Recycling: A path to sustainable construction

There is growing global concern about the environment. Social awareness and legal obligations encourage recycling work in most developed countries. However, waste and waste management are major environmental challenges for modern societies. The difficulties stem not only from the increasing volume of waste, but its treatment as well.
The legal framework on environmental issues varies considerably from one country to the next (even within the same country there are regional differences), which makes harmonising the criteria complicated.
Despite the challenges in harmonising legal structures, industrialised countries often have a political structure and policy development on recycling. For example, the tightening of legislation in areas such as Western Europe and the US is leading to greater reuse of materials such as recycled aggregates.
Directive 2008/98/EC sets minimising the negative effects of waste generation and management on health and the environment as the first objective of any waste policy. Developing on this directive, the Sixth Environment Action Programme of the European Community, entitled Environment 2010: Our future, our choice, establishes a means of collaboration with businesses and consumers to achieve more environmentally friendly ways of production and consumption.
According to the European Environment Agency, the European Union?s total waste consists of industrial (26 per cent), materials from mining and quarrying (29 per cent), construction and demolition (C&D) materials (22 per cent), municipal solid waste (14 per cent) and agricultural residues and forestry (nine per cent). In 1990, the European Commission declared C&D materials as a ?priority waste stream? because of its vast quantity and its high potential for recycling.
If C&D materials are not properly treated, it harms the environment and may pose a risk to human health; it is a source of contamination for water and air and causes a host of inconveniences for citizens. The improper disposal of waste increases the risk of forest fires emits polluting gases and odours, and causes soil and landscape degradation and groundwater and surface water pollution.
Sustainable management of C&D materials preserves natural areas as it contributes to a reduced need for mineral resources and creates new jobs owing to the introduction of innovative economic activities. On-site waste recycling also saves production expenses, transport costs and taxes in construction.
As a result of the economic situation in some countries, C&D materials recycling has decreased due to the possibility of depositing waste in low cost landfills, without prior treatment and often without compliance with regulations. It requires strong commitment from the authorities, industries and consumers to ensure that the environment does not suffer the consequences of C&D materials mismanagement.
Proper processing of demolition debris results in quality recycled aggregates. They are suitable for various applications in the construction sector according to material size, eg drainage, filling and pavement sub-bases, amongst others. 
A prior recovery process is essential to produce high quality recycled aggregates. Inert waste must be properly separated from non-inert or even dangerous waste to avoid impurities and to ensure a high quality end product.
The production plants for recycled aggregates are fairly similar to natural aggregates crushing plants. They also include crushers, screens, conveyors and equipment for removing pollutants and magnets to separate steel, among other things. Metso, a leading company in the sector, offers state of the art technology in both stationary installations and mobile crushing and screening plants for recycling.
Although C&D materials evoke negative images (landfills, waste, toxic waste, etc), it is, in fact, a business opportunity with great potential for development. Aggregates have always been one of the most important materials for the development of society. After water, it represents the most consumed resource by humans. 
Proper C&D materials management can reconcile progress with respect for the environment so that the concept of ?waste? gives way to the concept of ?resource?.
Sara Carabello is a publicist and writer for Metso.

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