Page 166 - Soil Degradation, Conservation and Remediation

6.2 Sources of Soil Pollutants 155

The allocation to fossil or biogenic carbon has a crucial influence on the calculated
amounts of climate-relevant CO 2 emissions. Other gases from incinerators include
N 2 O, CH 4 , NO x , CO, and NH 3 .

6.2.1.5 Disposal of Incinerator Ash

Bottom ash is mainly glass and ceramic-like materials, also containing heavy metals
and some organic carbon material. Dioxins were measured in the range 0.64–
−1
23 ngTEQ kg (Friends of the Earth 2002 ). Bottom ash contains levels of dioxin
similar to those found in urban soil. During the 5 years of the study period, 79 % of
bottom ash from the Sheffi eld incinerator went to landfi ll and 21 % for bulk fi ll or
substitute aggregate in construction blocks or asphalt. By 2000, 42 % of bottom ash
was being processed. The report points out that bottom ash is used for engineering
purposes in the Netherlands (100 % of ash), Denmark (70 %), France (50 %), and
Germany (50 %). At bottom ash processing facilities, the ash is weathered to absorb
water and reduce alkalinity. Oversize objects are removed, and then it is screened

for size. Thirty-eight percent is used for bulk fill, road construction or asphalt,
and 8 % for construction blocks. Thirty-eight percent goes to landfill and most of

the rest into stockpile. The report estimated that dioxin levels in blocks made from
−1
bottom ash would be around 4 ng TEQ kg . As this is comparable to levels found
in soil, dust from drilling these blocks should be no more hazardous than dust
from soil. Therefore, the report (Environment Agency Report; Friends of the Earth
2002 ) concludes that the use of bottom ash for aggregate is safe.

6.2.1.6 Municipal Solid Waste Landfi ll

A municipal solid waste landfill unit is a discrete area of land or an excavation that
receives household waste and that is not a land application unit, surface impoundment,
injection well, or waste pile. The municipal solid waste types potentially accepted

by MSW landfills include (most landfills accept only a few of the following categories)

MSW, household hazardous waste, municipal sludge, municipal waste combustion
ash, infectious waste, waste tires, industrial nonhazardous waste, construction and
demolition waste, agricultural wastes, oil and gas wastes, and mining wastes. In the
USA, approximately 57 % of solid waste is landfilled, 16 % is incinerated, and 27 %

is recycled or composted (USEPA 1992a ). There were an estimated 2,500 active

MSW landfills in the USA in 1995. These landfills were estimated to receive 189

million Mg of waste annually, with 55–60 % reported as household waste and
35–45 % reported as commercial waste.

Landfills are dangerous places; there are continuous release of volatile gases and
leakage in the form of leachates. The chief gas emissions from landfi lls include meth-
ane (CH 4 ) and CO 2 and are produced by microorganisms within the landfi ll under
anaerobic conditions (USEPA 1991 ). The environmental threats from two landfi ll
areas of the USA, Volney and Colesville, show the danger of landfi lls. These landfi lls