Energy crops: current status and future prospects

Energy crops currently contribute a relatively small proportion to the total energy produced from biomass each year, but the proportion is set to grow over the next few decades. This paper reviews the current status of energy crops and their conversion technologies, assesses their potential to contribute to global energy demand and climate mitigation over the next few decades, and examines the future prospects. Previous estimates have suggested a technical potential for energy crops of~400 EJ yr⁻¹ by 2050. In a new analysis based on energy crop areas for each of the IPCC SRES scenarios in 2025 (as projected by the IMAGE 2.2 integrated assessment model), more conservative dry matter and energy yield estimates and an assessment of the impact on non-CO₂ greenhouse gases were used to estimate the realistically achievable potential for energy crops by 2025 to be between 2 and 22 EJ yr⁻¹, which will offset~100-2070 Mt CO₂-eq. yr⁻¹. These results suggest that additional production of energy crops alone is not sufficient to reduce emissions to meet a 550 μmol mol⁻¹ atmospheric CO₂ stabilization trajectory, but is sufficient to form an important component in a portfolio of climate mitigation measures, as well as to provide a significant sustainable energy resource to displace fossil fuel resources. Realizing the potential of energy crops will necessitate optimizing the dry matter and energy yield of these crops per area of land through the latest biotechnological routes, with or without the need for genetic modification. In future, the co-benefits of bioenergy production will need to be optimized and methods will need to be developed to extract and refine high-value products from the feedstock before it is used for energy production.