Modern society depends
on the availability of mineral resources, which can be considered a nonrenewable
heritage from the geologic past. This section should foster your understanding
of material in the text regarding the environmental consequences of mineral
development and the union of biological processes and mining called biohydrometallurgy.
ENVIRONMENTAL ISSUE: Will Mining
with Microbes Help the Environment?
Mining is an ancient
technology practiced for at least 6500 years. To be economic, the
basic mining processes of digging and smelting require high grade ore and
cheap sources of energy as well as tolerance toward damage to the environment.
Although nonrenewable energy sources are expensive and disappearing and
concern over degradation of the environment and health threats to humans
and other species is growing, demand for minerals is increasing, because
of both population growth and technological development.
Mining of metals such
as copper has become more energy intensive and wasteful, and open pit mining
of copper causes acids and heavy metals to contaminate surface water and
groundwater. Smelting produces sulfur dioxide and other gaseous compounds
as well as particles, which contribute to air pollution.
produced by biotechnology offer an entirely new approach to mining.
By 1989, more than 30% of copper mined in the United States depended on
a biochemical process that begins with a microbe, Thiobacillus ferrooxidans.
Biological processes have also been used in mining uranium and gold.
Research is underway to use microbes to remove sulfur from coal and cyanide
from mining waste, a process called biohydrometallurgy.
In the future it may
be possible to use microbes on ores without removing them from Earth.
Metallurgists envision drilling wells into the ore and fracturing it, then
injecting bacteria into the wells and fractures. Biotechnologists
envision using genetic engineering to produce bacteria to mine specific
metals when naturally occurring bacteria do not exist.
The disadvantages of
biohydrometallurgy are that it is slow, requiring decades rather than
years, and methods for breaking ores into small enough particles for efficient
extraction are not yet available. Already, biological methods are
economically feasible for low-grade ores that elude conventional methods,
but further technological innovations may make them competitive in more
Photo Credit: US EPA