Paradigm Shift? The ‘Belief’ That Bioenergy Is Climate-Friendly Is Now Recognized As A ‘Major Error’

Governments vociferously promote bioenergy as renewable, sustainable, and carbon-neutral. But scientists are increasingly characterizing this “belief” as a “major error”, as bioenergy generates more CO2 emissions per kWh than burning coal does, and the projected rapid growth in bioenergy will serve to ‘increase atmospheric CO2 for at least a century’ as well as clear forests and destroy natural ecosystems.

DeCicco and Schlesinger, 2018

Opinion: Reconsidering bioenergy
given the urgency of climate protection

The use of bioenergy has grown rapidly in recent years, driven by policies partly premised on the belief that bioenergy can contribute to carbon dioxide (CO2) emissions mitigation. However, the experience with bioenergy production and the pressure it places on land, water, biodiversity, and other natural resources has raised questions about its merits. Recent studies offer a lesson: Bioenergy must be evaluated by addressing both the stocks and flows of the carbon cycle.”
[A] major reprioritization of climate-related research, policy, and investment is urgently required, a move away from bioenergy and toward terrestrial carbon management (TCM). Researchers and policymakers must pursue actionable mitigation approaches that have the best chance of significantly reducing atmospheric CO2 concentrations in the near and medium term.”
“Bioenergy displaces land from prior uses, resulting in both direct and indirect land-use change. This leads to the difficult conundrum of carbon debt, i.e., the time it takes for the release of carbon stocks linked to bioenergy expansion to be paid back through future carbon uptake, which can be decades. Moreover, the realities of bioenergy production exacerbate the effects of industrial-scale agriculture on soil health, water quality, biodiversity, and other ecosystem services.”
The assumption that bioenergy is inherently carbon-neutral, which is based on static forms of carbon accounting, is a major error (Haberl et al., 2012). Viewed objectively, it is quite a sweeping assumption: It asserts that a carbon flow into the atmosphere at one place and time (from bioenergy combustion) is automatically and fully offset by carbon uptake at another place and time (on ecologically productive land). Scientifically speaking, there is neither a sound basis nor a need to make this assumption. The extent to which the CO2 emitted from bioenergy use is balanced by CO2 uptake is an empirical question.”
“In short, a sound understanding of carbon-cycle dynamics shows that now and for the reasonably foreseeable future, the promotion of bioenergy is ill-premised for climate protection. This is particularly true if one respects the limited amount of ecologically productive land available for supplying food and fiber as well as sustaining and restoring biodiverse habitats.”

Sterman et al., 2018

Does replacing coal with wood lower CO2 emissions?
Dynamic lifecycle analysis of wood bioenergy

[G]overnments around the world are promoting biomass to reduce their greenhouse gas (GHG) emissions. The European Union declared biofuels to be carbon-neutral to help meet its goal of 20% renewable energy by 2020, triggering a surge in use of wood for heat and electricity (European Commission 2003, Leturcq 2014, Stupak et al 2007). … But do biofuels actually reduce GHG emissions?”
“[A]lthough wood has approximately the same carbon intensity as coal (0.027 vs. 0.025 tC GJ−1 of primary energy […]), combustion efficiency of wood and wood pellets is lower (Netherlands Enterprise Agency; IEA 2016). Estimates also suggest higher processing losses in the wood supply chain (Roder et al 2015). Consequently, wood-fired power plants generate more CO2 per kWh than coal. Burning wood instead of coal therefore creates a carbon debt—an immediate increase in atmospheric CO2 compared to fossil energy—that can be repaid over time only as—and if— NPP [net primary production] rises above the flux of carbon from biomass and soils to the atmosphere on the harvested lands.”
Growth in wood supply causes steady growth in atmospheric CO2 because more CO2 is added to the atmosphere every year in initial carbon debt than is paid back by regrowth, worsening global warming and climate change. The qualitative result that growth in bioenergy raises atmospheric CO2 does not depend on the parameters: as long as bioenergy generates an initial carbon debt, increasing harvests mean more is ‘borrowed’ every year than is paid back. More precisely, atmospheric CO2 rises as long as NPP [net primary production] remains below the initial carbon debt incurred each year plus the fluxes of carbon from biomass and soils to the atmosphere.”
[P]rojected growth in wood harvest for bioenergy would increase atmospheric CO2 for at least a century because new carbon debt continuously exceeds NPP.”
[C]ontrary to the policies of the EU and other nations, biomass used to displace fossil fuels injects CO2 into the atmosphere at the point of combustion and during harvest, processing and transport. Reductions in atmospheric CO2 come only later, and only if the harvested land is allowed to regrow.”

Fanous and Moomaw, 2018

A Critical Look at Forest Bioenergy:
Exposing a high carbon “climate solution”

“These nations fail to recognize the intensity of CO2 emissions linked to the burning of biomass. The chemical energy stored in wood is converted into heat or electricity by way of combustion and is sometimes used for combined heat and power cogeneration. At the point of combustion, biomass emits more carbon per unit of heat than most fossil fuels. Due to the inefficiencies of biomass energy, bioenergy power plants emit approximately 65 percent more CO2 per MWH than modern coal plants, and approximately 285 percent more than natural gas combined cycle plants.”
Furthermore, the Intergovernmental Panel on Climate Change (IPCC) states that combustion of biomass generates gross greenhouse gas (GHG) emissions roughly equivalent to the combustion of fossil fuels. In the case of forest timber turned into wood pellets for bioenergy use, the IPCC further indicates that the process produces higher CO2 emissions than fossil fuels for decades to centuries.”

Schlesinger, 2018

Are wood pellets a green fuel?

“Recently, attention has focused on woody biomass—a return to firewood—to generate electricity. Trees remove CO2 from the atmosphere, and burning wood returns it. But recent evidence shows that the use of wood as fuel is likely to result in net CO2 emissions and may endanger forest biodiversity.”
(press release    “Each year, some 7 million tons of wood pellets are shipped from the United States to Europe, where biomass fuels have been declared carbon-neutral with respect to fulfilling the commitments of the Paris Climate Accord. The current goal for the European Union (EU) is to generate 20 percent of its electricity by 2020 using renewable sources, including burning woody biomass.  In part to revive a languishing forest products industry, the U.S. Congress may also declare wood a carbon-neutral fuel. … With wood, there is the assumption, but no guarantee, that new trees will be planted and persist long enough to pay back the carbon debt created by combustion of the previous stands.  If that carbon stock is not restored, then burning wood may actually emit more CO2 to the atmosphere than burning coal. … [T]he recent science indicates that production of wood pellets for fuel is likely to put more CO2 in the atmosphere and maintain less biodiversity on the land during the next several decades.”

de Oliveira Garcia et al., 2018

Increasing biomass demand enlarges negative
forest nutrient budget areas in wood export regions

Increasing global woody biomass demand may cause additional pressure on forested ecosystems, enlarging negative nutrient budget areas.”
In 2014, wood and agglomerated wood products, i.e. pellets and briquettes, provided almost half (45%) of EU-28’s total inland energy production by renewables. Current European renewable energy policy will boost woody biomass demand and, considering 2015 as baseline, the global woody biomass demand is expected to be 23 × 106 t a−1 in 2024 representing a 70% increase. For 2050, global woody biomass use for energy is expected to increase by 1.6 × 1010 t a−1 (obtained from 2.3 × 1010 m3 a−1 by assuming 0.7 t m−3 as average woody biomass bulk density) representing a potential energy production ranging from 2.7–3 × 1020 J a−1 (for a 1.7–1.9 × 1010 J t−1 biomass’ energy output). By the late 21st century, the biomass energy production is expected to be 2.4–8.5 × 1020 J a−1 13, which is approximately two orders of magnitude [100 times] higher than the 2016 biomass energy production of 1.8 × 1018 J a−1 14.”

via NoTricksZone

November 1, 2018 at 07:35PM

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