Certain wastes in the mining sector present an opportunity to create alternative fuels, which can alleviate the energy supply challenges in the local industry, says waste management solutions provider Interwaste.

Repurposing waste for energy purposes can also reduce the reliance on landfills and the carbon footprint of the mining industry.

“The prevalence of mining waste provides an opportunity for waste-to-energy projects, and while these are not all ready for implementation, there is definitely a move towards identifying and exploring the opportunities afforded by waste solutions,” states Interwaste business development and marketing director Kate Stubbs.

The mining industry is responsible for more than 38% of local industries’ total energy consumption, she says. It also contributes 244-million tonnes a year of marketable coal and makes South Africa the fifth-largest coal producing country in the world.

The mining industry is crucial to the local economy, as it contributes to gross domestic product and significant exports. This, in turn, places pressure on the mining industry to reduce reliance on the national energy grid or to contribute towards downstream cleaner-energy initiatives.

Stubbs states that it is essential that the local industry explore alternative and innovative methods of incorporating the waste produced into its functioning.

One such example is the conversion of old oil into a light burner fuel for heavy machinery. This will enable the mining industry to power machinery, reduce energy consumption and carbon emissions, as well as provide other industries with fuel to contribute to larger energy relief.

Stubbs also highlights the importance of alternative energy sources, such as refuse-derived fuel (RDF) production facilities, and the vital role they can play in reducing South Africa’s reliance on traditional energy inputs.

RDF is a solid fuel source recovered through the shredding and bailing of certain presorted dry industrial nonrecyclable waste. The RDF produced by Interwaste requires no heat for drying, is cleaner and presents a higher heating value, similar to that of A-grade coal. It is also a suitable alternative to fossil fuel use.

Similar RDFs can be used for sole- and co-feeding plants, production plants for power, steam and heat generation, as well as cement kilns and other suitable combustion installations.

Stubbs cites rubber as another significant waste stream produced by the local mining industry. Rubber can also be converted into an RDF by removing the wire and beading from off-road equipment, and eventually shredding it to a fine size for RDF use in other industries.

“As the country moves towards a zero waste-to-landfill target, where hazardous waste-to-landfill is already prohibited, there is mounting pressure to find ways of repurposing waste. This can, and already does, contribute significantly to energy inputs at various production facilities, with the opportunity to increase this waste repurposing fundamentally.”

Proving the Business Cases

Stubbs emphasises the opportunity for a collective of mines to produce sufficient quantities of suitable waste to make a business case for developing a waste-to-energy project. This could be within a specific geographical area of operation, where mines could potentially pool suitable nonrecyclable wastes.

The business case would depend on the available volumes of suitable waste to sustain production and power outputs. Additionally, this model of the project is more feasible for mines in isolated areas with little access to waste removal support services.

“Mining houses are looking at reducing costs associated with waste management and want to leverage the waste value and economies of scale presented by operations’ waste production. One of the main challenges mines face is their being located in remote locations, which increases waste costs, owing to the waste having to be transported over long distances.”

To address this, mines would benefit from on-site processes to reduce the handling and transportation of waste materials; this would also add commercial viability to the overall operation, based on what technology is required and the waste volumes generated.

Interwaste could assist mines in this regard, as the company offers a fully integrated and tailored waste-management service that incorporates safety, as well as environmental, social and economic benefits.

The company has been involved in a variety of waste-related projects with mining companies this year.

This includes processing garden and wooden pallets on site for potential bioremediation or alternative-energy use. Additionally, Interwaste has used on- and off-site anaerobic digesters for canteens and food waste, which can then be used to generate energy in the form of steam or gas for other processing plants.

Lastly, Interwaste has also conducted pyrolysis of general waste tailings, and rubber or plastic products.

Interwaste is also working with a large local miner to achieve a zero waste-to-landfill goal by the end of the year.

Interwaste conducted an analysis of the miner’s facilities, which indicated that a large portion of the miner’s waste streams could be recycled and reused. However, a large portion of these waste streams are not recyclable or reusable.

“This is where Interwaste’s alternative-fuels business proves its worth, as it assisted the miner in contributing to its zero waste-to-landfill target, which is still under way,” she concludes.