Carbon dynamics of paper,engineered wood products and bamboo in landfills: evidence from reactor studies

Background

There has been growing interest in the development of waste-specific decay factors for estimation of greenhouse gas emissions from landfills in national greenhouse gas inventories. Although engineered wood products (EWPs) and paper represent a substantial component of the solid waste stream, there is limited information available on their carbon dynamics in landfills. The objective of this study was to determine the extent of carbon loss for EWPs and paper products commonly used in Australia. Experiments were conducted under laboratory conditions designed to simulate optimal anaerobic biodegradation in a landfill.

Results

Methane generation rates over incubations of 307–677 days ranged from zero for medium-density fibreboard (MDF) to 326 mL CH₄ g^?1 for copy paper. Carbon losses for particleboard and MDF ranged from 0.7 to 1.6%, consistent with previous estimates. Carbon loss for the exterior wall panel product (2.8%) was consistent with the expected value for blackbutt, the main wood type used in its manufacture. Carbon loss for bamboo (11.4%) was significantly higher than for EWPs. Carbon losses for the three types of copy paper tested ranged from 72.4 to 82.5%, and were significantly higher than for cardboard (27.3–43.8%). Cardboard that had been buried in landfill for 20 years had a carbon loss of 27.3%—indicating that environmental conditions in the landfill did not support complete decomposition of the available carbon. Thus carbon losses for paper products as measured in bioreactors clearly overestimate those in actual landfills. Carbon losses, as estimated by gas generation, were on average lower than those derived by mass balance. The low carbon loss for particleboard and MDF is consistent with carbon loss for Australian wood types described in previous studies. A factor for carbon loss for combined EWPs and wood in landfills in Australia of 1.3% and for paper of 48% is proposed.

Conclusions

The new suggested combined decay factor for wood and EWPs represents a significant reduction from the current factor used in the Australian greenhouse gas inventory; whereas the suggested decay factor for paper is similar to the current decay factor. Our results improve current understanding of the carbon dynamics of harvested wood products, and allow more refined estimates of methane emissions from landfills.

     

Land use changes due to energy policy as a determining factor for morphological processes in fluvial systems in São Paulo State,Brazil

The number of hydroelectric dams used for energy production and the cultivation of sugar cane crops for ethanol production have increased significantly in the southeastern region of Brazil. These land use/land cover changes (LULCC) associated with energy policy can affect landscape changes over a range of temporal and spatial scales. This article focuses on how human–landscape interactions have influenced geomorphological dynamics in the lower course of the Piracicaba River for two different scenarios that represent pre‐dam and post‐dam conditions in 1962 and 2007, respectively, and the expansion of sugar cane crops after 1975. This assessment was performed by mapping land use and geomorphological changes in the study area in the 1962 and 2007 scenarios, in addition to quantifying the sedimentation rates upstream from the Barra Bonita Reservoir using ²¹⁰Pb. The main land uses identified for the 1962 scenario were pastures, meadows, annual crops and forests. However, the main land use change was the expansion of sugar cane cropland from 4 to 39%. In the 1962 scenario, the lower course of the Piracicaba River had a predominantly meandering pattern, and there were pronounced alluvial plains in the region. In the 2007 scenario, oxbow lakes were not mapped, and the river terraces were reduced in area due to construction of the Barra Bonita Reservoir. The changes in the sedimentation rates indicate an association between the construction of the Barra Bonita Reservoir and the expansion of sugar cane crops. It was therefore not possible to assess the specific influences of each anthropogenic change on the sedimentation processes, reinforcing that the human–landscape systems in São Paulo State associated with energy policy are complex. Copyright © 2017 John Wiley & Sons, Ltd.