Recycling of construction materials will make a significant reduction in the environmental impact of construction.

 Recycle and Reuse of Construction Materials

 Recycle and re-use of construction materials and components is one option, which has to be considered in order to reduce environmental impact of construction materials. Figure 1.2 is suggesting that cycle rather then linear of building materials is good for the reduction of environmental impact of building products.

Input                                                                   Output

                                                                       

                                                                       

                                                                

                                                                 

                                                                      

 

                                                 

Figure 1.2 impact of recycling or re-use.

Source Building and Environment Journal

Recycling of construction materials may seem to be an ideal solution to many problems of the environment, but there are number of barriers to their implementation.  For instances,

1. Lack of conformity

(CIRIA PR28, 1999) A guarantee of a homogeneous material supply is usually prerequisite stipulated in a project specification. This ensures the quality of the supply. Obtaining this homogeneous for reclaimed materials is difficulty.

2. The economic element

The commercial nature of the whole construction industry means that decision making motivates is largely profit led. Anything that doesn’t add value to the project is discarded.

3. The risk element

A particularly influential barrier to the incorporation of waste materials in design (reclaimed or recycled materials) and materials standard is the (designer’s, specifiers’, contractors’ and clients’ perception of risk.  This will influence the decisions made to select/specify certain materials.

The specification of reclaimed materials could be a problem for indemnity insurance policy, which may exclude claims, where failure of non-BS materials has occurred. ( a project report prepared by Wimpey Environmental Limited) Therefore, it is important that clients understand and approves their use on a project and is prepared to take the risk, however in small, in using them.

And also the promotion of the above standards, which increase the ease with which alternative materials can be considered and used, is very important. Sorting and cleaning will add to the financial and energy burden, and require the disposal of waste water. However, re-use is more difficulty than recycling, since it is sometimes difficulty to remove components like windows frame with out damage. Please refer to figure 1.1 above. The substitution of reclaimed and recycled materials for primary materials helps to improve the sustainability of construction by reducing reliance on primary materials and also reducing the shocking volumes of construction waste and demolition. The opportunities of using second hand materials for a primary purpose was demonstrated when the BRE constructed a three-storey office block at their site at Garston. It incorporated reclaimed and recycled materials both from the building that was demolished. The following table will outline the estimated number of building materials that were either recycled or reclaimed for the construction of the new building.

Table 1.1 Source (CIRIA PR28, 1999)

 (CIRIA, 1999), stated that the contractor that was awarded the demolition contract was able to offset the salvage value of materials against the demolition cost. Only small percentage of waste was disposed of to landfill from the demolition-this was only estimated to be 4% by volume.

There is no doubt this building will a benchmark for those who care the environment and willing to reduce its huge impact on the environment. Reclaimed materials are materials that are directly reused, or reused with very little processing for example, bricks that have been cleaned with mortar. Recycled materials are that require reprocessing to be reused, for example aggregates that are made of crushed concrete demolition waste. From environmentally point of view, repair is generally preferable to reuse, reuse to recycling, and recycling to disposal.

The low impacts of reclaimed materials can be increased if they are transported very long distances compared with new materials. The following table shows the maximum distance a reclaimed material can be transported by road before it will have a greater impact on the environment then a new material manufactured locally. For example, a reclaimed brick up to 500 miles will have less environmental impact than new bricks. From a factory 250 miles away (Anderson Jane and Howard Nigel, 2000).

Maximum transport distance for reclaimed materials

Table 1.2- Transport energy

Source (The Green Guide to Housing Specification)

Both reclaimed bricks and tiles can be used in framed external wall construction. The table 1.2 shows the distance reclaimed bricks and tiles can be transported before the impact of transport becomes greater than the impact of manufacturing a new brick. The use of local recycled both for hardcore and within concrete will reduce resource consumption and will improve environmental performance. Table 1.2 also states the maximum recycled concrete aggregate can be transported before its impact exceeds that of origin aggregate. Therefore, energy for transporting construction materials is very important when considering recycled and reclaimed materials.

Some building materials such as concrete are of high density and low value and transportation will form high level of energy usage, so for such materials the location of the recycling plant in relation to the building is crucial in determining, the viability of recycling, where considerable distance is involved, then the use of new materials may in fact consume less energy then recycling. In contrast, recycling in a high value, low-density material such as aluminum is almost always viable, because the energy of the recycled product is less then one-tenth of that origin material. And transportation energy is considerably lower. It is these sorts of things that will have to be balanced in order to determine the environmental impact of construction materials.

Nigel and Suzy (1999) “Four materials compromise over 99% of construction mass aggregates (sand, gravel and crushed rock, cement (and hence concrete), brick (clay products and wood which is normally imported. Energy used to manufacture and transport these building materials represents 10% of the national totals. This is small compared 50% used to operate buildings or 22% consumed by personal transport”

Energy use

Energy is very important issue when considering reducing environmental impact of construction materials. The energy referred here is the embodied energy of construction materials, according to (Borer and Harris) the embodied energy is the primary energy used in all the different stages of product’s manufacture, service lifetime and disposal. Primary energy refers to the energy content of the fuel, plus all the energy needed for its extraction and processing including loss in conversion and transmission. The embodied energy largely relates to CO2 production and its effect on global warming.

This cradle to grave approach is also called Life Cycle Analysis (LCA), and is very important toll, which will enable you to compare and evaluate various building materials. As the construction industry is faced with a number of environmental issues ranging from its direct impact on climate change to its choice of materials and its methods of waste disposal. Increasingly there is a realization that the entire life cycle analysis of a building must be considered

When choosing a material for any application it is important to look at the whole of the product's life cycle. Life cycles analysis in fact goes far beyond the production processes alone. It also covers the impacts and benefits of the material throughout the life span of the different products, including its re-use and recycling.

Reducing Embodied Energy and Resource Depletion

Reducing embodied energy and resource depletion is paramount important when selecting building products and to do so the following must be considered.

Keep use of materials from non-renewable source to a minimum

Use low energy material

Use locally sourced materials

Reuse existing structure and buildings

Concentrate using second hand materials wherever and whenever possible

Minimize use of imparted materials (Class notes and handouts, 2001)

Energy in use

Reduce energy in use, this is the energy for operation, so if this energy is reduced the energy for production of building materials will only account greater part of building’s total energy use. Take the following steps to reduce the energy in use of the buildings.

1. Use passive and natural ventilation systems rather then mechanical
2. Use low energy lighting and electrical appliance
3. Use maximum possible low embodied energy insulation but with ventilation
4. Make use of passive and active solar energy whenever feasible (Class notes and handouts 2001)

 

   

Reduce waste

The Egan Report Rethinking Construction (DETR, 1998). Stated that the need to reduce waste at all stages of construction is a central message of Rethinking Construction. Over 90% of non-energy minerals extracted in Great Britain are used to supply the construction industry with materials. Yet every year some 70 million tonnes of construction and demolition materials and soil end up as waste. Some 13 million tonnes of that comprise material delivered to sites and thrown away unused. Poor design and planning also result in wasted time and money and reduced profits.  Minimizing waste through design can be achieved by avoiding over-specification of materials and services. A co-ordinated approach to design and construction within the supply chain will encourage designs, which better meet clients’ requirements and result in less waste. Every design does not have to be a prototype. Adopting standardized solutions can also help to reduce waste”

Borers Pat and Harris Cindy (1998) states that only 4% of this 70 tone of waste are recycled into high-grade uses (i.e. other building) and the majority is simply dumped as landfill for future generations to deal with. To this end, the government, which is the leading client of the construction industry, has a very active role to play in encouraging developers, and specifeirs of building materials to incorporate second hand materials to reduce waste. Recycling will surely reduce waste and environmental concerns as well. Furthermore, The government can help to create a market demand for the usage of second hand materials rather than Primary materials for specifying such demand when undertaking public projects.

Design for deconstruction

From environmental viewpoint, it is desirable that at the end of buildings’ life time as many as possible of its components and materials can be reclaimed and recycled for other construction applications. Apart from application of renewable and recycled products, clients and designers can allow for future recycling. When choosing the optimum material for each building an approach which takes account of the full lifetime of the material should be adopted, covering construction, use, maintenance and disposal phases. Materials should be chosen which can be easily and economically recycled and do not require disposal at landfill sites. When planning an environmentally sustainable and cost-effective building, the following design aims should be considered:

1. High material recyclability
2. Low material toxicity
3.  Minimal energy use
4. Minimal waste
5. Minimal maintenance
6. Minimal running costs
7. Maximum flexibility of function
8. Suitability for local climate

The initial intention of the designers has to make as much as possible of the building itself of recyclable. The theme is got to be resource recovery, which is used to refer to both materials recycling and burning with energy recovery. Moreover renewable such as timber, which is the most traditional eco-friendly material should be the norm for the designers and all those in the construction industry. But take into consideration the transportation-energy cost. Avoid the use of concrete, steel, and PVC products wherever possible as they are the most polluting products interns of the environment

Conclusion

The potential impact of construction materials on the environment is so huge in term of energy consumption and landscape. However, it is widely recognized that there is great potential in existence for recycling and reclaiming construction materials, if only the specifiers, clients and developers might wish to take on board with this idea when it comes to decision making. A lot of energy will be saved by recycling or re-use of building products compared with energy required to produce similar products from primary resources based on current practices. Several environmental impacts of building materials are shown in figure 1 and figure 1.2 and table 1 and 2 have been shown several available methods, which can be used to reduce the environmental impact of the buildings.  A number of assessment methods of building materials like the embodied energy and Life Cycle Analysis have been included in this essay. They are all very useful tools, which will aid in selecting greener materials for sustainability.

Bibliography

1. Smith P and Pitts A, Concepts in Practice – Energy, Batsford, 1997
2. Borer p and Harris C, The Whole House Book, CAT, 1998
3. D.J. Harris Building and Environment 34 (1999) 751-758
4. Building Research and Information (BRE, 2000) 28(3), 176-183
5. Jane Anderson and Nigel Howard (BRE, 2000). The Green Guide to Housing Specification
6. Construction Industry Research and Information Association (CIRIA, 1999). The Reclaimed and Recycled Construction Materials
7. Construction Industry Research and Information Association (CIRIA, PR28, 1999). Waste Minimization and Recycling in construction