Assessment of energy biomass potential and greenhouse gas emissions from biogas production from perennial grasses

Abstract

The research was aimed to investigate the energy biomass productivity and biogas production from silage of different perennial grasses with evaluation of greenhouse gas emissions through the entire process from biomass cultivation to processing. The experiments with perennial grasses – cocksfoot (Dactylis glomerata L.), tall fescue (Festuca arundinacea Scherb.) and reed canary grass (Phalaris arundinacea L.) were carried out at Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry in 2008–2010. The swards were grown in an Endocalcari-Endohypogleyic Cambisol (CMg-n-w-can), which contained: organic carbon – 1.61–1.75%, available P – 145–224 mg kg-1 and K – 128–158 mg kg-1, soil pH ranging between 6.7–7.0. The three perennial grass species with varying yields of biomass were used to ensure a steady operation of the selected biogas plant of 500 kWe electric power. The different quantities of biomass feedstock and varying energy input are required for such biogas plant. Therefore all data correspond to a biogas cogeneration plant of 500 kWe electric power. Required land area for the same amount of energy produced depends on species of perennial grasses, rates of fertilization and number of cuts. These results mainly depended on the biomass productivity and biogas yield from dry mass. Biomass yield from dry matter in the first year of use of tall fescue cut twice per vegetation season was higher compared to that cut three times, while cocksfoot and reed canary grass yielded better cut three times compared to cut twice. The highest yield was obtained in tall fescue swards cut twice and fertilized with N180. The total balance of greenhouse gas emissions showed their mitigation and ranged from 0.206 to 0.298 kg CO2 eq kWh-1.