High-rate biogas production from water hyacinth via co-digestion with cattle manure: Kinetic assessment, process stabilization, and energy recovery in an invasive-plant biorefinery

摘要

In this study, co-digestion of chopped water hyacinth (WH) and cattle manure (CM) is assessed with the help of an integrated framework that consisted of triplicate biochemical methane potential (BMP) analyses, kinetic interpretation, semi-continuous completely stirred tank reactor (CSTR)-based validation, and scenario-resolved energy assessment. The highest yield of the mixture was the 50:50 mix of the WH-CM (VS basis) (304 ± 9 mL CH4 g-1 VSadded), which was much greater than the yield of WH mono-digestion (192±7 mL CH4 g-1 VSadded). Gompertz parameters were the most preferred kinetics in the 50:50 blend, which were in line with a fast adaptation of microbes and a harmonious environment of co-substrates. With semi-continuous daily feeding of 10 L working-volume mesophilic CSTRs at 60 rpm, constant performance was observed between 1.0 and 2.0 g VS L⁻¹ d⁻¹, with pH 7.2-7.6, VFAs of less than 1.5 g L-1 as acetic acid and specific yields of methane of 270. Only slight VFA accumulation and a significant decrease of the yield were noticed at 2.5 g VS L⁻¹ d⁻¹. Mass-energy balance indicates that the experimentally based base case of 10 t d-1 fresh WH fed on 10 t d-1 fresh CM would generate about 367 m³ CH₄ d⁻¹ (13.1 GJ d-1) as compared to a not previously mentioned 2,400 m³ d⁻¹, which is a different scale-up equivalent that would require a much higher throughput. The findings indicate that the co-digestion with cattle manure is a feasible pathway towards stabilizing the digestion of the WH and the combination of invasive-plant suppression with renewable energy and nutrient retrieval.