Pruitt’s parting shot: a Clean Power Plan that will actually increase CO2 emissions

After suspending rollout of the Obama administration’s Clean Power Plan, EPA is releasing a scaled-down version to comply with the legal obligation to reduce CO2 emissions (section 111(d) of the Clean Air Act).  The New York Times[1] reports that according to industry insiders, the plan “would recommend regulating the emissions of individual coal plants, which would call for modest upgrades, such as improving efficiency or substituting fuel.”

Unfortunately, if the plan allows power plants to substitute biomass for coal, the result will be a decrease in plant efficiency and an increase in CO2 emissions.  As an extra bonus, substituting biomass for coal could significantly increase forest harvesting – pretty much a triple win for the Trump administration!

The Pruitt/Wheeler CPP is already much less ambitious than the Obama-era plan because rather than requiring emission reductions from the power sector as a whole, thus spurring wind and solar, the plan will solely focus on how individual plants can reduce emissions “inside the fence.”

Like the Obama era plan, the proposal requires increased efficiency at coal plants. According to industry sources,[2] a 1% increase in net unit efficiency results in a 2.7% reduction in CO2 emissions at constant power output for a typical pulverized coal-fired plant. The Obama plan was looking for an average 6% increase in efficiency in coal plants; we don’t know yet what the target will be under the proposed plan.

The primacy of efficiency is foreshadowed in the compliance plan Pruitt issued in 2014 when he was Attorney General in Oklahoma, which states “The only way to achieve cost-effective emission reductions for a coal generator would be to improve the efficiency of the unit, since increased efficiency translates into reduced CO2 emissions per unit of electric output.”[3]

One of the main ways to increase efficiency is to burn coal with less moisture in it, because boiling off fuel moisture takes energy and thus reduces the amount of “useful energy” available to generate electricity. However, co-firing biomass with coal generally increases COemissions, because freshly harvested wood is about 50% water by weight, in contrast to the coal typically burned in the US, which is 15 – 20% water by weight.[4]

The following table shows the theoretical emissions per megawatt-hour for power plants fueled by gas, coal, and biomass (actual emissions are probably higher, because many factors serve to increase energy loss and emissions, but none can reverse thermodynamics to wring more energy out of fuel than is present).

emissions chartFigure 1. Emissions from power plants. See endnotes for references.[5]

A power plant burning 100% biomass emits around 37% to 65% more CO2 per megawatt-hour than a plant burning 100% coal. Replacing some portion of fuel at a coal plant with biomass – “co-firing,” as appears to be proposed under the Trump CPP – will increase the amount of CO2 emitted per megawatt-hour as the proportion of biomass increases.  Likewise, decreased efficiency when burning biomass increases particulate pollution emitted per megawatt-hour, and often ground-level ozone precursors like nitrogen oxides and volatile organic compounds, as well.

Increased CO2 pollution from bioenergy isn’t a problem for the Pruitt/Wheeler EPA, however, because under a new policy,[6] the biomass CO2 simply won’t be counted.  In response to a Congressional directive, Pruitt proclaimed in April 2018 that “EPA’s policy in forthcoming regulatory actions will be to treat biogenic CO2 emissions resulting from the combustion of biomass from managed forests at stationary sources for energy production as carbon neutral.”[7]

There is plenty of peer-reviewed literature[8] showing that burning biomass increases net CO2 emissions, even under the best-case scenario when “forestry residues” are used as fuel. And it should be obvious to most that cutting forests deliberately for fuel, and thus liquidating forest carbon into the atmosphere in the name of mitigating climate change, is nothing short of insane.

Site1Figure 2. A North Carolina wetland forest after clearcutting by the wood pellet industry. Photo courtesy of Dogwood Alliance.

It doesn’t matter how much the Pruitt/Wheeler EPA huffs and puffs, there’s no getting around the laws of thermodynamics – burning biomass will generally degrade facility efficiency and increase emissions.  The degradation in efficiency is not as extreme when co-firing very dry biomass with coal, such as the wood pellets that the US ships to Europe as fuel which are about 10% moisture by weight, but drying biomass requires expending energy, a process that emits large amounts of CO2.

Co-firing biomass to “reduce” coal plant emissions is also a loser  because for an “inside the fence” strategy, it sure relies a lot on activity “outside the fence”- that is, the idea that trees growing somewhere else are taking up atmospheric CO2 from biomass burning, offsetting its effect on the atmosphere.

EPA already tried arguing this once, and lost. After CO2 became a regulated pollutant under the Clean Air Act (CAA), EPA tried to exempt biomass CO2 from regulation under the CAA’s PSD and Title V power plant permitting programs, and was consequently sued in the DC Circuit court by a coalition of environmental groups in 2013. EPA lost, with two of the three judges ruling that the Agency has no statutory authority to exempt biomass CO2 from regulation under the Clean Air Act.

In a concurrence,[9] Judge Brett Kavanaugh (yes, that Brett Kavanaugh) stated that
“There is zero basis in the text of the Clean Air Act for EPA to distinguish biogenic carbon dioxide from other sources of carbon dioxide that EPA is required (under our precedent) to regulate for purposes of the PSD and Title V permitting programs.”
EPA has sought to exempt biomass CO2 from regulation using administrative doctrines, but,

“The doctrines do not trump the fact that EPA simply lacks statutory authority to distinguish biogenic carbon dioxide from other forms of carbon dioxide for purposes of the PSD and Title V permitting programs.”

Kavanaugh observed that EPA favored treating bioenergy as carbon neutral because the agency “thinks that regrowth of plant life – and the resulting recapture of carbon dioxide – might ‘offset’ emissions of biogenic carbon dioxide.”

However, such “outside the fence” measures are not allowed under the Clean Air Act “But the statute forecloses that kind of ‘offsetting’ approach because the statute measures emissions from stationary sources that ’emit’ (or have the potential to emit) air pollutants. See 42 U.S.C. §§ 7475(a), 7479(1). The statute does not allow EPA to exempt those sources’ emissions of a covered air pollutant just because the effects of those sources’ emissions on the atmosphere might be offset in some other way.”

Given that the Obama EPA was also threatening to use bioenergy as a compliance measure under the CPP, what’s different now? We won’t know until the new CPP is issued, but the new policy of EPA to treat all biomass from managed forests as carbon neutral is a big departure from EPA’s stance previously, which at least acknowledged that bioenergy generating emission reduction credits (ERCs) under the CPP must be evaluated for its carbon impact:

“While the EPA believes it is reasonable to consider generation from these fuels and technologies to be forms of RE generation, the fact that they can produce stack emissions containing CO2 means that a section 111(d) plan seeking to permit use of such generation to serve as the basis for issuance of ERCs must include appropriate consideration of feedstock characteristics and climate benefits. Specifically, the use of some kinds of biomass has the potential to offer a wide range of environmental benefits, including carbon benefits. However these benefits can only be realized if biomass feedstocks are sourced responsibly and attributes of the carbon cycle related to the biomass feedstock are taken into account.”[10]

The wood pellet industry has been salivating for years at the prospect of expanding markets in the United States. Now they may get their chance.



Figure 3. Advertisement for wood pellet conference in 2015, emphasizing how industrial wood pellets can help with CPP compliance.
The East Coast just came out of an extreme heatwave that’s actually killed people as far north as Montreal.[11]  During the heatwave, a snapshot of electricity data from ISO New England[12] showed that just 6% of electricity was generated from renewables, and of that 6%, a full 71% was from burning wood and garbage. Figure 4. NE ISO data on electricity generation.
More power plant pollution probably isn’t what the American people had in mind for the Clean Power Plan, but under the Trump administration, that’s what they may get.


[3] Page 7 of “The Oklahoma Attorney General’s Plan” posted at
[4] See entries for “bituminous” coal and “anthracite” coal at
[5] References for power plant emissions table:
CO2 per MMBtu

a, b, c : from EIA at  Value for coal is for “all types.”  Different types of coal emit slightly more or less.
d:  Assumes HHV of 8,600 MMBtu/lb for bone dry wood (Biomass Energy Data Book v. 4; Oak Ridge National Laboratory, 2011. and that wood is 50%  carbon. Efficiency
a: DOE National Energy Technology Laboratory: Natural Gas Combined Cycle Plant F-Class (
b: International Energy Agency.  Power Generation from Coal: Measuring and Reporting Efficiency Performance and CO2 Emissions.
c. EIA heat rate data show the average efficiency for the U.S. coal fleet in 2016 was 32.5% (
d:  ORNL’s Biomass Energy Data Book  (; page 83) states that actual efficiencies for biomass steam turbines are “in the low 20’s”; PFPI’s review of a number of air permits for proposed biomass power plants reveals a common assumption of 24% efficiency.
[8] Eg, see Booth, M. S. (2018). “Not carbon neutral: Assessing the net emissions impact of residues burned for bioenergy.” Environmental Research Letters 13(3): 035001.
Domke, G. M., et al. (2012). “Carbon emissions associated with the procurement and utilization of forest harvest residues for energy, northern Minnesota, USA.” Biomass and Bioenergy 36: 141-150.
Laganière, J., et al. (2017). “Range and uncertainties in estimating delays in greenhouse gas mitigation potential of forest bioenergy sourced from Canadian forests.” GCB Bioenergy 9(2): 358-369.
[10] , page 492

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