sectoral economic costs and benefits of ghg mitigation - IPCC

Dave Cahn, Dale Louda and Michael Nisbe
Examples of energy efficiency by the cement industry
(A) Equipment Improvements
There are a number of plant upgrades, such as conversion of coal-fired systems from direct to
indirect firing, which reduce the quantity of low temperature air entering the kiln with the
pulverized fuel, or process modifications that reduce the heat loss from clinker coolers. But the
most effective way of improving fuel efficiency would be to convert the older and less efficient
kilns operating in the United States to newer, more efficient kilns. Currently older, less efficient
kilns account for 56 percent of installed clinker capacity.
The fuel efficiency gain achieved by replacing older, inefficient US capacity (about 42.3 million
tonnes per year) with newer kilns would achieve a reduction of 8.71 million tonnes per year of
CO 2 emissions. If the Kyoto Protocol came into force, the US cement industry would have to
reduce annual CO 2 emissions by about 15 million tons, assuming a scenario of moderate growth
in annual cement consumption of one percent. Thus conversion of all wet and dry process kilns
would not provide sufficient CO 2 emissions reductions to offset moderate growth in US cement
production.
Assuming a cost of $120 per tonne of new clinker capacity, the capital investment required to
replace 42.3 million tonnes of old capacity would be about $5.1 billion or $585 per tonne of CO 2
reduced. Under today’s economic conditions, the fuel cost reduction alone (about $6/tonne for a
wet process kiln conversion) would not provide an adequate return on the investment needed to
replace older cement manufacturing capacity. To provide an adequate return, replacement of old
capacity must be linked to an expansion of capacity.
(B) Fuel Switching
Reducing the emissions per unit of energy would require major increases in the proportion of
natural gas in the fuel mix. This would represent mismanagement of valuable energy resources;
cement kilns are better equipped to burn coal compared to many other industrial and commercial
applications. Additionally, switching to natural gas would increase NO x emissions from cement
kilns. To meet the emission targets set forth in the Kyoto Protocol, natural gas would have to be
increased from its current level of about 7 percent utilization to about 85 percent to accommodate
the moderate growth scenario.
(C) Alternate Fuels
Beginning in the early 1980’s, cement manufacturers have used selected waste materials with
high-energy contents, such as spent solvents, paint residues, used oil, and scrap tires, as kiln
fuels. The high temperatures in cement kilns assure effective combustion of these fuel
alternatives. At the same time, using these fuels in a cement kiln recovers the energy value of
these materials, which otherwise might have been landfilled or incinerated without any energy
recovery. Being able to use waste materials that would otherwise have to be incinerated reduces
CO 2 and NO X emissions in the US because the overall need for combustion is reduced. Alternate
fuels currently account for about 7.5 percent of the industry’s energy requirements. Combustion
of wastes in cement kilns emits roughly the same quantity of CO 2 per energy unit as coal.
The potential credit that could be allocated to cement manufacture for recovering energy from
waste would depend on the alternative disposal options. In the case of liquid wastes, as an
example, this would most likely be incineration without heat recovery and with emissions of
CO 2. If the wastes are used in cement manufacture to replace some conventional kiln fuel, the
CO 2 that would result from incineration could be avoided. However, if the avoided CO 2
emissions were credited to cement manufacturing there would still be a considerable distance to
the moderate growth scenario target.
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