A screening LCA of short rotation coppice willow (Salix sp.) feedstock production system for small-scale electricity generation

Technical viability of two small-scale electricity generation pathways based on willow short rotation coppice biomass was evaluated using a Screening Life Cycle Assessment (LCA) procedure. The system inputs included fuel and oil consumption in machine operations, fertilizer and herbicide production, transportation of willow chips biomass, and biomass-to-energy conversion. The analysis was based on net energy production, energy output–input ratio, and the related CO2 emission. Sensitivity analysis was conducted to determine the effect of fertilizer type and application technique, harvesting and drying techniques, energy conversion process and chips transportation distance. The results showed that key energy efficiency and environmental compatibility factors include: the choice of drying technique; fertilizer type and application technique (68.2% variation in net energy, 57.7% difference in output–input ratio, respectively), and; the type of biomass-to-energy conversion plant, which had up to 36.4% variation in net energy production, and 96.4% reduction in CO2 emission. Willow chips transportation up to distances of 38 km did not have significant impact on the net energy production and CO2 emission. Chip transportation over distances in excess of 38 km generated significant drop in energy efficiency (25.9% reduction in energy output–input ratio) which underlines the importance of transportation in the overall system productivity.