Burning Questions Surround Biomass-Based Removals
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By Angeli Mehta, Reuters
As part of developing a biomass strategy, the UK government asked a group of experts to look at whether using forest biomass for bioenergy with carbon capture and storage (BECCS) could deliver net permanent removal of carbon dioxide from the atmosphere.
They suggested it could, but only with tight regulation and robust monitoring of supply chains and forest stocks.
The whole logic of BECCS rests on the idea that the carbon dioxide released by combustion has earlier been sequestered from the atmosphere as trees grow. Moreover residues (such as tops and thinnings) might have been left on the forest floor where they would have decomposed or burnt, releasing carbon.
Capturing CO2 from the fuel stack of a biomass plant and storing it then delivers carbon negative emissions, or net carbon removal.
UK power plant Drax has been trialling biomass carbon capture technologies since 2018. It mainly relies on biomass sourced from managed forests in North America, where it owns 18 pellet mills. Last year it faced allegations, which it denies, that it sourced biomass from “environmentally important” forests in Canada.
The experts’ report says there is evidence that “improved forest management can lead to both an increase in standing forest stock and also forest biomass productivity. However, the challenge is to ensure that this continues to be the case going forward, if consumption of forest biomass is further increased owing to use of wood in construction, increased demand for bioenergy, and GGR (greenhouse gas removals).”
Liam Hardy, policy analyst at Green Alliance, says BECCS “could make sense with a truly sustainable supply of biomass, but I’m not sure it does at the moment.”
Careful management may increase carbon stocks, he says, but “what's the counterfactual? If you had done nothing with that piece of forest, would it have sequestered more carbon by not being touched? I don’t know if you can ever truly get a completely definitive answer on that.”
He adds that while the logic that waste would have been left to rot or burn is sound, “then you have to ask how much does that drive the logging and the timber industry because of the economics? And it might well have an impact, but Drax won't admit that.”
Policy uncertainty in the UK, and delays to the pipeline infrastructure that would take CO2 to be stored out in the North Sea, mean Drax’s first BECCS unit won’t be commissioned until later than planned – it says “by” 2030. According to Drax, this would deliver 4 million metric tons of carbon removal, with a second coming online soon after to take removals to 8 million tons/year. The government’s target is for 5 million tons of removals from all sources by 2030.
The company is in talks with the government about a “bridging mechanism” between the end of current biomass burning subsidies in 2027 (without which the project would be unviable) and BECCS commissioning.
Drax has also turned its attention to the United States, and has chosen two sites to build BECCS plants. It will be able to take advantage of the tax incentives available under the IRA, while also considerably shortening supply chains that currently bring wood pellets to the UK from southern U.S. plants. Drax says the two sites could capture 6 million tons of CO2 a year by 2030. It has already signed memorandums of understanding for carbon removals, some at $300 a ton.
Burning biomass for energy has also become big business in the European Union, with around 60% of renewable energy coming from biomass. None of the plants is capturing and storing emissions, but that could be about to change.
Stockholm Exergi plans to capture and store around 800,000 tons of CO2 emissions a year from its combined heat and power plant from 2026. It’s already signing up business customers who want to buy carbon removals, and the technology has attracted interest from as far afield as Indonesia. It anticipates two other locations could be up and running by 2030.
The energy required to capture carbon from flue gases can be a considerable chunk of the energy cost of the process, but the Stockholm plant will use excess heat from the capture facility to supply the city’s district heating network, reducing the extra cost of the capture energy to just 2%. The resulting emissions will be transported by ship to be stored under the North Sea.
In Denmark, Orsted aims to capture over 400,000 tons of emissions from burning straw and wood chips at two combined heat and power plants. Construction is expected to get under way at the end of the year, with Microsoft already committed to buying 250,000 tons of carbon removals each year for 11 years. The captured CO2 will be shipped to Norway’s Northern Lights carbon storage site also being developed in the North Sea.
Orsted insists its sourcing of biomass meets Denmark’s stringent requirements on ecosystems, biodiversity and carbon accounting, and is backed by third-party verification. But what happens if stocks are destroyed by fire, for example.
A spokesman says “the forest biomass we receive in a year are the residues from management of thousands of forests and forest product industries in Europe and North America. So, you can say our contingency plan is to distribute the risk between many countries and many forests in those countries.”
But biomass need not be directed only at producing electricity. In California efforts are under way to rethink agriculture waste supply chains and help clean up the state’s dire air pollution. There’s a new acronym on the block – BiCRS (biomass with carbon removal and storage) that puts the emphasis on removals rather than energy production.
California-based Clean Energy Systems intends to repurpose existing biomass plants, which once took thinnings and other residues from the fruit and nut orchards of the state’s central valley. The plants were mothballed when power purchase agreements ran out, and by which time wind and solar were far cheaper, explains vice president of business development Rebecca Hollis. Farmers now have no avenue for the waste other than to burn it.
“The supply chain is still there. We’ve already started talking to the farmers, who ask ‘how soon can we give you our waste, we literally have nothing to do with it’. So that's key. We're not going out and growing things, we're not harvesting trees. This is actually a waste disposal issue for California,” says Hollis.
The technology, proven in the aerospace industry, involves heating the biomass until it turns into a gas, then burning that in the presence of only oxygen to produce steam for electricity and a pure stream of carbon dioxide. The electricity produced covers the energy required by the process, and any excess can be sold to the grid.
All the CO2 captured will be pressurised and stored below the plant, in well-studied geologic formations. Between its first two plants Hollis anticipates the net removal of around 1 million tons of CO2 a year, with the first up and running in 2026, assuming permits are granted for storage. “We know exactly how much CO2 is going into the ground. And because we only have the agricultural waste coming in, we know that all the carbon that's going into the ground is only coming from that waste,” states Hollis.
By adding another step, Clean Energy Systems could also capture hydrogen from the synthesis gas, to be sold to industry or the transport sector. Indeed, California is making a big play for hydrogen, competing to become a hydrogen hub and so attract billions of dollars in federal funding.
Unlike Clean Energy Systems, Mote, a spin-out from California’s Lawrence Livermore National Laboratory, intends to produce clean hydrogen from the start.
A first plant is anticipated to begin operating in 2027, processing agriculture and forest residues to produce hydrogen and capture some 150,000 tonnes of CO2 each year. It’s been talking to Canada’s CarbonCure, whose process injects carbon dioxide into fresh concrete where it mineralises to be stored away.
With so many companies chasing agriculture waste, can any of them be confident of a future fuel supply? A state landfill directive, along with millions of dead trees that were infested with bark beetle or destroyed by drought, leads Hollis to be confident Carbon Energy Systems’ projects will not run out of fuel “any time soon.”
While the U.S. is pushing hard for carbon removals, there is a patchwork of regulations across states for carbon storage, which Hollis would like to see harmonised. On top of that, companies such as Microsoft are buying up carbon removals.
“It seems like they have their own verification and monitoring requirements, so there's almost a private industry coming, which is separate from the states and other countries,” says Hollis. “It would be lovely to have one system. If they could come together and agree, then we could deploy this in other states and other countries, and we would have a clear set of guidelines to follow.”
If biomass is to deliver certain and sustainable carbon removals, it’s clear that a lot of questions will have to be addressed to ensure the highest sustainability and monitoring standards, all along supply chains.
