input of 367 MMT of carbon dioxide from the air and 163 MMT of water for photosynthesis. Total oxygen generated was 206 MMT. Assuming the timber had an original moisture content of 48 percent, total water input must have been 545 MMT. Subtracting the water content of the air-dried wood output (51 MMT) from the original water content of the harvested roundwood (268 MMT) implies a water loss from wood dehydration of 217 MMT.

Trees have an estimated carbon-nitrogen-phosphorus ratio of 800:10:1 (Deevey, 1970). Because most of the nutrients are embodied in the bark and foliage, this is an overestimate for harvested wood. However, if it were correct, the nitrogen content of the wood removed from the forests would be on the order of 1.5 MMT, while the phosphorus content would be on the order of 0.15 MMT. As noted below, the phosphorus content of wood ash is about 1 percent, and the ash itself amounts to 2 percent of the total mass of undebarked wood. This implies a total mineral, or ash, content of 6 MMT for the wood harvested and a probable phosphorus content on the order of 0.06 MMT, which is only 40 percent of the loss rate implied by the Deevey C:N:P ratio. Not all of this ash is removed from the forest as some debarking operations are carried out at the logging site.

The total mass of roundwood consumed by U.S. lumber and plywood mills in 1988 was 155.8 MMT. The mass of lumber produced in 1988 was about 49.7 MMT (Ulrich, 1990, table 7). The mass of plywood and veneer produced was 11.1 MMT; hardboard, insulating board, and particleboard amounted to 8.8 MMT. Total processed wood products added up to 69.6 MMT. Allowing for 43.7 MMT of wood chips from lumber mills used for pulping, exports of 6.9 MMT, 11.8 MMT to other uses, and fuel use of 25.8 MMT, there were 4.9 MMT of unutilized waste, equal to about 3 percent of inputs.

The total weight of inputs to pulp was 142.6 MMT, which consisted of just over 105.7 MMT in domestic pulpwood, and 43.7 MMT in chips from lumber mills. U.S. domestic woodpulp production in 1988 was 57.9 MMT (Bureau of the Census, 1991, table 1195).11 Domestic production of pulp was essentially entirely from domestic resources.12 Net U.S. exports of woodpulp in 1988 were 0.535 MMT, while chemical uses of dissolving-grade pulp amounted to 1.24 MMT. However, virgin pulp available for domestic paper production was 56.8 MMT. There is a small statistical discrepancy of 0.7 MMT.

Wastepaper collected for recycling in 1988 was reported to weigh 23.8 MMT.13 To obtain a match between inputs and outputs of the paper sector, we calculate that 17.7 MMT of recycled pulp must have been consumed, of which 4.9 MMT was from internal waste and the rest was postconsumption wastepaper. Allowing for internal recycling, exports, and other uses, 14.2 MMT of wastepaper would have been repulped. About 10 percent (1.4 MMT) of this mass, consisting mostly of inorganic fillers and coatings, would have been lost in the repulping process (United States Congress, Office of Technology Assessment, 1984, figure 24), leaving 12.9 MMT as secondary pulp for paper and paperboard production. Thus, total domestic pulp supply, including internal recycling, was



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