In the worldwide exertion of replacing fossil fuels with renewable energy sources and new feedstocks for biofuel and manufacturing industries, the use of biomass as a sustainable renewable resource is drawing an increasing interest from the scientific community.

The European agricultural sector can currently supply bio-refineries with more than 144 million tons of biodegradable municipal waste, an excellent source of lignocellulosic material.  The lignocellulosic substrate treatment accounts for a large amount of products derivatives, such as high-value chemicals, organic acids, amino acids and biofuel. However, due to its structure, lignocellulosic biomass requires pretreatment to break its matrix.

Though a wide variety of pretreatments have been developed, including physical (e.g. autoclaves), chemical methods (e.g. acid), biological treatments or combinations of the above, none of these has been established as preferred. This is mainly due to the fact that most options are expensive, energy intensive and utilize chemicals which require special disposal and handling.

The project US4GREENCHEM (consortium members: ttz Bremerhaven, University of Torino, Weber Ultrasonics GmbH, Environmental Systems GmbH, Teknologian Tutkimuskeskus VTT, Biocentras, Latvijas Valsts Kokmsnes Kimijas Instituts, FeyeCon, Fundacion Tecnalia Research & Innovation, Jowat) is introducing new energy- and cost-efficient method for treatment of agro-forestry biomass to valorize the replacement of carbon from fossil sources in the manufacture of chemicals and biofuels.

FeyeCon, together with the partners, is working on a combined supercritical (sc) CO2 and ultrasonic pre-treatment of the lignocellulosic feedstock. The experiments were performed in a pilot-scale Sc-CO2 extraction unit, where different conditions of pressure, temperature and duration were tested. Simultaneously the effect of the sample moisture and the ultrasound and mild solvent (acid or water) were taken into account. This scientific approach is based on the capability of CO2 to form carbonic acid when dissolved in water, which catalyzes the hydrolysis of hemicellulose in mild conditions.

The results obtained show that biomass moisture content played a very important role in the lignocellulose disintegration.