In 1994, manufacturing establishments had more cogeneration technologies present than actually in use--only 62 percent in use in 1994--possibly using the technologies as backups. (Note: MECS did not collect this data in 1998.)

Although the number of establishments with the different cogeneration technologies seems to have risen between 1994 and 1998, during the 1994 MECS, respondents could answer "other" and "unknown".  Some of the technology reported in these two categories may actually belong in one of the other categories.  These categories were not present in the 1998 MECS. When reviewing data, it is important to understand the differences in the data.

In 1994, all establishments had cogenerated 127.8 trillion kWh of electricity --125.3 trillion kWh of electricity  had been cogenerated in 1998--although the difference is not statistically significant (NS).

In 1998, waste gas was 14 percent higher than in 1994--petroleum coke was 12 percent lower (NS) and blast furnace gas was 18 percent lower.

Of all byproducts, waste gas was 40 percent of all the byproducts used in 1998--36 percent share in 1994.

The petroleum industry uses more than half of the byproducts used as an energy source--most of the petroleum industry byproduct use was waste gas (1,399 trillion Btu in 1998).  

The chemical industry experienced the fastest growth in waste gas--267 trillion Btu in 1994 to 416 trillion Btu in 1998. 

In 1998, the paper industry used 29 percent of the byproducts--mainly pulping or black liquor and wood chips or bark--showing no growth in the use of byproducts since 1994.

Although only a small percent of all byproduct use, softwood veneer and plywood manufacturers doubled their use of wood chips or bark (58 trillion Btu in 1994 and 122 trillion Btu in 1998.