Biomass ‘carbon neutrality’ debate continues to divide opinion

Using biomass, specifically energy derived from burning wood, as a crux in the UK's effort to transition towards a low-carbon economy has come under scrutiny again, after the former secretary for energy and climate change and his ex-special advisor clashed over its use.

new report from Chatham House, authored by former Government advisor Duncan Brack, was released late last week, claiming that emissions from wood pellet-based biomass were higher than traditional coal use.

The report noted that biomass, which is Europe’s biggest source of renewable energy, has been placed under an assumption that it is carbon neutral due to a supposed balanced footprint by planting more trees. However, the report found that replacement trees absorb and store less carbon due to their young age. Soil carbon losses during the harvesting of trees can delay a forest’s role as a carbon sink by 10-20 years.

Brack attended a Channel 4 debate on Thursday night (23 February), alongside former energy secretary Chris Huhne. Brack acted as a special advisor to Huhne on renewables policies between 2010 and 2012. The two were at odds over the labelling of biomass as carbon neutral. Brack believed that subsidies spent on biomass conversions, notably by Drax, should be reviewed immediately, noting that solar, wind and energy efficiency upgrades to buildings could be boosted by re-aiming the subsidy streams.

“We treat biomass as a renewable energy and we consider it under UK and European policy to be zero carbon, but in reality, it isn’t,” Brack said. “You produce CO2 at a higher capacity than coal or gas because wood is less energy dense.

“The fact is, because of our push for renewables, we should be putting our money into zero-carbon technologies like solar and wind, or energy efficiency. But instead we are taking stored carbon and burning it and releasing at the cost of public money.”

In response, Huhne claimed that pursuing zero-carbon biomass was “too puritanical”, noting that current biomass methods can be 60% less carbon intensive compared to traditional coal-powered plants. Huhne also warned that if foresters were unable to sell-off wood pellets as biomass, money drains would lead to forest land being sold-off to form farming space, removing large swathes of carbon sinks in the process.

“There’s an increase in the amount of carbon stored in US forests,” Huhne said. “If you didn’t have that [biomass], a lot of the land would go to farming, trees would be cut down entirely.

“In the Northern Hemisphere, if the wind doesn’t blow and the sun doesn’t shine and we reach peak energy demand, we’ll need renewables like biomass. We need to be realistic about this and actually compromise on a source of renewable energy.”

Huhne noted that only “sustainable” biomass, materials that can cut emissions by 60%, receive the funding. However, the Chatham House report noted that UN climate rules dictate that emissions from trees are only counted when they are harvested. Canada, Russia and the US – large biomass suppliers for the UK – do not use this accounting method, meaning that the carbon from burning effectively goes “missing”.

The UK is the biggest importer of wood pellets in the European Union (EU), shipping in more than seven million tonnes from the US and Canada in 2015. The UK has spent around £450m subsidising power stations to burn these pellets.

Drax conversions

Biomass has played an increasingly significant role in Britain’s energy mix, with generation levels more than tripling from 6.6TWh in 2009 to around 22.4TWh in 2015, or 9% of total national generation.

One notable company to benefit from the scheme is Drax. The company first announced plans to convert its coal-powered stations to biomass in 2012. Two other units were also upgraded in 2013 and 2014. At the time, the conversion project represented the largest decarbonisation project in Europe and Britain’s largest renewable power generator – estimated to cost between £650-£700m. The approval for the third unit conversion was given in the context of the Government’s push to end coal-fired generation by 2025 and promote clean energy generation.

The successful conversion of all three units at Drax will look to cut 12mtCO2e per year from the power station’s operations. Drax believes that, with support from the Government, the company could upgrade the remainder of the power station to run solely on biomass and provide up to 8% of the UK’s total electricity from sustainable sources. The firm also says the type of wood it burns and the trees it plants help reduce the carbon footprint of the biomass use.

In fact, the European push for more biomass pellets – in order to hit EU renewable energy targets – is developing a harvest and planting cycle that environmental groups are concerned about. Groups are worried that this cycle isn’t sustainable or sufficient for long-term horticulture practices.

Brack’s findings mirror those of a study released 17 October 2016 by US-based environmental organisation the Natural Resources Defense Council (NRDC). The study found that solar and wind were likely to be less expensive than burning trees for biomass, and that many forms of biomass – such as that from forests – have been producing higher carbon emissions than coal and natural gas for decades.

Burning wood for electricity emits around 40% more carbon pollution than burning coal to produce an equivalent amount of energy, the NRDC reports, as the carbon that trees have accumulated over long periods of time is released into the atmosphere when burnt. Moreover, the use of trees for biomass disrupts vital carbon sinks and impedes ongoing forest carbon sequestration.

However, the Wood Heat Association, founded by the Renewable Energy Association (REA) in 2013, refuted the claims made in the NRDC report. The Association claimed that wood used in biomass power production is typically from low-value wood such as harvest residues, thinnings, tree tops, limbs, and sawmill residues, as well as misshapen and diseased trees not suitable for other use. This is sourced from actively managed timber producing forests in the UK, EU, and US. 

Industry response

In response to the latest report from Chatham House, the REA has produced its own article of ‘myth-busters’, challenging many of the “misleading statements” made within the paper.

The REA’s chief executive Dr Nina Skorupska said: “This report hangs on the fallacy that it takes decades for a forest to recapture carbon. That isn’t true. A well-managed forest is continually growing and it locks in carbon at an optimal rate.

“Imagine you have 100 trees, all growing 3% bigger per year. You could remove two trees for timber, with offcuts going to bioenergy, and the forest would still absorb 1% more carbon than the year before. There’s no delay involved. This is true whether it’s a hundred trees or a hundred million.

“Biomass delivers a massive cut in carbon emissions compared to fossil fuels. That principle is at the heart of the industry. 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.”

Matt Mace

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