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

- 99 -8.5 Additional Opportunities for the Use of TimberThe Timber and TimberPlus buildings both use an increased amount of timber in theirconstruction (over and above a comparable concrete or steel building). However, the researchuncovered additional opportunities for the use of timber which were not included in thebuilding designs analysed for environmental impacts (designs had to be finalised at a fairlyearly stage of the research in order for energy modelling and LCA work to proceed).The Warren and Mahoney report identifies and provides details of some of these additionalopportunities including the greater use of timber products in the ceilings and interior walls, asinsulation and for floors, as well as externally.8.6 Current Situation in NZ for Recycling and Disposal ofTreated Timber ProductsThe conference paper “Extended Producer Responsibility of Treated Timber Waste”presented by Simon Love at the SB07 Sustainable Building conference in New Zealand in2007 (Love, 2007) provides a good overview of the current options for the recycling anddisposal of treated timber waste. A summary of the paper is included below.Treated timber is a waste stream of significant volume in NZ. Whilst exact figures for theamount of treated timber waste are not available, an estimated production volume of 830,250m 3 of treated timber in NZ in 2006 indicates that there is potential for a large supply of treatedtimber waste products in future years.Untreated timber, with no chemical preservatives, has many recycling options such as reuse,mulch, fibreboard, chipboard, animal bedding, compost and energy/heat recovery. Indeed,the utilising wood waste for the production of energy by thermal treatment (burning) is widelyused in some sectors of NZ industry (for instance, in sawmills and timber processing plants).Recycling of untreated wood waste appears to be market-driven, with the recyclers receivingwood waste for a fee, and selling mulched wood products to customers. These products areusually chipped wood for boiler fuel or shredded wood for use as garden mulch.However, utilising treated wood waste with infused chemical preservatives and/or superficialpaints and stains presents a much more problematic situation due to the presence of toxicproducts, such as arsenic and the possible release of harmful chemicals in to the atmosphere.Extended producer responsibility (EPR) is seen as an essential step towards being able toutilise timber waste.8.6.1 Thermal TreatmentThermal treatment encompasses incineration, gasification and pyrolysis. Incineration involvesburning the timber waste in air. This can result in the volatilisation of the chemicals in thewood, particularly arsenic when CCA-treated timber is burned. For an incineration process tobe considered as an environmentally responsible end-of-life solution, the emissions from theincineration process must be within acceptable limits. This could be achieved with a filtrationsystem. Incineration plants are currently being used to dispose of only untreated waste woodin Europe.