Would you eat vegetables and crops that have been irrigated with mine water? At first glance many people may scorn these ‘mine-veggies”, but research is showing that treated mine water yields crops every bit as nutritious as those irrigated by rain water.
The crop-growing project is one of the environmental research projects that coal mine research group Coaltech 2020 is driving in order to make coal mining more sustainable and to add value to mining operations. The research is based on the coal mining industry’s needs and challenges.
Coaltech 2020 is a collaborative research programme formed by the major coal companies, universities, the Council for Scientific and Industrial Research (CSIR), National Union of Mineworkers and the state. Its aim is to address the specific needs of the coal mining industry in South Africa, using local and international knowledge and skills.
Its mission is to help research, development and application of methodologies and technology that will enable the industry to remain competitive, sustainable and safe, well beyond 2020.
Coaltech’s research needs have been grouped into six technological areas with a common technological theme: geology and geophysics, underground mining, surface mining, coal processing, surface environment, and human and social factors.
The environmental side runs projects to find, for instance, uses for mine water and by-products of mining, while also investigating the best ways to rehabilitate dumps and the mines.
Results have been recorded in alternative water treatment processes, irrigation of crops with waste water, the beneficiation and briquetting of fine
and ultra-fine coal, the preparation of mine
closure guidelines and the measurement of greenhouse gases.
Partnerships
One-third of Coaltech’s funding for the research programme comes from the CSIR, a third from the Department of Trade and Industry and a third from the coal-mining industry.
Jaap Viljoen, the group manager: environmental management at Ingwe Collieries, says the
challenge of the research Coaltech is doing is to keep it practical and fast-moving. Ingwe Collieries, owned by BHP Billiton, participates in the
environmental research projects.
‘With the rising costs of mining, it is important to research ways to continue mining economically after 2020,” he says.
Viljoen says it is easy to get bogged down in detail while doing the research, but ‘we need to generate practical, usable knowledge for the mines that they can use in their day-to-day operations”.
He says one of the biggest successes of the
project has been the pace at which the research has been done. ‘On average, we yield results in about three years after the start of every project.
‘The development of technology and the application of research findings will enable the South African coal industry to remain competitive,
sustainable and safe well into the 21st century.”
Greenhouse gases
Viljoen is especially proud of the research results Coaltech’s greenhouse gas climate-changer project has yielded. The project was started in 2002 and completed this year.
He says in the past measurements of South Africa’s contribution towards methane emissions were based on an international standard, and they indicated that coal was responsible for 60% of all methane emissions in the energy sector. Based on this approach, South African coal mines were thought to be ‘greenhouse pariahs” pumping anything between 800 000 to over two million tons of methane into the atmosphere every year.
But Viljoen says, after conducting studies in the Coaltech 2020 programme and devising a credible model for underground mines, they found that the emissions are significantly lower, ranging between 62 000 and 92 000 tons a year.
‘We proved with the research that South African coal mines have the lowest emissions in the world, while the former perception was that we were one of the highest contributors,” he says.
This is because South African underground coal mines are less gaseous than those in the rest of
the world, because of the type of coal that is extracted. ‘This could have important and positive marketing implications for South African coal,” Viljoen adds.
Abandoned mines
Henk Lodewijks, a mining engineer at Anglo Coal, says mines abandoned 60 or 70 years ago are a thorn in the side of the local industry.
‘In those days there were no reference and rehabilitation requirements, so the mines were simply abandoned with no rehabilitation done,” he says.
The air and water pollution caused by these mines is a big challenge. Burning mines are a serious hazard to both land usage and people, who can fall into one of the burning mines.
Water pollution accumulates over the years and abandoned mines in the Witbank area are now affecting the water catchment area of the Olifants River.
Data about the abandoned mines is often sketchy because of the bad record-keeping of the early 20th century, and even the government today is unable to pinpoint exactly where all the abandoned mines are located.
‘No one is sure what is out there,” says Lodewijks.
Coaltech and its partners are busy with a project to identify the abandoned mines and to build a database of those mines that present the biggest risk and need the most attention. Lodewijks says a report is to be completed this year on what needs to be done to clean up these old mines.
Water solutions
South African coal-mine water is typically gypsi-ferous: high in calcium, magnesium and sulphate concentrations. Coaltech’s research has shown that the water can be treated at a cost currently above the prevailing potable water prices. The organisation expects that, with further research and the continued pressure on potable water consumption in the coal mining areas of Mpumalanga, it is not unreasonable to expect that coal-mine water treatment could become commercially viable.
Traditionally, the sustainable consumption of water in the mine industry has been the industry’s biggest headache, says Lodewijks. ‘But now we can do something about it,” he adds.
In 1992 the industry started experimenting with water desalination. The salinity of waste water from coal mining renders it unsuitable for direct discharge into river systems.
Two pilot water treatment plants were commissioned at Landau Colliery by Anglo Coal as part of the sulphate reduction project. The biological plants are now working at their full capacity, but the cleaning up of the water has not been a cheap venture for Anglo Coal.
Coaltech 2020 also has a pilot plant called the CSIRosure plant, which uses a biological sulphate-removal process.
Lodewijks says cleaning up mine water could prove to be a blessing in disguise. The Olifants River catchment area is extremely water-stressed and will become even more so in the future. Clean mine water would be able to relieve some of the area’s water problems. ‘We are sitting on water and that water must be utilised.”
He says though they are happy with the results of the biological plant, the next plant will probably be mechanical because of the high costs involved. But as technology improves desalination will become more affordable, Lodewijks believes.
Recycling residues
The environmental impact of placing coal residue, fine coal residue and ash in mined-out areas is also being investigated.
Large volumes of coal residue are produced in coal mining and currently many mines are disposing of these by-products by dumping them into underground mines, worked-out open-cast mines and ‘ash dumps”.
But some of these methods are extremely expensive and unsustainable, not to mention the horrific impact they are having on the environment. And future mining will make these practices even more expensive and environmentally unsustainable.
Coaltech 2020 has developed a plan to produce briquettes made of coal fines and slurries. The
35-tonne-an-hour plant was recently moved to
the Landau Colliery and competent binderless
briquettes have been manufactured over the past two years.
If the current super-fine coal, which is discarded, can be dried and agglomerated, it could create an additional income of approximately R200-million a year. And for every year the life of the Witbank-Highveld coalfield can be extended, a potential income of some R30-billion will be achieved.
Another Coaltech 2020 project used an experimental set-up built by the Department of Water Affairs and Forestry (DWAF) in KwaZulu-Natal, and proved that, when rehabilitating coal mine residues, the design of the soil cover, and specifically the thickness of the cover, had a major effect in limiting the flow of water through the cover. This reduced the volume of potential acid mine drainage.
The cover also had a major effect on the flow of air, thereby limiting one of the essential elements for the formation of acid mine drainage.
The current project assesses the performance and sustainability of existing in-field covers of coal discard dumps in the Mpumalanga coalfield, while analysing the expected efficiency of the most promising new soil cover designs. The general aim of this project is to measure and improve the effectiveness of various cover configurations in limiting rainfall infiltration and oxygen ingress into coal discards and spoils.
Spontaneous combustion
The Kleinkopje Colliery, owned by Anglo Coal, recently participated in a Coaltech 2020 study to characterise gaseous and particulate emissions from spontaneous combustion at a typical opencast mining operation in the Witbank area. This will reveal more about the air pollution and how to control it.
Crop irrigation
Investigations into the irrigation of crops with gypsiferous waste water have exceeded expectations, says Lodewijks. Trials have indicated that higher crop yields can be obtained under irrigation with mine waste water.
Studies at Anglo Coal’s Kleinkopje Colliery showed that gypsiferous mine water was sustainable for irrigation in the medium term, with
negligible impact on ground water. The crops that grew the best with the treated water were potatoes and maize.
‘Farmers in the area have been very enthusiastic,” says Lodewijks. ‘They have been begging us for water, but we will have to wait for DWAF’s approval.”
The future
Over the past few years, Coaltech 2020 has tackled nearly 100 projects, many of them concerned with the improvement of the environment. The successes have been encouraging, but the organisation realises that many other solutions have to found to make the coal industry sustainable by 2020.
There is still no lasting solution for problems associated with spontaneous combustion and the sustainability of water salination can also still be improved. But Coaltech 2020 is definitely making a difference to South Africa’s coal industry, a difference that will ensure its survival.