane extract of pine branch wood contained the bulk of the resin and fatty acids and a small portion of the pinosylvin monomethyl ether. The ethanol extract contained the stilbenes pinosylvin and pinosylvin monomethyl ether as well as the lignan nortrachelogenin with some traces of resin and fatty acids.
Novel pulping and matrix opening technologies
Catalytic matrix opening reactions, catalytic alkaline oxidation, CatOx, and alkaline oxidation, AlkOx, to pine (wood, needles) and alkaline matrix opening reactions for eucalyptus (leaves), birch (bark, leaves) and pine (wood, bark, needles) were studied by UH. All wood material fractions tested were easily oxidized in catalytic and alkaline oxidations in lab scale. In these treatments lignin is solubilised and if preferred can be collected with filtration after precipitation with acid. When extractive-free lignin is wanted, the starting material can be extracted before CatOx and AlkOx with hexane or heptane for two days following one day extraction with acetone. The fibre length distribution analysis indicated that the length of the AlkOx birch fibres is comparable to kraft pulp whereas the length of AlkOx eucalyptus and pine fibres is slightly shorter than average kraft pulp fibres.
UH also studied the fibrillation of hardwoods by ionic liquids (ILs). For hardwood (birch), a high number of different imidazole derivatives was screened, but only N-ethyl,N-methyl imidazolium acetate [EMIM][OAc] promotes wood fibrillation. Based on the composition analysis it was concluded that the fibrillation might be due to removal of pectins. In addition to the characterization work of IL fibrillated wood, further delignification of the IL fibrillated birch chips with another IL, Amim-Cl, or kraft cooking was conducted. The results revealed that Amim-Cl is able to dissolve the birch fibres essentially completely. Regeneration of the dissolved fibres showed that it is possible to partially fractionate birch components by precipitation in organic solvents and their water mixtures.
Two separate existing sulphur and chlorine free matrix opening technologies, pre-hydrolysis soda cooking with oxygen delignification and WoodOx, were further developed by Innventia. The pre-hydrolysis soda cooking of Eucalyptus globulus together with a harsh oxygen delignification step (Fig. 9) resulted in a high purity cellulose pulp (cellulose content >98%) at 37% yield after only three – totally sulphur and chlorine free – process steps. The pulp is well suited for special applications after triacetylation.
Figure 9 Pre-hydrolysis soda cooking followed by harsh oxygen delignification - only three process stages; results in high purity cellulose pulp (>98% cellulose) at 37% yield when using Eucalyptus globulus pulp wood
A low-temperature oxidative delignification method, WoodOx (Fig. 10), has earlier proven to produce a bright, low lignin containing pulps at approx. 70% yield in one step from softwood. In this project WoodOx was successfully applied to eucalypt wood reject (0-2 mm thick) which in the pulping industry mainly is used for burning. Although further optimization of both delignification methods is needed they are promising concepts for production of specialty cellulose pulps. The pre-hydrolysis soda is considered more advantageous than WoodOx even though the yield is lower.
Figure 10 WoodOx process, low-temperature oxidative delignification combined with alkaline extraction, produces cellulose pulp at high yield from wood reject, 0-2 mm thick. PAA= peracetic acid
The existing Lignofibre (LGF) organosolv cooking process characteristic of its phosphinic acid chemical additive was further developed by VTT. In AFORE the LGF process with acetic acid as a cooking chemical was made industrially more feasible by shortening the cooking time, recycling the cooking chemical and enhancing the recovery of the wood-based components (Fig. 11). Furthermore, LGF cooking was successfully performed at pilot-scale for birch chips and positive economics were shown when combined with subsequent triacetylation. In the lab scale cooking experiments with eucalyptus and birch wood chips fibre yield between 55-59% was obtained. The lignin-containing pulps had high cellulose (70-80%) and very low xylan (eucalyptus 1-2%, birch 2-5%) content. Xylan dissolved during the LGF cooking was converted promarily to furfural. The delignification of pine was less efficient in the LGF cooking than that of birch and eucalyptus. Interestingly, the birch LGF pulp was very prone for further delignification and high final brightness (>88.7% ISO) and low lignin content (kappa below 0.5) pulp suitable for subsequent triacetylation was obtained by the chosen chlorine free bleaching sequence. After various process considerations it can be concluded that the LGF organosolv cooking should be limited to kappa level 20-30, corresponding to cooking times 3-4 h with alkaline extraction
Figure 11 The LGF organosolv cooking process for fractionation of wood chips to added value components
UP-GRADING AND PERFORMANCE OF PRIMARY PRODUCTS
Further purification, characterisation and up-grading of the primary products separated from various wood residues and process side streams has been carried out. Interesting properties and performance in respect to applications have been identified for hemicellulose, lignin and several component groups of the extractives as well as cellulose residues. Advanced analytical techniques have been developed both for the lignin composition analysis, the molecular mass determination of polymeric hemicelluloses, and the structural characterisation of oligosaccharides. All advanced techniques have been used in AFORE and recently, the latter was successfully exploited in applied for the characterisation of acidic xylo-oligosaccharides.
Hemicellulose in applications
New type of adhesive components was developed from wood derived xylan by VTT. Current polymers in hot melt adhesives are most commonly synthetic polymers. However, the market for bio-based adhesives is increasing and here non-food components such as hemicelluloses are attractive as raw material. Simple derivatization of xylan by hydroxypropylation was utilized for production of an adhesive component in AFORE. The glass transition temperature of the modified xylans was with 60 °C lower than that of pure xylan (171°C). The modified xylan was blended successfully in the compounder with oxidized cellulose acetate and a plasticizer to produce a tacky blend. This hot melt adhesive formulation showed good adhesion in cardboard gluing (Fig. 12). Slow tearing showed a tacky seam and no fiber damages were observed whereas fast tearing resulted in fiber rupture. It was thus demonstrated, that the hydroxypropylated xylans have potential as adhesive components. Patent applications of this new method to produce xylan based hot melt adhesives are pending.
Figure 12 Xylan hot melt glue samples in testing
Chemically functionalized xylans were successfully synthesized and tested as paper strength additives by Innventia. Birch and eucalyptus black liquor xylans and kraft pulp xylans were derivatized by carboxymethylation using sodium monochloroacetate under aqueous alkaline condition. The functionalized xylans synthesized demonstrated high and low degree of substitution with anionic CM-groups, respectively. The chemically functionalized black liquor xylans differed with respect to molar size and distribution. The carboxymethylated xylans adsorbed onto the fibres and thereby increased the frequency of anionic functional groups on the surface. The paper strength properties of sheets prepared from CMX activated pulps were improved, e.g. the z-strength increased. Carboxymethylated xylans synthesized from birch and eucalyptus xylans can thus be employed to activate bleached softwood pulps and improve their dry strength properties.
Carboxymethylated birch and eucalyptus xylans produced by GreenValue were shown to be effective additives to improve concrete fluidity. These products can therefore be considered novel renewable non-sulfonated dispersants that are also expected to be highly biodegradable.
Lignin in applications
The performance of various lignins in selected material applications was clarified by Green Value. Kraft lignin was shown to be applicable after modification for both novolac- and resole-type thermoset applications. For concrete additive (to improve fluidisation) the modified kraft lignins performed as well as commercial references. Kraft lignin plasticized by GreenValue also performed well in the biopolymer composites developed by PPIMC, significantly improving strength parameters after accelerated weathering.
Thermal treatment of kraft lignin is a promising method to convert the lignin into an efficient adsorbents, in particular for gas applications, if modified prior to carbonization as shown by Innventia. Activation of the lignin-derived carbon adsorbent may further improve the quality.
The catalytic pyrolysis of lignin together with biomass was found to be applicable. In the lab scale co-pyrolysis of LignoBoost kraft lignin and vegetable oils PPIMC showed that the distribution of compounds in co-pyrolysis oils is strongly affected by both the lignin and the catalysts. The heterogeneous catalytic pyrolysis of LignoBoost kraft lignin to bio-oil using a novel catalyst developed by SINTEF in AFORE and a commercially available catalyst was demonstrated in pilot scale in CERTH. The preparation of the 5 kg pilot plant batch of the novel catalyst was performed using a SINTEF recipe. Formulation of this batch was performed successfully. Both catalysts (novel and commercial) were tested for lignin catalytic pyrolysis in the circulating fluid bed pilot scale reactor in CERTH (Fig. 13). For the demonstration of the technology a new system for lignin feeding and a new lignin/biomass pre-treatment procedure were developed. It was concluded that lignin can be catalytically pyrolyzed with both catalysts by co-feeding the lignin with biomass up to 25%wt content. The oil produced from this process has low oxygen content and it can be used as fuel after further upgrading or as source for chemicals and phenols.
Figure 13. The process of heterologous catalytic pyrolysis of kraft lignin to bio-oil
Added-value extracts from wood
Various extractives including triterpenic acids, polyphenols, and stilbene glucosides were observed to have bioactivity and/or other application value. An interesting new birch extract based material for surface hydrophobisation was invented by SepRes.
The antioxidant activity of both methanol and methanol:water extracts of E. globulus bark was measured by UAVR to be in the same level than that measured for ascorbic acid (Table 3). These results are in agreement with the total phenolic content of the extracts suggesting that the phenolic compounds are the main responsible for the antioxidant activity in these extracts.
Table 3 Antioxidant activity of ascorbic acid and eucalyptus bark extracts (values expressed as mean ± standard deviation (n=3))
Ursolic (UA), oleanolic (OA), butilinic (BA) and betulonic acids (BOA), as well as total and fractionated Eucalyptus ssp bark extracts have been tested in order to better characterized their anti-tumor activity on human breast and colorectal cancer cells. The content of triterpenic acids, especially BOA, in the bark extracts correlated with the inhibition of cell proliferation and induction of cell death in the case of colorectal cancer cells. Among the bark extracts studied E. nitens extracts were more active than E. globulus extracts apparently due to its specific composition of triterpenic acids. E. nitens extracts concentrated with triterpenic acids is about two times more effective than the crude extract in inducing the inhibition of cell proliferation. Regarding human breast cancer cells, pure triterpenic acids also presented a strong anti-proliferative capacity, which was proved by significant alterations in cell cycle progression. Thus, to fully exploit the anti-tumor potential of eucalyptus bark extracts purification and concentration of triterpenic acids already started in AFORE needs to be further developed.
Wood material-polymer composites
The applicability of cellulosic materials origin from different AFORE matrix opening processes for polymer composites was studied by PPIMC. Wood-polymer composites comprising polypropylene (PP), MAPP (3%) and 60% CARBOCEL residue were first designed. Their behavior in accelerated weathering indicated that for applications such outdoor decking only extracted CARBOCEL material should be used.
Composites comprising 15% unbleached LGF organosolv pulp as such or after hydrophobication by chemical modification, 15% PLA, 3% MAPP and PP were prepared and tested before and after weathering. Weathering incresed substantially the dynamic water sorption capacity of the composite samples. The moisture absorption was much lower for samples comprising modified pulp fibres as compared to samples with untreated fibres. The composites prepared were concluded to be a good alternative for wood plastic composites that need to be subjected to damp places, such as the interior of bathrooms, wood decks, food packaging, etc, since the water absorption of these materials was considerably lower.
Polymer composites consisting lignin and PLA were prepared. Lignins used were hardwood LignoBoost kraft lignin as such or after plasticization by Green Value, and LGF organosolv lignin from beech. A good adhesion between the lignin and PLA matrix was observed. Use of plasticized lignin resulted into the best mechanical and thermal properties. Also, it recorded the lowest water sorption capacity. The blends containing lignins exhibited decreased melt viscosity compared to the matrix, the reason being related to the fact that they act as plastifiers, reducing the resistance of the matrix to the external forces and thus determining an improvement of flow for PLA-lignin systems. After weathering due to the fact that lignin contains chromophoric groups that are more susceptible to degradation, but also the degradation products could form hydrogen bonds that strengthen the material structure, the thermal and mechanical properties were not highly affected.
POTENTIAL MARKETS FOR WOOD COMPONENTS
The comprehensive market assessments made by WoodKPlus have evaluated the potential markets of the AFORE primary products. Ten business to business surveys with more than 400 companies contacted and two consumer surveys were made to clarify the market potential and product value, barriers and incentives, consumer acceptance and perceptions related to the wood based components in end products. Table 4 summarises the different market analysis and shows the market potential in terms of market volume and market value with the barriers and incentives for the different applications.
Table 4. Summary of the market potential of possible AFORE concept products
ENVIRONMENTAL CONSIDERATIONS
In addition to the LCA evaluation carried out by VTT for the most potential separation and fractionation technologies of AFORE, the existing regional environment simulator SIMPLOT allowing the estimation of harvested biomass by tree components and thus the availability of raw material for the bio-refineries have been further developed by UTL. The SIMPLOT designed for Portuguese forest management was updated to obtain a first prototype that can provide annual estimations of the amount of forest residues that can be extracted from the forest if using different harvesting methods with a same known scenario of wood and biomass demand, fire occurrence, rate of planting and deforestation, and forest management approaches. Based on the updated information around 1-2 million tons of forest residues per year can be extracted in Portugal depending principally on the harvesting method and on the fire episodes. From these forest residues, around 25% is eucalyptus bark that could be used as raw material for the new bio-refinery concepts developed in the project. The total biomass available represented by the eucalyptus stands, was found to decrease along the simulated period with expected increase in demand of woody biomass. This can have important consequences, not only on an economic aspect, as the wood available and demand may not be met in the future, but also from an environmental point of view if there will be a significant reduction of the carbon stocked by eucalyptus plantations. The reduction of carbon stocked in the eucalyptus stands has already been and can in future be more pronouncedly compensated by an increase of the carbon sequestered by the forest products from the highly material efficient forest biorefineries.
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Potential Impact:
Socio-economic impact
This project contributed towards the overall RTD needs and objectives defined in the European Forest Technology Platform, FTP, SusChem Technology Platform strategic research agendas and the 7th FP Work Programme 2008 by promoting the transformation of European forest industry by creating additional sectoral and cross-sectoral product applications. In particular, Theme 4: Nanosciences, nanotechnologies, materials and new production technologies, NMP, was well addressed in the project. The AFORE project brought together interdisciplinary scientific groups and the representatives of forest based industry and wood component refining industry, especially SMEs, to exploit new and emerging research opportunities in the area of forest biorefineries. The project addressed economic, social and environmental challenges in forest based industries. More specifically, the need to renew forest industries, to generate new revenue sources for the industry in a sustainable manner based on the use of all wood components to added value products and thus to keep the European industry vital employer also in the future was addressed. Particularly, the project focused on the call FP7-NMP-2008-LARGE-2 and its topic NMP-2008-4.0-6: “Sustainable new products and markets through bioproduction of green forest-based chemicals and materials with the special target on developing novel, industrially adaptable and techno-economically viable and sustainable methods and technologies for the separation, fractionation, and primary upgrading of wood polymers and low molecular weight compounds from forest residue or process side-streams.”
The project contributed to the above mentioned goals by providing the following major outcomes:
• In total 6 separation, fractionation and up-grading processes for forest residues or process side-streams demonstrated in pilot scale. Three of the processes are related to current kraft pulp mills and three are self-standing concepts for future forest biorefineries. The primary techno-economic feasibility and LCA evaluation of the concepts is available as a basis of further exploitation
• Valuable knowledge and expertise of the other novel, innovative technologies for wood matrix opening and further separation, fractionation and upgrading of valuable wood components to be used as a basis of future wood biorefineries.
• New methods and tools including two new inventions to up-grade and exploit the wood components for material and chemical applications
• Information of the performance of wood components in selected material and chemical applications
• Information of the markets of materials and chemicals for which valuable wood components could be applied and the product requirements to be met by the wood components
• Information of the environmental, economic and social effects of exploitation of forest residues in Portugal as a regional European case
• Business concepts for techno-economically and environmentally sustainable products and applications based on the valuable wood components
The impact of these results is following. They
• promote the use of wood side streams for added-value products instead of burning/energy source
• promote the novel business opportunities for existing wood refining and pulp industry through up-grading of side stream components
• generate novel business opportunities for fractionation machinery, equipment and process companies
• promote the generation of new product value chain opportunities based on wood components
• support thus restoring or even generating employment in existing European forest based industries
• promote science based SME industries by integrating advanced technologies for the development of new, high value, products and processes and even leading to new industries
• promote sustainable production of chemicals which does not originate from petrochemical by providing alternative wood based sources
• in Portugal, assist the sustainable management of forests together with the promotion of efficient and profitable forest based biorefinery business in short, middle and long term
The project supported European forest based industry, especially pulp industry represented by Södra, Södra Cell and CELBI in AFORE. Europe has traditionally been very strong in pulp and paper production with the largest pulp companies worldwide. As the bulk production of paper pulp is gradually shifting to southern hemisphere, the efficient use of all wood components to added value products along with the current main products that is, pulp and paper, has identified as means to enhance the competitiveness of the European companies. Separation and up-grading of added-value components of wood and process side streams to be used in value chains novel to forest based industries opens up new revenue opportunities. There is, however, a gap between the forest based industry and the value chains new to the industry. It is thus essential to introduce and support new companies, especially SMEs like Separation Research, NATEX and hte, to the area of separating, fractionating and up-grading the added value components from the wood and process side streams. Furthermore, the project supported the companies such as Green Value and Danisco/DuPont, interested in exploiting the wood based components. The interaction of the industrial players from the different sites of the wood component based value chains was one of the main strengths of the AFORE project. It is clear that the means to further promote the collaboration within the wood component based value chains from the raw material owner and producer to converter to end product producer in the defined cases should be further generated in the future to push forward the exploitation of AFORE result and business generation throughout the value chain.
Combined efforts and European level collaboration with scientists and the industry are needed for developing future wood based biorefineries for economical and sustainable production of novel product openings along with the main products pulp and paper. The project aimed at new, industrially adaptable and techno-economically viable and sustainable methods and technologies for the separation, fractionation, and primary upgrading of wood polymers and low molecular weight compounds from forest residue or process side-streams. This aim was well achieved by bringing together research-oriented and technology-oriented partners from different countries. The project successfully combined various expertises, including
• raw material processing by physical, chemical and biotechnical methods both in laboratory and industrial scale
• up-scaling of disassembly, separation, fractionation technologies for forest biomass and its fractions
• modern chemical and physical analytics of wood raw materials and wood chemical components
• physical, chemical, and enzymatic modification of primary products originating from wood
• applications of wood-derived components, especially hemicellulose, lignin, and extractives and solid cellulosic materials
• techno-economic and environmental modelling, simulation and impact assessment needed in evaluation of the applicability of novel technologies and biorefinery concepts
• product and market knowledge and the methods to assess these
Collaboration among the partners was excellent. This can be seen by various co-publications and visits between the members. Without the shared knowledge, resources and facilities the goals would not have been possible to obtain.
Education and training of PhD students and other academic personnel was also carried out within AFORE. Due to the multidisciplinary nature of the project, the project offered great opportunities for the students. Altogether twelve Master’s theses and four PhD theses were completed in the project. In addition one Master’s theses is in progress. Project and project results have been disseminated in many scientific and technical meetings. In addition, one training school and four open AFORE workshops have been organized.
Dissemination activities
Net pages for the AFORE project can be found at: http://www.eu-afore.fi. The pages contain both a public and restricted site, latter available only for the AFORE consortium members. Four leaflets presenting the AFORE progress have been published. One press release has been published. AFORE has also been presented in the Portuguese Pasta el Papier and in the national radio interview by UAVR.
Altogether 33 peer reviewed scientific papers have been published so far in the AFORE project, six papers have been submitted and five will be submitted in the near future. In addition, several other manuscripts are in preparation by partners. The results from the project have been disseminated in various scientific meetings.
Exploitation of the results
The expoitation issues within the project have been constantly reviewed and discussed in Expoitation Committee, twice a year. Stephan Kallus (hte) was nominated and has been acting as the exploitation manager for the AFORE project. The companies Södra, Södra Cell, CELBI, SepRes, NATEX, hte, Green Value and Danisco/DuPont are in first hand responsible for the exploitation of the obtained results and discoveries. The project has generated a lot of data, methods and information which will be exploited after the AFORE project by partners. The main exploitable results in AFORE can be summarized as:
• A novel method for preparation of hemicellulose based tacky glue (patent pending)
• A novel method for hydrophobisation based on birch bark extracts (patent pending)
• A novel process for lignin catalytic pyrolysis including a novel catalyst
• Protocols for scaling up of following processes/methods: xylan separation from kraft process liquors, xylan extraction from bleached birch kraft pulp, production of xylo-oligosaccharides from wood based xylan, hardwood bark fractionation, scCO2 extraction of triterpenic acids from eucalypt outer bark, and lignin catalytic pyrolysis
• Novel physical and chemical wood separation and fractionation methods
• Improved sulphur free methods, pre-hydrolysis soda cooking, LGF organosolv cooking, and catalytic and alkaline oxidation of wood, to open up the wood structure
• Information of the composition and end use performance of the hemicellulose, lignin, added value low molecular mass components and cellulose fractions produced by novel separation and fractionation and upgrading methods
List of Websites:
http://www.eu-afore.fi
Project coordinator:
Dr. Anna Suurnäkki, VTT Technical Research Centre of Finland
Tel: +358 20 722 7178
Fax: +358 20 722 7071
E-mail: anna.suurnakki@vtt.fi
