Use of ethanol production and stillage processing residues for biogas production

In Latvia, ethanol is produced mainly from wheat grains. The production processinvolves the formation of the by-products of wheat bran, grains residues and stillage. By-productsfrom production of alcohol distilling dregs (stillage) contain much organic matter therefore couldbe useful for the production of the biogas The product with high protein content usable for feedcan be produced from the stillage too. A liquid residue is formed during the production process.Purpose of study is the assessment of the methane volume obtainable from the stillage processingresidue mixed with wheat brans and grains residues in anaerobic fermentation process and fromwheat brans and grains residues mixed only with inoculum. Investigation was provided in 16bioreactors operated in batch mode at 38°C. Stillage processing residues mixed with the wheatbrans and inoculum were filled into 4 bioreactors, mixed with grains residues were filled into 4bioreactors and only inoculum was filled into two bioreactors for control. Wheat brans withinoculum were filled into 3 bioreactors. Into others 3 bioreactors were filled grains residues withinoculum. The yield of biogas from wheat brans was 1.151 L g-1DOM and methane 0.593 L g-1DOMafter 30 days of anaerobic digestion. The yield of biogas from wheat brans with stillage processingresidue was 1.098 L g-1DOM and methane 0.600 L g-1DOM. The yield of biogas from grains residueswas 0.915 L g-1DOM and methane 0.451 L g-1DOM. The yield of biogas from grains residues withstillage processing residue was 1.01 L g-1DOM and methane 0.523 L g-1DOM. The studydemonstrates that the investigated products are very good raw material for the production ofmethane. Stillage processing residue acted as a catalyst for the process.