Biomass, raw material for biofuels
Biomass contribute with 14% to world energy consumption, and for three quarters of world population living in developing countries, biomass represents the most important source of energy. In the European Union it is expected to create over 300 000 new work places in rural area, for biomass processing and production of biofuels. At this moment, in EU, 4% from energy consumption is assured from biomass.

ABSTRACT

THE CELLULOSIC AGRICULTURAL WASTES (STRAW, CORN STOVER ETC) ARE IMPORTANT SOURSEC OF ENERGY. TO BE ECONOMICALLY VIABLE, THE PRODUCTION COSTS OF ETHANOL FROM LIGNOCELLULOSE MUST BE BELOW MARKET VALUES FOR OTHER FULES. IN THIS PROJECT WE TRY TO ELABORATE A COST-EFFECTIVE TECHNOLOGY FOR CONVERSION OF LIGNOCELLULOSIC BIOMASS TO ETHANOL. THE PROCESS BEING ANALYZED HERE CAN BE DESCRIBED AS USING DILUTE ACID PREHYDROLYSIS OF THE LIGNOCELLULOSIC BIOMASS WITH ENZYMATIC SACCHARIFICATION OF THE REMAINING CELLULOSE AND COFERMENTATION OF THE RESULTING SUGARS TO ETHANOL. THE FEEDSTOCK IS FIRST PRETREATED AND DETOXIFICATED. BIOMASS IS TREATED WITH DILUTE SULFURIC ACID CATALYST AT A HIGH TEMPERATURE FOR A SHORT TIME, LIBERATING THE HEMICELLULOSE SUGARS AND OTHER COMPOUNDS. SEPARATION WITH WASHING REMOVES THE ACID FROM THE SOLIDS FOR NEUTRALIZATION. OVERLIMING IS REQUIRED TO REMOVE COMPOUNDS LIBERATED IN THE PRETREATMENT THAT ARE TOXIC TO THE FERMENTING ORGANISM. DETOXIFICATION IS APPLIED ONLY TO THE LIQUID PORTION OF THE HYDROLYSIS STREAM. ENZYMATIC HYDROLYSIS (SACCHARIFICATION) COUPLED WITH CO-FERMENTATION OF THE DETOXIFIED HYDROLYZATE SLURRY IS CARRIED OUT IN ANAEROBIC FERMENTER. CELLULASE ENZYMES ARE ADDED TO THE HYDROLYZATE IN THE HYDROLYSIS TANK THAT IS MAINTAINED AT A TEMPERATURE TO OPTIMIZE THE ENZYME’S ACTIVITY. THE FERMENTING ORGANISM IS FIRST GROWN TO OBTAIN INOCULUM FOR FERMENTATION. THE INOCULUM, ALONG WITH OTHER NUTRIENTS, IS ADDED TO THE FERMENTER ALONG WITH THE PARTIALLY SACCHARIFIED SLURRY AT A REDUCED TEMPERATURE. THE CELLULOSE WILL CONTINUE TO BE HYDROLYZED, ALTHOUGH AT A SLOWER RATE, AT THE LOWER TEMPERATURE. THE GLUCOSE WILL BE CONVERTED TO ETHANOL, AND THE ACTIVITY OF CELLULASE WILL NOT BE AFFECTED BY INHIBITION. AFTER SEVERAL DAYS OF SEPARATE AND COMBINED SACCHARIFICATION AND COFERMENTATION, MOST OF THE CELLULOSE AND XYLOSE WILL HAVE BEEN CONVERTED TO ETHANOL.