What is the difference between closed-loop recycling and downcycling?

What is the difference between closed-loop recycling and downcycling?

Although most UK demolition waste is now recovered following demolition (it is estimated that >90% of UK demolition arisings are currently recovered and reused in some form), it is important to know how easy it is to recover and recycle different products/materials and to understand the relative benefits of different forms of recycling and reuse.

Construction materials differ significantly in the ease with which can be recovered and recycled and if we ignore this aspect then, in effect, we are equating products that are recycled with products that are landfilled!

Metals, for example, are infinitely recyclable, i.e. they can be recycled again and again into functionally equivalent products. This is the most environmentally beneficial form of recycling and is called closed-loop recycling.

Many other construction products are downcycled into new products that are only suitable for lower grade, lower values applications because the recycled product has different, usually lower, material properties. Although waste is diverted from landfill by downcycling, only lower grade primary resources are saved. For example, crushing bricks and concrete for sub-base or general fill saves aggregates but does not save the resources required to make new bricks or new concrete.

The methodology generally used in construction to quantify these relative recycling or circular economy benefits is called Module D.

Recycling construction products is important to conserve resources and to reduce environmental impacts. Although most end-of-life building products are now recovered following demolition (it is estimated that >90% of UK demolition arisings are currently recovered and reused in some form), it is important to know how easy it is to recycle different products/materials and to understand the relative benefits of different forms of recycling and reuse.

Construction materials differ significantly in the ease with which can be recovered and recycled and if we ignore this aspect then, in effect, we are equating products that are recycled with products that are landfilled! Preserving resources through reuse and recycling is vital to achieve a more circular economy and to reduce greenhouse gas emissions.

The benefits of recycling and reuse are well understood and include:

  • Reducing waste, i.e. diverting waste from landfill,
  • Saving resources, i.e. substituting primary production,
  • Saving energy and associated greenhouse gas emissions through less energy intensive reprocessing.

Although these benefits apply to many commonly recycled materials, there are some important differences in material properties that influence the environmental benefit of recycling and particularly how these benefits are quantified.

Metals, for example, are infinitely recyclable, i.e. they can be recycled again and again into functionally equivalent products. This is the most environmentally beneficial form of recycling and is called closed-loop recycling. By carefully blending scrap steel it is also possible to produce new steel with superior properties and higher value, e.g. engineering and stainless steels. This is called upcycling.

Other construction products are downcycled into new products that are only suitable for lower grade, lower values applications because the recycled product has different, usually lower, material properties. Although waste is diverted from landfill by downcycling, only lower grade primary resources are saved. For example, crushing bricks and concrete for hardcore, sub-base or general fill saves aggregates but does not save the resources required to make new bricks or new concrete.

For recycling to be sustainable in the long term, it is important that the recycling process is financially viable. This is frequently the biggest hurdle to recycling, particularly for products and materials that are downcycled into lower grade, low value applications. These products often require incentives or regulation to encourage recycling.

Steel scrap, on the other hand, has a high economic value that ensures it is always highly recycled. This process is enhanced by steel’s magnetic properties that allow it to be easily recovered from mixed waste streams. An established infrastructure exists to collect, sort and process scrap efficiently.

The methodology generally used in construction to quantify these relative recycling or circular economy benefits of different products is called Module D and is explained in the next FAQ Why are UK sections produced via the primary (BF-BOF) production route?