Forest conservation is a major challenge for the Democratic Republic of Congo, the world's second biggest green lung after the Amazon, amid a paucity of energy production and renewable alternatives.

The country's massive tropical forest, four times the size of France, covers some 1.55 million square kilometres (600,000 square miles), mainly in the north.

It includes most of the Congo basin which is the second-largest oxygen supplier on earth after the Amazon forest.

For the time being this green capital, home of the greatest biodiversity in Africa, remains "relatively intact", according to Achim Steiner, the executive director of the UN's environment programme (UNEP), who gave a presentation in Kinshasa this month.

However "the intensification of deforestation in response to a growing energy demand", as well as the spread of slash and burn farming were "alarming signs", he added.

Only nine percent of the 62 million Congolese have access to electricity despite the 100,000 megawatt potential of the Inga dam on the mighty Congo River, underexploited due to a lack of equipment and maintenance.

Therefore the people cut down some 400,000 hectares (988,000 acres) of forest every year just for their heating and lighting needs, according the UNEP.

"Conservation is directly linked to development, because if there's no energy how can you stop the people from going and chopping down the forest for firewood? It's impossible," Environment Minister Jose Endundo said.

He insisted however that "we are evolving towards a green economy," under the aegis of the United Nations Collaborative Programme on Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (REDD), foreseeing a multiplication of initiatives for reforestation and the use of less polluting energy sources.

At Nsele, in Kinshasa province, a pilot project for "integrated bio-economic" farming has been imported from Ethiopia.

With UN support it, for example, recycles pig urine to produce a biogas for braziers and lamps.

"We have the capacity to stock 50,000 cubic metres," explained Getachew Tikubet, the Ethiopian behind the project which is also being tested in provinces in the country's east and west.

Around Ibi Village, also in Kinshasa, is another preservation project.

There it is planned to plant a forest of acacia trees, surrounded by manioc, to provide a 4,200-hectare forest for energy use, at the same time trapping in five years a million tonnes of carbon dioxide.

The World Bank's BioCarbon Fund, along with French enterprise Orbeo, -- a joint venture between chemical group Rhodia and Societe Generale bank -- have each bought "500,000 tonnes" of carbon credits to resell to polluters to recompense their greenhouse gas emissions, the Ibi Village project head Delly Kayuka told AFP.

However Kayuka voiced his disappointment at the asking price, at $4 dollars per tonne of CO2.

According to the UNEP the Democratic Republic of Congo's reserves of carbon dioxide, estimated at over 27 million tonnes, could generate up to $900 million per year up to 2030.