Image copyright Getty Images Image caption There has been rapid growth in the use of wood chips and pellets for generating electricity

Using wood pellets to generate low-carbon electricity is a flawed policy that is speeding up not slowing down climate warming.

That's according to a new study which says wood is not carbon neutral and emissions from pellets are higher than coal.

Subsidies for biomass should be immediately reviewed, the author says.

But the industry rejected the report saying that wood energy cuts carbon significantly compared to fossil fuels.

Critical role

While much of the discussion has focussed on wind and solar power, across Europe the biggest source of green energy is biomass.

It supplies around 65% of renewable power - usually electricity generated from burning wood pellets.

EU Governments, under pressure to meet tough carbon cutting targets, have been encouraging electricity producers to use more of this form of energy by providing substantial subsidies for biomass burning.

However this new assessment from Chatham House suggests that this policy is deeply flawed when it comes to cutting CO2.

According to the author, current regulations do not count the emissions from the burning of wood at all, assuming that they are balanced by the planting of new trees.

Image copyright Getty Images Image caption Wood chips and pellets are often burned used alongside coal in power plants

Duncan Brack, the independent environmental policy analyst who wrote the report, says this idea is not credible.

"It doesn't make sense," said Mr Brack, who is also a former special adviser at the UK Department of Energy and Climate Change.

"The fact that forests have grown over the previous 20 or 100 years means they are storing large amounts of carbon, you can't pretend it doesn't make an impact on the atmosphere if you cut them down and burn them."

"You could fix them in wood products or in furniture or you could burn them, but the impact on the climate is very different."

Mr Brack says the assumption of carbon neutrality misses out on some crucial issues, including the fact that young trees planted as replacements absorb and store less carbon than the ones that have been burned.

Another major problem is that under UN climate rules, emissions from trees are only counted when they are harvested.

However the US, Canada and Russia do not use this method of accounting so if wood pellets are imported from these countries into the EU, which doesn't count emissions from burning, the carbon simply goes "missing".

Burning wood pellets can release more carbon than fossil fuels like coal per unit of energy, over their full life cycle, the author argues.

Often the products have to travel long distances increasing the emissions associated with their production and transport.

Image copyright Southern Environmental Law Center Image caption The map shows the concentration of wood pellet plants in the south-eastern US exporting to Europe

Within the EU, the UK is the biggest importer of wood pellets for heat and power, with some 7.5m tonnes shipped from the US and Canada in 2015-16. Most of these imports come from the south-east US, where there are growing concerns about the trade.

"This report confirms once again that cutting down trees and burning them as wood pellets in power plants is a disaster for climate policy, not a solution," said David Carr, General Counsel of the Southern Environmental Law Centre in the US.

"Forests in our region, the south-east US, are being clear cut to provide wood pellets for UK power plants. The process takes the carbon stored in the forest and puts it directly into the atmosphere via the smokestack at a time when carbon pollution reductions are sorely needed."

Within Europe the push for pellets is also providing incentives for the forest industry to plant more and harvest more trees. Environmentalists are worried that the system is creating a cycle that can't keep up with itself.

"If you keep increasing your harvest over a period of time you will never be able to recoup your emissions from burning that growth, you will never catch up with yourself," said Linde Zuidema from Fern.

"They are shooting themselves in the foot, they are not taking into account that increased harvesting of trees will actually have an impact on the role that forests play as a carbon sink."

Biomass industry sources though have been critical of the report saying that it is a fallacy that it takes decades for a forest to recapture carbon.

"Biomass delivers a massive cut in carbon emissions compared to fossil fuels. That principle is at the heart of the industry," said Dr Nina Skorupska from the Renewable Energy Association.

"The whole supply chain is monitored in detail to ensure we cut greenhouse gas emissions by at least 60% compared to fossil fuels, although the reality is often closer to 80%.

"On top of that, there is a significant body of peer-reviewed academic studies, ensuring that this industry is doing what it says on the tin. And it is: biomass cuts carbon, supports forests and delivers reliable renewable energy at a lower cost."

BECCS is bad?

As well as the core concern that biomass is a flawed approach to renewable energy, the new study also highlights concerns over the use of BECCS - bio-energy with carbon capture and storage.

Scientists, including the Intergovernmental Panel on Climate Change (IPCC), have suggested that this system could be used to suck carbon from the atmosphere to keep the world from dangerous levels of warming.

"It's really worrying," said Duncan Brack.

"The number of scenarios that the IPCC reviewed that rely on BECCS for ambitious climate change targets, it's crazy, I'm not the only person who's said that."

Concern is growing about the continued use of wooden pellets and chips for electric power. The EU has proposed a new system for biomass under its revised Renewable Energy Directive.

Duncan Brack says it's a good opportunity to review the current methods of giving subsidies for the use of wood energy across Europe. The use of saw mill waste should be encouraged - but the burning of pellets should be curtailed.

"The simplest way is to limit support to those type of biomass that really represent genuine carbon savings, primarily sawmill waste and post-consumer wood waste," said Duncan Brack.

"I would rather see support for forest industry, not forest energy."

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