Researchers near Tokyo have started trial production of a type of charcoal that could improve the quality of farm soil and tackle climate change at the same time.

Japan's National Agriculture and Food Research Organization on Tuesday fired-up a new production machine in Sakura City in Chiba Prefecture.

Making the so-called "biochar" involves heating bamboo and tree branches for long periods of time at about 600 degrees Celsius.

The researchers believe that spreading biochar on farmland may offer such benefits as improved water drainage.

Turning plants into charcoal is also a way to trap the carbon dioxide they absorbed while they grew. This prevents the release of the greenhouse gas back into the atmosphere.

The city provides the project with culled bamboo. Other materials include branches from orchards that grow pears, a specialty of the prefecture.

Sakura Mayor Nishita Sango said: "We should eliminate global warming, otherwise we cannot pass the Earth on to our children. We hope to expand the use of biochar to the world."

The research organization says it will arrange for local farmers to use the biochar and then check for changes in crop harvests.