How much energy can giant reed and Miscanthus produce in marginal lands across Italy? A modelling solution under current and future scenarios

Abstract

Practical strategies for bioenergy planning in the face of climate change should rely on ready-to-use yield projections. Perennial grasses grown in marginal lands (MLs) provide abundant feedstocks to be converted into different energy vectors. The aim of this study was to provide a model-based assessment of how much energy, in the form of biomethane and bioethanol, can be achieved by Miscanthus and giant reed across Italy. Marginal lands were here conceived as low profitable non-irrigated areas, without mechanization and/or nature conservation constraints. Marginal lands eligible for simulations were selected crossing environmental factors and ecological requirements of the two crops. The biophysical model Arungro was calibrated considering rainfed/full-irrigated systems using multiple-site and multiple-year datasets. The model was connected to a georeferenced database, with information on (i) current/future climate, (ii) agronomic practices, (iii) soil physics/hydrology, (iv) MLs, and (v) crop suitability to environment and simulations were performed at 500 × 500 m spatial resolution across all Italian regions. Under baseline conditions (i.e., 1981–2010), the total area of MLs available for energy crops (i.e., 49,100 km²) allowed to obtain 23,500 (giant reed) and 23,700 (Miscanthus) Giga-m³ CH4-STP of biomethane and 18,600 (giant reed) and 24,400 (Miscanthus) Giga-liters of bioethanol. While the amount of energy carriers is expected to increase, on average, of +4.6% in 2055 and + 0.4% (mean of +9.2%—South, −2.4%—Center, −5.4%—North Italy) in 2085 for Miscanthus, giant reed-based productions are projected to be more stable across the country and time frames (+6.7% in 2055; +2.8% in 2085). This study contributed to define a modular and detailed procedure aimed at quantifying attainable energy yields from bioenergy grasses in MLs. The consideration of fine-resolution multiple-scale heterogeneity allowed for an in-depth investigation of biomass productivity, attainable energy yields, and related stability under current/climate change scenarios, highlighting critical spots and opportunities within the country.