Digging up clues for greenhouse
From the Winter 2007 edition of Bush Telegraph Magazine.
Assumptions about the environmental impact of commercial timber plantations are being questioned by NSW Department of Primary Industries (NSW DPI) research into carbon loss from wood samples buried 44 years ago.
About 500 samples of old building materials, furniture and fences recently dug up from a Sydney landfill are currently being examined for evidence of bacterial damage.
NSW DPI forestry researcher, Fabiano Ximenes, has just finished measuring and labelling the wood samples and these will now be examined under the microscope for evidence of deterioration caused by fungi or bacteria.
“Any degradation after the wood was placed in the landfill would be of a bacterial nature, as bacteria are capable of degrading wood under anaerobic conditions,” Fabiano said.
“If there is no sign of bacterial degradation in the wood, then none of the degradation would have taken place in the landfill. All the carbon present in the wood at the time it was buried would still be there.”
Fabiano will also trace the species of tree used in some of the wood products found in the landfill and test the timber density and moisture content.
The proportion of the main chemical components found in the wood – cellulose, hemicellulose and lignin – will then be compared with control samples of the same timber species.
“This will tell us how much carbon is still stored,” he said.
Carbon accounting schemes worldwide assume carbon is released as soon as trees are felled.
“Our results to date indicate this undervalues the carbon stored in trees used commercially and reduces the incentive to establish more plantations for carbon sequestration”, Fabiano said.
Future landfill excavations will seek to determine the rate of decomposition of wood and paper products by digging in different parts of operational landfills that contain waste buried at different times.
Public Affairs & Media, Orange
