The paradox of sustainable biomass

Alternative fuels

A recent press statement by FuelsEurope, Europe’s largest petroleum lobbying group, suggests that biomass is the key to decarbonizing the transportation sector. Not only does the group claim that European biomass resources are “more than sufficient to supply feedstock for bio-based liquid fuels to aviation, maritime, and a share of road transport,” it also states that these equivalent quantities of biomass are sustainable. But, do the numbers check out?

The underlying research behind the FuelsEurope statements come from a study commissioned by Concawe, a European oil research association, and conducted by researchers at Imperial College London (ICL). The ICL study estimates European biomass resource availability in 2030 and 2050 under three scenarios. These can be roughly summarized as: Low, business-as-usual; Medium, improved forestry and cropping management practices; and High, the medium scenario plus advances in research and innovation. The report acknowledges significant uncertainty in later year projections, so we focus on the medium 2030 availability scenario. Although FuelsEurope has marketed the results of the study as European sustainable biomass potential, we find that many of the feedstocks included in ICL’s estimates are highly unsustainable.

In the study, ICL’s biomass projections only include “advanced” or second-generation biofuel feedstocks as defined under the Annex IX list of the Renewable Energy Directive (RED). Most of these feedstocks are considered to be generally more sustainable and lower-carbon than first-generation, food-based alternatives, but not all of them. Perhaps the clearest violator is stemwood, simply defined as “the wood of the stem(s) of a tree.” Felling trees for fuel and power releases large quantities of carbon that cannot be replaced within a reasonable timescale. In some cases, it may take over 300 years for re-growing forests to reabsorb lost carbon stocks. In their study, ICL counts the amount of stemwood from net tree growth in Europe as available for biofuel—i.e. how much can be harvested without reducing total forest carbon stocks. While this may sound sustainable at first, removing any forest carbon stock that would otherwise have remained there results in a high carbon debt. It’s better to let Europe’s forests grow and keep sucking in CO2 than to release that CO2 back to the atmosphere. Despite this well-known climate risk, stemwood accounts for the largest source of biomass resource availability under ICL’s medium growth scenario. Removing these quantities from study estimates would reduce total availability projections by roughly one third.

Another unsustainable feedstock included in ICL’s projections are tree stumps. Harvesting tree stumps results in significant soil carbon and biodiversity losses. The ICL study acknowledges this point, describing the high risks of biodiversity loss as well as Member State level regulations that prevent stump removal under sustainable forest management practices—but they still include stumps.

The use of several other feedstocks included in the ICL analysis for biofuel production would result in indirect sustainability impacts. Secondary forest residues, including wood chips, saw dust, and black liquor, are entirely used up within the forestry sector, either burned at sawmills for heat and power production, or used to produce composite wood products like particleboard. If these sawmill residues are instead diverted to biofuel production, the mills will have to find other sources of heat, power—and these might be fossil fuels. Alternatives to particleboard such as polypropylene and plywood sourced from stemwood also have high emission footprints. The risk of high indirect emissions impacts also applies to agricultural residues like cereal straw. Agricultural residues are used in animal feed and bedding, mushroom cultivation, and heat and power production. A study by Searle and Malins found that competing uses for these materials accounted for roughly 42% of total harvestable biomass in 2020 after factoring in in-situ retention rates to improve soil quality. While the ICL study states that it subtracts biomass needed for competing uses based on results from the CAPRI economic model, a closer look reveals that CAPRI does not explicitly account for competing feedstock uses other than cereal straw consumption in livestock feed. So, ICL failed to account for most competing uses of biomass after all. Thus, a large portion of 2030 agriculture and forestry residue estimates included in ICL’s analysis are quite unsustainable.

Other assumptions from the ICL study that challenge sustainability principles include the inclusion of 5 million tonnes of used cooking oil (UCO) imports from China and up to 0.5 million tonnes of UCO imports from Japan. It is widely believed (and in some cases verified) that many UCO imports are fraudulent virgin vegetable oil like palm oil. In addition, increased demand for UCO imports could displace them from competing uses like soap-making, resulting in increased virgin vegetable oil consumption in those uses. The ICL predictions for cellulosic energy crop potential grown on degraded land also far exceed other literature estimates. While ICL estimates 65 million tonnes of energy crop biomass in 2030, a study by the Institute for European Environmental Policy found that only a maximum of 17 million dry tonnes of biomass could be mobilized, still with significant environmental impact including biodiversity loss.

FuelsEurope has made sweeping claims that Europe possesses enough biomass resources to both technically and sustainably meet the entire 2030 and 2050 fuel demand from Europe’s aviation and maritime sectors, and a portion of on-road fuel demand. Low-carbon liquid fuels do have a role to play in climate mitigation, especially in hard to decarbonize sectors like aviation. However, the question comes down to what makes a biofuel feedstock both low-carbon and sustainable. Unfortunately, sustainability risks are not limited to first-generation biofuels and policymakers have been slow to update regulations to fully account for high-risk feedstocks. Under a shrinking carbon budget, industry and government must scale up solutions that are unequivocally sustainable—for the road sector, this means zero-emission battery and fuel cell electric vehicles powered by renewable electricity and green hydrogen. There’s no way around it: pretending there will be enough sustainable biofuels to keep running internal combustion engines is a major—and dangerous—distraction.