At a road block in western Tanzania, miles from anywhere, a uniformed official raises a flagged barrier. Nearby is a spill of black, like an oil slick.

This is one of several checkpoints which have been set up around the country in a half-hearted attempt to curtail the largely unregulated trade of charcoal, widely used across the continent as a fuel for cooking.

The guard on duty has confiscated six sacks. They lean against one another and bleed black dust into the sand.

Over the next 50 miles there are dozens of sacks propped up under trees. These will be loaded up by truck drivers who pay around $4 a bag to sell for up to six times the price in the city.

The guard at the roadblock has clearly opened his hand for "kitu kidogo" - a pay-off from coal traders in search of a quick buck.

The numbers tell the story - according to the Tanzania Association of Oil Marketing Companies, 20,000 bags of charcoal enter the capital Dar es Salaam every 24 hours.

Millions at risk

But the impact of this unregulated coal trade is chilling.

Aid agency Christian Aid estimates that 182 million people in Africa are at risk of dying as a consequence of climate change by the end of the century.

Meanwhile, Oxfam believes climate change is frustrating the efforts of millions on the continent to escape poverty.

Nobel laureate Professor Wangari Maathai offers a solution.

Why is climate change such a harbinger of doom? Andrew Simms from the New Economics Foundation explains: "Global warming means that many dry areas are going to get drier and wet areas are going to get wetter."

This imbalance will make subsistence farming, upon which millions of Africans depend, even more precarious. It will also exacerbate famine and disease.

"One adaptation option for Africa is to keep her forests standing so that they provide essential environmental services such as carbon sinks," she said.

It is estimated that carbon is accumulating in the atmosphere at an annual rate of 3.5 billion metric tonnes.

A 40-year-study by the University of Leeds of African forests - which account for a third of the world's total tropical forest - demonstrates that Africa is, indeed, a significant carbon sink.

Lee White, a climate change expert, concurs: "To get an idea of the value of the sink, the removal of nearly 5 billion tonnes of carbon dioxide from the atmosphere by intact tropical forests should be valued at around $25 billion a year. This is a compelling argument for conserving tropical forests."

But Africa has not been very good at this.

According to the UN the continent is losing forest twice as fast as the rest of the world.

"Once upon a time, Africa boasted seven million square kilometres of forest but a third of that has been lost - most of it to charcoal."

Lucrative business

The reality, however, is that in sub-Saharan Africa only 7.5% of the rural population has access to electricity.

Wood and its by-product charcoal are, unless radical steps are taken, likely to remain the primary energy source for decades.

Additionally, charcoal is a lucrative business - not only for those collecting wood to burn.

In the Kenyan capital, Nairobi, over 70 tonnes of charcoal dust is discarded daily. Some 10% of that waste is absorbed by a company called Chardust, which salvages it from charcoal traders across the city and processes it with binders as a charcoal alternative.

The company manufactures 250 tonnes of saleable product a month.

Some though are trying to look beyond the finite resource. To the west of Nairobi, Cheryl Mvula of the Tribal Voice consultancy has introduced the extraordinary Cow Dung Fuel Initiative to counter deforestation in the Mara Triangle of Kenya's Masai Mara.

Here dung is mixed with waste paper and water, fashioned into briquettes and sundried for use.

Since the project's inception in March 2009, firewood collection has reduced by 75% in the five villages where the scheme has been piloted.

Organic alternative

Back in Tanzania, where the charcoal market remains largely backstreet, the industry is valued at upwards of $150 million a year.

This figure encouraged Briton Nicholas Harrison to get involved. His company, the East Africa Briquette Company, is the only producer of an organic alternative in a region where 90% of people use charcoal.

The company's product, Mkaa Bora, is prepared from waste and post-harvest products - sawdust, charcoal dust, maize cobs and even banana skins.

Effectively, local "recipes" are designed according to a given area's crop predominance.

The waste burns more slowly and is 30% hotter than traditional charcoal.

The production is also much leaner than traditional charcoal-making, where just 40% of the wood felled is converted into a useable fuel.

But how to balance job creation with the need to protect the environment?

In Uganda, for example, which has lost half of its forest cover in the past 30 years, charcoal production yields 20,000 jobs and generates more than $20 million in income every year. In Kenya it is 10 times that figure.

Clearly any future charcoal alternative has to fill the gap.

Whether any African governments are keen to break away from the convenient job-creator - particularly during a challenging economic climate - to invest in alternatives will be a true test of their commitment to the environment.