For more than 10 years, Denis Matembe had been roasting chicken over a charcoal stove in Kampala’s Wandegeya suburb.
His work starts at 4pm, when he lights the stove and ends late in the night. For years, he used up one sack each week, depending on the quality of the charcoal.
Quality charcoal takes a long time to reduce to ash and therefore depends on the kind of tree it is produced from such as mvule, mango, and shea nut.
However, the government has now banned the felling of these tree species for charcoal.
In 2016, Matembe’s boss, Joseph Kalema, heard of something called “wonder rocks.”
Mr Kalema, who owns and operates several chicken roasting stoves in different parts of Kampala, which spent at least Ush600,000 ($160.25) on charcoal per month, was told the rocks would reduce his charcoal bill by more than 75 per cent.
“The cost of charcoal continued to increase while the quality remained poor. I heard about the volcanic rocks and sought to find out if they would work for me,” Kalema said.
He soon replaced Mr Matembe’s old stove with the modern Eco Stove.
“It sounded ridiculous and unbelievable. How can stones cook?” Mr Matembe remembers asking himself.
Like regular charcoal, these rocks are stacked in the stove and charcoal dust is spread liberally atop them.
Twigs of pine or any highly flammable species are then inserted in the middle of the rocks and lit with a match. Within minutes, the stones catch fire and it spreads throughout the stove.
Behind these wonder rocks is Eco Stove, a company that is working with several women’s groups.
The founder of Eco Stove, Rose Twine, says the firm has employed 17 women’s groups, each with a membership of 12 in Kisoro district, to extract the rocks.
The groups are given start-up capital and trained in extracting the rocks from the hillsides. The stones are transported to Kampala and stored at the company factory in Bujjuko, on Mityana Road.
Here, the rocks are cut into different sizes to suit the end-users’ stove size. For instance, the rocks destined for use in institutions are normally bigger compared with those for domestic use.
The blocks are then dipped into hot water for a few minutes, and left to dry for at least one week, a process that prevents them from emitting sparks when they are finally lit.
Ms Twine said the rocks only work in the solar-powered Eco Stove, which comes with an internal air supply system that helps heat up the rocks.
The stove is also fitted with an on-off switch that enables the rocks to burn when turned on, and cool and return to their natural state when turned off. The stove comes with a radio, phone charger and has two lights.
Unlike charcoal which burns down to ash, these rocks can be used multiple times without losing their power or texture.
Domestic stoves retail at Ush200,000 ($53) together with the rocks while a “bag” of the rocks alone sells for Ush35,000 ($9) for domestic use and can last up to six months.
Ms Twine says since the stove does not emit smoke, those using it are protected from indoor pollution.
“They [rocks] do not produce smoke, burn for a long time and you do not need charcoal anymore,” she adds.
“We seek to help groups that utilise these rocks. The law does not stop people from extracting surface rocks found in places such as Karamoja, Mbale, Kisoro and Rukungiri districts for home use,” Vincent Kendi, an official from the Ministry of Energy and Mineral Development said.
“If their activities are regulated, this can be an alternative source of energy. You see what charcoal and fuel wood extraction has done to our forests,” Mr Kendi added.
Christine Akello, National Environment Management Authority deputy executive director, said the authority does not regulate volcanic rock extractions.
Ministry of Water and Environment data shows that natural forests outside protected areas declined by 35 per cent (from 3.46 million hectares in 1990 to 2.3 million hectares in 2005).
A 2017 Joint Water and Environment Sector Review Report estimates the country’s forest cover at nine per cent.
The decline has been blamed mainly on the country’s dependency on fuel wood to cook and power small industries.
More than 90 per cent of the households in the country depend on firewood and charcoal as their source of energy for cooking.