Compost offers greener option for brownfield
The Government is keen to push the specification of green materials such as
compost for sustainable, brownfield regeneration. Richard Swannell explains why
Brownfield regeneration remains key to the Government’s plan for creating sustainable communities. As much as a third of the 66,000 hectares of brownfield land identified by the National Land Use Database readily available for development. But crucial to brownfield regeneration are the issues of restoring the land to a high quality as quickly and cheaply as possible, especially if it is contaminated.
There is also the issue of ensuring regeneration and resulting development are as environmentally sound as possible. As the largest client of the construction and regeneration industry, the Government has the potential to be a powerful force in helping the sector achieve UK sustainable development objectives, and take a leadership role in greening brownfield regeneration. When you look at the power and influence of the regional development agencies and the local planning offices over land restoration projects, the Government is singularly placed to lead the debate, and to initiate the implementation of green, sustainable brownfield regeneration.
This is, to some extent, already happening. Some construction projects are already specifying the use of recycled products, such as construction materials and compost in brownfield developments. This is by no means universal, and there is scope to use them more widely. So, taking the use of compost as an example, what are the benefits of using recycled material in development?
Developers of brownfield projects have often imported quality topsoil on to sites where it is scarce, and disposed of subsoils and mineral wastes to landfill, which can be costly. The waste & resources action programme (WRAP) has been working with partners to investigate methods for creating and improving the quality of topsoils which are both cost-effective and sustainable.
When used in the manufacture of topsoil, high-quality compost such as that produced to the PAS 100 standard can help create ideal soil conditions for plant growth and development. If soil manufacturing is carried out in-situ, using existing subsoils/mineral wastes and locally sourced quality compost, the need to import new topsoil from elsewhere can be cut. This saves on transport costs. Compost can help create a soil that is rich in nutrients and helps improve moisture retention.
It sounds like the perfect, sustainable solution. But convincing developers to switch to recycled materials can prove difficult, especially when they are unfamiliar with the approach. This is where government can help influence them by ensuring developments specify a minimum recycled content. WRAP can help government do this in tender documents, and help developers work out how this might be delivered on the ground.
Specifying recycled materials, such as quality compost, not only makes environmental sense, it could also help improve the bottom line on many regeneration projects. By manufacturing topsoil on site, using quality PAS 100:2005 compost, developers can reduce the costs associated with sourcing and transporting alternative materials traditionally used in manufacturing replacement soils.
Putting it into practice
Recent trials using compost in brownfield sites have shown financial and environmental benefits such as the regeneration of the Royal Ordnance Factory at Chorley. The factory, based on 265 hectares of land, produced explosives between 1936 and 1990. As part of a drive to restore natural areas in the North West of England, BAE Systems led the redevelopment of the site, transforming it into the village of Buckshaw, which also included a business park.
There was insufficient topsoil available locally for all landscaping, so PAS 100:2005 compost was mixed with on-site subsoils to produce quality topsoil. The untreated subsoil was deficient in organic matter, nitrogen, phosphate, and potassium, and was highly alkaline, rendering sustainable plant growth impossible. More than 7,000 tonnes of compost was sourced locally and mixed with a similar quantity of sandy clay loam subsoil in a series of batches. The newly created topsoil produced healthy trees with dark green foliage. And the soil created in-situ with the existing subsoils and compost saved the project more than £100,000.
Once the land has been remediated, it will be developed to accommodate a mixture of light industry and residential housing. The latest phase at Chorley involves manufacturing 26,000 tonnes of topsoil using a mixture of BSI PAS100:2005 compost and sandy clay loam subsoil, to enable the establishment of wildflower meadows, amenity grassland and woodland habitats. Research is also being done into the potential for carbon to be stored in the soil. Manufacturing soils with compost could allow long-term storage of organic matter, reducing the release of CO2 into the atmosphere.
There is, however, still a challenge in reassuring developers that, when they specify PAS 100:2005 compost for use in topsoil manufacture, they will be using a product that has been manufactured to a consistently high standard. The BSI PAS 100:2005 certification provides that level of security.
With increased support from the Government in guiding developers to specify recycled products, combined with the increased recycling of municipal organic waste, the supply of PAS 100:2005 compost has the potential to meet current and future demands.
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