Slowly the old woman stacks freshly cut branches into a bundle and puts it on her head. Bent and burdened, she shuffles along a dusty footpath to a humble tin shack on the outskirts of Windhoek.

"There are fewer trees left to get firewood. When I came here five years ago to live with my daughter, there were more trees than shacks. Today there are shacks all over but few trees," said Laimi Mbinga.

"It is sad -- the trees are vanishing."

Unable to afford electricity, the 58-year-old widow needs firewood to cook. But as she and other migrants have moved to Namibia's capital, their tree-chopping has helped the desert expand, leaving the country even more exposed to the threats of global warming.

The Windhoek municipality is taking a first step toward fighting climate change with a scheme to harness methane produced by decomposing landfill waste to generate electricity.

Under the Kyoto Protocol's Clean Development Mechanism (CDM), Namibia can sell "credits" generated by reducing the methane output to companies in the rich world that need help meeting emissions-cutting targets.

The sale of those credits is estimated at 2.3 million Namibian dollars ($280,000, 207,000 euros) annually, which would cover the cost of the investment within five years, while cutting down the city's electricity use.

A similar project will harness methane from the digestion of sewage sludge at a wastewater treatment plant to generate electricity for the city, said the city's chief engineer Cobus de Waal.

"Registering it as a CDM project together with expected savings in the monthly electricity bill will cover costs for the upgrading of the bio-digesters and installation of the gas engines," said De Waal.

Pierre van Rensburg, a private consultant advising the city on the project, said methane was far more damaging to the atmosphere than carbon emissions.

"Damage caused by methane to the earth's atmosphere is estimated to be approximately 21 times higher than that of carbon dioxide," he told AFP. "Utilising methane to generate power is considered an optimal solution."

The environment ministry has green-lighted the project, and a detailed project design will be submitted to the UN for approval in early 2012.

"Namibia so far has no successfully registered CDM projects and should the City of Windhoek be successful, this will be a first for Namibia," Van Rensburg told AFP.

As a middle-income country that is wealthier than much of the continent, Namibia is well placed to tap into such schemes, with a healthy supply of local engineers to oversee it.

Namibia is also in greater need of action against climate change.

Temperatures in the country have already risen three times more than the global average over the last century, according to a study by the London-based International Institute for Environment and Development.

By 2065, temperatures are expected to rise by one to four degrees Celsius, Namibia said in July in its latest report to the UN Framework Convention on Climate Change (UNFCCC).

Parts of Namibia already receive as little as 25 millimetres of rainfall a year.

Even if rainfalls remain the same over the next five decades, the warmer temperatures will boost evaporation rates, leading to water shortages, the report said.

Rising sea levels will likely swamp Walvis Bay, Namibia's main port, it added.