Comparative life cycle assessment of three biohydrogen pathways

A life cycle assessment was performed to quantify and compare the energetic and environmental performances of hydrogen from wheat straw (WS-H2), sweet sorghum stalk (SSS-H2), and steam potato peels (SPP-H2). Inventory data were derived from a pilot plant. Impacts were assessed using the impact 2002+ method. When co-product was not considered, the greenhouse gas (GHG) emissions were 5.60 kg CO2eq kg−1 H2 for WS-H2, 5.32 kg CO2eq kg−1 H2 for SSS-H2, and 5.18 kg CO2eq kg−1 H2 for SPP-H2. BioH2 pathways reduced GHG emissions by 52-56% compared to diesel and by 54-57% compared to steam methane reforming production of H2. The energy ratios (ER) were also comparable: 1.08 for WS-H2, 1.14 for SSS-H2 and 1.17 for SPP-H2. A shift from SPP-H2 to WS-H2 would therefore not affect the ER and GHG emissions of these BioH2 pathways. When co-product was considered, a shift from SPP-H2 to WS-H2 or SSS-H2 decreased the ER, while increasing the GHG emissions significantly. Co-product yield should be considered when selecting BioH2 feedstocks.