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Cellulosic feedstock Ethanol
As cellulosic feedstock are more difficult to break down into fermentable sugars than starch and sugar based feedstock, the cellulosic biochemical conversion (2nd generation bioethanol technology (2G)) requires additional steps to standard treatments: biomass pre-treatment and cellulose hydrolysis.
To break down cellulose – the primary source of sugar in fibrous biomass – hemicelluloses and lignin that surround the cellulose in a protective sheath need to be cut across. The overall approach for converting cellulosic material to ethanol is pre-treatment to open up biomass to enzymes, biomass hydrolyse and sugars fermentation followed by ethanol recovery and purification as well as residues processing.
Acids can break down the long chains in hemicelluloses and cellulose to release sugars contained in these materials through hydrolysis reactions. Thanks to their high specificity, enzymes known as cellulase can achieve higher yields of glucose from cellulose and are often favoured.
As to survive in nature, cellulosic biomass has developed a structure that resists enzymatic attack; it must first be pre-treated to better expose the cellulose to enzymes. Over the years, biological, chemical, mechanical, physical and thermal pre-treatments have been experimented, but currently, only methods that treat biomass at temperatures around 80 – 200 °C with one or more chemicals have been able to realise high sugar yields essential to economic viability. Leading thermo chemical pre-treatment options include diluted sulfuric acid, ammonia fibre expansion (AFEX), neutral pH and lime, although the choice depends on many factors including the nature of the substrate, enzymes and organisms and other process details.
DSEC’s expertise in the field can guide both technology providers and investors on the path from experiments to industrial realisations with all related off-sites.