Environmental risk of mining - Environmental Deterioration and Contamination: Problems and their Management - page 129

- Using paste backfill to stabilize underground excavations. A mix of paste and

cement is pumped into previously mined stopes to form a rock solid material.
The paste backfill can also serve as a working platform in a mine. By using paste
backfill the mines can be utilized more efficiently and above all, safely (Meggyes &
Jefferis, 2012; Environmental Protection, 2013).

- Environmentally friendly and cost-efficient binders can support mine shafts instead

of Portland cement which is often used in underground mining to shore up shafts to
prevent collapses. Although very effective to sustain shafts, the production of one
tonne of Portland cement produces 1 tonne of carbon dioxide. Natural Resource
Canada (NRCan, 2013) has produced an environmentally friendly binder called
slag binder for use in mine shafts and that is made of waste rock and calcium
hydroxide. These materials are available at the mine site and can be mixed readily
(Mine, 2013).

- Using biotechnologies is a sustainable alternative to conventional mining and

mineral processing methods. Biomining, the use of micro-organisms to recover
precious and base metals from mineral ores and concentrates, has developed into
a successful and expanding area of biotechnology. Nowadays the production of
copper from low-grade ores is the most important industrial application, and
a significant part of world copper production already originates from heap or
dump/stockpile bioleaching. Biomining is based on bioleaching and biooxidation.
Bioleaching is the conversion of an insoluble valuable metal into a soluble form by
means of microorganisms (Schippers et al. , 2013). Biomining uses autotrophic,
acidophilic, iron- and sulfur-oxidizing microorganisms to produce ferric iron and
sulfuric acid. These chemicals are capable of oxidizing a variety of minerals con-
taining insoluble metal sulfides such as Fe 2 S, CuS, NiS, and ZnS into their soluble
sulfate forms e.g., Fe 2 SO 4 , CuSO 4 , NiSO 4 , and ZnSO 4 , respectively. This results
in their extraction into water from which they may be more easily recovered.
Metal leaching is carried out from mineral waste dumps, or more typically and
especially from constructed heap or stirred tank reactors. In addition to copper
and gold production, biomining is also used to produce cobalt, nickel, zinc, and
uranium (Rawlings & Johnson, 2007). Up to now, biomining has merely been
used as a procedure in the processing of sulfide ores and uranium ore, but labora-
tory and pilot procedures already exist for the processing of silicate and oxide ores
(e.g., laterites) and for the leaching of processing residues or mine waste dumps
(mine tailings) (Schippers et al. , 2013).

- Reutilization of mine waste rock for industrial purposes including acid neutraliza-

tion as well as the capture and long-term disposal of anthropogenic carbon dioxide
(Hitch et al. , 2010).

- Sustainable reutilization of exploited underground or open pit mine space that

cannot serve a purpose for the mining industry. Abandoned mines are already
being used for various purposes, ranging from final waste disposal to energy
storage and the heating and cooling of spaces. The use of low enthalpy geother-
mal energy stored in abandoned mines for heating and cooling of buildings and
industrial processes has already been implemented in Canada, Germany, USA and
UK, with ongoing assessment projects in some communities in Europe (Ramos &
Falcone, 2013).