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Biomass Carbon Neutrality in the Context of Forest-based Fuels and Products Al Lucier, NCASI ( alucier@ncasi.org ) Reid Miner, NCASI ( rminer@ncasi.org ) May 2010 Annual U.S. Production of Renewable Materials and Biomass Energy Feedstock Circa 2005 Forest Sector & Climate Mitigation

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biomass carbon neutrality in the context of forest based fuels and products

Biomass Carbon Neutrality in the Context of Forest-based Fuels and Products

Al Lucier, NCASI (alucier@ncasi.org)

Reid Miner, NCASI (rminer@ncasi.org)

May 2010

slide2

Annual U.S. Production of Renewable Materials

and Biomass Energy Feedstock Circa 2005

forest sector climate mitigation
Forest Sector & Climate Mitigation

“In the long term, a sustainable forest management strategy aimed at maintaining or increasing forest carbon stocks, while producing an annual sustained yield of timber, fiber or energy from the forest, will generate the largest sustained mitigation benefit.” 

IPCC 4th Assessment Report (2007)

the neutral biomass carbon cycle
The “neutral” biomass carbon cycle

Carbon transfers from geological reserves

VS

Atmosphere

Non-biogenic CO2

Atmosphere

CO2

Biogenic CO2

Biomass

Carbon

Fossil Fuel

Biogenic carbon is part of a relatively rapid natural cycle that impacts atmospheric CO2 only if the cycle is out of balance

Fossil fuel combustion transfers geologic carbon into the atmosphere. It is a one-way process

implications for carbon accounting
Implications for Carbon Accounting
  • Fossil Fuels: CO2 emissions at point of combustion are dominant factors in “carbon footprints.”
  • Forest Biomass Fuels: Changes in forest carbon stocks can be dominant factors in “carbon footprints.”
  • This is why there are different carbon accounting methods for fossil fuels and biomass fuels.
biomass carbon neutrality bcn
Biomass Carbon Neutrality (BCN)
  • Practical Contexts:
    • National Greenhouse Gas Inventory & Reporting
    • Cap & Trade Programs
    • EPA Regulation of CO2
national ghg inventory reporting
National GHG Inventory & Reporting
  • BCN means that a CO2 emission factor of zero is used for biomass fuels at point of combustion.
    • Emissions associated with the production of biomass fuels are measured where they occur.
  • National GHG Inventory has two main components:

(1) Emissions other than biogenic CO2

    • Changes in carbon stocks
  • Biogenic CO2 emissions are captured in (2).
    • To avoid double counting, a CO2 emission factor of zero is used for biomass fuels at point of combustion.
cap trade programs
Cap & Trade Programs
  • BCN is used in cap & trade programs to:
    • encourage use of biomass fuels in place of fossil fuels.
    • maintain consistency with National GHG Reporting.
    • Some stakeholders have expressed concerns about unintended consequences of incentives in cap & trade programs to use biomass and other energy options.
epa regulation of co 2
EPA Regulation of CO2
  • BCN is being discussed in context of EPA’s plan to regulate CO2 as a pollutant under the Clean Air Act. Key topics include:
    • Legal basis for distinguishing between fossil and biomass sources of CO2.
    • Concerns about excessive use of biomass.
    • Concerns that regulating CO2 from biomass would encourage switching from biomass fuels to fossil fuels.
why would eliminating bcn encourage switching from forest based biomass fuels to fossil fuels
Why Would Eliminating BCN Encourage Switching from Forest-Based Biomass Fuels to Fossil Fuels?
  • At point of combustion, CO2 emissions per unit of energy produced are generally higher for biomass fuels than for fossil fuels.
    • This is due primarily to the higher water content of biomass fuels.
  • CO2 emissions at point of combustion could be reduced by shifting fuel mix away from biomass.
    • However, overall CO2 emissions would increase in most cases.
biomass carbon neutrality
Biomass Carbon Neutrality
  • Does not measure reductions in GHG emissions attributable to using bioenergy instead of fossil energy.
quantifying ghg benefits of bioenergy
Quantifying GHG Benefits of Bioenergy
  • Construct scenarios.
  • Estimate cumulative emissions for each scenario.
slide14

What if a new biomass production system is gradually replacing forest that has higher carbon stocks?

Net cumulative emissions for biomass system increase to reflect stock losses , but stop increasing after all plots have been converted to production forest.

Biomass energy

Fossil fuel energy

Cumulative CO2 combustion emissions

Net Cumulative CO2 combustion emissions

Time

Time

slide15

This increases the time required for biomass to show net benefits, but after the “break even point” the benefits of biomass continue to accrue.

Biomass energy

Fossil fuel energy

Cumulative CO2 combustion emissions

Net Cumulative CO2 combustion emissions

Biomass lower from here forward

Time

Time

slide16

If reductions in land-based carbon are lower, the time to “break even” is reduced.

Biomass energy

Fossil fuel energy

Cumulative CO2 combustion emissions

Net Cumulative CO2 combustion emissions

Biomass lower from here forward

Time

Time

slide17

Of course, the opposite can happen. Land can be converted to higher carbon stocks to provide biomass energy (e.g. afforestation).

Biomass energy

Fossil fuel energy

Cumulative CO2 combustion emissions

Net Cumulative CO2 combustion emissions

Cumulative fossil fuel carbon emissions continue to increase indefinitely

Time

Time

Cumulative net biomass emissions remain below zero

slide18

So, we have seen that the net cumulative emissions of biogenic carbon vary depending on whether and how the overall carbon stocks on the land are changing.

In the United States, carbon stocks on wood-producing land are stable or increasing, so the national situation is best represented by this line.

Convert land to much lower carbon stocks

Net Cumulative biogenic CO2 emissions

Convert land to somewhat lower carbon stocks

Keep land in same general forest type

Time

This means that the forest biomass carbon placed in the atmosphere is offset by new forest growth on wood-producing land

Afforestation or other increase in carbon density

timberland growth removal ratio by region
Timberland Growth/Removal Ratio By Region
  • Growth-removal ratio is calculated based on annual growth on timberland divided by annual removal as of reported years. No specific data for growth and removal in between reported years.

Source: Forest Resources of the United States, 2007 – Table 36

life cycle emissions of greenhouse gases other than biogenic co2
“Life Cycle” Emissions of Greenhouse Gases Other than Biogenic CO2

Data sources: IPCC, USDOE USLCI Database, other public life cycle databases

summary
Summary
  • US Forest Sector
    • A world leader in biomass energy production & use.
    • Part of the solution to greenhouse gas mitigation.
  • Biomass Carbon Neutrality (BCN)
    • In theory, an attribute of biomass energy systems where the biogenic carbon cycle is in balance.
    • In practice, an accounting convention in national greenhouse gas inventories.
summary22
Summary
  • In the United States,
    • forest carbon stocks are stable or increasing;
    • therefore, GHG emissions per unit of energy are much lower for forest biomass fuels than for fossil fuels.
  • EPA is considering whether to eliminate BCN for purposes of regulating CO2 as a pollutant under the Clean Air Act.
    • EPA deferred decision on BCN in “tailoring rule”
    • Eliminating BCN in this context would encourage replacement of biomass will fossil fuels, resulting in substantial increases in GHG emissions.