Tackling industrial waste Cement kilns versus Incinerators - An environmental comparison

6. Which treatment option leads to lower environmental impacts?

This assessment concludes that the environmental performance of thermal treatment of all 5 types of industrial wastes in cement kilns is better compared to thermal treatment in waste incinerators. This is true for the vast majority of environmental impact categories considered.

Is treatment in a cement kiln the better option for a specific waste and environmental impact?

10 environmental impact categories 5 types of waste
Solvents & waste oils Sludge Filter cake Paint
& ink residues
Fluff (plastics, textiles)
Depletion of resources Yes Yes Yes Yes Yes
Global warming Yes Yes Yes Yes Yes
Ozone layer Yes Yes Yes Yes Yes
Human health No Yes Yes Yes Yes
Freshwater ecosystems Yes Yes Yes Yes Yes
Marine ecosystems Yes No Yes Yes No
Terrestrial ecosystems No Yes Yes No No
Smog Yes Yes Yes No Yes
Acid rain Yes Yes Yes Yes Yes
Eutrophication Yes Yes Yes Yes Yes

In both cases the use of a tonne of waste generates energy which would otherwise have been provided by other sources. In the cement industry, the energy would otherwise be provided by petcoke (fossil fuel), which needs to be transported and which leads to emissions to the atmosphere.

If the incinerator did not burn the tonne of waste, it would recover less energy as electricity and steam. The electricity and steam would instead have to be produced by other Belgian energy providers.

In the case of cement kilns, burning 1 MJ of waste is as efficient as burning 1MJ of petcoke (fossil fuel). Burning 1 MJ of waste in an incinerator however is far less energy efficient than burning 1 MJ of fossil fuel in a power plant. As a result, more fossil fuels and thus greenhouse gas emissions are spared when using the waste as an alternative fuel in cement production.

When burnt, waste generally leaves behind some ash. In the case of incineration, the leftover ash is disposed of in landfills. In cement production this ash is incorporated in the final product, in effect replacing some of the raw materials that would otherwise have been added to the product. More...

 

6.1 Impacts of the treatment of solvents & waste oils

Figure C  considers the ten environmental impact categories. For each category it presents the net effect of treating an extra tonne of solvents and waste oils in a cement kiln or in a rotary kiln waste incinerator while producing the same overall amount of cement or energy as in the reference situation (without the extra tonne of waste). The figure compares the two treatment options for each impact category; a comparison is only possible within an impact category and not between different types of impacts, because in each case units are different. To be able to present the various impacts with different units in a single chart they have been expressed in percent (as normalised results).

For all environmental impact categories except marine ecotoxicity, using a tonne of solvents and waste oils as alternative fuel in a cement kiln is better for the environment than using the petcoke it replaces.

For 6 out of 10 environmental impact categories recovering energy from the incineration of a tonne of solvents and waste oils in a rotary kiln incinerator is better for the environment than using the energy source it replaces.

When comparing cement kiln and incinerator:

Even if the hypothetical situation of using solvents and waste oils to replace some of the diesel oil needed to start up the incineration process is considered, incineration only has the lowest impact in 2 out of ten impact categories, namely effects on human health and terrestrial ecosystems.

In conclusion, the environmental performance of thermal treatment of solvents and waste oils in cement kilns is better compared to thermal treatment in waste incinerators for the vast majority of environmental impact categories considered. More...

 

6.2 Impacts of the treatment of sludge

Figure D  considers the ten environmental impact categories. For each category it presents the net effect of treating an extra tonne of sludge from industrial or municipal wastewater treatment plants in a cement kiln or in a fluidised bed waste incinerator while producing the same overall amount of cement or energy as in the reference situation (without the extra tonne of waste). The figure compares the two treatment options for each impact category; a comparison is only possible within an impact category and not between different types of impacts, because in each case units are different. To be able to present the various impacts with different units in a single chart they have been expressed in percent (as normalised results).

In both a cement kiln and an incinerator, using a tonne of sludge as alternative fuel is better for the environment than using the energy source it replaces. This is valid for all environmental impact categories except effects on terrestrial ecosystems.

When comparing cement kiln and incinerator:

In conclusion, the environmental performance of thermal treatment of industrial sludge in cement kilns is better compared to thermal treatment in waste incinerators for the vast majority of environmental impact categories considered. More...

 

6.3 Impacts of the treatment of filter cake

Figure E  considers the ten environmental impact categories. For each category it presents the net effect of treating an extra tonne of filter cake from industrial and municipal wastewater treatment plants in a cement kiln or in a rotary kiln waste incinerator while producing the same overall amount of cement or energy as in the reference situation (without the extra tonne of waste). The figure compares the two treatment options for each impact category; a comparison is only possible within an impact category and not between different types of impacts, because in each case units are different. To be able to present the various impacts with different units in a single chart they have been expressed in percent (as normalised results).

For all environmental impact categories except effects on terrestrial ecosystems, using a tonne of filter cake as alternative fuel in a cement kiln is better for the environment than using the petcoke it replaces.

For only 2 out of 10 environmental impact categories (effects on resource depletion and the ozone layer) recovering energy from the incineration of a tonne of filter cake in a rotary kiln incinerator is better for the environment than using the energy source it replaces.

When comparing cement kiln and incinerator:

In conclusion, the environmental performance of thermal treatment of filter cake in cement kilns is always better compared to thermal treatment in waste incinerators. More...

 

6.4 Impacts of the treatment of paint and ink

Figure F  considers the ten environmental impact categories. For each category it presents the net effect of treating an extra tonne of paint and ink residues in a cement kiln or in a waste incinerator while producing the same overall amount of cement or energy as in the reference situation (without the extra tonne of waste). The figure compares the two treatment options for each impact category; a comparison is only possible within an impact category and not between different types of impacts, because in each case units are different. To be able to present the various impacts with different units in a single chart they have been expressed in percent (as normalised results).

For all environmental impact categories except marine and terrestrial ecotoxicity, and photochemical smog, using a tonne of paint and ink residue as alternative fuel in a cement kiln is better for the environment than using the petcoke it replaces.

For only two environmental impact categories (abiotic depletion and thinning of the ozone layer) recovering energy from the incineration of a tonne of paint and ink residue in a rotary kiln incinerator is better for the environment than using the energy source it replaces.

When comparing cement kiln and incinerator:

In conclusion, the environmental performance of thermal treatment of paint and ink residues in cement kilns is better compared to thermal treatment in waste incinerators for the majority of environmental impact categories considered. More...

 

6.5 Impacts of the treatment of fluff

Figure G  considers the ten environmental impact categories. For each category it presents the net effect of treating an extra tonne of fluff in a cement kiln or in a waste incinerator while producing the same overall amount of cement or energy as in the reference situation (without the extra tonne of waste). The figure compares the two treatment options for each impact category; a comparison is only possible within an impact category and not between different types of impacts, because in each case units are different. To be able to present the various impacts with different units in a single chart they have been expressed in percent (as normalised results).

Using a tonne of fluff as alternative fuel in a cement kiln is better for the environment than using the petcoke it replaces for all environmental impact categories.

For all but one environmental impact categories (global warming) recovering energy from the incineration of a tonne of fluff in a fluidised bed incinerator is better for the environment than using the energy source it replaces.

When comparing cement kiln and incinerator:

In conclusion, the environmental performance of thermal treatment of fluff in cement kilns is better compared to thermal treatment in waste incinerators for the majority of environmental impact categories considered. More...


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