What does concrete have to do with zero waste?

When it comes to anthropological, or man-made, influences on climate change, it’s easy to get confused and overwhelmed. Even though there’s plenty of information about how to be more green, why some things are eco-friendly and why others aren’t isn’t usually explained. Is the purpose to reduce pollution? Does it fight CO2 emissions?

Beyond that is the question of what we can actually impact immediately as individuals, and there exist industries with huge impacts contributing to climate change and greenhouse gas emissions. Concrete falls here, as a sneaky and under-the radar emitter of the gases contributing to increase in global temperatures. According to the BBC, it’s the second most consumed resource on the planet, following water. If the industry were a country of its own, it would be the third most emitting country in the world, contributing far more CO2 than plane emissions and almost as much as agriculture.

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Concrete is generally sand, gravel, a binder, and water; most cement used these days is Portland cement, a mixture created from roasting limestone and clay in an oven and grinding it, resulting in what is called clinker. As for the wide use of the product, it’s historically and contemporarily a great building material. The use of concrete increases with urbanization and economic development, meaning its’ use is in no way decreasing. According to the BBC, “production has increased more than thirtyfold since 1950 and almost fourfold since 1990.”

There are various byproducts of the industry, including air pollutants like sulfur dioxide, nitrogen oxide, and carbon monoxide. Sulfur dioxide is a concern for those with respiratory issues and carbon monoxide, as most of us know, can be deadly in high concentrations. Nitrogen oxide is bad news, as well; according to the EPA, “nitrogen oxide (NOx) can cause or contribute to a variety of health problems and adverse environmental impacts, such as ground-level ozone, acid rain, global warming, water quality deterioration, and visual impairment.” In other words, emissions from the cement industry can damage our health, threaten water supplies, and contribute to raising global temperatures.

Quarrying for materials like limestone causes air pollution in dust, and the use of kilns requires huge amount of energy, usually from burning fossil fuels. Combined with making clinker, 90% of the cement industry’s emissions come from creating this heat. Most toxic emissions come from the kiln used to heat limestone and other materials; in fact, 60% of carbon emissions from cement production occur due to the chemical reaction from heating the limestone. Pollutants are also emitted from grinding, cooling, and during the material handling steps of making cement.

As for actionable steps to combat the negative impact of cement production, it seems change is in its infancy. Some suggest implementing more carbon capture to store carbon emissions of the industry, however, this type of solution aims at trying to manage the negative impact while maintaining current practice rather than innovating a more sustainable process. As they say, when the sink is overflowing, you turn off the faucet before you start cleaning up the water, and carbon capture doesn’t fix the root of the problem. Cement is a resource that cannot be avoided and its’ central role in construction and development means that reducing our use of the efficient product is unlikely, so pressures to hold the industry accountable until innovation has occurred will most likely be necessary.

On a happier note, there are already some green cement options. Architect Ginger Krieg Dosier is co-founder and CEO of BioMason, which is a start-up that uses bacteria to grow bio-concrete bricks. The resulting product is akin to coral, takes three days to process, and can be made at room temperature, meaning that there’s no need to burn fossil fuels.

While there isn’t a perfect individual action to combat emissions from cement, there needs to be awareness of problems before solutions are demanded.