South Africa has started geological mapping at the country's first carbon capture and storage (CCS) site, where it plans to inject vast quantities of CO2 deep underground from 2023, a senior Council for Geoscience official said.

The project will be based around the town of Leandra, Mpumalanga province, in South Africa's north east, a carbon emissions hotspot and home to several coal-fired power stations as well as Sasol's Secunda coal-to-liquids fuel plant, the world's largest.

Releasing around 470 million tonnes of carbon dioxide (CO2) a year, South Africa is the continent's biggest emitter of greenhouse gases, and coal provides the bulk of its electricity.

CCS is controversial, with environmentalists saying it risks becoming an excuse to continue burning fossil fuels, and could lead to neglect of nature's own carbon capture system, forests, which also sustain biodiversity and rainfall.

Others however see it as essential to meeting the goal of a net carbon zero world economy by 2050. Its most enthusiastic backer is the global coal industry.

The South African government has repeatedly defended its right to tap into abundant coal deposits even as the country increases its use of renewable energy.

"South Africa will still be using coal for a very long time, so... we need to try and use it responsibly to limit CO2 emissions," David Khoza, the CGS executive manager running the project, said.

The deadline for tapping a $23 million World Bank grant to fund the CCS project was originally set for December this year, but has now been pushed out to June 2023, a bank spokesperson told Reuters.

Khoza said the project will link a pipeline transporting compressed CO2 from major emitting sources such as Secunda directly to the identified injection site that is overlain with an "impermeable rock cap".