Wood from the trees
Paul Suff takes a look a the realities of biomass after the Renewable Energy Association joins industry in calling for greater subsidies for the fuel
Drax reported its annual financial figures a few weeks ago and again made a plea to the government to change the rules governing biomass.
The company operates Western Europe’s largest coal-fired power station, providing around 7% of the UK’s electricity, and has aspirations to become a major source of renewable power.
The Yorkshire power station is the largest single emitter of CO2 in the UK, but if government subsidies for biomass increased, Drax, and other coal-fired power plants, could have a lower carbon footprint than gas-fired power stations, says the company.
Drax has been using biomass to co-fire the 3,870MW plant since 2003, gradually increasing it to supply 8% of fuel in the 12 months to the end of June.
The environmental benefit of increasing biomass at the expense of coal is considerable, as, according to the European Biomass Industry Association, the substitution of one tonne of coal with refined biomass reduces net CO2 emissions by three tonnes.
CEO Dororthy Thompson says the proportion of biomass at Drax could rise to 50% or more if the level of financial support was higher. Currently, biomass generation is awarded only half a ROC – renewable obligation certificate – per unit of electricity, whereas two ROCs are awarded for each unit produced by offshore wind.
The government is due to make a decision on subsidy levels for biomass by the end of the year, but any rise, and subsequent upsurge in biomass use by coal-fired plants, raises questions about the source of the feedstock.
Biomass is any biological material, derived from plant or animal matter, which can be used to produce heat and/or power, so wood, straw, energy crops, sewage sludge, waste organic materials and animal litter are all classified as biomass. It is a low-carbon resource if the feedstock is from sustainable sources.
Using biomass to generate electricity and heat is a renewable source of fuel because the CO2 released through combustion is largely offset by the CO2 absorbed during growth or which is captured by new biomass to replace that used for energy purposes.
Around one million tonnes of biomass is currently burnt or co-fired in UK power stations each year, but expansion plans could see demand for biomass soar to 60 million tonnes a year.
The UK has its own, largely undeveloped, stocks of biomass, but supplies will need to increase significantly, and a supply chain established, if it is to become a relatively common feature of the energy mix.
Imported biomass already makes up more than half of the feedstock used for co-firing in power stations, and the government has acknowledged that the UK will continue to rely on imports. Drax says it will aim source as much as possible from the UK, but admits that imported biomass will also be required.
Although the energy company has a strict sourcing policy, there is a fear that growing demand for biomass will lead to vast tree plantations solely for energy, increasing pressures on land access and food security in some of the world’s poorest countries and communities. And, even if it is from sustainable sources and does not displace food crops, the carbon emitted by transporting the biomass from other parts of the world will substantially reduce the benefit of burning it.
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