Forest Biopower Is Far From Carbon Neutral
New Study Debunking the Carbon Neutrality of Forest Biomass Demonstrates that Forest Biopower from Wood Pellets Will Not Deliver Climate Benefits
Cutting down trees and burning them to make electricity is not a “carbon neutral” climate solution, and now that picture is even more clear. When it comes to wood pellets for electricity in power plants, upstream lifecycle emissions alone—even excluding the emissions from the power plant stack—can exceed the average emissions generated from the US electrical grid.
Biomass Study Findings
A new study by NRDC quantifies “lifecycle” emissions in each step in the wood pellet supply chain. These sources include drying the wood and processing the pellets; transporting the wood supply and finished pellets; and the foregone sequestration in the forest after logging.
The analysis further rebuts the biomass industry’s argument purporting the “carbon neutrality” of forest biomass, which boils down to this specious and dangerous claim: since forests can regenerate and sequester carbon in the process, the regrowth offsets the stack emissions from burning wood for electricity—automatically and instantaneously. Their arguments have already been roundly rejected by the Environmental Protection Agency’s own science advisors and in scores of studies demonstrating that forest biomass for electricity produces stack emissions of CO2 at levels comparable to fossil fuels, and those emissions stay in the atmosphere for decades to centuries—well beyond timeframes to address the worst impacts of climate change.
The process of generating electricity by burning wood pellets starts long before combustion in the power plant. Generating that electricity requires cutting down trees, transporting the trees, drying the wood, turning the wood into pellets, and transporting the pellets. Each of these steps takes energy and produces emissions. In addition, after a forest is cut, its capacity to sequester carbon during regrowth is diminished. This foregone sequestration represents a net addition to atmospheric CO2 as well.
All of these sources of carbon to the atmosphere have one thing in common: they are uncapturable. Because these emissions occur offsite—away from the power plant—they cannot be mitigated by capturing stack emissions through carbon capture and storage, even assuming forest regrowth occurs immediately.
Bioenergy With Carbon Capture and Storage
The new study analyzes one specific and common scenario: pellets made of wood from pine plantations in the southeastern United States fueling a bioenergy plant with carbon capture and storage (BECCS). Even when stack emissions are captured, the scenario is not carbon negative—and is not even close to carbon neutral.
Standalone biomass power plants emit approximately 923 kilograms of carbon at the stack for every megawatt-hour of electricity produced. These emissions are comparable to the stack emissions at coal-fired power plants and they can last for decades to centuries in the atmosphere. The uncaptured emissions assessed in our study total approximately 558 kilograms of carbon for every megawatt-hour of electricity produced. This means that the offsite, uncaptured emissions equal approximately 60% of the stack emissions at the site of the power plant.
For comparison, a natural gas power plant emits about 360 kg CO2 per MWh at its smokestack, and the average emission rate from the US electricity grid is 430 kg CO2 per MWh.
Federal Missteps in the Fight Against Climate Change
These numbers shed light on the highly consequential error in recent congressional efforts to direct federal agency policies to uniformly “reflect the carbon neutrality” of forest biomass through a rider to a long-running spending bill. Not all biomass fuels are created equal: different feedstocks will have different degrees of carbon impacts. For example, power generated from wood waste at a pulp mill in the northern states will have a different carbon profile than biopower from mature trees in the west.
Wood pellets from southeast plantations are a sure loser and come nowhere close to carbon neutrality. A congressional rider that continues to promote the categorical carbon neutrality of forest biomass will set back our efforts to address climate change in the short time we have to achieve true emissions reductions—precisely because the “carbon neutral” label could allow this type of feedstock to become highly subsidized as a clean energy source. This will add carbon to the atmosphere while drawing precious resources away from deployment of true clean energy technologies.
An Opportunity to Correct Our Path
Congress has the opportunity to correct its appropriations rider, which could be interpreted to mean that all forest bioenergy is carbon neutral. They should heed a dire warning in a letter from nearly 800 scientists including winners of the Nobel Prize and the US Medal of Science, and lead authors of multiple IPCC reports, who write “using wood deliberately harvested for burning will increase carbon in the atmosphere and warming for decades to centuries.” Now we know that the upstream lifecycle emissions of wood pellets for electricity make their case only stronger.
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