What the cash crop claim gets wrong
A short rotation biomass tree is a fast growing tree planted specifically to be cut down and burned or turned into charcoal for fuel. Farmers are sometimes told that planting one gives them a cash crop, wood or charcoal they can sell for a steady income. No source checked for this article puts a price on selling the wood or the charcoal from these trees. What is documented instead is that charcoal made from 1 of these trees returns more money than selling the raw wood as firewood, though without a price attached, and 1 study did find a real income gain, through a different route than a sale.
How fast these trees are ready to cut again
Three fast growing trees are farmed this way, Gliricidia sepium, Calliandra calothyrsus and Leucaena leucocephala, all legumes that fix their own nitrogen in the soil rather than using it up. Coppicing means cutting a tree near the ground and letting it regrow from the stump instead of replanting it. A Calliandra calothyrsus tree grown this way regrows to 3 metres tall, ready to cut again, in 6 months. A Leucaena leucocephala tree can be cut again on a 3 to 5 year cycle. A conventional fuelwood plantation, mostly eucalyptus trees grown the ordinary way, needs 12 to 20 years before the first cut.
The Calliandra calothyrsus figure comes from source 2 and the Leucaena leucocephala figure comes from source 3.
Show the numbers
| Calliandra calothyrsus coppice | 6 months |
| Leucaena leucocephala cut cycle | 3 to 5 years |
| Conventional eucalyptus plantation | 12 to 20 years |
What one hectare of the fastest of the 3 produces
A hectare of Calliandra calothyrsus yields 15 to 40 tonnes of wood a year once established, and that wood can be turned into about 14 tonnes of charcoal a year. Farmers who keep bees among the trees can also harvest about 1 tonne of honey a year from the same hectare. The database that compiles these figures states plainly that charcoal from this tree returns more money than the raw wood does as firewood, because the wood burns fast, though it gives no price for either.
Wood yield is reported as a range. Charcoal and honey are reported as single figures, shown as a fixed point rather than a range.
Show the numbers
| Wood | 15 to 40 tonnes |
| Charcoal | 14 tonnes |
| Honey | 1 tonne |
What the trees do to the soil
All 3 trees are also grown to protect or rebuild soil, not only for fuel. Gliricidia sepium establishes on slopes as steep as a 40% gradient and is planted in hedgerows to stop soil washing away and to reclaim land stripped bare by farming. Leucaena leucocephala sends down a taproot that breaks up compacted soil beneath the surface and cuts how much rain runs off instead of soaking in, and it is described as a strong candidate for restoring forest cover on steep slopes. Leucaena also fixes 100 to 300 kilograms of nitrogen into the soil a hectare a year, nitrogen that would otherwise have to come from fertilizer.
The real income finding, and what it is not
The only checkable income figure in this article comes from a study of 406 smallholder households in Kasungu district, Malawi, using data collected in 2017. Of those households, 179 grew Gliricidia sepium planted between rows of maize, for its nitrogen, not to sell as fuel. After statistically matching growers and non growers for age, education, land and soil, the study found growers had 54 US dollars more household income a month than non growers, a difference significant at the 1% level. The gain came through better soil and a bigger maize harvest, not through selling wood or charcoal.