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PROcesses for Value added fibres by Innovative Deep Eutectic Solvents

Periodic Reporting for period 2 - PROVIDES (PROcesses for Value added fibres by Innovative Deep Eutectic Solvents)

Reporting period: 2017-01-01 to 2018-12-31

The pulp and paper industry has been bio-based for centuries. Technologies that are currently applied for biomass fractionation and recovered paper treatment were developed more than a century ago, and have been optimised ever since. The PROVIDES consortium shows that a revolutionary change is now possible. New, mild pulping technologies based on natural Deep Eutectic Solvents lead to a significantly more sustainable process that is energy-, cost- and resource-effective. This technological innovation produces cellulose fibres for papermaking, while simultaneously producing high-quality lignin and hemicellulose fractions for high-volume applications.

The PROVIDES project partners developed innovative technologies that operate at lower temperatures and pressure, using environmentally friendly solvents. These solvents, which are known as Deep Eutectic Solvents (DES), are nature-based, renewable, biodegradable, low-volatile and cost-effective.

The overall objective of the DES concept is to achieve a 40% reduction of energy use and an 80% reduction of CO2 emissions in pulp and papermaking through the application of Deep Eutectic Solvents. The DES concept will enable the industry to:
• obtain a radically new, sustainable and techno-economically feasible pulping technology by using DESs to dissolve lignin from lignocellulosic biomass and use this lignin for further processing into materials and chemicals with a high added value;
• create more efficient processes for the decontamination of recovered paper (i.e. removing stickies and inks and/or dissolving cellulose);
• regenerate and recycle the solvent, as well as selectively recover dissolved components.
PROVIDES obtained the following achievements:
• More than one hundred new Deep Eutectic Solvents, including the first hydrophobic DES ever
• 95% lignin removal by DES delignification
• Cellulose fibres with good tensile strength and extreme internal bond
• Total DES pulping concept with similar energy consumption and operational costs compared to kraft pulping
• Proof of principle for lignin recovery

Fundamental research provides answers to questions as to ‘why’ DESs are effective, supporting the search for even more effective DESs and assisting application-oriented research. At the same time, the preparations for the pilot phase have been started to study the DES process at a larger scale to gain better insight into the process kinetics and physical transport required for further upscaling, using larger amounts of products for application testing, and validating production costs, climate benefits and environmental effects. Application-oriented research was performed on the functionality of DES as a dissolving/separation agent for lignin, cellulose, stickies and ink.

DES delignification
The main aim of the PROVIDES project was to develop radically new, sustainable and techno-economically feasible pulping technologies. This includes both an energy-efficient pulping process to separate high-quality fibres and lignin, as well as an efficient process to recover and recycle DES while maintaining its physico-chemical and dissolving properties. So far, two potential DESs for pulping by dissolving hardwood and softwood lignin are known: (1) Lactic Acid : Choline Chloride and (2) Malic Acid : Tetraethyl Ammonium Chloride. Temperature, pulping time, wood/DES ratio, pre- and post-treatments were optimised to improve the efficiency of the process, the extent of lignin isolation and the pulp quality. A technology roadmap was prepared, elaborating on all the parallel steps that need to be taken in the technology development in order to allow implementation in 2030.

DES recovered paper processing
The aim was to develop DESs that were able to either dissolve and isolate contaminants from ‘paper for recycling’ to achieve clean fibres for recycling or dissolve cellulose to obtain pure cellulose. For this purpose, hydrophobic DESs were developed. Hydrophobic DESs do not mix with water, significantly facilitating the process of isolating components from aqueous pulp.
A variety of hydrophobic DESs were tested on the dissolution of specific contaminants. Hydrophobic DESs appear able to dissolve volatile fatty acids, metal ions and some ink and sticky contaminants. Although the mineral oil content was halved, deinking trials did not lead to higher brightness.

DES and component recovery
Research was also performed on efficient recovery technologies for both the DESs and the dissolved components. Although dissolved components can easily be separated from DESs by adding water as an anti-solvent, this process is not favoured, as the subsequently required water evaporation implies high energy consumption. A liquid-liquid extraction technology was therefore developed, achieving energy savings of 80% in the recovery process.

Fibres obtained from the DES pulping process are well shaped and straight, with normal drainage. Paper produced from the fibres has extremely good internal bond and good tensile strength. The tear strength is still somewhat lower than regular kraft fibres.
Lignin isolated by DES pulping of Eucalyptus was characterised by GPC and HSQC spectroscopy.
Deep Eutectic Solvents are a completely new class of solvents that have never been used in the pulp and paper industry or for any other biomass fractionation before. This means that many technological questions still need to be answered and gaps filled to bring this laboratory technology to the next stage. The DES cluster aims to fill these gaps and achieve the following impacts:
- Reduced process energy intensity by at least 40% compared to traditional pulping processes;
- Reduced investment costs by 50% compared to current pulping installations, thanks to pressure-free layout and simplified chemical recovery;
- Strengthened market position of current wood-based products (e.g. paper and board), as well as new high-added-value applications, such as for the textile and chemical industries.

The first important steps have been made towards calculating the economic and ecological feasibility of the total process of delignification.
The concept based on the laboratory findings is already cost comparable with the kraft process developed 100 years ago. Only specific investment costs as well as personnel costs are higher, as we aim for smaller mills (50,000 ton) to facilitate the first implementation of the technology and to achieve important savings from biomass logistics. Smaller capacity mills will make it possible to use raw materials produced closer to the mills, thus reducing transport needs.

Energy savings in the pulp and paper sector are estimated to be about 40%, representing huge potential annual savings of more than 160,000 GWh in Europe. The corresponding potential CO2 emission savings are estimated to be about 10%, which represents a reduction of more than 4 Mt of CO2 emissions at European level. In a broader perspective, beyond the boundaries of the current pulp and paper industry sector, the implementation of the new DES pulping processes in a biorefinery concept will produce both pulp and bio-based chemicals. Taking into account the simultaneous production of an equal tonnage of chemicals, the total energy use and CO2 emissions of the combined system can be 90% lower than with the separate systems of pulp and fossil chemicals production.

The public report can alsobe downloaded from the project website: www.providespaper.eu
left and right: the indivual components of a DES, solid at room temp. In the middle: the DES
Lignin extraction by LLQ
extraction of metal ions by hydrophobic DES
DES fibres
progress in delignification
lignin precipitation by water as anti-solvent
DES lignin properties
DES delignification roadmap
DES produced paper
DES paper properties
DES business case
first DES lignin produced
The first hydrophobic DES
progress in processing time
CO2 emission reduction by DES concept