Mining and the environment
The impact of the mining industry on the environment has been a public concern, with growing appreciation of the natural environment and increasing awareness of the possible harmful effects that the industry's activities can cause. The industry and government have responded with a number of initiatives and regulations to protect and manage the environmental effects of mining activities.
The extractive nature of mining operations creates a variety of impacts on the environment before, during and after mining operations. The extent and nature of impacts can range from minimal to significant depending on a range of factors associated with each mine. These factors include: the characteristic of the ore body; the type of technology and extraction methods used in mining and the on-site processing of minerals; and the sensitivity of the local environment. The environmental impacts of mining, although significant, are generally confined to local areas. Apart from direct physical impacts of extractive activities, contamination of air, land and water may also result. However, mining in isolation may not be the main land use that upsets ecological systems, as environmental effects are cumulative in nature and other past activities or events may have contributed to these effects.
This article briefly discusses the main environmental impacts of mineral mining, such as wastes, and the rate of resource use (where the supply of minerals depends on the rate of resource use, which is affected by the economic life of mineral deposits and the rate at which new reserves are discovered). The article also summarises environmental management initiatives, such as the use of legislation, environmental impact assessments, environmental protection expenditure, rehabilitation and industry self-regulation.
Impact of the mining industry on the environment
Mineral exploration can impact on the environment. Its effect depends on the scale of exploration and what equipment is used in the exploration phase. Initial exploration may involve the use of satellites and aerial photography, with the latter impacting through noise and proximity to wildlife areas when conducted at a low altitude. Activities at ground level often require the use of bore holes, excavation pits and transect lines. The use of support equipment also leaves an impact on the environment; exploration vehicles require access tracks, and even helipads, if left unrehabilitated, can have medium- to long-term effects.
Environmental impacts may also occur through mine establishment, ore extraction, mineral concentration and associated transport, provision of infrastructure (which may include whole townships) and downstream processing.
Inherent to mining and mineral processing operations is the generation of wastes. These are mostly in the form of waste rocks, including surface waste rocks, rocks between ore bodies or layers and other unwanted material. This form of waste contains low or nil concentrations of the material desired and is often relatively toxic. Normally, waste rocks are stockpiled or dumped adjacent to or near the excavation area, to be used later as backfill during reclamation.
Mineral processing produces wastes in grain sizes of fine sand, silt and clay fractions. Referred to as mine tailings, this type of waste contains significant concentrations of minerals that are not amenable to recovery at the time of initial mining. Tailings are usually disposed of in specially lined tailings dams, which are normally capped and revegetated to prevent the release of environmentally harmful materials. Other wastes from mining may be in the form of water and air pollution. The majority of air emissions associated with the mining industry include dust, oxides of nitrogen, sulphur dioxide and carbon monoxide. Some of these come from mining vehicles and on-site plant machinery. Water quality may be affected by:
Acid mine drainage - when large quantities of excavated rock containing sulphide minerals interact with water and oxygen to create sulphuric acid.
Heavy metal contamination and leaching - heavy metals occur naturally in many ores, and are often released in the mineral extraction process. Metals (i.e. arsenic, cobalt, copper, cadmium, lead, silver and zinc) contained in an excavated or exposed rock may be leached out and carried downstream by flowing water.
Processing chemical pollution - spilling, leaking or leaching of chemical agents (i.e. cyanide, sulphuric acid) from the minesite into nearby water bodies.
Erosion and sedimentation - erosion of cleared land surface and dumped waste material resulting in sediment loadings into the adjacent water bodies, particularly during rainfall.
Environmental impacts resulting from mining are not limited to current mining operations. Mining residues and scars at old mining sites may also impact on local environments. The legacy of abandoned, unrehabilitated minesites has required comprehensive remediation efforts paid for with taxpayers funds. One example is the Upper South Alligator River (north of Katherine) which forms part of Stage III of the Kakadu National Park World Heritage area. As the numbers of visitors increased to the area, a hazard reduction works program was conducted during the early 1990s (Mudd 2000).
Rate of mineral resource use
Minerals, oil and gas are finite and non-renewable resources; their consumption today poses a threat of scarcity to future generations. The mining industry has an obligation to operate within the concept of sustainable development. This is defined by the World Commission on Environment and Development report Our Common Future (The Bruntland Report) as 'development which meets the needs of the present without compromising the ability of future generations to meet their own needs' (WCED 1987). For the mining industry to be sustainable, it would need to maintain a rate of resource use which is reasonable, that is, its consumption of resources does not go beyond a level which can ensure the availability of resources for the future of the industry and the people. This rate of resource use depends on a variety of factors including the rate of use of existing known resources, the rate at which new resources are discovered, and the rate of recycling of existing materials. If discoveries or recycling do not keep pace with the rate of use, depletion will result.
Geoscience Australia has estimated that Australian stocks of crude oil will be exhausted in eight years if the current rate of production is maintained and there is no discovery of new reserves (GA 2001a). However, with continuing advances in technology for exploration and mining activities, the rate of discovery of new reserves has kept pace with the rate of production, allowing for changes in the actual and potential stocks of minerals, oil and gas. Modern technology has been a contributing factor to the efficient recovery of minerals, and the consequent fall in the cost of finding additional reserves of base metals in particular (ABS 2001a). For example, declining costs (and rising commodity prices) mean that processing of areas such as tailings and slag heaps becomes economically viable. Resource scarcity is also lessened by recycling and/or substitution.
As the previous section outlined, in 2000 Australia's economic demonstrated resources (EDR) of bauxite, brown coal, copper, diamond, magnesite, mineral sands, nickel, phosphate, tantalum, uranium and vanadium increased, while those of black coal, gold, iron ore, manganese ore and lithium decreased (GA 2001b). EDR of zinc, lead and silver were maintained at levels similar to those reported in 1999.
Use of energy and water by the mining industry
The mining industry is not a major user of energy as compared to other industries like manufacturing and electricity. It used about equal proportions of both primary and secondary energy sources in the period 1992-93 to 1997-98 (table 18.16).
The mining industry's use of total energy was 314 petajoules (PJ) in 1997-98, as compared to 121 PJ in 1992-93.
The mining industry is not a high user of water. Between and 1993-94 and 1996-97, it accounted for 3% of total water consumed (table 18.17). Most of water consumed was sourced from the environment.
18.16 MINING INDUSTRY ENERGY USE
|(a) Industries, households and exports.|
(b) Primary energy sources include solar, wind, wood, bagasse, coal, oil and gas, and uranium concentrates.
(c) Secondary energy sources are those mainly derived from a primary energy source such as thermal electricity, which is derived mainly from coal, and refined petroleum products (e.g. automotive petrol) derived from crude oil.
Source: ABS 2001b.
In order to mitigate the adverse impacts from mining activities mentioned above, the mining industry and government undertake environmental management measures. These measures are aimed at the prevention, reduction or elimination of pollution or any degradation of the environment. They include waste management and protection of biodiversity, landscape, air and climate (MCA 2002). Protection mechanisms are backed by environmental legislation from the states and, increasingly, the Commonwealth, which has been assuming more responsibilities and imposing standards on the states.
In Australia, the state and territory governments own and administer mineral and petroleum rights over land, and seaward to three nautical miles from the sea baseline. In these areas, although the Commonwealth Government has some responsibilities regarding the environmental protection, the states and territories are the main authorities for environmental management of most mines within their respective jurisdictions.
Environmental management involves the use of mechanisms in the development, operation and subsequent rehabilitation of mine sites. These mechanisms are supported by legislation. The mining industry has also introduced its own code for self regulation.
Competing land use values
There is little choice in where mining occurs as it depends on the location of the minerals. As a result, there is often competition relating to land use between mining and for example, urbanisation, agriculture and conservation. Mining operations are therefore required to comply with comprehensive measures to control their environmental impacts. One measure is the use of buffer zones where land around a mine site is used for other purposes such as grazing (such as the Bengalla Mine near Muswellbrook, New South Wales). In cases where mines are located close to urban centres, a number of mechanisms, both formal and informal, must be in place to ensure that sustainable relationships are established by companies with various stakeholders, including local communities (between Bendigo Mining NL and the City of Bendigo). Particularly stringent regulations apply where mining operations are located near or next to ecologically sensitive areas, requiring comprehensive environmental protection measures and agreements with governments and local communities (such as the Century Zinc mine lease in north-western Queensland and the 1997 Gulf Communities Agreement).
Legislation on environment
Under Australian constitutional and legal arrangements, the state and territory governments have key responsibility for the management of mineral resources on land. Offshore the Commonwealth has overall responsibility with administrative arrangements shared with state and territory governments (Mining Working Group 1991). The Commonwealth may also exercise its powers and responsibilities where developments may affect the national interest.
The key Commonwealth legislation dealing with environmental impacts, the Environment Protection and Biodiversity Conservation Act 1999 (Cwlth) (EPBC Act), came into effect on 16 July 2000. Under the Act, actions that are likely to have a significant impact on a matter of national environmental significance are subject to a comprehensive referral, assessment, and approval process. The Act has relevance to mining (particularly uranium mining as a nuclear related matter) and any impact it may have on a Commonwealth area (such as a national park).
States and territories administer mineral rights through the issue of permits for exploration and mining according to their own mineral end environmental legislative frameworks. Prescribed standards of environmental performance are set out in respective state and territory legislation establishing powers and regulations which control the collection of royalties, and inspection and control of exploration and mining (Hancock 1993). Regulatory authorities in the states and territories are usually departments of mines and/or environmental protection authorities.
The Commonwealth and each state and territory has legislation relating to Environmental Impact Assessment (EIA) (EA 2002). EIA is the process of assessing likely environmental impacts of a proposal and identifying options to minimise damage. It is only necessary for a project that has a potential significant environmental impact. The main purpose of EIA is to inform decision makers of the likely impacts of a proposal before a decision is made.
The amount of 'rehabilitation' to an area disturbed by mining can range from restoration, where an area is brought to as near as possible to pre-mining condition, to recontouring and revegetating to a state that is non-polluting and compatible with environmental regeneration and community expectations (Hancock 1993). Recontouring can involve construction of pit walls and waste dumps, covering of reactive materials, dismantling of buildings/plant, revegetation, and ongoing environmental quality monitoring. Under legislation, mining companies are required to pay performance guarantee bonds which act as an administrative and environmental management tool. Bonds are usually paid to a state mining authority (repaid after successful rehabilitation), creating a financial incentive to ensure that rehabilitation is carried out. Bonds also provide a source of funds for remediation efforts in the event of a corporate failure of a mining venture.
Minerals Industry Code
A key industry initiative is the Australian Minerals Industry Code for Environmental Management. The aim of the code was not to set standards or to instruct companies how they should run their operations, but to change values and behaviour towards improving environmental performance and public accountability. The minerals industry launched the Code (which is voluntary) in December 1996. As at 1 January 2002, 43 companies have committed themselves to the 2000 Code, representing over 300 operations and well over 85% of production in the Australian minerals industry (AMEEF 2002).
An essential feature of the Code is provision for greater public accountability and verification of the industry's impact on the environment measured against the implementation of the Code's principles. A company's performance is assessed on key areas covering energy use and efficiency, water consumption, land rehabilitation, air emissions, biodiversity, and incidence and severity of environmental issues.
At least 45 company environmental reports have now been released since the Code was initiated in 1996. An External Environmental Advisory Group was also established to serve as a forum for the industry to seek independent advice on assessing and improving environmental performance (MCA 2001). More recently the mining industry has developed expertise in environmental management, to ensure that environmental protection is achieved in planning and operating resource developments. This expertise has been built up across a wide variety of climatic and geographic conditions in Australia and overseas.
Many environmental impacts associated with the mining industry are now reduced or removed, due to improved management by the industry and an increase in environmental responsibilities of the industry imposed by government. Part of the improvement lies in the requirement for companies to budget for expenditure on environmental protection measures, including rehabilitation of mined-out areas and waste control.
Environment protection expenditure by the mining industry
Total expenditure for environment protection by the mining industry increased by 6% from $368.9m in 1996-97 to $390.6m in 2000-01. Metal ore mining accounted for most of this expenditure (58%), followed by coal mining (24%), and oil and gas extraction (8%).
In 2000-01, current expenditure accounted for 73% of total expenditure (table 18.18), an increase from 62% in 1996-97. This was due to an increase in current expenditure of 24% and a decline in capital expenditure of 24% (table 18.19).
18.17 NET WATER CONSUMPTION
|(a) Industries and households.|
Source: ABS 2000.
18.18 CURRENT ENVIRONMENT PROTECTION EXPENDITURE(a), Mining industry
Mine site rehabilitation
|Oil and gas extraction|
|Metal ore mining|
|(a) Current expenditure generally relates to payments of a non-capital nature, for example payments to government agencies or private businesses for waste removal services, environmental audits, site cleaning and environmental impact assessments.|
(b) Includes current expenditure in Services to mining which accounts for $12.7m. This industry was not covered in the 2000-01 survey.
Source: ABS 1999; ABS 2002.
ABS (Australian Bureau of Statistics) 1999, Environment Protection Expenditure, Australia, 1995-96 and 1996-97, cat. no. 4603.0, ABS, Canberra.
ABS 2000, Water Account for Australian, 1993-94 to 1996-97, cat. no. 4610.0, ABS, Canberra.
ABS 2001a, Australian National Accounts: Balance Sheet, cat. no. 5241.0.40.001, ABS, Canberra.
ABS 2001b, Energy and Greenhouse Gas Emissions Accounts, Australia, 1992-93 to 1997-98, cat. no. 4604.0, ABS, Canberra.
ABS 2002, Environment Protection Expenditure: Mining and Manufacturing, Australia, 2000-01, cat. no. 4603.0, ABS, Canberra.
AMEEF (Australian Minerals and Energy Environment Foundation) 2002, Facing the Future; The Report of the Mining Minerals and Sustainable Development Australia Project.
EA (Environment Australia) 2002, An outline of the Commonwealth Environmental Impact Assessment process (under Environment Protection (Impact of Proposals) Act 1974), http://www.ea.gov.au.
GA (Geoscience Australia) 2001a, 2000 Oil and Gas Resources of Australia.
GA 2001b, Australia's Identified Mineral Resources 2001.
Hancock P 1993, Green and Gold: Sustaining mineral wealth, Australians and their environment, Centre for Resource and Environmental Studies.
MCA (Minerals Council of Australia) 2001, Minfo, August 2001.
MCA 2002, Mineral Industry Survey Report, 2001.
Mudd GM 2000, Remediation of Uranium Mill Tailings Wastes in Australia: A Critical Review, Contaminate Site Remediation: From Source Zones to Ecosystems, Proceedings 2000 CSRC.
WCED (World Commission on Environment and Development) 1987, Our common future (Brundtland Report).
18.19 CAPITAL ENVIRONMENT PROTECTION EXPENDITURE(a), Mining industry
Mine site rehabilitation
|Oil and gas extraction|
|Metal ore mining|
|(a) Capital cost can be regarded as expenditure on the acquisition of assets designed specifically to assist with environmental protection measures.|
(b) Includes capital expenditure in Services to mining which accounts for $1.1m. This industry was not covered in the 2000-01 survey.
Source: ABS 1999; ABS 2002.