Wood Bioenergy Carbon Accounting – Beyond Carbon Neutrality Ken Skog, Project Leader USDA Forest Service Forest Products Laboratory Madison, Wisconsin 2011 National FIA User Group Meeting Sacramento, CA March 8-10, 2011

Topics  What are the “right” or “helpful” research questions to ask about wood bioenergy carbon emission offsets?  A Joanneum Research study – GHG offsets by wood source over time –Carbon neutrality number over time – CN(t) Logging residue [temperate forests] Intensified thinnings [Austria] Intensively managed forest plantations – on fallow ag land – by clearing existing forest (if time)  More forestry research questions

Possible “right” or “helpful” questions (my translation of sources)  Searchinger et al. – to what degree does an increase wood energy use decrease GHG emissions [over time] by alteration of forest growth/ emissions.  6/18/2010 letter from Forestry groups to EPA Administrator – Is an increase in wood energy use “good” as long as forests are managed sustainably and forest carbon is increasing? (letter says yes) Good? = less carbon emissions “overall” to the atmosphere?  Manomet study – How quickly (years) and by how much will emissions from fossil fuel power system be offset by increasing use of Mass. forest biomass in selected wood-power systems?  Joannuem Research – By increasing use of a specific source of wood fuel use in place of fossil fuel for power, what fraction of a fossil systems emissions would be offset by using specific wood sources in t years?

Question: By increasing use of a specific source of wood fuel use in place of fossil fuel for power, what fraction of a fossil power emissions would be offset by using specific wood sources in t years? Bioenergy system Fossil fuel system Source: Giuliana Zanchi

Setting up the problem - 1  Focus: –What is the emission offset of an increase in wood use ( to a new constant level) to make electric power/ heat and power  Assume –kwh / kg wood carbon = kwh / kg of coal carbon –Kwh / kg natural gas carbon = 0.6 kwh / kg wood carbon  Exclude emissions to obtain and transport wood or fossil fuel

Setting up the problem - 2  Compute carbon neutrality number, CN(t) –Fraction of fossil emissions offset by time t by increase in wood use from a given source CN (t) = [E FF (t) – NE w (t)] / E FF (t) E FF (t) = Cumulative fossil fuel emissions avoided NE w (t) = Cumulative wood emissions to time t – Change in forest growth/ emissions due wood energy use to time t CN(t) than fossil emissions CN(t) = 0 cumulative net wood emissions = fossil emissions CN(t) = 1 net wood carbon storage totally offsets fossil emissions

Examples: CN(t) for wood use from 1. Additional harvest from a managed forest 2. Logging residues from a managed forest 3. New plantations on fallow land 4. New plantation after harvesting existing forest

Illustrative case studies Biomass net emissions (green) Fossil fuel emissions (orange) CN factor (black) Model: GORCAM (Graz Oak Ridge Carbon Accounting Model) Growth curve based on Austrian yield table for Spruce No disturbances included Source: G. Zanchi

1. Additional fellings from a managed forest (1) Rotation period: 90 years Rotation forest: 90 hectares Harvesting: a) Baseline: 60% of increment b) New Management: 80% of increment The additional biomass is used for bioenergy Source: G. Zanchi

1. Additional fellings from a managed forest (2) Biomass net emissions (green) Fossil fuel emissions (orange) CN factor (black) CN(t) = 0 at ~ t = 180 yrs CN(400) = ~ 0.5 Source: G. Zanchi Rotation period: 90 years Rotation forest: 90 hectares Harvesting: a) Baseline: 60% of increment b) New Management: 80% of increment The additional biomass is used for bioenergy

2. Felling residues from a managed forest Rotation period: 90 years (  90 ha) Baseline: Logging residue left in the forest New Management: 2/3 logging residue to bioenergy Source: G. Zanchi Biomass net emissions (green) Fossil fuel emissions (orange) CN factor (black) For a coal alternative CN(30) = 0.6 If natural gas is the alternative CN(30 ) = 0.3

3. New plantations Baseline: low carbon change land (e.g. cropland) New Management: new forest to produce bioenergy (no forest land use change) Source: G. Zanchi Biomass net emissions (green) Fossil fuel emissions (orange) CN factor (black) CN(t) >1 for all t

Forestry research questions for the U.S. on wood energy carbon offsets  For logging residue – what is CN(t) by location? (generate U.S. map using logging residue decay curves)  Are there better metrics of emission offset over time ? (e.g. relative cumulative radiative forcing – wood vs fossil fuel)  CN(t) for current timber management with more thinnings, by forest type  CN(t) for fire hazard reduction thinnings?  CN(t) for mill residue (is landfill the alternate decay if not used? Composite products? pulp?)  Are there broad management guidelines for thinnings to attain say CN(100) > 0.5? (e.g. Marland and Marland 1992)

Publications Manomet study: Walker, T. (Ed.). Contributors: Cardellichio, P., Colnes, A., Gunn, J., Kittler, B., Perschel, R., Recchia, C., Saah, D., and Walker, T Biomass Sustainability and Carbon Policy Study: Report to the Commonwealth of Massachusetts Department of Energy Resources. Manomet Center for Conservation Sciences. Report No.: NCI Repo A., Tuomi M., Liski J., Indirect carbon dioxide emissions from producing bioenergy from forest harvest residues. GCB Bioenergy, no. doi: /j x McKechnie J., Colombo S., Cheng J., Mabee W., MacLean H.L. Forest bioenergy or forest carbon? Assessing trade-offs in greenhouse gas mitigation with wood-based fuels. Environ Sci Technol Jan 15;45(2): Palosuo T, Wihersaaari M, Liski J, Net Greenhouse Gas Emissions due to energy use of forest residues –Impacts of soil carbon balance. Woody biomass as an energy source – Challenges in Europe. EFI proceedings no 39, 2001 Schlamadinger B and Spitzer J, CO 2 mitigation through bioenergy from forestry substituting fossil energy. In: Biomass for energy, environment, agriculture and industry. Proceedings of the 8th European Biomass Conference.Vienna, Austria, 3-5 October 1994, Volume 1. Ed. Chartier P., Beenackers A.A.C.M., Grassi G., pp Schlamadinger B, Spitzer J, Kohlmaier GH, Lüdeke M, Carbon balance of bioenergy from logging residues. Bioamss and Bioenery 8 (4): Schlamadinger B and Marland G, The role of forest and bioenergy strategies in the global carbon cycle. Biomass and Bioenergy 10 (5/6): Source: G. Zanchi

Thank you Ken Skog –

4. New plantations – existing forest is converted Baseline: Existing forest is converted New Management: new forest to produce bioenergy Biomass net emissions (green) Fossil fuel emissions (orange) CN factor (red) CN(t) < 0 for t < ~80 years Source: G. Zanchi