The extraction, production and use of building materials generate significant amounts of embodied greenhouse gases. Reducing these emissions is essential for reducing global warming.
Many of these emissions can be avoided by choosing more sustainable materials. For example, using rammed earth instead of cement reduces emissions significantly. Wood also sequesters carbon and has much lower embodied energy than concrete and steel.
Wood
Wood is one of the few building materials that can actually mitigate climate change, because it naturally sequesters carbon. However, the climate benefits of using wood in buildings are largely dependent on how the material is harvested and used. Nearly all studies claiming that CLT is carbon neutral or even net-positive exclude forest-based carbon storage from their accounting (Hill, 2019).
Generally speaking, harvesting trees for use in building construction decreases the amount of carbon stored in forests relative to a no-harvest scenario. It’s a bit like withdrawing money from your savings account each year—your balance may not decline, but you’re still poorer than you would be if you simply left the money in your bank to grow.
To avoid these consequences, the building industry needs to embrace CLT and other mass timber technologies that can be produced locally from sustainable sources. It also must invest in research and development of the technology, and ensure that new construction complies with rigorous energy and environmental requirements.
Governments must set mandatory building codes that will require zero-carbon standards as soon as possible. Private investors must also increase their investments in the building sector, and provide debt and equity capital to accelerate a transition to low-carbon mass timber buildings. This investment could help reopen mills that have closed and revitalize rural communities.
Concrete
Since the romains perfected concrete in around 125AD, the material has become the world’s most widely used manmade building material. But this ubiquitous construction material comes at a high cost — the production of concrete and cement contributes to up to 5% of all global man-made carbon dioxide emissions. NewsHour Weekend’s Mori Rothman takes a look at the many ways that researchers are working to reduce these emissions from concrete.
Almost a quarter of the planned savings involve making concrete and cement more efficiently. That could include heating kilns with waste wood instead of fossil fuels or by replacing some of the limestone in the concrete mix with other materials. A few start-ups are also experimenting with completely new chemistry for concrete, without the need for calcium carbonate. One example is a material inspired by nacre, the substance that coats the shells of oysters and abalone.
Some of these strategies can deliver a double co-benefit: They not only cut climate change impacts but can help slash water consumption and prevent depletion of natural resources, such as wood. But other approaches may actually increase these impacts, if they require burning more fossil fuels to make clinker or to produce and transport concrete. That’s because the processes involved in producing these materials can trigger local air pollution that exacerbates health damages from greenhouse gases.
Metals
The production of building materials is one of the major contributors to climate change. The extraction of materials such as concrete, steel and glass requires significant amounts of energy and releases greenhouse gases in the process. They also deplete natural resources and contribute to the degradation of ecosystems. Fortunately, there are ways to reduce these negative effects by using less traditional materials such as wood.
In addition, metal buildings are highly energy-efficient. They are able to reflect most of the sun’s rays, which reduces air conditioning costs in summer and heating costs in winter. Moreover, they are highly insulating and can be built with fiberglass or rigid board insulation, which can help to keep heat inside during the winter and outside during the summer.
Another concern is that metal contaminants in surface runoff may negatively impact the urban water cycle. These contaminants are transported through rivers and may be remobilized due to the melting of arctic ice and accelerated soil erosion caused by floods and torrential rains (Visser et al., 2012).
There is a growing push for sustainable and eco-friendly construction projects. This is because these types of buildings can withstand future natural disasters and other risks while maintaining functionality. As such, architects and builders are increasingly turning to metal as their go-to building material. Its elite durability and versatile aesthetics make it a top choice for many different types of projects. Moreover, it is easy to recycle and reuse, making it even more sustainable.
Plastics
For the building industry to reduce its greenhouse gas emissions, the materials it uses need to be low impact. Unfortunately, many current construction materials emit substantial quantities of air pollutants and greenhouse gases during the production stage.
One of the biggest culprits is plastic. Plastic is created using fossil fuels, and the process of extracting oil and natural gas is incredibly carbon-intensive. Companies use fracking to drill through the earth’s surface until they reach a layer of rock and then inject sand, water and chemicals into the well to break up the rock and release gas and oil. Once the fossil fuels are extracted, they must be transported to processing plants where they will be turned into plastic pellets. This is a very energy intensive activity and if the global plastics industry were a country, it would be the fifth largest emitter of greenhouse gases in the world, according to a 2021 report from Beyond Plastics.
If the growth of plastic production continues to accelerate, it could make limiting the rise in global temperatures to 1.5 degrees Celsius impossible. The CIEL report estimates that by 2030, emissions from plastics production and incineration could reach 1.34 gigatons of CO2 per year—or the equivalent of 189 coal-fired power plants. Plastic is also so lightweight that it can easily travel far distances, with pieces as small as a human hair found in pristine oceans downwind from their presumed source.