Improving biodiesel sustainability by double-cropping oilseed and oil-less seed cake recovery: A field approach in northern Italy

This work proposes a new bioenergy supply chain based on double-cropping oilseed (Camelina sativa and Ricinus communis) in northern Italy, to produce biodiesel from oil and biogas from co-products, improving biodiesel sustainability according to the Renewable Energy Directive (RED II). To achieve this, the crops were cultivated on silty-sandy soil during two seasons. Rainfall was below the annual average during the first season (460 mm) and regular during the second (713 mm); irrigation was provided during summer. After milling, oil and seed cakes were chemically characterized. Subsequently, the potential bio-methane production (BMP) of seed cakes was evaluated. Field trials resulted in average seed yields (values reported as average ± std dev) of 6,948 ± 330 kg TS ha−1 year−1. Chemical characteristics of oil were considered compatible with biodiesel synthesis, while seed cakes BMP (values reported as average ± std dev), i.e., 239 ± 10 NmlCH4 g TS−1 and 337 ± 15 NmlCH4 g TS−1 for C. sativa and R. communis, were comparable to maize. The impact analysis was based on life cycle assessment (LCA); comparison with fossil fuels employed the Fossil Fuel Compensator value, established by RED II. Calculations are based on the reference impact of transport in the European Union (94 gCO2eq MJ−1). LCA showed a 75% GHG reduction vs. petrol diesel; moreover, using nitrification inhibitors (NIs) to reduce N2O emissions, the reduction could reach 81%. Economic viability is based on double cropping and dual energy production; the costs of NIs and cake processing for biogas being negligible.