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This month's issue is a review of the EPA-454/R-93-032 document entitled National Air Pollutant Emission Trends, 1900-1992 dated October, 1993 and what it says about cement manufacturing. The report was prepared by the Office of Air Quality, Planning and Standards at Research Triangle Park, NC.
The report covers CO, NOX, VOC, SO2, Pb, and PM-10 emissions. Only the NOX, SO2, Pb, and PM-10 emissions data included specifics applicable to cement manufacturing. Table I is a synopsis of that data for cement manufacturing.
The data presented by the EPA are estimates using various modeling techniques with major changes in 1984, 1985, and 1986. Furthermore, the PM-10 data did not include "Fugitive Dust" until 1985. Fugitive Dust includes "wind erosion", "unpaved roads", "paved roads", "construction", and "agriculture tilling". This exclusion is very important in the following discussion. We would also point out that the quantity and types of data that are presented make it possible to "play games" to prove almost any point. For example, cement manufacturing PM-10 emissions in 1990 were estimated at 226,000 tons. This is 0.44% of the total PM-10 emissions. Assuming 200 kilns operating 85% of the time, this averages at approximately 300 lbs/hr. This compares favorably with one small plant where the PM-10 emissions for 1992 was calculated at 871 tons.
The argument then begins by the environmentalists that newer, more technological advanced precipitators can reduce emissions by half coming out the stack. That has to be good for the environment. While this makes a good argument, it is highly misleading. Current measured data shows that PM-10 emissions from a cement kiln stack is 10 to 20 lbs/hr with some as high as 50. Reducing stack emissions by 10 lbs/hr on the average over 200 kilns would reduce cement manufacturing emissions by approximately 3% and total PM-10 emissions in the USA by less than 0.02%. Can the costs really justify this insignificant improvement? It is very apparent that what people think they see in the way of dust coming out of a cement kiln stack is not a major source today. From the EPA data, we can point out that fireplaces/woodstoves provide twice the PM-10 emissions than cement manufacturing. Further, unpaved roads are almost 70 times more at fault. Paved roads and agricultural tilling each place about 35 times more PM-10 in the air then cement manufacturing. In 1990, wind erosion by itself was almost 19 times worse than cement manufacturing.
Now let us look at what has really been accomplished from 1970 to 1990 by cement manufacturers to reduce emissions. PM-10 emissions were reduced from 1,731,000 tons in 1970 to 226,000 tons in 1990, an almost 87% reduction in two decades. To calculate a percentage of the total we added 42,000,000 tons of fugitive dust into the totals prior to 1985. Cement manufacturing contributed 3.5% in 1970, 0.85% in 1980, and 0.44% in 1990 to the total PM-10 emissions. This is quite an accomplishment.
Electric utilities only had a 32% reduction in that time period and highway vehicles went the other way with an increase of almost 54%. In spite of all the environmental progress and effort the total PM-10 emissions in the USA from 1970 to 1990 has remained almost constant.
Except for some anomalies apparently due to the modeling techniques, Pb emissions from cement manufacturing has remained almost constant, at least from 1986 to the present, contrary to what certain lobbying groups contend. The level of emissions presented by the EPA is equivalent to 0.032 lbs/hr for each cement kiln on the average. For 1990, cement manufacturing contributed 0.46% of the lead emissions to the USA total. From 1970 to 1990 cement manufacturing has worked to achieve a 95% reduction in Pb emissions. During that time period highway vehicles really made progress with a 99% reduction in their emissions. However, highway vehicles still contributed 30% of the lead emissions to the USA total in 1990.
From the EPA data, the SO2 emissions from cement manufacturing took a big nose dive in 1985 when compared to prior years. From 1985 to 1992, the reduction in SO2 emissions from cement manufacturing was over 13%. In that same period highway vehicle emissions of SO2 increased over 36% and electric utility emissions decreased by only 2.5%.
In an opposite move from the SO2 data, NOX data took a sharp rise in 1985. From 1985 to 1992 the reduction in NOX emissions from cement manufacturing was 14%. In that same period highway vehicles emissions decreased by 7.8% and electric utilities increased by 11.8%. It is interesting to note that over the years from 1970 there has been negligible change in total NOX emissions in the USA.
Cement Manufacturing Emissions