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Burning wood for power generation can be worse for the climate than burning gas, even when the resulting carbon dioxide emissions are captured and stored, new research has shown.
The findings cast doubt on plans by several governments, including the UK, to offer subsidies or other financial support for carbon capture attached to wood-burning power.
Bio-energy with carbon capture and storage (BECCS) has been touted as a clean way of producing baseload power, substituting for gas and coal, which could even result in “negative emissions” as when replacement forests are grown they take up CO2 from the air.
But such systems could take 150 years to be “carbon negative”, researchers from the US, UK and China have found, in part because of the long time it takes to regrow forests, and because of the damage done when existing savannah, pasture or cropland is converted to grow biomass for burning.
Burning wood from existing forests, especially old-growth areas, was also found to be problematic, but even when half of the wood was judged to come from waste sources and half from fast-growing plantations, the models found it could take decades to reach “negative emissions”.
The scientists, who describe their work in the peer-reviewed journal Nature Sustainability, used data modelling techniques to show that most of the emissions from burning wood were generated before it reaches the power plant, and therefore could not be captured. Wood can emit twice as much carbon per unit of energy produced as fossil gas and is far less efficient in generating energy.
Tim Searchinger, a senior research scholar at Princeton University, who led the study, said: “Governments should not subsidise burning wood from existing forests, with or without carbon capture and storage. Doing so will increase carbon emissions for decades, even compared with doing nothing, and greatly raise people’s energy prices.
“Governments should reform laws that declare the carbon emitted from smokestacks by burning wood somehow doesn’t count – in other words, does not add to global warming. It does.”
Campaigners said governments should halt the generation of power from wood. In the UK, the main generator of biomass electricity is the Drax power station, the country’s biggest single source of CO2 emissions. Drax took nearly £1bn in subsidies last year from burning wood, according to a thinktank’s estimates this week.
Douglas Parr, the chief scientist at Greenpeace UK, said: “Common sense tells you that cutting down trees to burn them and then burying the resulting carbon emissions is a bad idea. This scientific study confirms that. Removing trees from one country to balance our carbon budget in the UK leaves the whole world poorer.”
Matt Williams, a senior forest advocate at the Natural Resources Defense Council, said the new findings backed up research he and others conducted last year. “The UK is better off without BECCS,” he said. “We need to find other genuinely clean sources of power that do not rely on imported fuels.”
Drax has “paused” its investment in BECCS, citing a lack of certainty on government subsidies for the technology. A Drax spokesperson said: “We agree that biomass for BECCS and bioenergy should not be sourced in the way described in the paper, which assumes all of the harvest is used for BECCS or bioenergy. We only source from well-managed, sustainable forests including sawmill residues, low-grade roundwood and forest residues.
“We also recognise the need for our biomass to deliver positive outcomes for climate and nature, which is why we monitor the forests we source from and invest in tools to enhance supply chain transparency, such as our biomass tracker.”
They added: “We are not aware of any managed forest areas where the type of harvesting described in the paper would be economically viable for land managers, much less the BECCS and bioenergy industry. Existing BECCS methodologies – including our own – have strict sustainability requirements in place which would not allow material harvested in the manner described to be used for the generation of verified carbon removal credits.”
Trevor Hutchings, the chief executive of the Renewable Energy Association, a trade body whose members include the biomass industry, noted that the UK government’s plans to reach net zero by 2050 relied on BECCS and other forms of carbon capture.
“The paper highlights many of the complexities and risks around BECCS, yet it’s important to recognise that, without BECCS and other forms of negative emissions, we will not achieve our legally binding net zero targets,” Hutchings said.
He added: “It is clear that BECCS lifecycle emissions depend heavily on feedstock choice, with wastes, residues and other biogenic sources offering materially different outcomes. The focus should be on deploying BECCS sustainably within a wider renewable energy system that delivers emissions reductions, energy security and affordability.”
A spokesperson for the Department for Energy Security and Net Zero rejected the report’s findings. “We do not recognise these claims,” they said. “No final decisions around the deployment of large-scale bioenergy with carbon capture and storage projects have been made, and any support would need to provide value for money for taxpayers and meet our sustainability criteria.”
