Biomass yield and energy content of grass from urban roadside verges

摘要

Grass from urban roadside verges is a widely unused, yet potential material for energy generation systems such as (1) anaerobic digestion and (2) integrated generation of solid fuel and biogas from biomass (IFBB), which provide a press fluid for anaerobic digestion and a press cake for combustion. Urban investigation sites were established and managed in 2013 and 2014 with 4 cuts for anaerobic digestion, 2 cuts for IFBB and 8 times mulching as reference in accordance to the current management scheme.Mean annual biomass yield was 3.24, 3.33 and 5.68 t dry matter ha~(-1) for the mulching, 4-cut management and 2-cut management, respectively, with higher yield in 2014 due to favourable weather conditions. Specific methane yield of material cut on 4 dates was 232 1N kg"1 volatile solids and of press fluid of material cut at 2 dates was 269 1N kg"1 volatile solids. Press cake had a lower heating value of 16 MJ kg'1 dry matter. Gross energy output was 26.4 GJ ha'1 for anaerobic digestion and 84.4 GJ ha 1for IFBB. To what extent fossil energy and greenhouse gas emissions might be saved by energetic utilisation of urban biomass has yet to be investigated.