Switching 100 households from consuming 200 tonnes of harvested wood a year to 1.8 tonnes of LPG would annually save one hectare of forest.

Some 540 million households around the world, use biomass to fuel their cooking. Perhaps half of these use wood intentionally harvested for fuel that could be used for other purposes or simply left standing, while the other half use residues such as dung, rice husks or sticks.

Supplying this wood demands the annual harvest of 2.4 million hectares of forest. If this were instead supplied by an equivalent amount of liquefied petroleum gas (LPG), 43 million tonnes, 2.4 million hectares of forest would be spared annually – equivalent to nearly half the rate of global deforestation.

240 million households converted to LPG could save 2.37 million hectares of forest, IE 46% of annual net global deforestation.

At a more personal scale, switching 100 households from consuming 200 tonnes of harvested wood a year to 1.8 tonnes of LPG would annually save one hectare of forest. Each household would save about 100 square metres of forest. Seen at user scale, a typical 13-kg cylinder of LPG would avert deforestation of a 7 m2 forest area.

A developing world household consumes 2 tonnes of wood per year which is the equivalent of approximately 10 trees

Deforestation is a well-recognised problem, and is actually a proxy for a number of problems.

Probably the most prominent are carbon depletion, desertification, habitat endangerment (reduction of biodiversity), impairment of social amenity, soil erosion and threat to local livelihoods.

Sadly, in much of the developing world, the tree does not even grow back, slowly or otherwise. As the UN’s Food and Agricultural Organisation points out in its latest ‘Global Forest Resources Assessment’ of 2010, deforestation is continuing its centuries-long march.

Globally it slowed slightly over the last decade compared to the 1990s, but this is in large part due to afforestation in the developed world as well as in parts of India and China. Of course this is welcome, but it comes off a severely depleted base. Meanwhile, across most of the developing regions of Africa, Asia and Latin America, unsustainable harvesting drove carbon stock in forests down to record lows.

The shift by 2015 of 445 million people from wood to LPG would spare 440,000 hectares/year of forest a year. By 2030, with over a billion people switched to LPG, 1.2 million hectares/year would be saved – equivalent to nearly one-quarter of current global deforestation.

At the whole-earth level, says the FAO, half of the wood harvested was for fuel. The question is: how much of this wood was intentionally harvested as such, and how much was a ‘residue’ or waste of harvesting for other reasons (lumber, plantation, pasture, cropping or industrial/commercial/residential use).

This clearly deserves further investigation, yet a survey of the science suggests a rough 50/50 split. Particularly in urban areas, wood supplies are being sourced as on-purpose products, not unavoidable residues or wastes.