The three little pigs built houses out of straw, sticks and bricks to protect themselves from the big bad wolf. But what if the big bad wolf of the construction sector is its big bad environmental impact? Which materials would the little pigs choose then? As it turns out, in this case, fending off the wolf is complicated, and…spoiler alert…bricks probably aren’t going to be the main saviour.
No building material is perfectly green
The construction industry has an enormous environmental footprint. In the UK in 2018 it was responsible for 62 per cent of waste and 25 per cent of territorial greenhouse gas emissions. Its material footprint is equally huge. This industry consumed 177 million tonnes of virgin aggregates, 15 million tonnes of cement and two billion bricks in 2016. More and more attention is being paid to the carbon emissions related to all this material use, but less attention has been given to other non-carbon related environmental impacts, such as the effects on nature, water and waste generation, which could continue to be a problem, even as climate impacts are tackled. That is, unless resource efficiency is prioritised.
The greatest share of environmental damage comes from a material’s extraction and processing. Steel made in a blast furnace needs 2.4 tonnes of raw material for every tonne of steel produced and, unfortunately, most iron ore extraction happens in species rich or critically important environments, often encroaching on protected areas. Extraction is also demonstrably fuelling community conflicts worldwide. And when it’s being produced, blast furnace steel causes high carbon emissions and needs 8,000 litres of water for every tonne of product.
Although concrete manufacture has 15 times less production emissions than blast furnace steel per tonne, the vast quantity used, often avoidably, by the UK construction sector means its upfront carbon footprint is twice as large. It’s difficult to remove carbon from the production of concrete because of the chemical makeup of the raw materials needed. Low levels of recycled aggregate used also means high demand for mineral extraction for virgin aggregates. This is damaging local ecosystems and releasing particulate matter which is harming human health.
Timber isn’t necessarily a good substitute for the concrete jungle
You might like to think that the pig who chose sticks is the aspiring environmentalist. Timber has been lauded as the sustainable alternative to common carbon intensive construction materials, not least due to its ability to sequester carbon while in use. The average three bedroomed semi locks up around four tonnes of atmospheric carbon dioxide in the wood it contains. Timber is seen as a renewable resource, as stocks can be replenished once harvested, and well managed forests can improve local nature and water quality. The Climate Change Committee says using wood for construction is the best use of limited biomass resources.
But, there are big risks if timber used in construction isn’t sourced or managed sustainably. Forestry involving clear cutting or slashing and burning can cause the loss of up to 50 per cent of local species, which largely occurs with timber operations outside Europe (although most of the timber the UK uses is sourced from within the EU). The current end of life treatment of timber is also far from exemplary, with half of wood waste in the UK burnt as biomass to produce energy, releasing carbon that could otherwise be stored if the material was reused or recycled. As it stands, only 2.5 per cent of timber in construction is sent to high grade recycling.
Continuing to build in the same ways only risks greater and greater environmental harm. But, if we just cut the amount of raw material used in the first place, and increased the efficiency with which we use existing materials, the construction industry’s environmental impacts would be significantly reduced. This important defence against the big bad threats of the environmental crisis is hugely underutilised. The good news is the opportunities to do it are already available. We recently reported on how much latent potential there is for the industry to reduce its material use by 35 per cent by 2035 (cutting its carbon emissions by nearly 40 per cent) given the right policies to support change.
Those three little pigs would go far (and would all survive) if they were just a bit more careful with what they choose to build their houses out of.