The following are summaries of papers published in other parts of ICE Proceedings during 2005 that readers of Waste and Resource Management may find of interest. Summaries of all papers in ICE journals are freely available and fully searchable at the ‘journals online’ section of the ICE website. See www.ice.org.uk/journals for details.
Waste to low-energy cement substitute
I. Richards
Proceedings of the Institution of Civil Engineers—Civil Engineering, 158, No. 3, August, 100
A four-year research programme in Wales has found a new, low-energy way to make effective cement substitutes out of ordinary industrial wastes. Ivor Richards of the research team leader Richards, Moorhead & Laing reports.
Energy and material flow of waste-processing operations
P. Dacombe, V. Krivtsov, C. J. Banks and S. Heaven
Proceedings of the Institution of Civil Engineers—Engineering Sustainability, 158, No. 1, March, 17–23
Although waste continues to be produced in large quantities-the rate of increase in waste production being more or less in line with the rate of growth in the economy-society is still grappling with the problem of sustainable waste management. One of the best ways to assess sustainability is in terms of mass and energy balance. A project at the University of Southampton looked at the ‘energy footprint’ for waste management. The project brought together data from existing work on waste quantities, materials flow and mass balance studies for a range of materials including paper, glass, plastics, metals and organics. These data have been combined with information on the energy requirements for different types of collection and processing systems for reuse, recycling, recovery and disposal of such materials. Taking into account energy benefits from any of these options, the information has been used to produce an energy and materials balance, and the results show the energy footprint and materials output of the current waste management practices in Southampton. This work allows exploration of alternative methods and highlights areas where insufficient information is available, or where improvements in collection or processing technologies could have a significant impact on the final energy and material balance. The greater Southampton area was used as a case study, but the methods developed could be applied to other areas by modifying the input data.
Eliminating hazardous materials from demolition waste
N. Strufe
Proceedings of the Institution of Civil Engineers—Engineering Sustainability, 158, No. 1, March, 25–30
To achieve optimum environmental and economically feasible recycling of construction and demolition waste (C&DW) materials it is paramount to ensure ‘clean’ (i.e. detoxified) materials. Mixed C&DW requires special treatment and costly disposal of unnecessarily large quantities of materials. A precondition for ‘clean’ demolition waste is careful sorting of the waste at source as an integrated process of the demolition work. This requires that during the demolition process planned and concise sorting of the different materials be carried out, thereby preventing any mix of the waste with hazardous materials, including materials such as asbestos, lead, mercury, PVCs, solvents and adhesives containing polychlorinated biphenyls (PCBs). Therefore, an initial identification of the presence of these materials in the buildings and structures is required. In this paper examples are given of a hazardous substance, namely PCB, found in buildings.
Energy recovery from thermal processing of waste
L. Yassin, P. Lettieri, S. Simons and A. Germanà
Proceedings of the Institution of Civil Engineers—Engineering Sustainability, 158, No. 2, June, 97–103
In the developed world, 75% of the population live in urban areas, a figure projected to rise to nearly 83% by 2030, while in the developing world, the rate of urbanisation is even faster. One of the most important environmental problems associated with urbanisation is the amount of waste that is generated at a rate that outstrips the ability of the natural environment to assimilate it and authorities to manage it. If, therefore, we are to deliver a more sustainable economy, we must do more with less by making better use of resources and putting these materials to good use. The use of municipal solid waste to produce energy or fuel is not only an important waste treatment option in itself but it also cuts down on the use of fossil fuels and hence can help meet renewable energy targets, address concerns about global warming and contribute significantly to achieving Kyoto Protocol commitments. This paper reviews the state-of-the-art technologies used in the thermal treatment processes of waste including combustion, gasification and pyrolysis. It also highlights some non-technical barriers to commercialisation of these technologies.
Organised recycling in Gaborone, Botswana
B. Bolaane and M. Ali
Proceedings of the Institution of Civil Engineers—Engineering Sustainability, 158, No. 4, December, 223–234
Solid waste reduction through recycling is widely viewed as a viable strategy. This has been promoted in many countries by government policies and legislation with more drive towards organised recycling. Organised recycling refers to the programmes where municipalities require waste generators to set aside certain materials so that they do not enter the mixed waste stream but can be collected and delivered for recycling. In developing countries, its promotion is often not preceded by an objective assessment of practical conditions on the ground in terms of potential constraints and opportunities. This paper discusses the existing state of recycling in Gaborone and highlights the potential constraints and opportunities of such an approach. A field investigation was carried out to examine possible constraints and opportunities to recycling. The investigation involved characterisation of household and commercial waste, a survey of secondary materials markets, key informant interviews and physical observations. It was found that some of the constraints to organised recycling are lack of specific incentives to promote recycling, limited municipal implementation capacity and lack of reform of the municipal waste management departments. Fragmentation of the recycling industry, sourcing materials free of charge and municipal officials' attitudes that favour the status quo are also possible constraints. However, there are also some opportunities for the enhancement of recycling, such as policy and legislative support and high recovery for some selected materials by the private sector that operates relatively unaided. The paper concludes that on the basis of the identified constraints and opportunities, adopting organised recycling may not be a viable option. The emphasis of a recycling strategy for Gaborone and other cities with similar characteristics should be on supporting private sector initiatives through appropriate incentives.
Strength and durability of concrete with ash aggregate
P. A. M. Basheer and Y. Bai
Proceedings of the Institution of Civil Engineers—Structures and Buildings, 158, No. 3, June, 191–199
A previous investigation to replace natural sand in concrete with furnace bottom ash (FBA) from a coal-fired thermal power plant in Northern Ireland, UK indicated that the water demand of fresh concrete decreases with the increase of the FBA content.
Therefore, in the current study the water content was decreased for concretes containing FBA for a given slump and a constant cement content of 382 kg/m3. The natural sand was replaced with the FBA at 0, 30, 50, 70 and 100% by mass and three slump ranges, 0–10, 10–30 and 30–60 mm, were considered. The water content of the mixes was determined by carrying out trials. The effect of FBA on water demand, density, compressive strength, pull-off tensile strength, abrasion resistance, drying shrinkage, air permeability, sorptivity, carbonation, chloride diffusion and salt scaling resistance of concretes containing FBA was studied. The results indicated that the water demand of fresh concrete decreases with an increase of FBA content while it has no significant effect on density, compressive strength, pull-off tensile strength or abrasion resistance. The air permeability, sorptivity and drying shrinkage increases beyond 30% FBA content, but the resistance to chloride ingress and salt scaling improves. The depth of carbonation also increases with an increase in the FBA content beyond the 30% replacement level. Overall, FBA content up to 30% as fine aggregate can be incorporated in structural concrete with mostly beneficial effects to various properties of concrete, provided the cement content is kept constant and the water content corresponds to that for low-slump concrete mixes.
