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Jewelry Making Over Heat

Wood Heat Concerns

C. Initial CO2 Release

The Manomet Center for Conservation Sciences’ ”Study of Wood Biomass Energy” in 2010 examined the complex question of biomass CO2 emissions and the life-cycle effect of various biomass harvest and combustion scenarios in Massachusetts. Although their results were drastically misconstrued by the press, they concluded that thermal biomass can drastically reduce net carbon emissions compared to fossil fuels.

The confusion stemmed from the findings that all biomass burning will initially release some carbon and the “pay-back period” or period of time before the next generation tree growth recaptures that carbon can vary and may be quite a long time in some cases. While the Manomet study cautions that the carbon pay-back period for replacing traditional electricity sources with biomass can be very long, it was concluded that using biomass for thermal energy has a short CO2 payback period because of the higher relative efficiency. They state that, “replacement of oil-fired thermal/CHP capacity with biomass thermal/CHP fully offsets the carbon debt and lowers greenhouse gas levels.” 1 There is a potential for biomass to be ‘carbon neutral,’ but this is dependent on future forest management strategies. Other reports on the subject disagree with the carbon ‘debt-then-dividend’ viewpoint, because it only considers one stand rather than the forest as a whole. The alternative argument is that as long as the forest continues to grow, then it is a case of dividend-then-debt.2

A 2006 study on Australian firewood found that, “the use of firewood for domestic heating has lower net CO2 emissions than non-renewable energy sources such as gas and electricity, particularly when firewood is collected from thinning slash and other resides of commercially grown plantations.” 3

Additionally a study by the Stockholm Environment Institute has found that utilizing woody biomass harvesting residue for residential heating to displace fossil fuels, “provides the greatest reduction in net GHG emissions relative to the common practices of on-site combustion and on-site decomposition.” The practice of burning harvest residues (slash piles), which takes place across much of the Pacific Northwest, produces far more green house gasses than using that biomass to displace fossil fuel would. For a discussion on the low carbon implications of biomass heat see Chapter 3, Section B: Biomass for Heat is a Low Carbon Renewable Energy.

1 Lee. C, et al. Greenhouse gas and air pollutant emissions of alternatives for woody biomass residues. Stockhold Environment Institute. November 2010. Pg. 17
2 Walker et al. “Biomass Sustainability and Carbon Policy Study” Manomet Center for Conservation Sciences. June 2010. Pg 7
3 Struss W. How Manomet got it Backwards: Challenging the “debt-then-dividend” Axiom. FutureMetrics. May 2011
4 Paul K. et al. Net Carbon Dioxide Emissions from Alternative Firewood-production Systems in Australia. Biomass and Bioenergy 30. January 2006. Pg. 645

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