Global warming impact assessment of a crop residue gasification project—A dynamic LCA perspective

Bioenergy from crop residues is one of the prevailing sustainable energy sources owing to the abundant reserves worldwide. Amongst a wide variety of energy conversion technologies, crop residue gasification has been regarded as promising owing to its higher energy efficiency than that of direct combustion. However, prior to large-scale application of crop residue gasification, the lifetime environmental performance should be investigated to shed light on sustainable strategies. As traditional static life cycle assessment (LCA) does not include temporal information for dynamic processes, we proposed a dynamic life cycle assessment approach, which improves the static LCA approach by considering time-varying factors, e.g., greenhouse gas characterization factors and energy intensity. As the gasification project can reduce greenhouse gas (GHG) discharge compared with traditional direct fuel combustion, trade-offs between the benefits of global warming mitigation and the impact on global warming of crop residue gasification should be considered. Therefore, indicators of net global warming mitigation benefit and global warming impact mitigation period are put forward to justify the feasibility of the crop residue gasification project. The proposed dynamic LCA and indicators were then applied to estimate the life cycle global warming impact of a crop residue gasification system in China. Results show that the crop residue gasification project has high net global warming mitigation benefit and a short global warming impact mitigation period, indicating its prominent potential in alleviating global warming impact. During the lifetime of the project, the largest emitters of the crop residue gasification project are the operation and construction stages, attributed mainly to the consumption of crop residue, electricity and steel. In addition, the comparison of the results obtained with both traditional and dynamic LCA approaches indicates that there is an exaggeration of the global warming impact reduction potential of crop residue gasification projects. This dynamic LCA can also make the decision maker acknowledge the real-time GHG performance during the lifetime of a production process, and thus make timely decisions to minimize the lifetime GHG emissions.