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Environ Technol

Title:		Evaluation of the biomethane yield from anaerobic co-digestion of nitrogenous substrates
Author(s):		Allen E; Browne JD; Murphy JD;
Address:		"Department of Civil and Environmental Engineering, University College Cork, Ireland"
Journal Title:		Environ Technol
Year:		2013
Volume:		34
Issue:		13-16
Page Number:		2059 - 2068
DOI:		10.1080/09593330.2013.806564
ISSN/ISBN:		0959-3330 (Print) 0959-3330 (Linking)
Abstract:		"This paper examines three substrates for anaerobic co-digestion: abattoir waste; cheese waste and food waste. These substrates were assessed in detail for suitability for biomethane production. Biomethane potential (BMP) assays were carried out in mono and co-digestion for the three substrates and two mixes: T1 (40% abattoir waste; 50% cheese waste and 10% food waste on a wet weight basis) and T2 (30% abattoir waste; 40% cheese waste and 30% food waste). The C:N ratio of both mixes was below optimum. Low levels suggest that the production of free ammonia (NH3) in semi-continuous digestion was of primary concern. Both mixes were digested in a semi-continuous process for 25 weeks. The recommended operating condition for T1 was a loading rate of 3 kg VS mn(-3) day(-1) at a retention time of 23 days. The biomethane yield was 305 L CH4 kg(-1) volatile solids (VS) which was 87% of the BMP value and equivalent to 61% biodegradability. For T2 (with the higher C:N ratio) a higher loading rate of 4kg VS mn(-3) day(-1) at a lower retention time of 15 days was recommended. The biomethane yield was 439 L CH4 kg(-1) VS (99% of the BMP value and 84% biodegradibility). At these conditions, levels of total ammonical nitrogen (TAN) were 4109 and 4831 mg L(-1) for T1 and T2, respectively. These values are on the large side according to the literature. The temperature was reduced to 35 degrees C to minimize toxicity associated with TAN. Ratios of volatile acids to bicarbonate were typically in the range of 0.2-0.3 suggesting stable operation"
Keywords:		"Ammonia/*metabolism Anaerobiosis *Biofuels Bioreactors Food Industry Hydrogen Sulfide/metabolism Industrial Waste Methane/*analysis/*metabolism *Sewage Temperature Volatile Organic Compounds/metabolism Waste Disposal, Fluid/*methods;"
Notes:		"MedlineAllen, Eoin Browne, James D Murphy, Jerry D eng Research Support, Non-U.S. Gov't England 2013/12/20 Environ Technol. 2013 Jul-Aug; 34(13-16):2059-68. doi: 10.1080/09593330.2013.806564"