Environmental Impacts of Multi-Storey Buildings Using Different ...

- 103 -The Waste Minimisation Bill stemmed from the Ministry for the Environment WasteStrategy. The most relevant part of this strategy to treated timber is the statement: “ByDecember 2008, there will have been a reduction of construction and demolition waste tolandfills of 50 percent of December 2005 levels measured by weight.” This will significantlyaffect wood waste, as inert wastes such as concrete are already sent to clean-fills.8.6.5 Sorting of Timber WasteIdeally, in time, a recycling/disposal technology that can process both treated and untreatedtimber will eventuate. However, if this is not feasible, any recycling of treated timber wastewould have to involve a sorting process to separate treated timber from untreated wood. Anumber of options could offer sorting solutions ranging from visual sorting and PAN stain (astain formulation that can detect copper-containing preservatives), to X-ray fluorescence (anon-destructive characterisation technique that can detect different elements in solid or liquidsamples) and laser-induced breakdown spectroscopy (LIBS; use of a laser to ablate and ionisewood into a plasma).8.6.6 The Way Forward for NZThe Scion conference paper “Extended Producer Responsibility of Treated Timber Waste”(Love, 2007) offers recommendations for the future utilisation of treated timber.New Zealand’s treated timber producers should strive to establish a voluntary EPR schemebefore any legislation is put in place. This would require establishing who the responsibleproducers of treated timber are (wood producers, treatment chemical producers, forestrycompanies) and what processes should be implemented to deal with treated timber waste.There are many different sorting & treatment options available, in varying stages of maturity,and the option that should be chosen depends on whether carbon sequestration, energyproduction or life-cycle thinking are the key priorities and also on ongoing research, such asthat into leaching and decomposition rates for treated wood in landfills.Research would give a clearer idea of whether landfilling is actually an environmentallyacceptable practice for treated timber. At present, nowhere else in the world has landfillingbeen considered an acceptable solution for treated timber waste in the future, due to theunknowns about the behaviour of treated timber in landfills over much longer time periodsEnergy recovery from treated (and untreated) timber waste provides a way to significantlyreduce the volume of wood waste which would normally end up in landfills. The downside tothis is that the sequestration of CO 2 in the timber is no longer a benefit, as CO 2 will bereleased upon incineration, gasification or pyrolysis of the timber. This is still considered a‘carbon neutral’ process as the CO 2 that is released is essentially carbon that the plantabsorbed during its life time. The debate here is between ‘carbon neutral’ processes that couldprovide energy, and carbon-reducing processes that take up space in landfills and couldpotentially leak arsenic into the earth.