Figures & Tables

Figure D: Net effects of treating an extra tonne of sludge

in a cement kiln or in a fluidised bed 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 waste treatment options for each of the 10 environmental impact categories (CML method).

A comparison is only possible within an impact category and not between different types of impacts.

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 each case, the largest effect (positive or negative) is indicated as 100% and the effect of the other treatment option is expressed as percentage thereof.

Net effects of treating an extra tonne of sludge

A higher score represents a greater environmental impact. A negative score (below zero) represents an environmental bonus – which means that using the tonne of sludge as alternative fuel has a lesser environmental impact than if other energy sources were used. More negative points reflect a better result from an environmental point of view.

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 (normalised results).

In each case, the largest effect (positive or negative) is indicated as 100% and the effect of the other treatment option is expressed as percentage thereof.

Source: TNO,  LCA of thermal treatment of waste streams in cement clinker kilns (2007)

17-12-2007