CARBON BUDGET OF UNITED STATES FORESTS

A: Carbon in wood harvested from forests ends up in a variety of uses, from bring sequestered in lumber in buildings or furniture for a century or more, to quickly being released into the atmosphere as logging debris is burned in preparation for planting. We consider four general categories for the fate of wood: products, landfills, energy production, and decomposition without energy production. Carbon in historical removals was estimated beginning in 1900.

In 1995, a net annual average of about 37 million metric tons (MMT) C/yr. was being stored in products and landfills (Heath and others 1995) , which is approximately two-fifths of the carbon being sequestered in forest trees of the U.S. (Birdsey and Heath 1995). An additional 50 MMT C/year is emitted when wood is burned for energy. Because of the large magnitude in the wood burned for energy category, how one accounts for emissions from wood used as a substitute for fossil fuels can have a great influence on how forests are managed for carbon sequestration. See Figure 1 for carbon flux in disposition categories over time.

Harvests are projected to continue to increase under "business-as-usual" assumptions about population and society over the next 50 years. Approximately 20 MMT C/yr. will be stored in forest products, and about the same amount will be stored in landfills. If all harvesting in the United States ceased in 1990, the annual average flux of carbon emissions from existing products would be about 53 MMT/yr., and about 12 MMT/yr. from landfills.

The U.S produced about 20% of the sawnwood, 25% of wood-based panels, 30% of paper and paperboards, and about 5% of the fuelwood as compared to the rest of the world in 1990 (Brooks 1993). This roughly means that C in wood products in the world is currently increasing about 100 MMT C/yr.

(insert Figure 4 from the BANFF.wdp file).

SOURCE: Heath, L.S., R.A. Birdsey, C. Row, and A.J. Plantinga. 1996. Carbon pools and flux in U.S. forest products. In: Forest Ecosystems, Forest Management, and the Global Carbon Cycle, (M.J. Apps and D.T. Price, eds). NATO ASI Series I: Global Environmental Changes, Volume 40, Springer-Verlag, p. 271-278.