Will energy crop yields meet expectations?

• Published in: Biomass & bioenergy 2014-06, Vol.65, p.3-12
• Main Authors: Searle, Stephanie Y., Malins, Christopher J.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Alternative fuels. Production and utilization; Applied sciences; Biofuel; Biological and medical sciences; Biomass; Cellulosic ethanol; Energy; Energy crop; Eucalyptus; Exact sciences and technology; Forestry; Fuels; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; Generalities. Production, biomass, yield. Quality; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; Miscanthus; Miscellaneous; Panicum virgatum; Populus; Production. Biomass; Renewable energy; Salix; Yield
• ISSN: 0961-9534; 1873-2909
• DOI: 10.1016/j.biombioe.2014.01.001

Expectations are high for energy crops. Government policies in the United States and Europe are increasingly supporting biofuel and heat and power from cellulose, and biomass is touted as a partial solution to energy security and greenhouse gas mitigation. Here, we review the literature for yields of 5 major potential energy crops: Miscanthus spp., Panicum virgatum (switchgrass), Populus spp. (poplar), Salix spp. (willow), and Eucalyptus spp. Very high yields have been achieved for each of these types of energy crops, up to 40 t ha−1 y−1 in small, intensively managed trials. But yields are significantly lower in semi-commercial scale trials, due to biomass losses with drying, harvesting inefficiency under real world conditions, and edge effects in small plots. To avoid competition with food, energy crops should be grown on non-agricultural land, which also lowers yields. While there is potential for yield improvement for each of these crops through further research and breeding programs, for several reasons the rate of yield increase is likely to be slower than historically has been achieved for cereals; these include relatively low investment, long breeding periods, low yield response of perennial grasses to fertilizer, and inapplicability of manipulating the harvest index. Miscanthus × giganteus faces particular challenges as it is a sterile hybrid. Moderate and realistic expectations for the current and future performance of energy crops are vital to understanding the likely cost and the potential of large-scale production. •This review covers Miscanthus, switchgrass, poplar, willow, and Eucalyptus.•High yields of energy crops are typically from small experimental plots.•Field scale yields are lower due to real world harvesting losses and edge effects.•The potential for yield improvement of energy crops is relatively limited.•Expectations must be realistic for successful policies and commercial production.