Applying a science‐based systems perspective to dispel misconceptions about climate effects of forest bioenergy

Abstract

The scientific literature contains contrasting findings about the climate effects of forest bioenergy, partly due to the wide diversity of bioenergy systems and associated contexts, but also due to differences in assessment methods. The climate effects of bioenergy must be accurately assessed to inform policy‐making, but the complexity of bioenergy systems and associated land, industry and energy systems raises challenges for assessment. We examine misconceptions about climate effects of forest bioenergy and discuss important considerations in assessing these effects and devising measures to incentivize sustainable bioenergy as a component of climate policy. The temporal and spatial system boundary and the reference (counterfactual) scenarios are key methodology choices that strongly influence results. Focussing on carbon balances of individual forest stands and comparing emissions at the point of combustion neglect system‐level interactions that influence the climate effects of forest bioenergy. We highlight the need for a systems approach, in assessing options and developing policy for forest bioenergy that: (1) considers the whole life cycle of bioenergy systems, including effects of the associated forest management and harvesting on landscape carbon balances; (2) identifies how forest bioenergy can best be deployed to support energy system transformation required to achieve climate goals; and (3) incentivizes those forest bioenergy systems that augment the mitigation value of the forest sector as a whole. Emphasis on short‐term emissions reduction targets can lead to decisions that make medium‐ to long‐term climate goals more difficult to achieve. The most important climate change mitigation measure is the transformation of energy, industry and transport systems so that fossil carbon remains underground. Narrow perspectives obscure the significant role that bioenergy can play by displacing fossil fuels now, and supporting energy system transition. Greater transparency and consistency is needed in greenhouse gas reporting and accounting related to bioenergy.

Time is of the essence when it comes to forest bioenergy

“…The latest IPCC report (IPCC, 2021) reinforces a sense of urgency concluding that 'unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach'. We argue this strengthens the case for limiting subsidies to bioenergy projects with short payback periods, a conclusion that Cowie et al (2021) specifically reject.…”

“…Debate continues in this journal on the climate impacts of burning woody biomass from forests. A recent review by Cowie et al (2021, GCB Bioenergy, 13(8), 1210-1231 addressed what it called 'misconceptions' in papers by us and other authors that examined issues of carbon debt and when burning forest biomass for energy could have a net climate benefit. This letter re-emphasizes the critical importance of the time dimension in assessing impacts, and takes particular issue with Cowie et al's lack of concern over substantial delays in reducing emissions and increasing the risks of crossing climate tipping points.…”

“…This letter re-emphasizes the critical importance of the time dimension in assessing impacts, and takes particular issue with Cowie et al's lack of concern over substantial delays in reducing emissions and increasing the risks of crossing climate tipping points. Cowie et al (2021) provide an interpretation of the science to support the status quo whereby forest biomass is treated generically as climate-friendly renewable energy, thereby attracting substantial subsidies from renewable energy budgets. Their review pays particular attention to the undersigned authors' papers but draws different policy conclusions than those in our original papers, generally rejecting calls for tighter restrictions on the use of forest bioenergy in electricity generation.…”

“…EASAC, 2020; Raven et al, 2021). Rather than repeat these arguments here, we wish to point to recent events that are relevant to two key arguments in Cowie et al (2021).…”

“…On a second issue, Cowie et al (2021) downplay risks of crossing tipping points, as in the following 'Risks related to climate tipping points are sometimes raised in relation to the timing of GHG savings: crossing thresholds, for example, associated with forest dieback or thaw of permafrost, could lead to large, irreversible changes in the global climate system. A recent study found a low probability of crossing a tipping point in the global climate system if warming does not exceed 2°C.…”