Coppice Counts

UK study shows short-rotation coppice could play an important role in meeting renewable energy targets.
By Lisa Gibson | May 23, 2011

A recent U.K. Energy Research Centre study found that 7.5 million metric tons (8.2 million tons) of biomass can be produced from short-rotation coppice energy crops in England, making a substantial contribution to renewable energy targets in the country.

The report, “Estimating the supply of biomass from short-rotation coppice in England, given social, economic and environmental constraints to land availability,” found that such large biomass production from willow and poplar would require 800,000 hectares (2 million acres) and could be grown almost entirely on marginal lands. “We therefore conclude that short-rotation coppice energy crops have the potential to play an important role in meeting U.K. renewable energy targets without compromising environmental sustainability or food production,” the study’s four authors write.

The U.K. Renewable Energy Strategy specifies 15 percent of all energy and 30 percent of all electricity demand be met by renewable sources by 2020. Additionally, the Renewables Transport Fuel Obligation demands that biofuels comprise at least 5 percent of all transportation fuel by 2014. About 7.5 million oven-dry metric tons of biomass will be required for energy crops to meet their share of these targets, the report says.

That amount of biomass per year would theoretically generate 15.5 terrawatt hours per year of electricity, about 4 percent of the U.K.’s current demand. The southwest and northwest portions of England alone produce more than one-third of that figure, the report cites. High yields of short-rotation coppice can be achieved on even the poorest grades of agricultural lands in England, it adds, particularly in areas with high rainfall, like the northwest, and/or high soil water availability, like the east.

As of 2009, biomass met only 2.8 percent of the U.K.’s electricity demand and 2.6 percent of energy demand, according to the report. Most of that material was landfill gas, waste wood or other residuals. Dedicated energy crops such as poplar, willow and miscanthus are responsible for less than 0.1 percent of the U.K.’s electricity and energy markets.

Current energy crop yields are generally achieving less than 50 percent of potential, suggesting step-change improvements are likely over the coming years, according to the study. Further expansion of crops’ potential through new technologies, breeding and climate change could minimize the conflict with food production. “As a result, we are likely to see an increase in the value and production of these crops as feedstocks for heat, power and liquid transportation fuels,” the authors write. “This presents considerable challenges to future land use in England and more widely; making the best of the land available to us will ensure future viability of energy crops.”

—Lisa Gibson