Ecofriendly abiotic resource extraction

Truck and excavator for the degradation abiotic raw materialsClick to enlarge
Abiotic resource extraction
Source: nikitos77 / Fotolia.com

Increasing amounts of abiotic resources are being extracted with each passing year. These elements are converted into or used to make raw materials, with the aim of meeting growing worldwide demand. In increasingly ecologically sensitive areas, this evolution is exacerbating worldwide environmental problems such as climate change, soil degradation, and biodiversity loss.

Table of Contents

 

Sustainable raw materials use

Various approaches are used to keep environmental pollution attributable to raw material extraction within reasonable bounds. We need to use raw materials more efficiently and judiciously in the manufacturing and consumption domains. Waste management and product stewardship laws also make a key contribution in this regard, in that they allow primary raw materials to be replaced by secondary raw materials. Another possible approach is to intervene in actual primary raw material extraction processes, which often generate massive amounts of pollution. As an industrialized nation that exports large numbers of cars and machines, Germany is highly dependent on imported primary raw materials. A large portion of Germany’s non-ferrous, mineral raw materials (sand, gravel, certain industrial minerals) are obtained within Germany, thus ensuring a reliable domestic supply of these elements in whole or in part. But on the other hand, Germany is highly dependent on imported metallic raw materials, certain industrial minerals, and energy raw materials, as well as the products derived from these elements. Hence much of the pollution engendered by Germany’s raw materials needs occurs beyond our borders, and from a life cycle standpoint we are partly responsible for this pollution. Hence the UBA advocates that the ecological and social aspects of German raw materials activities be taken into greater consideration. When it comes to raw materials extraction, the UBA supports the optimization and dissemination of internationally recognized environmental and social standards, as well as best available techniques (BATs).

Environmental impact on the life cycle of a putative raw materials extraction projects

Any given raw materials extraction project normally entails a series of life cycle phases (exploration, development, extraction, closure and rehabilitation) each of which impacts the environment very differently. The key factors in this regard are the impact on local ecosystems and biodiversity, the impact on the water balance, handling mining wastes, energy consumption, and water, soil and air emissions. The nature and extent of each of these vary greatly depending on factors related to the following:

• the raw materials that come into play
• technology
• policies and institutions
• society
• ecology.

The environmental impact of raw materials extraction unfolds over a long stretch of time, and during the extraction phase along a concurrently unfolding but often spatially distributed process chain extending from extraction to processing to refining. The environmental impact normally becomes considerably more severe during exploration, development and extraction operations. On the other hand, the environmental impact tapers off during the extraction site shutdown and cleanup/rehabilitation phases.

Exploration

This phase involves determining, using geological, geochemical and geophysical techniques, whether extracting raw materials from the target site is technically and economically feasible. The ecosphere interventions comprise exploratory drilling, sampling, initial mining, and processing tests. The environmental impact of this phase is relatively minor.

Development

During the development phase, which is relatively brief, preparations are made to extract materials from the target site. This involves the construction of the necessary project infrastructure elements such as roadways, conduits, buildings and installations. Conveyor and processing apparatuses are also installed, and basins for tailings are dug if necessary. The exact infrastructure elements needed for a given site can vary greatly depending on the location and surroundings of the deposit, whereby these elements mainly comprise the following: construction of a project infrastructure; building railroad lines, highways, ports, airports, power plants, water treatment plants, and even whole cities replete with schools and hospitals. And of course the environmental impact of the development phases varies accordingly.

During the open-cast mining development phase, the upper rock layer (which is of little or no value) is stripped away so as to expose the actual deposit and allow for raw materials extraction. This process normally generates massive amounts of mine waste that is dumped to form mounds, which of course permanently alter the landscape and occupy land and natural areas. Mine dumps can cause water, soil and air pollution, depending on the aforesaid parameters. They can also generate dust emissions, provoke acid mine drainage, and mobilize heavy metals and radionucleides. In underground mining, shafts and tunnels are dug into a mountain so as to expose the deposits. These operations can engender residues (albeit to a lesser extent than open-cast mining) in the guise of valueless waste rock, which needs to be dumped above ground.

Extraction phase

During the extraction phase, the deposit’s raw materials are extracted over a period extending from a number of years to decades. The oftentimes extremely severe environmental impact of raw material extraction and the subsequent processing of converting the extracted raw materials into a finished raw material are described in the next section.

Shutdown and rehabilitation phase

During the rehabilitation phase, the mine is closed and the various installations are usually dismantled. Mining often results in chronic environmental problems, irreversible environmental changes, and land that is rendered irreversibly unusable. The extent to which this occurs is mainly determined by the practices that were used during the extraction phase, as well as the nature and scope of the cleanup and recultivation measures. In order for site rehabilitation operations to achieve success, the project’s mining permit should specify exactly which rehabilitation measures are to be carried out (recultivation, site stabilization, cleanup). 

 

Ore mining

Environmental impact along the supply chain: from rough raw material to refined raw material (ore mining)


Extraction

Extraction (i.e. removing raw materials from nature) is the phase in the raw materials supply chain that entails the most extensive intrusion into the natural environment. However, the environmental impact of extraction is largely determined by the type of mining involved and the mining techniques used. Open-cast mining usually has a more severe environmental impact than underground mining, since the former requires more space, the impact on the water balance is greater, and larger amounts of earth and rock are moved around.

The first step in ore mining involves the use of explosives to dislodge the rock and ore. The rock is loaded using electric or diesel driven equipment, for transport to the processing installation. To this end (and depending on the properties of the extracted ore) the ore is conveyed either continuously on belts or via pipes, or is conveyed non-continuously by vehicles. The waste rock, which is of little or no value, is piled in aboveground mounds, or is used as backfill for the mine. Such mounds can cause severe environmental damage, depending on the precautionary measures that were taken and how the ore was extracted. Acid mine drainage can occur, and toxic or radioactive substances can be released into waterbodies or the soil. Acid mine drainage can be prevented or at least minimized by separately processing residues entailing differing hazards, and by covering mine waste that can potentially cause acid mine drainage. If acid mine drainage cannot be prevented, control measures can be taken, or the acid components can perhaps be treated.

Processing

In the processing phase, the ore is converted to a commercial product (ore concentrate). The raw material processing method used is determined by factors such as the type of raw material involved, the mineralogical conditions of its extraction, the nature of the target commercial product, and the subsequent processing steps. The following main process steps come into play for metal ore:

The ore is crushed using crushers and mills (which consume considerable amounts of energy), so as to allow for subsequent separation of the ore and waste rock. This is done via a series of processes whose nature is determined by the physical or physicochemical properties of the ore. The amounts of water, energy and chemicals used vary greatly depending on the process or combination of processes involved (e.g. sedimentation, flotation, adsorption, filtration, leaching). These factors also determine the amount of wastewater, solid waste and air and water emissions that occur. Processing, which is often carried out at the mine site, consumes massive amounts of water and energy (particularly for low-concentration metal ores) and generates greenhouse gas and air emissions. The large amounts of processing sludge (some of it toxic) are taken to massive sedimentation basins, where the sludge is stabilized and then dumped in mounds. Terrestrial and/or waterbody ecosystems can be contaminated in the event of a dike breach, faulty sedimentation basin sealing, or sludge instability. The practice, now common, of extracting materials with ever lower ore concentrations in large open-cut mines has in recent decades resulted in a dramatic increase in processing residues and mining material.

Smelting and refining of the now processed raw material (ore concentrate) is partly carried out at the mine site, but is also performed at metal foundries and refineries around the world, depending on transport costs and target value creation. Depending on the technique and raw material that come into play, these final process steps in the raw material to refined material supply chain generate waste such as slag, result in air and greenhouse gas emissions, and release toxic substances into waterbodies, soil and the air.

 

What are abiotic resources?

Abiotic resources comprise all raw non-biotic raw materials, i.e. all raw materials that are not derived from living organisms. These resources include fossil fuels, ore and other mineral raw materials, construction minerals such as sand, gravel, and rock, and industrial minerals such as silica sand and potash.

Abiotic resources comprise all non-renewable, non-recyclable resources of natural origin that are usable in one or more production processes.
Fossil fuels are a special case in this regard. For while they are derived from biomass that was produced millions of years ago, by virtue of their having attained their current state through extremely gradual geological processes, they qualify as abiotic resources.