Carbon Storage and Emissions from Forest Products in Australian Landfills

Abstract

<p>Approximately 3.1 Mt of forest products are discarded in Australian landfills annually, with only limited knowledge on the extent of decay for the various products. As organic materials decay in landfills they release methane and carbon dioxide. The main aim of this study was to improve understanding of the extent of decomposition of wood and paper products in landfills in Australia, based on the analysis of carbon dynamics in forest products excavated from landfills in New South Wales and Queensland, and investigations of the fate of carbon in forest products under controlled laboratory conditions designed to optimise anaerobic decay.</p> <p>There was typically little or no decay in the wood samples from the landfills in Sydney. Although there was significant decay in rainforest wood excavated from Cairns, decay levels for other wood types found both in Cairns and Sydney landfills were lower (0.7-9.0%). Climate did not influence decay in wood and engineered wood products (EWP). Microscopic analyses revealed that most decay patterns in wood analysed from Sydney MSW landfills were consistent with aerobic fungal decay. Estimated carbon loss ranged from 0.6 to 9.0% for EWPs and 0 to 58.9% for paper. Papers produced from mechanical pulp had lower carbon loss than those produced via chemical processes. Climate impacted on decay levels for papers made from chemical pulp. Lower carbon losses were observed for EWP and paper excavated from the C&D landfill compared with MSW landfills. Decay factors for paper should therefore reflect pulp type, climate and landfill type.</p> <p>Carbon losses ranged from 0.2-3.8% for wood species tested in the reactor studies. The suggested factor for carbon loss for wood in landfills in Australia is 1.4%. Microscopy analyses in the wood revealed evidence of bacterial attack only. Addition of copy paper did not increase carbon loss for the wood species tested. Carbon losses for particleboard and MDF ranged from 0.7-1.6%. Carbon losses for bamboo (11.4%) were significantly higher than for EWPs. Carbon losses for the three types of copy paper ranged from 72.4 – to 82.5 %, and were significantly higher than for cardboard (43.8%). Differences in carbon loss between paper types were statistically significant. A decay factor for combined EWPs and wood in landfills in Australia of 1.3% and for paper products of 47.7% is proposed. The new suggested decay factors represent a significant reduction from factors currently used for forest products, with substantial impacts on greenhouse gas estimation from landfills. </p>