From John Bush
I see Ning Zeng is considering burying wood to lock up carbon dioxide (3 May, p 32). I agree with him that we should be growing the wood, but has he not realised that the burying has already been done by nature long ago in the form of coal? Why not simply leave the coal where it is, already buried, and burn the wood instead?
Wherever in the world there is enough rainfall, we could grow trees to be burnt in small electricity-generating plants surrounded by the plantations producing their fuel. Come on somebody, we need you to design modern, farm-sized power stations specifically to burn plantation timber grown on the spot.
Modern technology could build plants needing little manual labour, but it could also be done where labour is cheap, with simple engineering methods and local rural manufacturing and maintenance; just what the world will soon need. The whole cycle would be CO2-neutral and not limited by fluctuations in sunshine or wind.
Here around the port of Albany, Western Australia, something like a third of all farmland has gone over to timber production in the past 15 years, producing wood chips for paper production. This has proved to be more profitable than the meat and wool production that it has displaced. There is no doubt we can grow trees.
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Does Ning Zeng really want us to bury wood so that we can continue to dig up coal?
From Peter Marshall
On our farm we bury a tree every day, without the expense of the backhoes and bulldozers suggested by Richard Lovett. We cut “long fodder” (willow, poplar and bamboo) from wood lots and shelter belts and throw it over the fence onto pastures. Goats and sheep come running to strip off nutrient and mineral-rich leaves and bark. Then we distribute the stripped poles around the grazing land, where they act as micro-terraces – trapping water and reducing soil erosion, wind speed and evaporation.
Over a year or two the protected pasture grows over the wood. It disappears as chunks of carbon into the soil, where it lasts for many years.
The technology is simple enough: sharp saws, billhooks and solar-powered electric fences to protect the coppice blocks from destruction by stock browsing. That fencing also makes a productive foreign-aid gift to goat-browsed countries such as Afghanistan. Without it the task of growing trees must be near impossible.
Braidwood, New South Wales, Australia
Mount Barker, Western Australia
