Determination of the efficiency and kinetics of biogas production from energy crops through nitrogen fertilization levels and cutting frequency

Abstract

The efficiency and kinetics of methane fermentation were evaluated for six energy crops when cultivated at three different nitrogen (N) fertilization levels, specifically, maize, sorghum, sunflower, triticale, reed canary grass (RCG), and Virginia mallow (VM). In the case of the perennials, RCG and VM, the impacts of individual swath and cutting frequency were examined. A new model for predicting the methane yield based on the substrate chemical composition was developed and validated. A raised N fertilization dose increased the biogas, methane yield, and the specific rate of their production. The highest increase in methane yield was observed in VM from 145 to 197 dm3 kg-1 of volatile solids (VS) due to a 15% rise in biodegradability. This resulted from a decrease in the lignin content and favorable changes in the lignin to structural carbohydrates ratio. Moreover, in the case of perennials, more efficient biogas production was observed for the biomass collected at an earlier stage. The results in this investigation are important for the production of high-quality biomass for biogas plants, without competition for arable land areas with food and feed production.