Energy potentials, negative emissions, and spatially explicit environmental impacts of perennial grasses on abandoned cropland in Europe

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Cultivating perennial grasses on abandoned cropland for bioenergy production is a promising option to meet future renewable energy demands at lower risks for food security and environmental degradation. Studies on the potential environmental impacts of perennial grasses mostly focus on specific locations, while effects and potentials of a large-scale deployment on abandoned cropland are still unexplored. This work performs a spatially explicit life cycle assessment of agricultural production of three perennial grasses (miscanthus, switchgrass, and reed canary grass) on abandoned cropland in Europe under rainfed and irrigated conditions. We estimate the primary bioenergy potentials and potential environmental impacts on climate change (including soil organic carbon changes), freshwater and marine eutrophication, terrestrial acidification, fossil resource scarcity and water scarcity footprint. Under rainfed conditions, switchgrass has the largest supply potential (174 MtDM yr−1) while miscanthus has the lowest average climate impact (169 kg CO2 tDM−1). Irrigation increases biomass yields by 97% for miscanthus, 62% for switchgrass and 29% for reed canary grass, but climate change impacts per tDM increase by 24%, 32% and 44%. Water scarcity footprints also increase, ranging from 4.7 to 9 world m3eq. kgDM−1. When soil organic carbon changes are considered, the net climate effects turn to negative for all perennial grasses under rainfed conditions (and for miscanthus with irrigation as well), showing a potential for land-based negative emissions by storing carbon in soils while delivering renewable energy. Bioenergy potentials range between 1 and 7 EJyr−1 (corresponding to 1–10% of today's EU primary energy demand) and the scale of negative emissions can be up to −24 Mt. CO2-eq. yr−1 (equal to 5.6% of EU's agricultural sector emissions). The consideration of site-specific conditions for water supply and crop affinity can identify the best local agricultural practices for energy yields and negative emissions at reduced environmental trade-offs.