engleski

Life Cycle Assessment of Biogas and Digestate from Residue Grass: Analysis of Different Utilisation Pathways

The aim of this research is to evaluate environmental impacts of utilizing biogas and digestate produced by anaerobic digestion (AD) of residue grass. Three different grass types (grass from the uncultivated land area − RG1, riverbank grass − RG2 and verge next to the highway – RG3) from uncultivated lands have been considered. Experimental research on grass digestate quality has shown the share of macronutrients is impacted by the position where grass grows. In that means the following share of macronutrients has been determined: nitrogen − between 0.148 and 0.161 kg(N)/kgTS, phosphorus − between 0.0161 and 0.0184 kg(P)/kgTS, and potassium − between 0.391 and 0.655 kg(K)/kgTS. Using data on biogas yield and digestate quality as an input for Life Cycle Assessment, the following four scenarios have been studied: i) Production of heat and electricity using biogas without digestate utilisation (a base scenario) ; ii) Production of heat and electricity using biogas followed by utilisation of a digestate as a fertiliser ; iii) Upgrading of biogas to biomethane without digestate utilisation, and iv) Upgrading of biogas to biomethane followed by utilisation of a digestate as a fertiliser. Results of the research have shown that RG2 grass type gains the greatest benefits in terms of health category within the single score, but also the highest increase in Global warming potential (GWP) compared to other grasses. Upgrading of biogas to biomethane contributes significantly to single score benefits, but also to slightly higher GWP compared to electricity and heat production using biogas. On the other hand, application of grass digestate as a fertiliser positively contributes to environmental performance, increasing the overall single score by ca. 2-fold and decreasing the GWP potential by ca. 10 %.

residue grass ; anaerobic digestion ; biogas and digestate ; utilisation pathways ; life cycle assessment

nije evidentirano