In the low carbon transition that underpins energy policy in most developed economies, coal-fired plant’s long-term future is dependent on the successful development of emission sequestration technology. But this technology still firmly remains in the demonstration phase, with the prospects for its commercialisation by the end of this decade uncertain owing to poor investment levels by governments and utilities during a period of fiscal constraint. And now coal’s medium-term prospects may also be uncertain with growing calls to re-classify the use biomass in combustion, including its co-firing with coal.
Give the uncertain future of unconstrained coal-fired plant, co-firing with biomass provides an opportunity to extend the lifetime of coal-fired plant and guarantee more baseload supply security. A major proponent of biomass co-firing is Drax, Europe’s largest coal-fired generator. Drax has been lobbying the UK government to provide more subsidy support for biomass under the Renewable Obligation scheme, arguing that without additional subsidy support it will be uneconomic to increase the share of its co-fired coal-fired generation, which in turn will impede the generator’s emission reductions and consequently could impact on supply security.
There has never been any disagreement over the potential contribution of biomass to generation; unlike other mainstream renewable resources, such as wind and solar, biomass is flexible, enabling a quick response to changes in electricity demand, and it is arguably more reliable than other renewable resources with a high, and secure, availability. Proponents argue these attributes, together with biomass being one of the most economical of renewable generation technologies to construct, make it an ideal complement to intermittent renewable generation resources.
But unlike most other renewable generation technologies, biomass generation incurs costs in fuel procurement, as biomass fuels are more expensive than fossil fuels. And because of this fuel cost component, biomass is disadvantaged under the UK’s Renewable Obligation.
While the UK, and the EU, have identified biomass as a key renewable energy resource in the evolving low carbon energy mix it is not subsidised or regulated equitably with the other renewable resources. And now a new report by the European Environment Agency could derail biomass’ generation potential by calling for stricter regulations on biomass usage.
While biomass is classified as a renewable resource, as it is derived from biological material, its composition from carbon, hydrogen and oxygen means its is not carbon-neutral like other renewable energy resources. But CO2 emissions resulting from burning biomass have traditionally been excluded from emission inventories, with the biomass considered carbon-neutral as long as the emissions from its combustion are sequestered by growing new biomass sources, such as trees.
According to a recent paper by Dr. Francesco Cherubi, a fellow at the Norwegian University of Science and Technology, CO2 emissions from biomass combustion should no longer be excluded from Life Cycle Assessment studies or be assumed as having the same global warming potential as anthropogenic CO2 emissions. Cherubi explains that the global warming impact of biomass combustion depends on the interactions with the full carbon cycle and its sinks, which work on different timescales, and he has formulated impulse response functions to help predict the atmospheric decay of CO2 emissions from biomass combustion and an index to estimate the contribution of these emissions to global warming.
The implications for the UK of any biomass constraints could be severe. The government identified biomass as a preferred technology in the renewable road map published in July, and is believed to favour increasing the number of ROCs for its use in its forthcoming banding review. But the previous government was warned only two years ago to ensure that best practices are followed with only sustainable biomass used.
A 2009 report by the Environment Agency concluded that the best biomass power plants have the potential to cut carbon emissions by up to 98% compared to coal, but warned that poorly designed biomass combustion facilities could actually lead to a net increase in emissions.
The report also warned that there is a huge variation in the environmental and carbon benefits delivered by different biomass plants, and noted that while schemes delivering combined heat and power that use wastes or crops that have only been transported short distances can be almost carbon neutral, schemes generating only electricity and using large amounts of fertiliser to grow energy crops, or requiring high levels of energy to process and transport the biomass, can in some cases result in more emissions than coal-fired plants.
As a consequence of the EEA report, the agency’s Scientific Committee has called for EU regulations and policy targets to be revised in order to encourage only the use of biomass that reduces greenhouse gas emissions. But the problem of such a call, as Cherubi notes in his paper, is that there is currently no accurate and standardised procedure for quantifying the effective climatic impact of CO2 emissions from biomass combustion.
The risk associated with the EU’s adopting new biomass regulations before there is an accurate procedure for quantifying the climatic impact is threefold:
• Biomass combustion, including co-firing with coal, could be constrained in the unproven belief it was contributing to greenhouse gas emissions
• Biomass combustion receives less in the way of subsidies as a renewable resource, limiting its use, and
• Biomass used in generation requires emission permits, making it an uneconomical generation resource.
Collectively, the potential impact of these risks would be to undermine generation emission reductions and supply security, as well as creating more coal-fired generation uncertainty. While biomass has varied contributions as a renewable resource its major potential contribution is in co-firing with coal. With carbon capture and storage technology still possibly a decade away, and with medium-term supply security a major concern, Britain and other EU member states can ill afford to have their coal-fired capacity further constrained via new biomass regulations that may be based on un-quantified emission impacts.
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