Environmental assessment of giant reed and Miscanthus for bioethanol and biomethane production on Italian marginal lands

The Revised Directive EU/2023/2413 sets ambitious goals for 2030, requiring at least 42.5% of energy consumption to be supplied by renewable sources. Meeting bioenergy targets requires land allocation strategies that avoid significant competition with food production. In this context, marginal lands represent a promising solution for the cultivation of non-food energy crops, such as perennial grasses. However, assessment methods are essential to drive policymakers in land planning scenarios. This study proposes a cradle-to-gate life cycle assessment built on top of the ARUNGRO crop model to compare the environmental impacts of two lignocellulosic energy crops - giant reed and Miscanthus - from cultivation to the production of ethanol and biomethane. The experimental datasets represent three provinces in northern, central, and southern Italy, areas with a large extent of marginal lands and characterized by pedo-climatic and crop productivity constraints. The environmental footprint results of the agricultural phase, expressed per Mg of dry-weight biomass, identified land use change and human toxicity (carcinogenic) as the main hotspot impact categories out of sixteen, largely associated with annual harvesting operation for perennial grasses. Per GJ basis, biomethane outperforms ethanol, with central Italy showing the most favourable performance for both biofuels. The case study explores a projected 2044 deployment scenario, providing valuable insights into long-term environmental performance of perennial energy crops over 20-years. Overall, the findings highlight the importance of energy species production in marginal lands as optimal solutions for inedible feedstock intended for energy production. Policy reflections are offered at both European and national levels.