Energy crops in Ireland: Quantifying the potential life-cycle greenhouse gas reductions of energy-crop electricity

This study uses life-cycle assessment (LCA) to compare greenhouse gas (GHG) emissions from dominant agricultural land uses, and peat and coal electricity generation, with fuel-chains for Miscanthus and short-rotation-coppice willow (SRCW) electricity. A simple scenario was used as an example, where 30% of peat and 10% of coal electricity generation was substituted with co-fired Miscanthus and SRCW, respectively. Miscanthus and SRCW cultivation were assumed to replace sugar-beet, dairy, beef-cattle and sheep systems. GHG emissions of 1938 and 1346 kg CO₂ eq. ha^-1 a^-1 for Miscanthus and SRCW cultivation compared with between 3494 CO₂ eq. ha^-1 a^-1 for sugar-beet cultivation and 12,068 CO₂ eq. ha^-1 a^-1 for dairy systems. Miscanthus and SRCW fuel chains emitted 0.131 and 0.132 kg CO₂ eq. kWh^-1 electricity exported, respectively, compared with 1.150 and 0.990 kg CO₂ eq. kWh^-1 electricity exported for peat and coal fuel chains. 1.48 Mt CO₂ eq. a^-1 was saved from electricity production, and 0.42 Mt CO₂ eq. a^-1 was saved from displaced agriculture and soil C-sequestration. The total reduction of 1.9 Mt CO₂ eq. a^-1 represents 2.8% of Ireland's 2004 GHG emissions, but was calculated to require just 1.7% of agricultural land area and displace just 1.2% of the dairy herd (based on conservative Miscanthus and SRCW combustible-yield estimates of 11.7 and 8.81 t ha^-1 a^-1 dry matter, respectively). A 50% increase in cultivation emissions would still result in electricity being produced with an emission burden over 80% lower than peat and coal electricity. Lower yield assumptions had little impact on total GHG reductions for the scenario, but required substantially greater areas of land. It was concluded that energy-crop utilisation would be an efficient GHG reduction strategy for Ireland.