Cofermentation of organic wastes and agricultural manures

Cofermentation of organic wastes and agricultural manures increases the biogas yield and offers an environmentally friendly alternative to landfilling of organic wastes. However amount and quality of the added organic wastes have to be carefully watched to guarantee a safety operation of the biogas plant and a high biogas quality. Investigations carried out by the ILUET dealt with hydraulic residence times, with the effect of fat addition to cattle slurry and with the change of composition of the fermentation substrate during the anaerobic digestion. From the measurements practical conclusions are drawn fur the operation of biogas plants: the hydraulic residence time should not fall below 80 days, all parts of the biogas plant should be integrated in the gas bearing system, Fat should be added in small dosises (< 5 % of oDM) and the anaerobically digested slurry should be band spread to avoid ammonia emissions during and after the fertilisation.