Environmental consequences of energy recovery from agricultural crop residues in Sri Lanka

Abstract

Agricultural crop residues in Sri Lanka are abundant yet often mismanaged through open burning or dumping, contributing to environmental degradation and greenhouse gas (GHG) emissions. This study investigates the energy recovery potential of seven key crop residues rice, coconut, sugarcane, maize, tea, and vegetables, while evaluating their environmental impacts. Residue quantities were estimated, and their suitability for anaerobic digestion (AD), gasification, and pyrolysis was assessed based on proximate and lignocellulosic characteristics. The analysis revealed approximately 2 159 kt of rice residues and 1 365 kt of other major residues available annually. Open burning of rice husk, rice straw, and maize stover results in around 71 ktCO₂eq emissions. Anaerobic digestion showed an energy recovery potential of 6.1 PJ and a net GHG saving of −1.09 MtCO₂eq. Gasification offered the highest energy recovery at 24.3 PJ with net GHG savings of -4.18. Pyrolysis could recover 10.13 PJ with a GHG saving of −1.66 MtCO₂eq. These results are when excluding the biogenic CO2 While anaerobic digestion is well suited for wet organic residues, gasification and pyrolysis offer broader applications with higher energy recovery and environmental benefits. The study highlights the importance of selecting appropriate technologies based on feedstock characteristics and policy support. The findings support the development of decentralized bioenergy systems to enhance energy security and reduce GHG emissions in Sri Lanka.