Commenting on EPA expert panel report on biomass carbon accounting

The EPA’s Biogenic Carbon Emissions Panel held a teleconference call today to allow the public to comment on its latest deliberative draft. Below is a slightly expanded version of the comments I delivered on behalf of NRDC. (My oral comments were abridged to keep to the 3-minute time slot allotted to each speaker).  


Hello and thank you for the opportunity to comment on the Biogenic Carbon Emissions Panel’s March 13 deliberative draft on behalf of the NRDC.

The Science Advisory Board (SAB) has been charged with helping EPA develop a biogenic carbon accounting framework that can effectively assess the climate impacts of bioenergy combustion within the constraints of the Clean Air Act.

NRDC has concerns that while PSD permitting agencies may have some latitude to consider the special characteristics of bioenergy in making “best available control technology” (BACT) determinations, permitting agencies do not have legal authority exclude major sources from the requirement to obtain PSD permits by taking into account off-site carbon sequestration.  We have expressed this view in our recently filed brief in CBD v. EPA, challenging the three-year total exemption of biogenic CO2 sources from permitting requirements.

A framework for considering the lifecycle characteristics of biogenic CO2 emissions during BACT calls for a regulatory approach that is able to consider forest regrowth as mitigating net emissions at the smokestack, but which can be applied to a single facility and at a single point in time. 

NRDC recognizes the challenges associated with this charge, given the fact that many forms of bioenergy entail increased emissions upfront and re-growth, if it happens, occurs over decades or longer. In its Draft Accounting Framework, the EPA sought to deal with the inter-temporal nature of biomass regrowth by trading “time” for “space”—proposing to adjust the smokestack carbon emissions of a biomass-burning facility based on an assessment of regional forest stocks. The panel rightly rejected this approach as scientifically unjustified. We commend the SAB for this and for continuing to grapple with the foundational scientific components of an accounting framework that can assess what the atmosphere “sees” when a facility burns biomass for energy production.

In seeking an alternative system that would allow EPA to make a judgment about the climate impact of a biomass burning facility upfront while recognizing that some sequestration will occur down the road, the March 13th draft of the SAB’s report embraces an approach developed by Cherubini et al. The Cherubini approach calculates the effective global warming potential (GWP) of bioenergy as a function of biomass rotation length in order to generate a factor that can be applied to smokestack emissions to discount for future sequestration. This factor is calculated by comparing the radiative forcing from burning fossil fuels to the radiative forcing from burning biomass and then re-growing it.

While Cherubini provides a useful framework for evaluating the climate impacts of emissions from biomass once they occur, this does not mean it should be used as a basis for accounting for emissions and removals in a policy context. There are three main reasons for this:

First, a Cherubini-style GWP factor must be calculated with reference to a specific timeframe but the choice of timeframe is a policy decision.

Second, the factors provided by Cherubini do not capture key scientific and policy concerns that will influence how much damage global warming pollution causes.

Third, given a requirement to reduce carbon emissions, regulated entities will decide on the timing of their emission reduction investments based on market considerations, not carbon cycle dynamics.

When considering the timeframe for any analysis, we believe it is critical that the SAB acknowledge that a reduction in carbon emissions or a removal of carbon from the atmosphere today is worth more than the same reduction or removal taking place in the future. Whether considering emissions from biomass or fossil fuels, an emission of 100 tons of carbon today followed by removal of one ton per year for 100 years is very different from not emitting in the first place.

The most straightforward way to address this difference is to account for the actual emissions and actual removals as they occur. Doing so avoids the need to select an arbitrary timeframe and allows sources to evaluate for themselves the value of time-shifting emissions and removals.

Unfortunately, while the draft acknowledges that any timeframe is arbitrary, it focuses a great deal of attention on a 100 year time horizon and even emphasizes that EPA should consider timeframes beyond 100 years. We believe the SAB’s report should be clearer in stating that any one timeframe for assessing the impacts of carbon emissions is arbitrary, and should be more balanced in advising EPA to consider multiple timeframes, including ones shorter than 100 years. The IPCC included calculations for 20, 100, and 500 years and has always considered other timeframes no more or less relevant.

Once a range of emissions factors are calculated, it is important to lay the science and policy concerns over them. GWP factors do not capture key issues such as climate feedback loops, tipping points and path dependency, or risks associated with implementation. With perfect information about future emissions rates, biomass re-growth and the damage climate change will cause, we could make perfect tradeoffs between increased emissions now and re-absorption later. However, there are enormous uncertainties around land management commitments that extend beyond just a few years, making implementation extremely difficult and monitoring potentially very costly.

Given the complexity of monitoring landscape management commitments over long timeframes, NRDC believes the simplest and most defensible approach (scientifically and probably legally) for regulating biogenic CO2 under this framework is to account for actual carbon emissions at the smokestack and actual land-based carbon removals as they occur. The SAB should advise the EPA on the science underlying this type of annual carbon accounting approach. At minimum, the SAB should drive home the urgency of near-term reductions.