Production of bioethanol in a second generation prototype from pine wood chips

This paper deals with the production of bioethanol from ligno-cellulosic biomass, in particular a softwood biomass from forestry sector is tested: pine wood chip is a residual biomass obtained from coppice maintenance with a very interesting potential. Second generation bioethanol production prototype from ligno-cellulosic biomass consists of the following monitored parts: steam production system, steam explosion reactor for biomass pretreatment (temperature range 180-240 °C), enzymatic hydrolyser, fermenter and distiller. The maximum system size is around 2-3 kg input biomass each cycle. Selected biomass are tested modifying reaction temperature and retention time of the process and optimizing severity parameter (logR0 between 2.7 and 4.6). Enzymatic hydrolysis is conducted with Ctec2, cellulase complex which consists of a blend of aggressive cellulases (endocellulase and exocellulase), β-glucosidases and hemicellulase, while Saccharomyces cerevisiae yeast (“red ethanol”) is used for the fermentation stage. During hydrolysis and fermentation stages intermediate collections at different time are carried out and samples analyzed in order to evaluate the progress of each phase (maximum glucose concentration obtained 18.8 mg/ml). The results are presented in terms of raw (cellulose content around 32%) and steam exploded material composition, hydrolyzed sugars and acids content in samples, ethanol content after fermentation at different retention time. Both hydrolysis and fermentation are analyzed comparing real and theoretical efficiency. Finally, mass flows in the different selected conditions are evaluated providing a results in terms of ethanol percentage in function of raw material weight. As a result from 100 g of raw material dry basis (32 g of cellulose), 10.6 g of ethanol were obtained.