Exergetic life cycle assessment of hydrogen production from biomass staged-gasification

By combination of life cycle assessment (LCA) and exergy analysis, a modified exergetic life cycle environmental impact model was proposed. The model can quantitatively assess the environmental impacts of resources and pollution by using exergy to measure the deviation degrees of various emissions from the reference environment. Then the comprehensive indicators of resource and environment performance were defined and obtained without introducing subjective weighting factors. Two products of hydrogen (biomass staged-gasification hydrogen (BSGH), and natural gas steam reforming process hydrogen (NGSH)) were evaluated to illustrate the application of the proposed model. The comparison of two products shows that BSGH has significant advantages in both renewability and environmental sustainability. The environment-friendly performance of BGSH mainly exhibits in environment impacts of global warming potential (GWP) and photochemical ozone formation (POF). However, the thermal pollution (TP) of BGSH is slightly larger than that of NGSH. And this indicates that the excessive hot flue gas emissions in BSGH process result in more thermal pollution, and need to be noticed. Furthermore, the sensitivity analysis indicates that the conversion efficiency of tar has a larger influence on total cumulative exergy consumption and environmental index than the combustion efficiency of biomass in the staged-gasification process.