Last reviewed 16 May 2017

The circular economy is nudging construction waste up a gear, from recycling to higher value material reuse. There should be matching reductions in final disposal, energy consumption, carbon emissions and wet work. But new rules and a new mindset will almost certainly be involved, points out Jon Herbert.

Recycling is good, but not good enough. UK construction creates three times more waste than households. Only half is currently recycled.

To achieve the huge reduction in waste expected of it, the building and construction industry is beginning to raise the beneficiation bar up a notch, from breaking up, recycling and disposing of good materials to keeping them intact for a second or third life.

Instead of taking fresh raw materials, using them in dedicated structures and then pulverising the remains, the circular economy adopts a very different approach.

In some ways, it is Lego made live. If buildings can be assembled from units — increasingly modular components fabricated offsite — that can be disassembled again and have a known tradable value, then old structures can become new structures with minimum losses.

There will be basic rules: eg adhesives are likely to be taboo and will have to give way to reusable clamps, mechanical connections and novel fitting systems such as finely-machined high-friction joints. Or simpler still, push-fit joints of a type similar to the legendary children’s toy.

Suppliers and innovators

There are significant implications for supply chains and industry innovators. How things could be taken apart will have to be thought out at the beginning — not a step taken with the world’s earliest skyscrapers. BIM will help to ensure a shared supplier vision.

Moving from the present take-make-and-waste linear economy to the circular economy will be an opportunity for many companies to design and manufacture products that function in a different way with far longer lifespans.

Contractors will not only have to handle and work with different materials and products, but also get used to the idea of taking old structures apart carefully with minimum damage and a well-recorded provenance trail.

The evolution of new material technologies, such as structural insulated panel systems and board made from fibrous agricultural waste with low-formaldehyde resins, also adds strength to the circular economy argument.

Manufacturing components offsite is also eliminating wet trades other than for foundations and ground floor structures.

There will inevitably be logistical issues and drawbacks. It is reported that when one building waste reuse specialist was offered a significant amount of steel roofing from the London Olympic site that would have been ideal for a large new disabled sports centre, the offer couldn’t be taken up because the new centre was in Glasgow.

New legal codes

There will be other changes required that are not necessarily complex. For example, new legal machinery will be needed to create enforceable warrantees and manage liabilities created by a change of ownership after many years of use.

Accurate data systems will be required with software systems that will need to last and be interpreted for decades into the future. There will also need to be dispute-free systems for calculating the residual value of units and components.

As technologies move on, it may be necessary to retain the skills and tools needed to take apart physical systems that have become outmoded.

Another alien concept could be the leasing rather than buying of raw materials and building products. You may be able to hire the real “Lego” pieces on a long-term basis on the business assumption that, new developments notwithstanding in the interim, they retain a value and can be used again, perhaps in a less stressed role. Once more, dependable data will be essential.

But above all, from design through the full procurement, manufacture, assembly, disassembly and redesign cycle, the circular economy calls for a much greater level of co-ordination through the whole supply chain. However, there are benefits for everyone.

Changing the record

The UK construction sector consumes more than 400 million tonnes of materials annually, the Green Building Council notes. It is Britain’s largest raw material user.

At present, the industry invests a lot of time and energy in crushing concrete before cementing it back together again. The new idea is for value to be retained rather than lost.

The motor industry takes a different approach. Cars display all sorts of interesting and exciting shapes, contours and sizes on the outside. Inside, once you lift the bonnet or hood, they are largely based on very uniform modular designs. If a component fails, it is easily replaced.

Building and construction, however, are on the same track even though they have a lap or two to go to catch up on the “closed loop” concept.

Although any subsequent use is likely to have slightly less value than the previous use, the aim is for any fall in value to be much less than with recycling.

For example, reusing old asphalt products as new road-building feed can have a much smaller overall environmental and cost impact. Waste timber is increasingly used for wooden flooring.

Global reuse

Internationally, less than one third of world construction waste is recycled, let alone reused, says the World Economic Forum (WEF). Dealt with properly, construction sector reuse could represent a trillion-dollar opportunity, it adds, important when looking at exports and working overseas.

Construction also accounts for between 25% and 40% of world carbon emissions. Perhaps surprisingly, it is estimated that 54% of European demolition waste still goes to landfill. UK demolition contributes 120 million tonnes of waste every year, says the Green Building Council.

Part of the problem is fragmented knowledge of material components and their value.

On the positive side, analytics, building modelling and new technologies are intervening in the building cycle, from planning, design, operations and maintenance, to provide new levels of understanding.

Having resolved technical, environmental, energy and management issues, another priority will be to produce a business case to prove commercially that the circular economy work well on the bottom line.

SPECIFIC in Swansea

A ground-breaking university project has provided a coincidental example of the circular economy in practice.

The University of Swansea Sustainable Product Engineering Centre for Innovative Functional Industrial Coatings (SPECIFIC) programme, backed by Tata Steel and other partners, is studying how buildings can be turned into “power stations” with significant environmental and economic benefits.

Its aim is to develop functional coated steel and glass products transforming roofs and walls into surfaces generating, storing and releasing energy. The hope is to generate more than a third of the UK’s total target renewable energy by 2020, reducing CO2 emissions by six million tonnes annually.

The £20 million project needed a live demonstrator. It built the Active Classroom in just 14 weeks and this has become a master class in circular economy construction thinking, with all major components being 100% recyclable. The building creates more energy than it uses.

The reuse journey starts with the foundations; steel screwpiles 2.5m long were selected as being easy to install with minimum disruption and hopefully easy to remove and use again elsewhere. On them sit reusable steel beams. There is no plasterboard and no concrete.

Moving upwards, interlocking steel-framed structural panels made offsite are insulated and faced with fire-resistant board. The point is made that the locking system needed only hand-tools for low-noise installation. Rainscreen cladding was added.

Another feature is the use of microperforations in southern wall cladding as part of a transpired solar collector system. Even during winter, warm air is drawn in through the tiny holes in the steel using a fan to heat the building.

Circa 95% of the solar energy that falls on the cladding is said to be absorbed; warmed air rises within the wall space, is drawn off by small fans and taken into the building’s heating system.

Thin film solar cells bonded onto steel roof panels produce energy that is stored in two very large saltwater batteries with the capacity to power the classroom for a minimum of two days.