The waste hierarchy

The construction and demolition industry contributes disproportionately to the UK's annual waste output. Current levels of waste cannot be sustained and reduction remains a government priority.

Reducing the waste sent to landfill and increasing the re-use and recycling of waste materials can be achieved through the implementation of good waste management practices (including the actioning of site waste management plans).

The waste hierarchy is the recognised method of waste reduction (including on construction sites) and forms the basis of the government’s approach to waste management (driven by European legislation). There are 5 steps of the hierarchy, as summarised in Figure 1.

Figure 1: The waste management hierarchy

The environmental impact of each step increases from prevention to disposal; the further away the management option is from prevention, the less desirable it is.

Primarily the aim should be to explore all possibilities of reduction, before going on to consider the other options. Prevention and reduction may be more effective at the pre-construction stage (although they should be employed throughout the contract), while re-use and recycling will be more of a consideration during the construction phase.

Prevention

All members of the project team must be asked to consider means of avoiding waste generation in the first place. Questions should be asked as to whether there are viable alternatives to the proposed method of construction that could help to achieve this. Reducing waste saves materials and reduces the amount of energy used in their original manufacture and transport to site. Waste can be reduced through many methods, including: reducing material packaging; having materials delivered already cut to size; accurate material inventory keeping; and using re-usable containers on site.

Re-using

This step is dependent on whether the existing materials can be re-used (i.e. whether they are of sufficient quality or were intended to be re-used) and whether there is any scope to re-use materials on the site in question or any other. Re-using materials reduces the need for new materials, which helps sustain resources and reduces energy use and transport costs. Probably the most common example of re-use is the crushing of materials on site to be used as aggregate. The CL:AIRE Development Industry Definition of Waste Code of Practice provides a framework through which excavated soils can be re-used on site.

Recycling

Recycling sustains resources, and creating goods from recycled materials can often be more energy efficient. Disposal of waste to recycling and reclamation sites is often a less costly option (as landfill tax is not paid on recycled materials). However, while it is preferable to disposal, recycling will still have cost implications. Facilities will be required on site for the sorting and storage prior to removal of from site.

Disposal

Disposal to waste at landfill should be considered the last resort. An alternative is ‘other recovery’ which includes energy from waste. Landfill tax was introduced to discourage disposal of waste to landfill and to encourage industry to develop waste management options higher up the waste hierarchy.