Mixed Culture of Corn and White Lupine as an Alternative to Silage Made from Corn Monoculture Intended for Biogas Production

The production of biomass from legumes for energy purposes is considered an important element of sustainable agriculture. Leguminous plants allow the biological fixation of nitrogen (BFN), which contributes to reduction in the input of mineral fertilizers, and hence lightens the environmental burden. Replacing mineral inputs into crop production using BFN (the production of silage) represents an important step towards achieving greater sustainability of biogas station operation. This paper deals with the possibility of using silage prepared from a mixture of conventional energy crops—corn and legume (lupine) in biogas stations. The aim of the paper was to find out how the addition of legume affects the production of methane and to determine the optimal ratio of maize and lupine in silage. Different variants of silage were prepared: without the addition of legume (sole corn), with the addition of lupine at different ratios (50/50, 70/30, 90/10), and sole lupine. This silage was subjected to fermentation tests and analyzed in order to determine the nutrient content effect on the fermentation process. The lowest total methane production was detected in the lupine silage and the highest total methane production was observed in the maize silage (0.327 m3 CH4/kg VS) and in the mixed silage 90/10 (0.330 m3 CH4/kg of VS). It was found that with the increasing proportion of lupine in the silage, methane production (50/50 < 70/30 < 90/10) declines due to the increased content of poorly degradable organic substances.