Dynamic Hybrid Life Cycle Assessment of CO2 Emissions of a Typical Biogas Project

Biogas project has been earmarked as an efficient way to achieve climate change benefits due to the comprehensive utilization of biogas products. However, CO2 emission would occur during the construction, operation and dispose stages of biogas project, and it requires a holistic and systematic accounting framework to evaluate both emissions and reductions over the lifetimes. In this study, a dynamic hybrid LCA model combining both process analysis and input-output analysis was proposed to dynamically characterize both direct and embodied carbon emissions and mitigation of a typical household biogas project. Moreover, the time-varying social-economic development factors are also taken into account to reduce the uncertainty and increase accuracy. Results show that biogas project is a good choice to achieve carbon emission reduction with 17.09 tons of net CO2 emission reduction over the lifespan. In addition, indirect CO2 emission (5.45 tons) plays significant part in the total emissions, in which the construction stages are the largest contributor due to the large amount of energy-intensive materials consumption. Moreover, with the CO2 emission intensity of fertilizer changing over years, the net emission reduction decreases 2.18 tons. The proposed dynamic hybrid LCA framework could unveil both direct and indirect carbon emission and reduction of the biogas project with consideration of technology development.