A new Nature Sustainability paper just delivered a hard verdict on one of the most politically popular forms of carbon removal in Europe: burning trees to make electricity, then capturing the CO2. The answer, from Timothy Searchinger and colleagues at Princeton and the World Resources Institute, is that forest-fuelled BECCS (bioenergy with carbon capture and storage) will not produce net negative emissions for more than 150 years, emits more than unabated natural gas for decades, and roughly triples to quadruples the cost of electricity.

Why this matters

BECCS is load-bearing in most climate models. When the IPCC sketches pathways to 1.5 or 2 degrees, a huge share of the “negative emissions” wedge is BECCS. Integrated assessment models usually assume that biomass comes from dedicated energy crops on dedicated land. But actual policy is drifting elsewhere. European governments, including the UK’s Drax subsidy regime, are putting public money behind BECCS fuelled by wood from existing forests. Searchinger’s team built a model to test whether that real-world version of BECCS does what the theoretical version is supposed to do. It doesn’t.

What the model actually shows

The authors developed a transparent carbon-flow model called BECCS-Wood that tracks every tonne of carbon from standing tree to smokestack. They ran multiple sourcing scenarios, including US average wood supply, northeastern US forests, residues only, and blends with fast-growing plantations. Three headline results: No negative emissions for 150+ years. Across the realistic scenarios, cumulative emissions from a sustained BECCS programme stay positive for a century and a half. The climate math simply does not cross into negative territory on any timescale that matters for Paris goals. Worse than unabated gas for decades. A BECCS plant burning forest wood produces higher cumulative emissions than a natural gas plant with no capture at all, for decades after start-up. That is a striking claim. It means a policy designed to remove carbon performs worse, near-term, than the fossil fuel it is meant to displace, and worse than the fossil fuel even without any capture equipment. Electricity costs roughly 3.5x higher. Relative to alternatives, BECCS-from-forest-wood comes in at about three and a half times the cost per unit of electricity. Even a generous blend, half residues and half fast-growing plantations, only modestly improves the picture.

Why the numbers come out this way

Two physical facts drive the result, and they are not easy to engineer around. First, most of the emissions happen before the wood ever reaches the power plant. Cutting a mature forest releases carbon from soils, roots, slash, and foregone future growth. The capture unit at the plant only catches stack emissions. It cannot capture the carbon that escaped when the tree was felled, when the soil was disturbed, or the carbon that the forest would have kept absorbing had it been left standing. The authors call this the pre-plant emissions problem, and it dominates the lifecycle. Second, wood is simply a bad fuel for this purpose. It has roughly twice the carbon intensity of natural gas per unit of energy, and it burns at lower efficiency. So for every kilowatt-hour, a wood plant starts with a much bigger CO2 debt, even before you ask whether the forest grows back. Regrowth, when it happens, takes decades to a century. The capture equipment runs in real time. The accounting mismatch is the entire problem.

Implications for CDR policy

This paper is a direct challenge to the idea that forest-fuelled BECCS deserves subsidy as a carbon removal technology. If the Searchinger model holds up, every euro spent subsidising it is buying emissions, not removals, for the political lifetime of anyone designing the policy today. It also matters for how the CDR field talks about BECCS in general. BECCS is not one thing. BECCS from dedicated energy crops on marginal land is a different animal from BECCS on agricultural residues, which is different again from BECCS that cuts standing forest. Lumping them together, as many integrated assessment models do, hides exactly the sourcing question that determines whether the technology removes carbon or adds it. For CDR buyers and registries, the lesson is that feedstock accounting has to be forensic. “Sustainably sourced biomass” is not a verifiable claim without the kind of carbon-flow tracking this paper demonstrates.

Caveats

The paper models electricity and combined heat and power configurations. It does not rule out other bioenergy pathways, for example residues that would otherwise decompose quickly, or purpose-grown short-rotation crops on land that was not previously forest. The 150-year figure is a modelled projection, not an observation, and depends on assumptions about regrowth rates, harvest practices, and counterfactual forest carbon uptake. The authors have published the model so others can vary those assumptions. That transparency is welcome and unusual. This is also one paper. It joins a growing body of work from Searchinger and others questioning forest bioenergy accounting, but the BECCS-from-energy-crops pathway assumed in most IPCC scenarios is not what is being tested here. The honest read: if your BECCS supply chain goes through a mature forest, the climate case collapses. That is not the whole BECCS story, but it is the part governments are currently writing checks for.

Source: nature.com