14 THE CLIMATE CHALLENGE


Cradle to cradle – squaring the circle


Marco Abdallah of Drees & Sommer tells Housebuilder & Developer's deputy editor Jack Wooler what a ‘circular economy’ could look like, and what concrete steps the construction industry can take to achieve this ideal.


ircular economy’ is a buzz phrase that has become the aim of many in the UK construction industry, and across the world. That aim is to ensure that all resources used can serve as starting materials for new, pollutant-free products once their service life is over. Such a system would allow materials to circulate continuously in product cycles – instead of ‘downcycling,’ the aim is to enable ‘upcycling’ of products, drastically minimising waste as a result. Marco Abdallah, head of engineering UK at international planning consultancy Drees & Sommer, believes that this concept of a circular economy “is more than just a material science.” “It is the basis for a fully integrated sustainability concept for building,” he says, “covering all aspects including materials, water, air quality, health, energy, carbon and more.”


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WHERE WE’RE AT Housebuilding as it stands today falls woefully short of this ideal. A large amount of building waste cannot currently be recycled simply because it was not designed for this purpose. The UK construction industry as a whole follows this trend. According to a 2018 Government report, a staggering 60 per cent of all UK waste is created by construction, demolition and excavation. “This makes our industry the single


largest contributor of waste, meaning it is paramount we act to ensure sustainable building now,” says Marco.


Composite wall insulation, for example, often consists of 20 layers of different materials containing toxic pollutants that are all glued together; such materials


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cannot be properly recycled, and they often cannot even be burned because they are too toxic. “What we consider as recycling is often


a form of downcycling,” explains Marco. “Window glass is recycled to become a beer bottle which is recycled to aggregate, and finally ends up as waste. We often just postpone the move to landfill and ultimately lose the raw material.”


CRADLE TO CRADLE


‘Cradle to cradle’ is a movement to replace the industry’s current system of materials supply and its high levels of waste. According to Marco, the model “has the potential to bring the next revolution to the construction industry.” The set of design principles, developed in the 1990s by Professor Michael Braungart, William McDonough and EPEA Hamburg, “is inspired by nature,” says Abdallah. “The aim is not only to minimise negative influences, but also to leave a positive ecological footprint.” As a result, he believes “products,


processes, buildings and cities will emerge which are safe for humans, healthy for the environment and successful for business.” Marco explains that the term cradle to cradle simply describes the safe, and potentially infinite, circulation of materi- als, as well as ‘nutrients’. “If all constituents are chemically harmless and recyclable, waste as we know it today - which is generated according to the pre- existing take-make-waste model – would no longer exist, leaving only useful nutri- ents instead.”


PURITY OF MATERIALS First and foremost, Marco believes that biological materials which are biodegradable will be the leaders in the new circular economy – but they must be kept pure. Timber for example, which is often


used in our built environment, is a great solution. According to Abdallah however, it loses its beneficial characteristics when it is covered with a chemical coating or laminated.


Cross-laminated timber is one example


of this, he says; how much the material can be dismantled and reused in the future is not clear, but if it is burned in an incineration plant, many toxic compounds would be released into the air. Fortunately, he tells me that there are methods of biological protection and assembly which do not require glue. Alongside this, technical materials such


as facade systems also work well, he says, as long as they follow the principle of ‘design for disassembly’ and the materials are made for recycling. “The key, therefore,” he says, “is to use


pure materials and avoid compounds of different materials which cannot be separated during the later recycling process.”


EMBODIED CARBON Half of the carbon emissions created by buildings are those associated with embodied carbon. These ‘embodied carbon emissions’


are associated with the material use, including raw material sourcing, transportation, product manufacturing and installation on site.


Concrete forms an enormous chunk of embodied carbon emissions — in 2018, around 8 per cent of total global CO2 [SUBSCRIPT] emissions were related to cement production — and it is also responsible for a huge amount of construction waste because concrete in the past was barely ever recycled. Suppliers have recognised this however, so, besides the recycling of aggregates (which is starting to become common- place), methods of reclaiming cement are being developed that will significantly lower carbon emissions.


COSTS


Of course, when the bottom line comes into play many builders may become wary of such models – though even if costs were to be increased, it is argued by many that these costs are ‘easily' recouped through modern buyers’ desire for high performing buildings.


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