Case study

Zero waste to landfill: Construction waste collection good practice

Zero waste policies are a key step towards sustainable waste management. This case study examines the economic and environmental viability and implications of adopting a zero construction waste policy for a retail development.

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Background

Weir Waste Services Ltd has been providing waste management solutions for over 65 years. Weir’s provide bespoke solutions to optimise their clients’ waste management systems. One such example is the development of an efficient waste collection system to achieve zero waste to landfill at a Tesco retail development in Birmingham.

Service capability

Weir Waste Services Ltd operates a transfer station with advanced separation processes and a fleet of waste collection vehicles based in Birmingham. Every year, the company processes over 150,000 tonnes of construction and demolition waste through the transfer station, generating a turnover of nearly £8 million. The majority of the waste delivered into the transfer station is collected directly by Weir’s own vehicles. The company has signed up to WRAP’s Construction Commitments: Halving Waste to Landfill, a voluntary agreement that provides a framework for waste reduction. The company offers its clients a fully integrated service including collection, processing at the transfer station and compliance with legal requirements. Compacted and non-compacted materials are processed at the same site albeit some of the machinery used is different. The transfer station normally achieves an average recycling rate of between 85 - 95% with the remainder going to landfill or EfW. “Weir’s ability to be flexible and respond to our clients’ needs whilst being able to use a transfer station, provides the most efficient way to meet increasingly challenging [diversion] targets”. Anthony Brownsett. Compliance Manager

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Service provision

Tesco retail development in Hodge Hill

The Tesco retail outlet development in Hodge Hill, Birmingham, (delivered in partnership with Bowmer and Kirkland) has created a 65,000 sq ft food store and car parking facility. The overall waste arisings for the site were minimised through the off site pre-fabrication and production of many parts of the building’s infrastructure. This has reduced on site wastage significantly and is consistent with the principles of the waste hierarchy.

Service description

The service consisted of the provision of an integrated source segregation and off site separation service, selected on the back of Weir’s ability to minimise the residual element of waste arising from construction projects once the waste had been through the facility’s process. In the initial phase of construction, large volumes of inert materials were produced along with some green waste (predominantly trees from grounds clearance, etc). Later phases produced a wider variety of wastes including, wood, metal, brick, canteen waste, insulation, paper and glass. Weir’s supplied a mixture of types and sizes of containers, chosen at each phase in the development to achieve a balance between reducing the number of waste movements off site and adequately providing for material to be source segregated. The waste was moved to the skips using specialist tele-handlers and tipper skips moved by fork lift trucks. To maximise the efficiency and reduce

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the cost of the waste collection and recovery service, the largest practical sizes of containers were used. Where possible, large roll-on roll-off (Ro-Ro) containers were used for the bulky items such as the metal, inert materials, wood and the general waste. The separation of these materials minimised the volume of general waste that would need to be sorted off site. This in turn limits the financial risk associated with the use of EfW to avoid the use of landfill. Smaller front end loader (FEL) containers were used to collect cardboard, paper, mixed packaging and office wastes. Heavy brick and blocks were collected in smaller skips due to the density of the material to be lifted and the small volume of canteen waste was collected in 1,100 litre wheeled bins. Figure 1.2 Typical mix of containers used to segregate the waste on site

The larger containers containing clean, segregated materials were sent directly to local reprocessors; delivering these materials into the transfer station for sorting or bulking offered no additional efficiency. The hub and spoke method of collection for the waste types lends itself to the efficient delivery of such materials directly to the processor from the site of production. A hub and spoke collection system collects waste from a single site and transports the waste to the processor or another site such as a MRF. These services were collected using an on-demand service, maximising the capacity of the containers and reducing the number of

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movements required. Regular site inspections monitored the fill level and rate of the containers so that only full containers were removed. Collections were booked on a ‘just in time’ basis with most collections being completed within 24 hours of the request. Replacement containers were provided on an exchange basis. Paper, card, packaging and food wastes were collected as part of separate ‘milk-rounds’ and taken along with wastes from other sites to the transfer station prior to transfer to the relevant reprocessors. The collection of small volumes on a scheduled basis via a ‘milk–round’ was considered to be the most efficient method of collection. Mixed general waste was taken to the transfer station where it was sorted using a trommel and hand sorting to remove the recyclable fractions. This left a small amount of residual waste equivalent to 5-10% of the waste (by weight) collected. The residual waste was sent for energy recovery at a plant near Stoke-on-Trent, thus avoiding landfill altogether. There was a clear linkage in this project between the provision of a primary off site sorting of the general waste and a resultant reduction in the volume of waste sent for energy recovery.

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Service assessment

Key findings

The introduction of a zero waste policy improved the recovery rates of an already high performing WMC.

Achievement of a zero waste to landfill policy can be made through using a combination of on site and off site segregation.

The use of the largest practical containers to store and collect the waste from the site minimises container movements and associated CO2 emissions.

Material specific source segregation assisted in lowering contamination levels, improving material output quality and minimising recovery costs.

Benefits

The use of a transfer station offers the benefit of being able to bulk smaller amounts of specific waste materials into economically viable volumes for reprocessing. Off site sorting at the transfer station enables the percentage of general waste landfilled to be reduced from a baseline of 30% to between 1.5% and 3% of the total waste arisings. By achieving this diversion rate, additional costs of onward haulage and incineration are minimised. The segregation of the metals on site generates an income that is used to off-set some of the additional costs over landfill disposal of sending waste for incineration with energy recovery. The combination of source segregation and off site sorting, together with use of larger waste containers, has demonstrated the economic and environmental credibility of setting and being able to achieve a zero waste to landfill policy within a major retail development project.

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