Anaerobic manure treatment under extreme temperature conditions

Usually anaerobic treatment of manure is performed as one stage fermentatio n under mesophilic (30-35 degrees C) or moderate thermophilic (50-55 degree s C) conditions, with the aim to stabilize organic material for the use of digested manure as a fertilizer. The present study was conducted to develop a new approach for manure treatment, which concerned the sanitation of man ure and saving energy for its treatment. Laboratory scale experiments were performed on the digestion of cattle and pig manure under psychrophilic con ditions (5-20 degrees C) and extreme thermophilic (55-82 degrees C) conditi ons. Specifically, we were interested in the digestive activities of microb ial populations under low and high temperature conditions. Long-term adapta tion (or selection) of active psychrophilic microbial communities is essent ial to perform sufficient manure treatment at low temperatures. Results of this investigation indicated the development and accumulation of a specific microbial populations at high and at low temperatures in both cattle and p ig manure. An acclimated methanogenic microbial community active at 5 degre es C was obtained after 1.5-years incubation of cattle manure at low temper atures, prior to digestion under mesophilic conditions. Fermentation under high temperature conditions resulted in the development of a thermophilic a cidogenic microbial populations, with the observed accumulation of volatile fatty acids in the liquid fraction of manure. Thus, a two-step anaerobic m anure treatment is proposed in which the sanitation of manure and saving en ergy present. i) acidogenic fermentation at high temperature, ii) separatio n for solid and liquid fractions, iii) treatment of liquid manure fraction under low temperature conditions. (C) 1999 Published by Elsevier Science Lt d on behalf of the IAWQ. All rights reserved.