The Range of Environmental Concerns - Mining and the Environment: From Ore to Metal - page 539

Coal mining and coal use is of course a special case. Combined coal mining and use con-
tribute to climate change much more than metal or industrial mining. There are many
reasons for this; some follow.

13.5 COAL - A SPECIAL CASE

The coal cycle differs from the general mineral cycle in that, following mining, coal is
burnt or converted into other fuels ( Figure 13.9 ) . Coal combustion (as occurs, for exam-
ple, at coal-i red power plants at many mine sites) has direct environmental impacts, with
national and even international implications. Coal combustion and its environmental
impacts is a major topic on its own. Thus, the purpose of this section is not so much to
provide a thorough analysis of environmental impacts associated with coal use, as it is to
outline the main issues relating to air pollution and the generation of greenhouse gases.

Emissions from Coal Combustion

The most signii cant polluting residuals from coal are the emissions from coal combustion.
Flue gases contain sulphur dioxides (SO x ), nitrogen oxides (NO x ), carbon monoxide (CO),
carbon dioxide (CO 2 ), particulates, organic compounds, and some trace metals, including
mercury (OECD 1983 a,b). Each of these has been implicated in some form of undesirable
environmental impact: damage to human health, corrosion of materials, damage to veg-
etation, and in the case of CO 2 , contribution to global warming.
Acid deposition, a direct impact of SO 2 emissions, is recognized as a serious interna-
tional problem in the northern hemisphere. Generally coal has a sulphur content of 0.5 to
2.5% but can be found with contents up to 5%. During combustion, in the absence of emis-
sion controls, up to 95% of the sulphur present in the coal is oxidized to SO 2 and emitted
to the atmosphere. Besides petroleum use, the major portion of anthropogenic SO 2 emis-
sions is derived from coal combustion. These problems can be minimized by using low
sulphur coal and/or by installing l ue gas desulphurization (FGD) as a control technology.
Various FGD processes exist, generating different waste products such as calcium slurry,
gypsum (a saleable by-product if the economics are favourable), elemental sulphur, or sul-
phuric acid. However, the simplest way to reduce sulphur emissions to the environment is
through combustion of low sulphur coal. As a consequence, low sulphur coal commands

The simplest way to reduce
sulphur emissions to the
environment is through
combustion of low sulphur coal.

CASE 13.9
Citigroup Global Mining Report 2007

While some mining industry representatives continue to
debate anthropogenic contributions to climate change, a
Citigroup study published in 2007 identifi ed signifi cant
potential physical climate change impacts on mining com-
panies including more frequent or more severe weather
events, reduced supplies of fresh water, and thawing
permafrost impacts on Arctic infrastructure. Of the 12

major mining companies reviewed in the study, Citigroup's
research found that BHP Billiton, Rio Tinto, and Norilsk
'probably have the most signifi cant exposures to manage.'
The analysts noted in their global mining study that the
potential impacts of climate change may involve 'extended
operational shutdowns or removal of the license to oper-
ate due to environmental “disasters”. Some changes will

require adaptation and mitigation by operators.' Other
potential impacts include sea ice reduction, which could
open up new Arctic shipping routes, and 'food shortages
and increased tropical disease in Africa', causing social and
political instability.

Source: Citigroup 2008: Towards Sustainable Mining