Fuels burned by the US industrial and non-industrial bioenergy sectors, 2001–2016. Wood burning for electricity generation in the non-industrial sector increased by about 60% from the beginning of the period. Graphic: Booth, 2018 / Environmental Research Letters

By Justin Catanoso
2 May 2018
(Mongabay) – For the past ten years, Mary Booth, an ecologist with the Partnership for Policy Integrity in Pelham, Massachusetts, has immersed herself in the complex, nuanced, politically charged world of international carbon emissions accounting models as if the planet’s fate depends on it.
In many ways, it does.
Booth studies how countries count and report their emissions. In particular, she evaluates whether generating energy via the burning of wood pellets, or biomass, puts less carbon into the atmosphere than burning coal. In a rising trend, countries, especially in the European Union and United Kingdom, are converting existing coal-fired power plants to burn wood — a renewable, albeit controversial, fuel source.
Emissions accounting helps determine whether or not nations are on target to achieve their voluntary Paris Agreement reduction goals. That agreement also represents the global community’s pledge to keep the world from heating up by just 1.5 degrees Celsius (2.7 degrees Fahrenheit) by 2100 from a 1900 baseline (we’ve already warmed 1 degree Celsius).
Emissions tallies are reported regularly to the United Nations Intergovernmental Panel on Climate Change, or IPCC. But those figures aren’t just numbers on paper or political aspirations. The data, if accurately calculated, tell us how much greenhouse gas nations are actually putting into the air, and those combined totals help us know whether we are on target to avert climate change catastrophe.
Booth is darkly pessimistic — a price she pays for knowing too much, she told me.
“This is a message that no one has said yet. It’s what I believe to be true: there may not be a pathway to 1.5 [degrees] anymore — at all. Carbon capture and storage is a fantasy,” Booth told me in a series of interviews for Mongabay. “Growing forests may not work fast enough. We’re not reducing emissions fast enough. The sooner that story gets told, the sooner people understand what’s really required to keep the earth from burning up.” […]Booth’s research — Not carbon neutral: Assessing the net emissions impact of residues burned for bioenergy, published this February in the journal Environmental Research Letters — helps answer some thorny questions critical to our energy and carbon future.Her study examines the net CO2 emissions of biomass burned to replace coal at the UK’s massive Drax power stations and other EU power plants. Combined, those energy facilities consume tons of wood each year.One major finding, right out of the gate: Booth reports that — contrary to a largely accepted view — wood pellets aren’t sourced mainly from fallen limbs and lumber waste called residue, but rather from whole trees. However, she based her study on residue-derived wood pellets anyway because the biomass industry “so often claims residues are a main pellet source.”Even based on the false assumption that only wood waste, not whole trees, are being burnt, Booth found that “up to 95 percent of cumulative CO2 emitted [by the biomass burning power plants] represent a net addition to the atmosphere over decades.” In other words, biomass is not carbon neutral.More disturbing: Booth’s research opens up the IPCC to charges that its policymaking decisions regarding emissions accounting have been politicized — crafted by negotiators to include built-in loopholes that allow nations to underreport certain emissions while appearing to achieve their carbon-reduction targets.In particular, both the UK and EU appear to have slipped through a large loophole in order to “disappear” real emissions from their carbon accounting, as one source told me, thus undermining the Paris Agreement’s critically important carbon-mitigation strategies. [more]

UN forest accounting loophole allows CO2 underreporting by EU, UK, USCumulative net carbon dioxide emissions for four scenarios of U.S. wood-pellet burning. Graphic: Booth, 2018 / Environmental Research Letters

ABSTRACT: Climate mitigation requires emissions to peak then decline within two decades, but many mitigation models include 100 EJ or more of bioenergy, ignoring emissions from biomass oxidation. Treatment of bioenergy as ‘low carbon’ or carbon neutral often assumes fuels are agricultural or forestry residues that will decompose and emit CO2 if not burned for energy. However, for ‘low carbon’ assumptions about residues to be reasonable, two conditions must be met: biomass must genuinely be material left over from some other process; and cumulative net emissions, the additional CO2 emitted by burning biomass compared to its alternative fate, must be low or negligible in a timeframe meaningful for climate mitigation. This study assesses biomass use and net emissions from the US bioenergy and wood pellet manufacturing sectors. It defines the ratio of cumulative net emissions to combustion, manufacturing and transport emissions as the net emissions impact (NEI), and evaluates the NEI at year 10 and beyond for a variety of scenarios. The analysis indicates the US industrial bioenergy sector mostly burns black liquor and has an NEI of 20% at year 10, while the NEI for plants burning forest residues ranges from 41%–95%. Wood pellets have a NEI of 55%–79% at year 10, with net CO2 emissions of 14–20 tonnes for every tonne of pellets; by year 40, the NEI is 26%–54%. Net emissions may be ten times higher at year 40 if whole trees are harvested for feedstock. Projected global pellet use would generate around 1% of world bioenergy with cumulative net emissions of 2 Gt of CO2 by 2050. Using the NEI to weight biogenic CO2 for inclusion in carbon trading programs and to qualify bioenergy for renewable energy subsidies would reduce emissions more effectively than the current assumption of carbon neutrality.

Not carbon neutral: Assessing the net emissions impact of residues burned for bioenergy