S.T.S. Yuen

Water balance comparison between a dry and a wet landfill — a full-scale experiment

Abstract This paper describes a water balance study conducted in a full-scale experimental municipal solid waste landfill in Melbourne, Australia. The investigation identified the significance of various hydrological components of a ‘dry’ landfill (represented by half of the experimental cell as a control section) and a ‘wet’ landfill (represented by other half of the cell allowing leachate recirculation and working as a bioreactor). The information obtained is important and useful in terms of leachate management for both dry and wet cell operations, especially for landfills located in a similar climate region. The study also determined the in situ field capacity of the waste and compared it to published data. The implication of using this field capacity value in water balance study is discussed.

Waste management options to reduce greenhouse gas emissions from paper in Australia

A lifecycle assessment to estimate greenhouse gas emissions in Australia from the paper cycle is summarised. The greenhouse gas emissions from paper in Australia in 1999/2000 were estimated to be 12.1 million tonnes (Mt) of CO2 equivalent. Nearly half of this amount consisted of CH4 emissions from landfilled waste paper. Various waste management options were modelled to investigate the greenhouse impact of a tonne of paper over its whole lifecycle. Options that keep paper out of landfills significantly reduce greenhouse emissions, waste-to-energy recovery being most effective. Recycling is also beneficial, and is of particular interest from a management perspective because it can be controlled by the pulp and paper industry. These findings can be extended to other wood-based and organic wastes.

Detection of gas leakage from landfills using infrared thermography--applicability and limitations.

Although landfill gas emission can be greatly reduced by extraction and converting gas to energy, in practice not all gas can be collected and some leaks can still occur. Management of landfill gas can be improved if leaks can be detected and rectified effectively. This paper provides a brief review of methods available for detecting landfill leakage, with a focus on infrared thermography. It then describes a study which was conducted to test if an infrared camera can be used to detect gas leaks accurately by identifying them as anomalies. It examined the applicability and limitations of the technique by investigating fundamental factors such as weather conditions, ground conditions and distance of sensor from source. The paper also describes a test case conducted to reinforce the findings. It concluded that unless all the fundamental factors are clearly understood and addressed, the technique currently can only be used as a screening tool rather than as a precise tool to detect landfill gas leakages. For this reason, it would be difficult to use the technique as a basis for modelling gas emission from landfills.

A Sustainable Approach for Hydraulic Control of Landfills Using Quarry Scalpings and Native Plants

Abstract Phytocovers have been proposed as an alternative to traditional barrier covers, with aims to improve long-term environmental performance and reduce the fi nancial burden of closure costs, particularly for rural landfi lls. This research is exploring the potential for a phytocover to be implemented at a landfi ll in southeast Australia. Opportunities exist at this site to use basalt quarry scalpings typical of the Victorian extractive industry for purposes of the cover substrate, while vegetation selection has focused on indigenous plant species. Although the agronomic properties of the scalpings are not ideal, preliminary planting trials have shown that the scalpings have signifi cant potential for sustaining a careful selection of native trees and grasses. The application of mulch has not resulted in any overall plant growth advantage. A compaction trial conducted with full-scale machinery has enabled the method of placing the scalpings to be related to the in-situ dry bulk density achieved. Performance of the designed phytocover profi le will be monitored with four large test sections. Two of the test sections will employ lysimetry for the direct collection of percolation, while the other two sections will remain open to the normal fl uxes of landfi ll gas, heat and water vapour present in the landfi ll environment in order to observe their effects on the establishing vegetation cover.

The effect of using a geotextile in a monolithic (evapotranspiration) alternative landfill cover on the resulting water balance.

This paper examines the potential effects of a geotextile layer used in a lysimeter pan experiment conducted in a monolithic (evapotranspiration) soil cover trial on its resulting water balance performance. The geotextile was added to the base of the lysimeter to serve as a plant root barrier in order to delineate the root zone depth. Both laboratory data and numerical modelling results indicated that the geotextile creates a capillary barrier under certain conditions and retains more water in the soil above the soil/geotextile interface than occurs without a geotextile. The numerical modelling results also suggested that the water balance of the soil cover could be affected by an increase in plant transpiration taking up this extra water retained above the soil/geotextile interface. This finding has a practical implication on the full-scale monolithic cover design, as the absence of the geotextile in the full-scale cover may affect the associated water balance and hence cover performance. Proper consideration is therefore required to assess the final monolithic cover water balance performance if its design is based on the lysimeter results.

Observations of the impacts of some landfill leachates with clays

Abstract Compacted day liners are common, major, components of landfill leachate (fluid) containment systems. This is sensible, but knowledge and understanding of the long‐term performance and behaviour of clay mineral/ landfill leachate systems remain very limited. The authors studied the reactions of clay soil with leachate simulants related to three different climates and waste cultures. The clay came from a Tertiary sequence near Melbourne, Australia, a type in common use locally for landfill engineering. X‐ray diffraction was used to observe mineralogical change in 3 mm clay plugs caused by reactions with the leachate simulants. Changes in hydraulic conductivity were also measured. The results show both that the different leachates have distinct effects on the clay minerals, and that the leachate/clay reactions have direct, measurable and distinct impacts on hydraulic conductivity. The laboratory studies were completed at the University of Melbourne. The X‐ray diffraction work was completed at The Natural History Museum in London. The experimental results are discussed here and indications given of some potential implications