Coalgae: a combination of waste coal dust and algae. Microalgae slurry is mixed with coal dust and formed into briquettes. When heated up to about 450°C the briquettes produce a high-quality crude oil and a solid, clean-burning fuel.

Heather Dugmore writes for BDlive that a new fuel, Coalgae – produced from a combination of waste coal dust and algae – could save South Africa up to 40% of its crude oil imports. Professor Ben Zeelie and his team at Nelson Mandela Metropolitan University (NMMU) combined coal dust with algae to form neat, clean-burning briquettes. When heated up, they produce high-quality crude oil.

“The trigger that led us to Coalgae was completely accidental,” said Prof Zeelie, who heads a research-and-development institute at NMMU in Port Elizabeth, called InnoVenton. “We were experimenting with growing algae in plastic bags, when we noticed that some of it had leaked out of the bags and formed a concentrated algae cake. It got us thinking and we figured that if we bind the algae cake with coal dust, we could come up with a new fuel.”

Together with his team of academics, postgraduate and postdoctoral students, it has taken Prof Zeelie five years to perfect Coalgae, and to ensure they can produce it economically and at scale. The team is conducting the final consistent production runs to confirm the economics of the product for take-off agreements. Organizations in the US, China, France and Indonesia are interested, and Prof Zeelie says that they are looking at an international license.

“In coal mining you lose up to 30% of the coal as dust,” he said. “The dust is conventionally a waste product that needs to be buried because otherwise the wind would blow it away – 50 to 60-million tons of coal dust waste every year that needs to buried. This is both a huge economic loss and a huge environmental problem as it releases acid water and other chemicals into the soils over time.”

The team discovered, after they started experimenting with algae cake and coal dust, that the algae bind beautifully with the dust. The bacteria in the algae are able to change the complex structure of coal.

They grow the algae quickly in vast, shallow artificial ponds stacked with bioreactors to produce microalgae slurry. This is then pumped into settling ponds to produce an algae concentrate that is then mixed with the coal dust waste, and compressed into neat briquettes, which are dried.

“When we heat up the Coalgae briquettes to about 450°C in the absence of oxygen, we are able to produce a high-quality crude oil and a solid, clean-burning fuel,” said Prof Zeelie. “When we burn the Coalgae, it burns without smoke – the combustion behavior is totally different than burning coal. The oil can be processed in a normal oil refinery, while the solid fuel can be used as thermal coal for heat and energy generation.”