ENVIRONMENTAL BENEFITS OF RECYCLABLE TECHNOLOGIES

The environmental benefits of being able to dismantle and reuse or recycle materials are well understood.

Materials, energy and water are the three main resources required to construct and run buildings. A sustainable building design approach has to consider these three resources in terms of their depletion and the environmental and social impacts associated with their use. While the use of energy and water can be minimised, the use of materials is somewhat inevitable. However rather than designing buildings using materials as 'throwaway' resources, buildings that are designed for recycling become material resources for the future.

The resourcing of materials, their production processes, transport requirements and final disposal can involve wide reaching environmental damage, including global warming, pollution, depletion of natural resources, destruction of natural habitats, extinction of plant and animal species and waste production. While recycling or reusing materials does not completely avoid these impacts, it does reduce a substantial number of them and for this reason designing to enable building materials and products reuse and recycling is considered as a sustainable design approach.

Below are broadly outlined the environmental impacts associated with new materials. Using recycled and reused materials would help eliminate the impacts associated with material resourcing and disposal and can help to reduce the impacts of materials manufacture and energy use.

ENVIRONMENTAL IMPACTS ASSOCIATED WITH BUILDING MATERIALS AND PRODUCTS

Material resourcing
Manufacturing process
Materials, energy and transport
Materials in use
Material disposal

Material resourcing
Building products are derived from natural materials, which are harvested or extracted and then processed. The first issue to consider is the availability of the material resource, the risk being that resources may become depleted leaving future generations without that particular resource and at an almost certain disadvantage.
Materials are usually classified into renewable and non-renewable materials. Non-renewable materials include those with regeneration cycles of millennia (e.g. stone, coal, oil, metal ores) and renewable materials include those with regeneration cycles of decades or less (e.g. timber, flax, hemp, cork). Materials can be plentiful or scarce: sand is considered to be a plentiful resource, while oil reserves are limited and are estimated to last anything between 40 and over 100 years depending on consumption rates. Renewable resources are generally considered plentiful. However, if a renewable material is overharvested it may become scarce and ultimately even depleted; cork and timber being relevant examples. To avoid overharvesting the resources have to be managed and for timber a number of organisations, such as the Forest Stewardship Council, monitor and accredit forests that successfully implement a sustainable management system. Therefore while renewable materials should be used in preference to non-renewable scarce material this is subject to the renewable sources being sustainably managed.

Apart from the amount of resource available, the extraction or harvesting process itself can affect the surrounding environment and can be associated with pollution, the destruction of natural habitats and the reduction of biodiversity. The affects of small scale quarrying or mining on the local ecology can and often are restored, as with clay or sand pits restored to wetlands. Large scale mining, on the other hand, can cause more permanent changes; mining of bauxite strip to produce aluminium for example is associated with flooding of valleys to produce hydroelectric power schemes causing loss of rainforest habitat and consequently the loss of biodiversity. Pollution of water, soil and air can also be a consequence of material extraction, for example, the extraction of oil is associated with air pollution from flaring and marine or groundwater pollution from oil leaks and spills.

Increased concern about the environmental impacts of mining and resources extraction has resulted in some improvements in these practices, increasing numbers of forests are being managed sustainably and there is a move towards small scale mining in preference to large scale. However there is still scope for improvement and by taking these issues in to account when specifying materials, consumers can help push the market into adopting ever more sustainable practices.

Manufacturing process
Materials are rarely used in their completely natural state. Some preparation or manufacturing is generally necessary to create a usable building product. The impacts associated with manufacturing can include pollution to air, water and ground. Manufacturing also generally requires energy, which in the main is derived from fossil fuel and is associated with global warming and pollution.

At one end of the environmental impact scale there are 'natural' materials. These are materials that are found in nature (e.g. timber or stone) and that require minimal processing before use. A material with such minimal manufacturing impacts is the adobe brick made with earth and water and dried in the sun, a process that makes use of a plentiful naturally occurring material, uses manual labour and the sun heat rather than burning fossil fuels and consequently produces virtually no pollution or waste.

At the other end of the scale there are materials such as metals and plastics. The metal smelting industries and the chemical industry are the two top industries in terms of total emissions of toxins to the environment, including pollution of the air, land and water. The production of polyvinylchloride (PVC), one of the materials highlighted by environmental groups such as Greenpeace as being seriously environmentally damaging, is associated with emissions of organichlorides, dioxins, PCBs, furans, ethylene dichloride and vinyl chloride monomers as well as mercury pollution resulting from the production of chlorine.

Similarly to the improvements in mining and harvesting processes, manufacturing pollution and energy use are slowly decreasing. Energy efficiency improvements are being implemented and encouraged by government initiatives (e.g. the UK Climate Change Levy) and some manufacturers are now operating Environmental Management Systems and are seeking external party accreditation (e.g. ISO 14001). By demanding environmental information and accreditations from manufacturers, specifiers can highlight to the manufacturing industry the importance of considering environmental issues to succeed in an increasingly competitive environment.

Materials, energy and transport
Unlike the example of the adobe construction given earlier, most building materials require energy for extraction and manufacture. Energy is also required to transport the material to site, maintain it and finally dispose of it. The total energy used is known as the embodied energy. Energy is still mainly produced by burning fossil fuels and is therefore associated with global warming and pollution. Specifying low embodied energy materials is therefore generally desirable. Unfortunately estimates for the embodied energy of materials can vary depending on the method used to calculate it and can prove misleading. Embodied energy calculations do not generally differentiate between energy produced with fossil fuels and that produced with alternative means not associated with carbon dioxide emissions and they sometimes include the energy to transport materials to site, for maintenance and disposal and sometimes do not. When they include these, assumptions have to be made regarding the distance of transport and the life span of an element. Embodied energy figures also fail to take into account that different materials are require in different amounts to achieve the same purpose. Despite their limitations, embodied energy figures do give an idea of what are high and low energy materials. Low embodied energy materials should be used in preference to high embodied energy materials, but embodied energy should not be used as the only selection criteria.

The embodied energy has to be seen as an element of the total energy consumption of a building over its life: a building's running costs are still generally significantly higher than its embodied energy. Consequently the specification of certain materials with relatively high embodied energy, such as extruded plastic insulants, can be justified due to their significant contribution to lowering building running energy costs, whereby their embodied energy is recuperated many times over the life of the building.

A substantial reduction in the building's total embodied energy can be made by reducing transport requirements. The transportation of materials from the manufacturer to the building site is generally by road and is associated with carbon dioxide emission and air pollution. Reducing this transport energy requires material specifiers to select manufacturers located as close as possible to the building site.

Materials in use
Maintenance of materials requires both energy and materials and is associated with similar impacts to the construction of buildings albeit at a smaller scale. Minimising requirements for maintenance by designing for durability and longevity helps to reduce the life impacts of materials. Materials can also affect the building users in terms of comfort and health and these impacts should also be considered.

Material disposal
The building industry in the UK is currently responsible for 70 million tonnes of construction and demolition waste every year and most of it is sent to landfill. There are numerous problems associated with landfill sites, including the use of land, toxic materials leaching into groundwater, emissions of explosive gas and structural instability. Appropriate site waste segregation, designing to enable reuse and recycling and using reclaimed and recycled materials all contribute to diverting waste from landfill and other polluting waste disposal options.
Building design can also encourage recycling of domestic or commercial waste by providing appropriate recycling facilities in the building.