Co-production of ethanol, biogas, protein fodder and natural fertilizer in organic farming – Evaluation of a concept for a farm-scale biorefinery

• Published in: Bioresource technology 2012-01, Vol.104, p.440-446
• Main Authors: Oleskowicz-Popiel, Piotr, Kádár, Zsófia, Heiske, Stefan, Klein-Marcuschamer, Daniel, Simmons, Blake A., Blanch, Harvey W., Schmidt, Jens Ejbye
• Format: Article
• Language: English
• Subjects: Animal Feed - microbiology; Bioethanol; Biofuels - microbiology; Biogas; Dietary Proteins - metabolism; Ethanol - isolation & purification; Ethanol - metabolism; Fertilizers - microbiology; Organic Agriculture - methods; Organic farming; Pilot Projects; Process model; Technoeconomic analysis
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2011.11.060

► We investigated the addition of a biorefinery to an 1000ha organic farm. ► We performed a technoeconomic analysis based on results from laboratory experiments. ► Four products were generated in a 1000ha farm: ethanol, biogas, feed, and fertilizer. ► Such a biorefinery could supply 2 (based on fuel requirements) 1000ha organic farms. ► Such a biorefinery could supply 3–4 (based on electricity) 1000ha organic farms. The addition of a biorefinery to an organic farm was investigated, where ethanol was produced from germinated rye grains and whey, and the effluent was separated into two streams: the protein-rich solid fraction, to be used as animal feed, and the liquid fraction, which can be co-digested with clover grass silage to produce biogas. A method for ethanol production from rye was applied by utilizing inherent amylase activity from germination of the seed. Biogas potential of ethanol fermentation effluent was measured through anaerobic digestion trials. The effluent from the trials was assumed to serve as natural fertilizer. A technoeconomic analysis was also performed; total capital investment was estimated to be approximately 4MUSD. Setting a methane selling price according to available incentives for “green electricity” (0.72USD/m3) led to a minimum ethanol selling price of 1.89USD/L (project lifetime 25yr, at a discount rate 10%).