The UK Government's own science in 2013 showed that the use of whole trees from new harvesting in US forests can be up to four times more polluting than coal even 40 years after it has been burned.
A couple of months ago I took a trip to the world's newest global biodiversity hotspot: the North American Coastal Plain of North Carolina.
And it didn't disappoint. On a kayaking trip along the Black River and a boat trip along the Roanoke River we watched golden eagles circling above us and huge black and white belted kingfishers peeling out of the bushes to race downriver away from us.
The dogwood trees were just coming into bloom, adorning the sides of the highways with occasional polka dots of white. The wetland and hardwood forests in this part of the world are home to an amazing array of wildlife.
However, in many places along roads and rivers a thin screen, only three or four trees deep, hides a darker, shameful truth: huge clearcuts that are being driven by a new industry that has recently arrived in this part of the world. These clearcuts often lie right next to remaining stands of pristine forests, making the contrast and the impacts all the clearer.
The effects and scale of this industry were at their most stark when we saw the pellet mills with their huge stacks of logs piled up. These are turned into wood pellets and, in most cases, shipped to the UK to be burned in our power stations in response to our own renewable energy policies. Drax power station in Yorkshire, which is converting its boilers from coal to biomass, receives over £1 million per day in renewable energy subsidies for the practice.
Our friends at Dogwood Alliance, a US NGO, have followed trucks carrying whole trees from the clearcuts to the wood pellet mills. In turn, the pellet mills publicly declare that their supply contracts are for power stations in the UK. So the chain of supply is very easy to establish and we can directly link the burning of these trees for power in the UK to the impacts we saw on the ground.
I had a conversation with Adam Macon, the Campaign Director of Dogwood Alliance, which you can listen to here (or in embed, below). We spoke about his love of the forests, the threats they face from the wood pellet industry and the work he does to try to save them.
When we speak of renewable energy in the UK, we think of green, low impact technologies like wind and solar. But in fact, 72% of the electricity we count as 'renewable' comes from bioenergy - that is from burning plant matter (biomass) including trees. In 2015 the UK imported 2.7 million oven dried tonnes of wood from North America.
This isn't just an issue in the UK though. Across the EU as a whole around two thirds of all renewable energy generated comes from bioenergy. In the case of the EU there is a smaller dependence on imports and a greater reliance on the EU's own forests, although often with similar consequences. The UK's own use of biomass for power generation has been driven to date by EU renewable energy legislation.
Dirtier than coal
As well as the devastating impact on forests and wildlife, evidence now shows that the use of whole trees such as these could be resulting in increases in emissions relative to the fossil fuels they replace.
Bioenergy is often assumed to be a climate friendly energy source for two reasons. First, there is a public perception that bioenergy is carbon neutral because any emissions released when it is used will be reabsorbed by plant or tree regrowth. But trees grow slowly and in many cases it can take many years, decades or even centuries for the emissions to be recaptured, if ever.
Second, policy makers often assume that bioenergy can be counted as carbon neutral within the energy sector because the emissions will be counted under UN rules for harvesting forests. Unfortunately, problems with these rules mean that this simply isn't the case making it both incorrect, and highly misleading, to count bioenergy as carbon neutral in the energy sector.
One of the most obvious of these problems is that some countries, like the US, aren't even signed up to the UN's Kyoto Protocol, and so don't account for the emissions from harvesting their forests at all. This means the emissions from biomass imported from the US to the UK are not accounted for anywhere, by anyone, and simply end up in the atmosphere, treated as if they didn't exist.
But, despite such loopholes, the practice of defining biomass as carbon neutral persists - even receiving subsidies from the UK Government for it role in delivering supposedly low carbon energy. In fact, because wood is less energy dense than fossil fuels, it can often be more polluting.
Energy input can be 96% of energy produced
Despite this policy blind-spot, this situation has been recognised for a number of years in the scientific literature. The European Union's Joint Research Council concluded in 2011 that the assumption that bioenergy is carbon neutral is wrong. The UK Government's own science in 2013 showed that the use of whole trees from new harvesting in US forests can be up to four times more polluting than coal even 40 years after it has been burned. In a large number of cases bioenergy is a false solution for reducing emissions.
One specific problem highlighted in the government report is the high energy input that goes into producing the wood pellets - in harvesting, transport, drying (often using natural gas) and manufacturing, which can be as much as 96% of the delivered energy:
"The energy input requirement of biomass electricity generated from North American wood used by the UK in 2020 is likely to be in the range 0.13 to 0.96MWh energy carrier input per MWh delivered energy, significantly greater than other electricity generating technologies, such as coal, natural gas, nuclear and wind."
Many argue that if the overall size of the forest is growing (as it is in the EU and the US) then taking some trees out and burning them doesn't matter. But this overlooks the fact that if they hadn't been burned then the size of the forest would otherwise have been larger and more carbon would have been sequestered and stored.
It also overlooks the fact that in the US's case, for example, they are also relying on the growth of their forests to offset the emissions from their own economy. So counting bioenergy as carbon beneficial double counts this service that the forests provide by growing.
Using forms of renewable energy that potentially increase emissions rather than reducing them undermines the integrity of efforts to limit global temperature rises. Since the Paris conference the world has set a new goal to limit temperature rises not to 2C but to 1.5C. If we are to achieve this then utilising bioenergy that increases emissions is a mistake we cannot afford to keep making.
The solution: a limited and safe role for biomass
Bioenergy can play an important but limited role in the energy mix of many countries. However, it needs to be based on genuine emissions reductions, rather than false and unscientific claims.
The use of the highest carbon risk feedstocks, such as whole trees, needs to be ruled out almost entirely. A cap is needed on the use of bioenergy in line with available sustainable supply. And the use of bioenergy needs to be in line with the principle of a circular economy and optimum use (i.e. reuse and recycling need to be prioritised over energy uses).
The EU is due to introduce new sustainability criteria for the use of all bioenergy. However, because of the Brexit referendum result these may never apply to the UK. And the UK's own sustainability criteria fail to adequately protect nature, and treat biomass as if it were carbon neutral: they urgently need improving.
The UK's forthcoming Emissions Reduction Plan will set out how we will achieve our carbon budgets, the legally binding emissions reductions that the UK is signed up to under its Climate Change Act. Within this plan, bioenergy needs to play a limited role based on genuine emissions reductions.
These policy options will be essential if we are to stop driving the unnecessary destruction of forests such as those I visited in the spring. Only in this way can the great blue herons and pileated woodpeckers of North Carolina continue to thrive and prosper.
Matt Williams is a Policy Officer for the Royal Society for the Protection of Birds. He leads on their bioenergy and fracking policy. He's also the Associate Director of A Focus on Nature, the UK's youth nature network. Follow him @mattadamw and mattadamwilliams.co.uk.
The RSPB has produced scenarios showing how the UK could meet its energy needs and its emissions reductions targets by 2050 in harmony with nature.
Find out more about the work of Dogwood Alliance.
The UK Government's Department of Energy and Climate Change has produced its own science showing the carbon impacts of using whole trees.