Methane fermentation of dung from litter-free reared domestic animals — an optimisation study

Data on the quantity (27 453 tons from litter-free reared animals in Bulgaria, only) and the chemical and energy characteristics of dung produced in intensive management farms for domestic animals suggests that technologies combining biogenic elements recycling with energy utilistation and dung decontamination are expedient to be applied on these types of farms. To this effect a fermenter was designed and a mathematical model (a Chen-Hashimoto model based computer programme) was applied, as a result of which the optimum methane fermentation parameters were determined. The technological methane output (Y_v) — indicator of biogas production efficiency (output/dm³ fermentor volume) showed an optimum at temperature 55°C and period of exchange 6 days. The methane output per unit mineralised organic matter in the substrate (B) — assumed as an indicator of ecological efficiency (maximum organic matter degradation) exhibited an optimum at 33°C for 15 days period of exchange.