Use

6 September 2007

Recycling wood products extends the period between the use of wood as a building material and the release of carbon dioxide back into the atmosphere when a building structure reaches the end of its life through burning or decay. For example, radiata pine used in interior building uses has an indefinite life and can be used again and again.

New technologies examining the potential of biochar to sequester carbon dioxide are being trialled internationally. Biochar has enormous potential when applied to soil, and in addition to aiding soil productivity, it has also been found to reduce emissions of nitrous oxide and reduce nitrates leaching into water.

In forestry production systems waste is produced from forest and mill wood residues. Alternatively to using this waste as bioenergy, it can also be used to help absorb carbon in the soil as biochar.

Biochar or Agrichar is a black carbon output of a process called pyrolysis, which involves heating woody biomass without oxygen. When the agrichar is absorbed into soils, it continues to retain the carbon dioxide taken from the atmosphere – In this way, biochar is carbon negative – more carbon dioxide is taken from the atmosphere and stored than is released through the pyrolysis process .

Many forestry residues can be used to produce bio-char and can be applied to soil both to absorb carbon and to improve the production potential of crops. Forestry and mill residues have a high suitability for conversion to biochar.

Biochar is a very effective soil conditioner, and two thousand years of use in South America and Africa have shown that it considerably increases agricultural crop yields.

With the harvesting of new plantation forests in New Zealand in the next 20 years, it’s important that these new technologies are extensively researched and subsequently adopted to ensure that the environmental qualities of wood are maximised.