Page 165 - Soil Degradation, Conservation and Remediation

154 6 Soil Pollution

of sources of CO 2 , a distinction is drawn between carbon of biogenic and carbon of
fossil origin. The waste’s carbon content is generally in the range of 28–40 %.
Treatment in incineration plants is an output-controlled process. The combustion
temperature of the gases in the combustion chamber as measured for at least two
seconds after the last injection of combustion air is usually at least 850 °C. The
oxygen necessary for incineration is supplied via ambient air, as primary, secondary,
and/or tertiary air. At almost all municipal waste incineration plants, the heat
produced during incineration is utilized for steam generation.
Hazardous waste is treated almost exclusively by incineration. Incineration must
be understood here as an element of comprehensive logistics for the treatment of
those wastes which due to their harmful nature have to be managed separately from
municipal waste. Hazardous waste is waste requiring particular supervision, which
by its nature, condition, or amount poses a particular hazard to health, air, and/or
water or is particularly explosive or may contain or bring forth pathogens of
communicable diseases. Since hazardous waste is generated for the most part in
industrial production, notably the chemical industry, it is also referred to as indus-
trial waste or industrial residue. Hazardous wastes occur, for example, as residues
from petrochemical distillation processes, as undesirable by-products of syntheses
processes of the basic organic chemical industry and the pharmaceutical industry,
as well as in the recovery and disposal of contaminated or post-expiration-date
products such as solvents, paints, or waste oil. In addition, environmental protection
measures such as regulations prohibiting PCBs, CFCs, or halons may generate
streams of hazardous waste. With combustion temperatures between 800 and 1,200 °C,
the residence time of solids in the rotary kiln is up to 1 h, while for the combustion
gases, it is only a few seconds. The waste gas generated during the combustion process
is fed to an after burning chamber, in which the minimum temperature of between
850 and 1,200 °C is maintained for a residence time of at least 2 s.

6.2.1.4 Emissions from Incinerators

The incineration of municipal waste involves the generation of climate-relevant
emissions. These are mainly emissions of CO 2 (carbon dioxide) as well as N 2 O
(nitrous oxide), NO x (oxides of nitrogen), NH 3 (ammonia), and organic C, measured
as total carbon. CH 4 (methane) is not generated in waste incineration during normal
operation. It only arises in particular, exceptional cases and to a small extent
(from waste remaining in the waste bunker), so that in quantitative terms CH 4 is not
to be regarded as climate relevant. CO 2 constitutes the chief climate-relevant
2
emission of waste incineration and is considerably higher, by not less than 10 , than
the other emissions.
The incineration of 1 Mg of municipal waste in MSW incinerators is associated
with the production/release of about 0.7–1.2 Mg of carbon dioxide (CO 2 output).
The proportion of carbon of biogenic origin is usually in the range of 33–50 %.
The climate-relevant CO 2 emissions from waste incineration are determined by the
proportion of waste whose carbon compounds are assumed to be of fossil origin.