Environmental impacts of power-to-X systems - A review of technological and methodological choices in Life Cycle Assessments

Highlights: • Review of 32 Life Cycle Assessment studies on Power-to-X. • Electricity source and CO₂ supply for upgrading have an eminent environmental impact. • Power-to-Hydrogen and Power-to-Transport are most considered Power-to-X chains. • Climate change is the most analyzed environmental impact category. • A lack of LCA methodological specifications is evident. -- Abstract: This paper presents a review of 32 Life Cycle Assessment studies on Power-to-X. Due to their multiplicity, different Power-to-X chains are compared and influencing factors on environmental impacts are identified. Besides technological specifications, methodological choices of the publications are assessed. The majority of studies consider Power-to-Gas or Power-to-Transport. Additionally, six publications assess Power-to-Power, Power-to-Liquids or Power-to-Chemicals. Climate change is the most analyzed environmental impact category. Further impacts are assessed in 14 publications. The electricity source and the methodological concept of carbon dioxide consideration are crucial drivers of environmental impacts. The review reveals a lack of transparency on technological as well as on methodological level. Specifications like the multi-functionality approach used or in case of Power-to-Transport chains the life time mileage of vehicles are missing in most publications and hinder their comparability.