What should we do with biomass?
Probably not burn it, as it turns out.
In the UK, the conversation around use of biomass is centred around energy—at least as far as the government is concerned. The Biomass Strategy released this year focuses largely on energy. The plan goes like this:
In the short term (2020’s) continue to burn biomass for energy/fuel, not worrying about abating the emissions.
In the medium term (to 2035) burn more of it for energy/fuel, with some attempt to abate emissions through capturing and storing the carbon after it’s released.
In the long term, who knows? Looks like we’ll burn more biomass for energy/fuel. Maybe we’ll consider some other uses.
You can read the full strategy here, but fair warning: it’s 204 pages long.
Definition note: technically, biomass means any material of biological origin. In practice, it’s largely plant materials, like wood and crops.
So what’s the problem with burning biomass for energy? We definitely need energy, and it needs to not come from fossil fuels. The carbon in biomass was pulled from the air much more recently than the carbon in fossil fuels, which (as a general rule of thumb) makes it a more sustainable choice for burning. And if we use only sustainable biomass, as the UK claims to, then it’s fine, right?
The main problem is the definition of sustainable. In the UK’s 2021 Biomass Strategy Call for Evidence, less than half of respondents (38%) felt that the sustainability criteria currently in place are sufficient. The criteria cover land use, GHG savings compared to fossil fuel energy, ecosystem services (sort of), biodiversity, and protection of soil carbon stocks. The 2023 Biomass Strategy lays out some plans for strengthening the criteria.
Unfortunately, none of the criteria ask the fundamental question of whether burning biomass is more sustainable than not burning it.
That question was asked by the team at the US Lawrence Livermore National Laboratory in 2020. They started out with the intention of writing a roadmap for bioenergy carbon capture and storage (BECCS)—that is, burning biomass for energy and attempting to capture and store the released CO2, as the UK plans to do. They ended up concluding that burning biomass for energy is fundamentally ridiculous. Their analysis shows that the most valuable part of BECCS is the removal of carbon from the atmosphere, not the energy generation. The resulting document (only 65 pages long) is a roadmap for BiCRS—Biomass Carbon Removal and Storage—which is the strategy the US is now prioritising.
The argument is fairly simple. One oven-dry tonne of biomass has roughly 18 GJ of energy, and 0.5 tonnes of carbon (1.8 tonnes CO2eq). The energy is worth something, and can be compared to the value of an equivalent amount of energy (18 GJ) from standard energy feedstocks (oil, gas, coal, wood pellets). The carbon storage is also worth something, though is a bit harder to quantify. So let’s plot the value of 1 tonne of biomass in storing carbon (1.8 tCO2eq stored multiplied by various carbon prices), and figure out how expensive carbon has to be before the carbon storage value outweighs the energy value.
As it turns out, when carbon is priced at $25/tCO2, the carbon storage value of biomass outweighs the energy value if it’s priced like coal or wood pellets. At $35/tCO2, the carbon storage value of biomass outweighs the energy value if it’s priced like natural gas, and $65/tCO2, even an oil-like price for the energy value is an insufficient argument for burning biomass.
Let’s take a look at the World Bank’s carbon pricing dashboard. This shows the price of a tonne of CO2eq in USD, as implemented by various countries emissions trading schemes or tax mechanisms. The UK price, as of March 2023, was $88/tCO2e, while the EU price was $96.
At these prices, burning biomass for energy doesn’t make financial sense. The technology for BECCS is still not available at scale, despite endless promises of being around the corner. It makes more sense to grow the biomass and do basically anything else with it. Make chemicals, build houses, bury it deep in the ground or drop it in the ocean.
So why are we still talking about BECCS? We have massive amounts of actually renewable energy, like solar and wind, that need to be deployed more widely. Let’s focus our medium- and long-term planning on that, and how to apply biomass where it can do what it’s best at—removing carbon from the atmosphere.