Clean Mining
–– it also has imposed stringent requirements for post-mining land usage.
Land that has been subject to mining
activities can often not be used in the
short term for one of its most important
functions – agriculture. Mining affected
land is known to have low soil fertility,
and is often contaminated. This means
that mining companies are typically
restricted to rehabilitating their land
to grasslands or vegetated landscapes
with little beneficial use. Interesting
though, a changing climate is becoming
one of the factors that is causing mining companies to think differently about
post-mining land use.
Mining land – which is land that is
generally seen as having zero economic
value – is now being considered as an
asset that can (1) act as a carbon sink and
(2) be transformed into a self-sustaining,
renewable energy generation system
with commercial value. In 2013, Kumba
Iron Ore Limited (“Kumba”) established
a two hectare bamboo plantation to sequester around 1,300 tonnes of carbon
dioxide per annum. In the next year,
Harmony will begin planting Giant King
Grass – a plant known for its high carbon sequestration potential. The added
32
benefit of these sequestration projects
is that they can also be registered for
carbon credits, which can potentially
be used as offsets against South Africa’s
proposed carbon tax. Harmony is also
planting energy crops on mine impacted land. Once harvested, these crops will
be converted into a renewable energy in
the form of biogas through an anaerobic
digestion process. This biogas will be
used to replace fossil fuels in Harmony’s
metallurgical plants. The implementation of the first phase of this bio-energy
project will have a capacity to replace
71,000 GJ of fossil fuel at Harmony’s 1
metallurgical plant. The success of the
first phase will trigger a larger 185,000
GJ energy generation plant.
Water
The management of water-related risks
and opportunities is generally seen as a
high priority for most mining companies
in South Africa. These companies use
significant amounts of water in their operations, and the growth of their assets
is dependent on access to this critical
resource. Furthermore, these operations
are generally located in water stressed
areas.
PM Africa Magazine — january 2015
Some mining companies are taking
a novel approach to ensure their sustainability in water-constrained future.
Kumba, for example, experiences large
amounts of water ingress into its mining
pits. This water is not needed for its own
processes, and therefore allows bulk
water suppliers to withdraw the water
from their mines for use in surrounding communities and municipalities.
Kumba also uses the Water Efficiency
and Target Tool (WETT) to forecast water
consumption based on a business as
usual production profile up to 2020,
in order to better manage its demand.
Gold Fields has begun a pilot program
involving ultrafiltration and reverse osmosis, thereby reducing overall mine
water demand. The company is also
investigating a process to reduce water
discharge from its operations.
It is important to note that these companies are not also looking at water
as a resource in isolation. Both Gold
Fields and Kumba understand the link
between water and land. An improvement in the carbon sequestration of
mining land improves the biodiversity of the land which, in turn, improves
water quality and helps ecosystems to
withstand pressures from pollution. A
resilient ecosystem will help society to
adapt to a changing climate.
As energy costs continue to rise, and as
carbon and water become constrained,
the companies that take a holistic view
in tackling these issues are the often
the ones that will ensure their long
term sustainability in the years to come.
Mining companies need to understand
and build awareness around the convergence of land, energy and water
resources, and its implications for mine
development and planning.
Katie Ross
Katie Ross is a chemical engineer and senior advisor
at Promethium Carbon.
Promethium Carbon is a specialist carbon and climate change advisory company in Johannesburg.
With a vision to making a difference in climate
change in Africa, Promethium Carbon focuses on
technical advice and sustainable strategies.