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A gold mine of inspiration

Professor Peter Rose has pioneered a biotechnological process for rehabilitating coal mine dumps using indigenous fungi. Image provided by Clinton Wittstock.

A decade has passed since Peter Rose, Emeritus Professor of Biotechnology at Rhodes University, helped Anglo American to do in six months what Mother Nature left to her own devices would do in 60 years.

“I was approached by the Vice-President of the Coal Division of Anglo American to try find a solution to the huge problems they were having in their attempts to rehabilitate waste coal dumps and the land that they had damaged through their open-cast mining operations,” said Professor Rose, who is the man responsible for launching the first Biotechnology Department in South Africa at Rhodes University.

Professor Rose explained that although Anglo American stored the top soil they stripped from land they mined, by the time they were ready to use it to fill the huge open-cast mines, the soil had lost its living structure. None-the-less, they tried to fill the holes with it mixed with clay and attempted to grow grass on it.

Similar problems were experienced in covering waste coal dumps where they devastated hectares of land to harvest clay and soil for the dump capping process and the grass wouldn’t grow successfully due to the lack of nutrition. Moreover, when the rains came the soil was washed away, the water penetrated into the dump and started a very destructive process called Acid Mine Drainage (AMD).

"I went to investigate and while standing on the dumps I noticed the odd plant growing here and there. I kept on thinking, ‘How come these plants are growing in this hectares-huge wasteland of coal?’ I finally went to have a closer look, and was amazed at what I found,” said Professor Rose.

He explained that when he dug around the plants and pulled them out he was struck by a smell he had become accustomed to while studying mycology, suggesting that a fungus could be present. “When a fungus is active in soil it releases a gas called geosmin. The smell it produces is the same sort you get after thunderstorms or when digging in wet soil,” he explained.

Taking a soil sample back to Rhodes he confirmed that there was indeed a fungus present and was then able to isolate the species involved.

“We found out that a symbiotic relationship existed between the plant roots and this fungus, termed a mycorrhizal association,” Professor Rose said, explaining that as the grass grew and photosynthesised it released organic acid from its roots. The fungus fed on this acid, broke the coal down which in turn released the minerals the plants needed for growth.

He said that it was in fact a process of nature reversing herself. During coal formation, humus and organic material is compacted and solidified to become coal and in this instance the fungi reversed the process breaking the coal back into humus.

What is an geosmin?

Geosmin is an organic compound with a distinct earthy flavor and aroma produced by a type of Actinobacteria, and is responsible for the earthy taste of beets and a contributor to the strong scent (petrichor) that occurs in the air when rain falls after a dry spell of weather or when soil is disturbed.

Based on this knowledge, Professor Rose was able to develop a process which he has patented under the name Fungcoal and is used by Anglo American very successfully to rehabilitate coal mine dumps.

“The fungi are cultivated on a very large scale, the mine dump is simply shaped, without having to cover it up with top soil and clay capping, an environmentally devastating and costly procedure, and then the surface of the coal dump is inoculated with the fungi and a mixture of grass seeds,” said Professor Rose. “The mine dump is then irrigated, the fungi break the coal down into humus, the seeds germinate and the plants grow providing more nutrient support for the fungi, which then grow faster, breaking down even more coal, and so the cycle perpetuates.”

“In just a few months you end up with a prodigious crop of mixed vegetation, basically grassland, growing on the surface of the dump in a layer of about two foot of soil-like humid material, capping the dump off and protecting the environment from AMD,” he said, “doing in months what nature would take many decades to do. The process has also been used to improve the fertility of soils covering open cast mining sites.”

Professor Rose has been involved in other biotechnological inventions petitioned by the mining industry, Rhodes Biosure being one of those. The Witwatersrand is one of only a few conurbations world-wide that is not built alongside a major river and with many mines closing down during the past few years, the fragile and sparse aquatic-ecosystem is under threat.

According to Professor Rose, when production was running at the mines, companies would pump water out of the shafts to facilitate the operation, treat this water and then divert it into the Vaal Dam. Now that the mines have closed and the stakeholders have disappeared, it has become society’s problem to deal with - and it is not a problem that can be ignored. For instance, at the Sterkfontein Caves just outside of Johannesburg, AMD is flowing into the limestone beds, destroying the fossil beds and all the rivers and springs in the area.

Professor Rose’s answer to this catastrophe was an ingenious one, not only because of the biological mechanisms used to address the problem, but also because it linked to an existing process, traditional sewage wastewater treatment treatment plants, which contributed to providing a low cost and a long term solution.

Polluted water from the mine is pumped to the plant, organic matter from the wastewater treatment works is added, the bacteria use the organic material as food and the sulphuric acid in the water is broken down into hydrogen sulphide. Later on the hydrogen sulphide is extracted and converted into sulphur, whilst the treated water is pumped into the conventional water treatment plant and treated before being discharged into the Blesbok Spruit, where it eventually flows into the Vaal Dam.

“Once we had run a pilot project and shown the efficacy of Rhodes Biosure, we were able to set up our first plant on the East Rand in association with East Rand Water Care Company (ERWAT),” Professor Rose said. “Ten million litres of water are treated there daily, so effectively we have saved the Blesbok Spruit, which is a Ramsar site,” Professor Rose enthused, adding that the Marievale Bird Sanctuary forms part of this catchment area.

Professor Rose has over 20 patents in wastewater treatment and acid mine drainage and is well respected the world over. He attributes his success to a good grounding in fundamental science, creativity and what he likes to call “inspired observation.”

“It is like someone from somewhere steps down and gives you what you need at just the right moment,” he said.

This article by Clinton Wittstock first appeared in Blazing a biotechnology trail. You can read a review of the book here, and download a free copy here.

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