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OPTimized conversion of residual wheat straw to bio-ISObutene for bio based CHEMicals

Periodic Reporting for period 2 - OPTISOCHEM (OPTimized conversion of residual wheat straw to bio-ISObutene for bio based CHEMicals)

Reporting period: 2018-12-01 to 2020-05-31

Biomass is frequently considered as an alternative feedstock for substitution of fossil oil, as this may allow to mitigate climate change and resources depletion. This biomass may be derived from agricultural residues, forestry residues or agroindustry residues, all of them containing cellulose which is the most abundant organic polymer on earth. However, direct substitution is not possible and processes are needed for a preliminary conversion of biomass into intermediate products: the industrial biology sector provides such processes. As a feedstock for these processes, ligno-cellulosic sugars represent an attractive alternative to traditional sugars as they can be made from widespread resources, and do not titrate or compete with food or feed production.

Technologies currently used to produce ligno-cellulosic sugars deliver complex syrups containing inhibitors which hamper the fermentation performances and impurities which make the purification step for the desired molecule more difficult. Furthermore, biomass to building blocks technologies frequently propose to deliver molecules displaying characteristics that are significantly different from those of their fossil-based equivalents. Their use implies the need for heavy modifications and investments, taking place downstream in the value chain.

Isobutene is an important building block currently produced and used in the petrochemical industry for lubricants, rubbers, cosmetics, plastics, solvents, and fuels applications. Its global market is more than 15Mt a year and is growing 2.5% a year. At the same time, customers of fossil-based isobutene-derived goods are asking for more renewables.

The overall goal of OPTISOCHEM is to demonstrate the performance, the reliability and the environmental and socio-economic sustainability, of the entire value chains for the transformation of wheat straw, into bio-isobutene and derivatives. The project addresses two different isobutene derivatives families: oligomers and polyisobutylenes. These products are currently requested by the market for a wide array of applications. Presently these needs are satisfied by commercial processes designed to be fed with fossil-based isobutene. The project will demonstrate that these needs could be satisfied by the existing processes when fed with bio-based isobutene from sustainably extracted wheat straw. The outcome of the project will be to provide the backbone for a subsequent first of its kind 30kt per year flagship project and a series of numerous additional plants afterwards.
As management activities, the Steering board and Executive committee met regularly, allowing for very good alignment and risk assessment updating. This led to an important amendment of the Grant Agreement by which the project duration is extended by 10 months to a total of 58 months.
Optimization activities focused on one hand on searching new process parameters for substrate preparation and handling in order to alleviate clogging issues initially observed with wheat straw hydrolysate as well as eliminating unexpected inhibitors, and on the other hand on creating a series of matched strains with increased performances. Directed evolution in continuous culture techniques and rational metabolic engineering techniques were implemented in order to create and select new strains.
Upscaling activities consisted in producing more than 50 tons of wheat straw hydrolysate containing “ligno-cellulosic sugars “, in creating a new purified hydrolysate grade, in delivering these products to the lab, pilot and demo scales, and in performing fed batch at these various scales. A total of 105 bio-isobutene producing runs were executed at pilot and demo scales, among them 36 for the project and 68 out of the project, with increasing performances. Fermentative-isobutene was delivered for bio-based end-products validation activities. Samples of fermentation broth were analyzed and tested for recycling. Alternatives to classical sterilization of the sugars have been successfully tested at pilot scale.
End-product validation activities consisted in deep analysis of the bio-isobutene batches coming from upscaling activities in order to set a first set of specifications for the bio-isobutene to be accepted in conversion processes, experimental conversion into PIBs and experimental conversion into DIB.
Process engineering and business plan activities allowed preliminary work on economic analysis templates and delivered “optimized Process Flow scheme and Heat and mass balance” as well as impact indicators for the future commercial plant.
Dissemination activities provided communication materials (website, visual identity, slides, roll-up, flyers, video and twitter activity) and focused on presentation of the project at twenty-six events and delivered as well twelve articles, public reports and press releases.
Activities related to biomass supply, LCA, environmental and socio-economic performances, allowed to deliver an overview of straw availability in Europe, to complete a Life Cycle Inventory for production of fossil-based isobutene, for traditional-sugars-based isobutene and wheat-straw-hydrolysate-based isobutene, respectively.
OPTISOCHEM allowed so far to obtain matched strains which can consume glucose and xylose simultaneously, which was a crucial bottleneck identified at the beginning of the project. The impact of inhibitors during growth phase and production phase is largely alleviated, thanks to combined efforts in hydrolysate purification and strain adaptation, which was part of another identified bottleneck. Although an undesired “flubber” phenotype impacting oxygen transfer (and therefore, scale-up) was observed on matched strains to start with, an adapted strain with no undesired associated phenotype was created, and characterized for bio-isobutene production.
Upscaling activities allowed to get several batches of bio-isobutene and to identify the nature and content of impurities which could not be so deeply characterized before the start of the project. As the effects of most detected poisons, both on conversion of the isobutene to derivatives and on the quality of end-products are known, specifications could be proposed, thus allowing experimental trials of conversion to be conducted. An adsorption process was identified that allows to eliminate traces of impurities which can poison catalysts.

So far, both, traditional-sugars-based and hydrolysate-based isobutene show a significantly better greenhouse gas performance than fossil isobutene. It has also been identified that important parameters for maximizing the greenhouse gas saving of bio-isobutene compared to fossil isobutene are sugar feedstock and process energy generation.

The project is on track for creating a new building block and at least 2 new bio-based materials with increased yield, reduced cost, reduced energy consumption and for delivering this innovation which meets the needs of end-consumers to the European and global markets. This paves the way for strengthening the competitiveness and growth of companies and creating employment in rural areas.
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