Quick Dips

Sewage Gas and Climate Change

Climate change research is benefiting from waste gas from Christchurch's Bromley sewage works. Carbon dioxide is being separated from the methane and other gases produced by the works and piped into tree-filled chambers to see how possible changes in CO₂ concentrations and temperature could affect New Zealand forests in the future.

It's an expensive process, but a lot cheaper than having to purchase the gas industrially, according to Forest Research Institute scientist David Whitehead. He's also pleased at the opportunity to make use of a recycled resource in investigating an environmental issue.

The 16 plastic-covered chambers enable the researchers to vary the conditions, testing the effects of increased CO₂ and temperatures. A stand of beech and red pine trees outside provides a control.

"It's the interaction between temperature and CO₂ that we consider scientifically interesting and also important for our future climate," says Whitehead.

The research has been able to gain an 18-year headstart by using seedlings tissue-cultured from the buds of trees of that age. The seedlings respond as if they are 18-year-old trees and have the appearance of the older trees, but are small enough to grow in the chambers.

"The relevance of the results to forestry is much better than if we had to use [ordinary] seedlings," says Whitehead.

Over the next three to four years, the trees will experience conditions that might prevail in the middle of next century. According to Whitehead, very little work is being done on the response of large trees and forests to potential climate change. New Zealand has an obvious interest in how such changes could affect the distribution of native forests and the productivity of plantation forests.

The project, run in collaboration with Landcare Research, is part of the International Geosphere-Biosphere Programme. The chambers were provided by the USDA Forest Service and have been adapted from their original role in testing the effects of ozone and air pollutants. Local support has come from the Lotteries Board, ECNZ and Southpower.