Well, Is Bioenergy Carbon Neutral Or Not?

Guest Blog | March 2, 2012 | Clean Transportation, Energy Policy
I admit it. I’ve been impatient. For about two years now I’ve been carping to anyone who will listen that we don’t have sufficient scientific studies here in the Southeast to truly understand the implications of dramatically expanded biomass consumption. Yet the fossil fuels that biomass might replace continue to fill our atmosphere with climate forcing greenhouse gases (GHGs).

I attribute my impatience to the arrival of my son 19 months ago. Having kids changes our perspectives. I started asking myself, does the work I do today make my son’s world a better place? Will today’s biomass-related carbon emissions be re-sequestered by the time he gets to college? Is that even the relevant timescale? Can we transition to cleaner energy quickly enough?

My brain itches with questions: Would a thousand megawatts of new biopower capacity in our region help or harm the climate? Would a hundred new biofuels refineries consuming pulpwood help reduce our vehicle GHG emissions before it’s too late? What will be the impact on the climate of exporting 300 million tons per year of wood pellets made from large diameter logs?

I regularly receive jabs from my left and right sides from people who insist, “it’s simple – biomass is always carbon neutral!” OR “burning biomass will never be climate friendly.”

I really wish it were that simple, friends.

Decades of science show us that biopower from forestry residuals has been helpful to reducing our total greenhouse gas emissions. However, equally clear in recent studies is the fact that all energy sources have costs, and some take longer to repay these costs: Not all biomass energy is ‘climate friendly’ in the short term.

Fortunately, my impatience is a little relieved. Recently, there have been four noteworthy efforts to grapple with similar questions surrounding biomass.

In January, the Society of American Foresters (SAF) made public a task-force report entitled “Managing Forests because Carbon Matters: Integrating Energy, Products, and Land Management Policy.”

A new paper from Duke University’s Nicholas Institute, soon to be published in the journal Biomass & Bioenergy, focuses on the effect of assessment scale and metric selection on the greenhouse gas benefits of woody biomass. It sounds wonky, but stick with me.

In mid February, a collaborative of environmental groups published “Biomass Supply and Carbon Accounting for Southeastern Forests,” which is a first-of-a-kind breakthrough for reasons I’ll explain.

Finally, the U.S. Environmental Protection Agency (EPA)’s Scientific Advisory Board appears to be making significant progress in their work to advise EPA during the “three year deferral” on the question of how to regulate biogenic carbon emissions.

For those who care about biomass, forests, or the climate, each of these papers is worth reading.

SAF: Originally published in their subscription-only Journal of Forestry, this task-force report was a supplement to their October/November 2011 edition. A very impressive and comprehensive summary of the science of forest carbon and life-cycle benefits of intelligent forestry.

SAF Report: According to life-cycle analysis, wood frame construction is good for the climate, whereas steel-frame construction is not.

But, what does SAF say about bioenergy? Regrettably, the Task Force report does not address the debates over bioenergy efficiency, life cycle analysis (LCA) boundaries, or time-lag before re-sequestration. It would have been helpful to have the Society of American Foresters acknowledge the fact that not all bioenergy delivers unquestionable climate benefits in the near term.

The SAF Task Force argues that forestry and energy policy should be coherent in the recognition of the many climate benefits of forest products and well-managed forests. “Growing more forests and keeping forests as forests are only part of the solution, because focusing solely on the sequestration benefits of the forests misses the important (and substantial) carbon storage and substitution GHG benefits of harvested forest products, as well as other benefits of active forest management.” For example, the Task Force urges increased utilization of forest products in substitution for steel, concrete, and other energy intensive, durable materials. The take-away? We need to manage forests better to get the most climate benefit, and using more forest products can also help.

Nicholas Institute: With this new paper released by the Nicholas Institute at Duke University, Christopher Galik and Bob Abt deliver a dramatic new level of clarity to the fact that the spatial scale being considered in life cycle analysis really matters. It really matters. So, in my opinion, if you want to look for bias in biomass LCA studies, look for studies that cast a very broad or very narrow geographic lasso. (Now, that wasn’t so wonky, was it?)

BERC/ForestGuild/SIG/NWF/SELC: On that point, I am intrigued that the new BERC study casts a lasso in an innovative way, attempting to delineate the impacts within the actual zone of supply for each given biomass plant. We at SACE are pleased to see this new approach, called “landscape-woodshed,” despite the challenges inherent in such a dynamic model.

But I’m getting ahead of myself. First I must recognize the unique contributions of this new report by BERC, Forest Guild, and SIG. It is the first of its kind, specifically addressing bioenergy in the Southeast, our unique biomass resources and forestry practices. Given the dearth of such analysis for our region, this first attempt is admirably thorough, grappling with the complexities of bioenergy based on some realistic assumptions (e.g., many trees are grown to be harvested). We at SACE want to commend SELC and NWF for commissioning the study, and the Doris Duke Charitable Foundation for supporting it. It will undoubtedly help push the field forward.

The study has gotten some press coverage for illustrating the concern that new bioenergy industries might create a big new carbon debt before delivering a dividend of GHG reductions. But actually digging into the study gives the reader a different impression, with four clear take-aways:

BERC Report: Figure 18 reassures us that current biomass industries in the Southeast are indeed helping the climate – biopower generation today is “generally producing improved atmospheric carbon balance.”

1) Current bioenergy capacity is un-arguably reducing GHGs. (See Figure 18 at right.)

2) There is plenty of biomass in the Southeast to help us comply with a national RES, so future growth is possible.

3) European pellet demand is clearly an issue of market competition, domestic energy security, and ecological impacts, and

4) Bioenergy technology (e.g., CHP and other more efficient options) matters more than the balance of feedstocks (pine plantations vs hardwoods).

The overarching message of the BERC report is that the question of biogenic carbon impact is one with diverse and dynamic answers depending on the specific assumptions in the model. Biomass is a complex business, and predicting it is very challenging.

BERC Report: Figure 22 – Expanded bioenergy industries, if poorly sited, could result in a carbon debt in the near term.

The new model highlights a time lag between new bioenergy production and the landscape’s ability to capture that carbon. Some have called this a “spike” in carbon emissions. Indeed, the report is persuasive on the point that future bioenergy growth could have impacts both on the climate and on current biomass and forestry industries.

This is because the model assumes many new biopower plants and pellet mills will be built in close proximity to one another.

Also, the model aggregates different end-uses of biomass (i.e., pellets and biopower) together, blurring the climate and forestry impacts of each. Unfortunately, in this way the report does not present a clear picture for U.S. and Southeastern policymakers to discern what kind of bioenergy is actually beneficial. [For example, if you want to learn the climate benefit or detriment of new biopower as distinct from wood pellets, you’ll have to dig deep in the Technology Pathways chapter, pages 48-65.]

So, is bioenergy carbon neutral or not?

Comparing the magnitude of carbon flux in these two graphs is striking: Figure 18 shows current bioenergy delivering a dramatic reduction of carbon; Figure 22 shows an increase of carbon emissions, but only marginally exceeding those of fossil fuels. Growth of future bioenergy production is highly uncertain, and it is unlikely to occur in the manner this model projects (i.e., projects sited in dense proximity). From this perspective, it is not so clear that new biopower would be so harmful to the climate. But there are multiple factors that will determine the level and timing of benefits. That is the core issue.

Let me drill deeper here: To populate the model, the authors assumed that 22 new biomass facilities will be built in proximity to existing biomass industries, without revealing the criteria for project selection. This is a compelling hypothetical, asking “what if bioenergy grows rampantly and densely?” We appreciate the value of this paper, mainly in asking a worst-case, “what-if?”

In reality, though, risk averse investors might choose to build new projects much farther away from existing facilities, thus improving their profitability and reducing the overall climate impacts. Also, judging from the current lack of forward motion for the majority of biomass projects, we might not ever see 22 new biomass facilities get built in this region. (More on this in June when SACE releases our progress report on bioenergy in the Southeast.)

Many questions remain for further investigation, and the report helpfully suggests directions for additional research. For us the paper raises questions about the relevant timescale for reductions of very long lived GHG emissions.  Is 30 to 50 years the appropriate frame for a greenhouse gas (CO2) that remains active in the atmosphere for 200 to 300 years?

It would also be helpful to see continuation of this work, analyzing each type of bioenergy apart from the others: I.e., what is the climate benefit or detriment of new standalone biopower? Of new biomass CHP? Of new pellet mills? The value of SIG’s model has now been established, and different assumptions in future runs could be still more eye-opening.

These criticisms aside, the model and the report is a first of its kind for the Southeast region. Overall, BERC et al succeed in showing us that individual projects ought not be considered in isolation, and that energy policy needs to recognize and address potential climate and environmental impacts at all scales: local, regional, national (and international). The report recommends that project approval and policies should address forest management practices, because improved forest management can reduce the climate impact of bioenergy.

We certainly agree with this. And we also note the overlap between the the SAF report and the BERC report in this regard. They both emphasize that the key to climate mitigation is getting forestry policy right. We hope EPA, Congress, and state policymakers are taking note.

We need to use this information and consider it, and test it with additional modeling, to inform policymaking. As a region with such a wealth of biomass, we need the best biomass policies in the nation.

Finally, a few words about the EPA’s Science Advisory Board (SAB): The good news is that this advisory panel is making progress in helping EPA through this challenging process of the Three Year Deferral. The report issued in mid January is a deliberative draft, in response to EPA’s Framework for Biogenic Accounting. This draft response clearly shows that the SAB is grappling with these concepts of how to regulate biogenic carbon emissions, and there are still areas of disagreement among the panel. There was, however, agreement on the fact that “carbon neutrality cannot be assumed for all biomass energy a priori.” There was also agreement that EPA’s proposed Framework lacked scientific basis.

The SAB’s draft response offered three suggestions for how the Framework could be improved:

1) create different accounting factors for individual feedstocks (i.e., treating forestry residuals different from large diameter logs);

2) allow certification systems to ensure sustainability; and

3) create carbon offsets, where biomass consumers can contract with landowners to offset their emissions via forest protection and regrowth.

The EPA SAB will meet again in March to finalize their recommendations to EPA.

Biogenic carbon emissions are clearly complex, and regulation will be very difficult to work out. But it is so crucial that we get it right. There is too much to be lost by removing this option from our toolkit for fighting climate change.

Thanks to Anne Blair and John Wilson for their input on this blog.

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