Biopower Results – Life Cycle Assessment Review
To better understand on biopower systems, NREL completed a comprehensive review and analysis of life cycle assessments (LCA) on co-fired (with coal), direct combustion, gasification and pyrolysis biopower technologies published between 1980 and 2010.
Over the last 30 years, hundreds of life cycle assessments have been conducted to assess the environmental impacts associated with biopower technologies. However, differences in system design and performance, technology improvements over time, assumptions about resource quality, agricultural practices and land use change impact, along with variability in life cycle assessment methods and assumptions have resulted in inconsistencies in existing published data.
The figure here shows the results of the review and analysis of LCA studies published on biomass-fueled electricity generation (land use-related net changes in carbon stocks and land management impacts are excluded). The majority of life cycle greenhouse gas (GHG) emission estimates cluster between about 16 and 74 g CO2eq/kWh (4.4 and 21 g CO2eq/MJ), with one estimate reaching 360 g CO2eq/kWh (100 g CO2eq/MJ). Avoided GHG emissions (primarily methane from landfilling of biomass wastes) from non-harvest wastes and residues and using CO2 mitigation technologies like carbon capture and sequestration can result in significantly negative life cycle GHG emissions. This does not consider land use changes.
Overall, the life cycle assessments show that biopower is similar to other renewables and nuclear energy and much lower than fossil fuel in total life cycle GHG emissions. Additional life cycle assessments of biopower are needed to fill in important gaps in knowledge, particularly with respect to supply chains and land use change implications, and to corroborate the published results included in this study.