Co-Fermentation of Microalgae Biomass and Miscanthus × giganteus Silage—Assessment of the Substrate, Biogas Production and Digestate Characteristics

Abstract

The development of a sustainable bioenergy market is currently largely fueled by energy crops, whose ever-increasing production competes with the global food and feed supply. Consequently, non-food crops need to be considered as alternatives for energy biomass production. Such alternatives include microalgal biomass, as well as energy crops grown on non-agricultural land. The aim of the present study was to evaluate how co-digestion of microalgal biomass with giant miscanthus silage affects feedstock properties, the biogas production process, biogas yields, methane fractions and the digestate profile. Combining giant miscanthus silage with microbial biomass was found to produce better C/N ratios than using either substrate alone. The highest biogas and methane production rates—628.00 ± 20.05 cm3/gVS and 3045.56 ± 274.06 cm3 CH4/d—were obtained with 40% microalgae in the feedstock. In all variants, the bulk of the microbial community consisted of bacteria (EUB338) and archaea (ARC915).