Producing recycled aggregate

Aggregate feedstock from construction, demolition and excavation activities needs to be processed to produce a product that meets recognised specifications, such as the Specification for Highway Works L0356 This normally involves mechanical crushing to break up the material and then screening to remove contaminants and separate the aggregates into different sizes. If a higher quality aggregate is required, the material may be washed to remove fines or an air blower used to remove lightweight contaminants such as paper and wood.

Recycled aggregate may be produced at a fixed waste processing facility, or mobile equipment can be used to generate recycled aggregate at the construction site where it is produced.C0051 In the latter case the recycled aggregate can be reused on-site, eliminating transport costs. Mobile plant requires an environmental permit (as described in part one of this page) which must be obtained through the Environment Agency or the Local Authority depending on the category of the plant. Fixed facilities require planning permission from the Local Authority and an environmental permit or exemption from the Environment Agency. Fixed waste processing facilities are likely to be situated in industrial areas or on the same site as active mineral workings. Typically they have a relatively small throughput compared to natural aggregates quarries as they obtain their feedstock close (e.g. within 20 miles) to the site. The amount produced can vary from less than 20,000 tonnes per annum to over 250,000 tonnes.

Quality control

Recycled aggregate is predominantly used in unbound applications, such as for general fill, sub-base and capping in highway construction or for drainage. The same European Standards that apply to primary aggregate also apply to recycled and by-product aggregates; the Standards are based on the aggregates fitness for purpose rather than the source. L0364 The Quality Protocol for the Production of Aggregates from Inert Waste (Aggregates Quality Protocol) L0353 was produced by the Waste and Resources Action Programme (WRAP), Mineral Products Association (MPA), Highways Agency,L0356 and the Environment Agency L0367 to ensure that the recycled aggregate produced meets these standards and is no longer classified as waste (and subject to waste regulations). WRAP has produced checklists and guidance on applying the Protocol. L0357 L0358 L0359 L0360 L0361 L0362 L0368 Users should ensure that their recycled aggregates have been produced in accordance with the Quality Protocol.

Environmental impacts and regulations

Processing recycled aggregate produces dust and noise and may generate soil and water pollution if not properly managed. The transport of feedstock to the processing site and of products to construction sites also have environmental impacts associated with them, for example carbon emissions and noise. Compliance requirements are described in Pre-operational section of this page.

Before the feedstock is processed it is still classified as waste, therefore facilities operate under waste management regulations and are regulated by the Environment Agency. Waste processing facilities require an Environmental Permit or Exemption under the Environmental Permitting Regulations L0366 These place various restrictions on the facilities; including limiting the amount of feedstock stored (50,000 or 100,000 tonnes depending on the permit or exemption). Products are not classified as waste and so are not included in the restrictions, but are included in the conditions of the Planning Application granted by the local authority. Mobile crushing plants require a different environmental permit.