Life cycle inventory analysis of hydrogen production by the steam-reforming process: comparison between vegetable oils and fossil fuels as feedstock

Abstract

A life cycle inventory analysis has been conducted to assess the environmental load, specifically CO₂ (fossil) emissions and global warming potential (GWP), associated to the production of hydrogen by the steam reforming of hydrocarbon feedstocks (methane and naphtha) and vegetable oils (rapeseed oil, soybean oil and palm oil). Results show that the GWPs associated with the production of hydrogen by steam reforming in a 100 years time frame are 9.71 and 9.46 kg CO₂-equivalent/kg H₂ for natural gas and naphtha, respectively. For vegetable oils, the GWP decreases to 6.42 kg CO₂-equivalent/kg H₂ for rapeseed oil, 4.32 for palm oil and 3.30 for soybean oil. A dominance analysis determined that the part of the process that has the largest effect on the GWP is the steam reforming reaction itself for the fossil fuel-based systems, which accounts for 56.7% and 74% of the total GWP for natural gas and naphtha, respectively. This contribution is zero for vegetable oil-based systems, for which harvesting and oil production are the main sources of CO₂-eq emissions.