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Construction and demolition waste
Construction and demolition waste accounts for around 30% of the annual weight of all waste generated by the Region. Most of this waste mountain is produced during construction work as unused left-over materials constitute only a small fraction of construction waste. The nature of the waste produced is closely related to the type of work or type of building. It is predominantly inert waste. 75% to 80% of construction and demolition waste is thought to be recycled, particularly as a material for filling or raising ground.
Since 2009, several studies have been carried out at the request of Environment Brussels in order to gain a better understanding of the situation, and of the difficulties faced by the various actors, both on building sites and during the preparation of construction work and the subsequent processing of the waste. A number of studies also set out a prospective vision in terms of improving this type of waste data and optimising both voluntary and legally required waste management systems in order to increase sorting (and hence recycling) and the potential for reuse of construction and demolition waste.
In terms of number of businesses and size of workforce, the construction industry is not one of the main sectors in the Region (see entry context/socio-economic development). However, when we consider the constructed area (in m²) and the number of new and renovated buildings in comparison with the geographical size of each region, it is clear that the activity in the construction sector is very intense in Brussels, suggesting that a large amount of waste is produced. This is especially true as much of the work involves renovation, which produces a large proportion of total construction and demolition waste (CERAA-ROTOR, March 2012, pp. 11-14).
Construction and demolition waste accounts for around 30% of all waste (in ton per year) generated by the Region. Most of this waste mountain is produced during construction work (i.e. demolition on construction sites and left-over used materials). The remaining waste consists of unused new materials, as a rule the quantities of such waste are however small.
The nature of the waste produced is closely related to the type of work: demolition, renovation or new construction. Other factors that play a role are geographical location, the age and type of building, the materials from which it is made (e.g. whether or not these are hazardous), etc. Statistics can be compiled on the basis of building permit applications, but these are not sufficiently accurate to reflect the last two factors. Nor do building permit applications provide any information about projects involving a partial demolition, as no permit is required for these.
From an ecological perspective, deconstruction is preferable to demolition, because it allows for significant reuse and recycling of building materials. Due to the rise of certain building methods (reinforced concrete, cement, the marketing of new products, etc. which complicate deconstruction) and current building management principles (aesthetic or functional trends, change of use, financial analysis, etc., making demolition or reconstruction preferable to renovation), we can expect an increase in the amounts of construction and demolition waste.
To promote recycling, both the manufacturers of materials and the architects and contractors who prepare and manage a construction site need to take on the idea of “design/construction for recycling” (e.g. provisions in the specifications or the use of containers that are more suitable and offer more flexibility). This also means that the responsibility shifts from the contractors to the client (source: technical report on Exemplary Buildings, February 2011).
Composition and quantity of construction and demolition waste (indicative data)
We distinguish three classes of construction and demolition waste:
- hazardous waste (or Class 1 waste), which carries a specific risk to humans and/or the environment,
- non-hazardous waste (Class 2 waste not classified in the hazardous or inert categories), and
- inert waste (Class 3 waste), which undergoes no physical, chemical or biological modification that can cause environmental pollution or harm to human health.
The inert and mixed fractions make up the majority of waste generated. Estimates of their relative extent vary though. The table shows estimates from the CERAA-ROTOR study which we believe yielded the most reliable data. Their estimates are the result of a reasoned and detailed combination of the officially available data and extrapolations from practices on the ground. In order to calculate the generated waste quantities they combined the results given by two different approaches. The first is based on an estimate of the number of square metres built by the construction sector in the BCR (according to construction permit statistics, the land register and the SITEX database) and of the waste generation rate per square metre. This rate was calculated using various methods. The second approach is based on the administrative waste register of Environment Brussels. This register keeps a record of all waste in the BCR that has ended up in a sorting and grouping centre or has been disposed of by large demolition firms. To complement the statistics, the study also made use of surveys and an analysis of 42 work sites. These were selected on the basis of their representativeness for the construction, renovation and demolition sector, apart from the residential or other use of the building and the age of the houses and apartments. This empirical working method is certainly not free from subjectivity. On the other hand, it has the advantage of providing specific new information about the situation in Brussels that cannot be found in the scientific literature. It also reflects the complexity of real situations that the actors experience on the ground.
The current situation in the Region with regard to construction and demolition waste
Prevention of construction and demolition waste mainly involves modifying construction practices and using less toxic and less harmful products. As a result, prevention mainly takes place on the supply side, among other things via well-considered specifications. According to the CERAA-ROTOR study (2012), this aspect is very often neglected while ecological construction clauses mainly relate to energy. However, there are exceptions as in the case of certification of buildings (BREEAM, VALIDEO) or the BATEX exemplary buildings.
Construction and demolition waste is collected through various channels: collection in sorted streams on building sites (through “selective deconstruction” or by sorting into different containers), mixed waste collection on building sites followed by waste separation at a centre specializing in sorting and finally waste collection by private individuals at recycling centres.
Preparation for reuse
Everyone seems to agree that there is significant and hitherto untapped potential for reuse/repurposing (cf. Opalis studies; ROTOR study, May 2012). Today certain fractions of construction and demolition waste are recovered and fed into the reuse circuits, however most often in an informal way. There is no real circuit for supply, processing and disposal. Other significant obstacles to the reuse of materials on construction sites are, lack of time and space, cost, the need for storage and the attractiveness of the type of material.
Brussels construction sites usually have two containers: one for inert waste and one for mixed waste. Metals are rapidly disappearing from the construction and demolition waste circuit. As a rule, sorting the mixed waste containers at a sorting centre is much less efficient than sorting at the source. In addition, it entails a risk of downcycling. Problems have also been found to arise during the managing of hazardous waste, especially the smallest chemical waste items (hazardous waste was sorted at less than half of the 40 construction sites visited). In the various phases of construction work, small containers are in fact found for fairly unmixed waste, but these eventually end up in a container of mixed waste due to space or time constraints, or for budgetary reasons – above all due to municipal taxes on containers located on the public road. Improving certain conditions could enable these waste streams to be kept more separate.
The CERAA-ROTOR study shows that the management of hazardous waste is not always optimal, especially in the case of small items of hazardous waste (aerosols, remnants of adhesives, used pots) or waste produced in small quantities. Asbestos also still poses problems (in terms of both identification and compliance with the law by the various parties).
Useful application for energy and elimination
When the container arrives at the sorting centre, the mixed waste is often sorted. If sorting is efficient, a third of the inert waste and a third of the wood waste can be separated, alongside other fractions that represent a much smaller quantity. The remaining waste is then incinerated or placed in landfill. Since the increase in landfill taxes, the ban on use of landfill for certain waste streams and the introduction of a favourable tax policy for useful power generation, a drastic reduction has been observed in the amount of waste for disposal.
The construction industry today is thought to produce around 650,000 ton of waste per year. The sorted fractions (especially inert waste, metal and wood) account for 75% to 80% of the total waste mountain. This is quite a positive result, but at the same time 150,000 tonnes of site waste is still left unsorted every year; this is a non-negligible amount given the small size of the Region. The environmental impact report of the Waste Plan estimates the amount of non-domestic waste produced in the BCR at 1.75 million tonnes, of which mixed waste constitutes 9%.
Quantitative targets for recycling
Recycling is not possible without thorough sorting. The European Directive specifies a recycling rate of 70% for construction and demolition waste, by 2020. According to the final assessment of the 2003-2007 waste plan, 80% of construction and demolition waste is already recycled. The recycling that is taken into account in these statistics, however, is mainly based on the use of construction and demolition waste as ground filling material (this means that it is ground into different diameters). The fourth waste plan aims to achieve 90% recycling (by weight) of construction and demolition waste. However, this goal appears not to be reached yet according to the estimates in the studies (see table above).
Limitations of the data available today
The estimates forwarded in the study that we brought into focus are partly based on data from the waste register of Environment Brussels (these data were previously rendered anonymous). This register is however intended for individual monitoring of businesses and was never designed for statistical extrapolation. The data are therefore not perfectly adapted for the intended goal and may contain underestimates.