There are different methods of managing wastes, however, according to
the EU Waste Framework Directive (WFD) 2008/98/EC some of the
methods are more favourable to others in terms of ecological benefits. In ranking order, reducing the generation of waste from source is the most preferable option. The next preferable approach for treating the unavoidably generated waste is to reuse the material in one way or
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another. Nevertheless, not all the waste generated may be suitable for reuse, therefore, the next preferable method is to renew the materials through a recycling process most appropriate. The concept of giving priority to the most preferable to the least preferable approaches of waste management is famously known as the Waste Hierarchy usually represented as a Waste Pyramid diagram as in Fig 9 (DOE, 2012b; Gharfalkar, Court, Campbell, Ali, & Hillier, 2015; Kibert, 2005; McDonough & Braungart, 2009; Nowak et al., 2009; Williams, 2015).
Figure 9: Waste Pyramid (Adopted from DOE, 2012; Kibert, 2005; Nowak et al., 2009)
The efficacy of the waste hierarchy in reversing material throughput is arguably questioned in many discourses (Bartl, 2014; Gharfalkar et al., 2015), nonetheless it remains the most widely accepted framework for sustainable waste management. The features of the waste hierarchy are discussed below.
2.5.2.1 Reduce
There are four ways of preventing or reducing waste, production with minimum resources, extending the life span of products, reusing materials
Reduce
Reuse
Recycle
Energy Recovery
Disposal in Landfill
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without restoration efforts, and minimising hazardous materials (DOE, 2012a).
In the opinion of Weiszackor, Lovins and Lino cited in Kibert (2005), one quarter of the resources currently consume by humanity is adequate for sustainable living. Lee Eng Lock on the other hand, believes that 90% of the energy consumed by mechanical systems may not be required as only 10% could be enough with the appropriate technology (Kibert, 2005). This is doing more with less termed as “eco-efficiency” and sometimes “dematerialisation” in the wordings of McDonough and Braungart (2009). Waste prevention starts from the design stage of a product (DOE, 2012b; McDonough & Braungart, 2009), however, some quantity of waste may be unavoidable and therefore will require another approach.
2.5.2.2 Reuse
In line with the WHO definition of waste as what is adjudged to have no current or perceived market value and the titleholder cease to desire at a particular place and time (DOE, 2012b), then the situation will be reversed if any of the two conditions is substituted. This implies that, when a market value or desire for an item by the original or any other owner is restored, it ceases to be a waste but a commodity. Reuse, is therefore, another way of expressing a renewed value and interest in the particular item in question and is usually done in two ways. According to the DOE (2012b, p. 8), when a material is used without undergoing any process, it falls into the first and best category of waste management approaches - prevention. However, if the whole or part of an item undergoes any process of checking, cleaning, refurbishment, or repair, then it is classified under the second position in the hierarchy of waste management approaches. The feasibility of reusing an item can also be improved from the design stage (DOE, 2012b; McDonough & Braungart, 2009).
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2.5.2.3 Recycle
Material recycling is the third preferable waste management approach in the waste hierarchy. According to the EU Waste Framework Directive, recycling refers to the material recovery by reprocessing of waste materials into products (Bartl, 2014; Kibert et al., 2000). It provides a solution whereby the material otherwise designated as a waste can be used as a raw material for the production of another material (Kibert et al., 2000).
Recycling adopts the idea of industrial ecology which Ayres and Ayres, (1996, p.6) described as making raw material in one process out of the waste of another process as inspired by natural ecological processes such as carbon cycle. The objective of recycling as described by Mcdonough and Braungart (2009) is to minimise the need for sourcing raw materials and bringing all resources otherwise designated as waste back into economic cycle. Wastes are rather viewed as resources in the wrong place.
The ability of repeatedly restoring material to its original state without losing any value like the case of steel can be described as closed-loop material cycle (Sassi, 2008); whereas reprocessing of a material into another product of lower value which may not be able to be recycled again is called downcycling (Kibert, 2005; McDonough & Braungart, 2009; Sassi, 2008). The reprocessing of material into another of higher value is termed upcycling (Kibert, 2005). However, some products are recycled through the natural process of biodegradation (Bartl, 2014; Sassi, 2008). According to McDonough and Braungart (2009), there are two types of metabolism activities in the universe, the biosphere- natural metabolisms or cycles and technosphere- industrial metabolisms or cycles. While an exchange of materials between these two cycles can be observed, the
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concept of waste can be eliminated if products can fit back into one of the two cycles as a raw material (McDonough & Braungart, 2009).
There are four (4) key issues concerning recycling through industrial processes, these are the potentials for infinite recycling, the efficiency of the process, the quality of the product and the threat posed by the process to the environment and health. On the other hand, the European Norm EN 13432 standard prescribed some requisite requirements for industrial reprocessing (Sassi, 2008).
While some materials can be recycled indefinitely without losing their quality, some other materials will require an addition of some fresh materials to restore their original quality. EN 13432 stipulates 10% maximum quantity of such fresh materials. There are records of materials that do not lose their quality through the recycling process, however for the other category, it should not be more than 10%. In England and Wales, the hazards associated with the recycling processes should be controlled within the limits set in Pollution Prevention and Control Regulations 2000 (Sassi, 2008).
Wastes from materials that are biodegradable on the other hand, may be treated by the natural process of composting - disintegration and consumption by microorganisms or any other living organism (McDonough & Braungart, 2009). This is superior to landfilling more especially if the two criteria stipulated by the British Standard (BSI, 2007) and European Norm (EN) 13432 is satisfied. This includes a full disintegration within three months and 10% maximum material waste; and the disintegration process should not be hazardous to human health and the environment. Associated side effects may not be avoidable however, which EN 13432 conditionally accommodates more especially if relatively lower than the side effects of processing virgin material (Sassi, 2008). Conversely, some materials are not biodegradable and not suitable for any form of
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recycling, but can be managed through other systems such as energy recovery by incineration.
2.5.2.4 Energy Recovery by Incineration
This is another approach of waste treatment that is below recycling, whereby energy is generated from waste (Berge, 2009). It is sometimes described as “waste to energy” and considered superior to landfilling. As the idea of waste management and the ultimate goal of eliminating waste is conservation of resources, waste to energy may not be considered as a recommendable approach, because valuable materials are rather destroyed on the long run (McDonough & Braungart, 2009, p. 55). Nonetheless, burning is not the only technic used to generate energy from waste.
There are three ways of recovering energy from waste: energy recovery as heat, and by conversion of the waste into fuel known as Waste Derived Fuel (WDF) or Refused Derived Fuel (RDF), and as methane gas recovered from dumping grounds. The use of waste to generate heat is usually done from plants for mass incineration whereby the heat is used for district heating schemes, factory space heating, and for some manufacturing processes. It is not recommendable to have an incineration plant without a ready market for the heat to be generated- a reason that makes the WDF more versatile (Royal Commission on Environmental Pollution, 1985).
It is possible to store WDF to be used at the most convenient time and by any interested party, not necessarily any particular customer. While the Pellets can be used in the conventional boilers, the shreds are more suitable for use in the large combustion units like kilns. However, WDF are unpopular with customers relative to coal (Royal Commission on Environmental Pollution, 1985). As noted by McDonough and Braungart (2009, p. 55), another side effect of generating energy from WDF is the
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risk of toxic gasses emission associated with the process. The other source of energy from waste is in the form of the gas - methane.
Methane gas can be harvested for use as a fuel and may constitute up to 65% of the gasses generated from landfills. Additionally, methane gas is a pollutant that is associated with several side effects including damages to plants, and possibility of explosion. Therefore, harvesting it has the potential to serve the dual purpose of controlling pollution and generating energy. Even though there were success stories of exploiting methane in commercial quantity, a stable production from any landfill may not be guaranteed. Moreover, the processing cost may make its exploitation unfavourable to a commercial venture (Royal Commission on Environmental Pollution, 1985). Contrariwise, should there be landfills in the future?
2.5.2.5 Landfilling
Dumping waste in the landfill is the least preferable method of managing waste, and should be avoided for the associated negative environmental impacts. As stated in section 2.5.1, landfills usually constitute a hazard to humans and other living organisms. Furthermore, it signifies a destruction of the finite natural resources and spaces for amenity and recreation (Royal Commission on Environmental Pollution, 1985). In the UK there is landfill tax that is designed to discourage waste going to the landfill (Secretary of State for Environment, 2005). In line with the sustainability principles landfills should cease to exist.
2.5.2.6 Discussion
From the foregoing discourse, it can be argued that the most sustainable waste management techniques in line with sustainability principles and the idea of waste hierarchy are the 3Rs of “reduce”, “reuse”, and
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“recycle” in order of preference. Thereafter, the options of “energy
recovery” may be considered as the least sustainable alternative while “landfill” is discouraged (McDonough & Braungart, 2009). Nevertheless, is this principle applicable to the massive amount of waste generated from building demolition activities?
Buildings and other man-made structures may possibly be similar to the other products in making imprints on the environment, nonetheless, it is argued that buildings are unique and “one of a kind” product that differs from manufactured products in many respect (Koskela, 2000; Solís, 2009). In the following sections (2.6 and 2.7) the role of the built environment in the sustainability agenda in general and demolition wastes in particular will be discussed.
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