was 28.05 MMT. Salable weight of red meat, after processing, was 18.14 MMT, a reduction of roughly 10 MMT, or nearly 36 percent. By-products of meat processing include lard and tallow (about 3.8 MMT),7 hides (1.02 MMT undressed),8 dog and cat food, glue, bone meal, blood meal, meat meal, and tankage. The last two items are utilized in animal feed concentrates (2.3 MMT in 1988; United States Department of Agriculture, 1992, table 73). About 2.7 MMT remains unaccounted for. Some of this may be pet food, for which we have no explicit data. We conjecture that most of the missing mass is evaporative water loss in the production of meals and concentrates.

Exports of red meat products in 1988 amounted to 0.4 MMT, and imports, mostly of beef, amounted to 1.63 MMT. Thus, domestic supply of red meat was 19.37 MMT. However, final consumption of meat (''as purchased") was only 16.25 MMT. The difference of 3.16 MMT is waste fat and bone, largely generated by meatcutters in retail shops. This waste ends up ultimately in municipal landfills.

In the case of poultry, live weight was 12.95 MMT in 1988. Dressed carcass weight of poultry for the United States was either 9.5 MMT or 10.07 MMT.9 This implies a by-product and waste flow at the processing plant of 3.0-3.5 MMT, part of which (2.0-2.5 MMT) is probably recycled as animal feed. The rest, mostly feathers, is dumped or burned. Final consumption of poultry ("as purchased") was 6.37 MMT in 1988. Thus, a further loss of 3.1-3.5 MMT presumably occurred at the retail level. The latter ends up in municipal landfill or in waterways (as biological oxygen demand).

The grain and oilseed milling sector is rather complex. Marketed grain and oilseed milling products consist of vegetable oils (6.4 MMT), flour (17.4 MMT), and corn syrup (7.6 MMT), a total of 31.4 MMT. The imputed output of feed concentrates, by this calculation, is 30.8 MMT (62.2 - 31.4). (We calculated above that 31.6 MMT must have been produced. The match is quite close.)

In summary, we have identified mass losses from the domestic food processing sector as follows: grain and oilseed milling, 9.7 MMT; fermentation, 3.0 MMT; sugar milling, 42.7 MMT; vegetable and fruit canning and freezing, 20.7 MMT; meat and poultry packing, 1.0 MMT (plus about 6.3 MMT in retail shops); dairy processing, 26.1 MMT; egg marketing, 0.6 MMT; and fish packing and retailing, 4.6 MMT. For the sector as a whole, including retail shops, losses total 110 MMT, plus an additional 6.8 MMT of carbon dioxide from fermentation. However, some of this lost mass was not wasted but was converted into animal feeds.

Of the 110 MMT of mass disappearance identified in 1988 (Figure 1), it appears that at least 66.2 MMT consisted of water vapor from evaporative processes in the manufacture of cheese and dried milk products, sugar and corn syrup production, drying and freeze-drying of fruits (such as oranges for juice, prunes, and raisins), and from the production of meat meal and fish meal. An additional 34.5 MMT of mass loss was solid waste of vegetable origin from sugar beets and

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