We hear a lot about plastics destroying ecosystems and fossil fuels dooming us to climate catastrophe; but a lesser discussed material — a top greenhouse gas emitter, water user, and threat to fertile soils — is looming all around us.
What is this climate menace hiding in plain sight? Concrete.
Concrete is the second most widely used substance on the planet, eclipsed only by water. If the cement industry were a country, taking in all stages of production, it would be the third largest carbon dioxide emitter in the world. It is responsible for nine percent of global industrial water withdrawal. And to make matters worse, 75 percent of water demand for concrete production occurs in water-stressed regions. Industrial expansion has replaced miles of arable soil, grasslands, forests, and other regions of ecological diversity with the brutal material — a process incredibly resource-intensive (if not impossible) to reverse.
Concrete has been called “the foundation of modern life” due to its unimpeachable durability. It is heavy and hard and yields minimally to nature. Early instances of the substance can be found in an ancient recipe for mortar, documented in 30 B.C.E. One need look only to The Pantheon in Rome, the largest non-reinforced concrete dome in the world, still standing 19 centuries after it was built, to grasp just how long-lasting cement can be (though concrete of today requires repair or replacement about a hundred years in, due to the less stable ingredients we concoct it with).
The use of concrete exploded after WWII, when it was poured prolifically to rebuild cities that had been torn apart by the war. Everything from dams to bridges to parking lots, all hewn from concrete, helped advance urban and industrial environments. But the very qualities that made it ideal for those applications also set its course for ecological destruction. Cement production has increased 25-fold since 1950 and ****demand for concrete is only growing as urban expansion continues to develop globally. According to a 2018 Chatham House report, “On a ‘business as usual’ trajectory, global cement production is set to increase to over five billion tons a year over the next 30 years.”
Over half of greenhouse gas emissions attributed to the concrete sector occur in the process of producing clinker, a product of the chemical reaction that occurs when clay and limestone are mixed and heated, and one of the main ingredients in cement. Because these emissions are a byproduct of a reaction intrinsic to the “recipe” they cannot be averted by changing energy sources or increasing efficiency. Therefore, exploring alternative materials that could reduce the need for clinker is critical to reducing the climate impact of concrete production.
There are countless avenues down which we might find sustainable solutions for cement. And as we love to say here at Farm, a patchwork of strategies is usually superior to any single silver bullet. Since the technique for making Portland Cement, the most commonly used variety, has been stagnant for over a century, there is plenty of room for improvement.
One strategy is incorporating biochar into cement mixtures. Endorsed by the IPCC, the use of biochar as a carbon capture technology is currently deployed mostly in agriculture. But research shows that the use of biochar as the aggregate in a concrete dry-mix could lead to significantly reduced CO2 emissions.
To back up a bit, biochar is a charcoal-like substance produced by burning organic matter in a low- or zero-oxygen environment. This carbon-sequestering wonder-dust is estimated to maintain its stable carbon content for millennia. Biochar has been employed in regenerative agriculture contexts to increase carbon sequestration and fertility of farmed soils. If biochar can be successfully integrated into a durable concrete product (studies are showing promise that it’s possible) we may be looking at a carbon-negative version of what is now a climate nightmare.
Innovations in this field abound. A research team at Purdue University recently found that adding a small amount of titanium dioxide to the concrete mix nearly doubles the amount of CO2 that concrete absorbs once it’s solidified. Montreal-based carbon removal technology company, Carbicrete, has bypassed cement entirely by producing pre-cast concrete that replaces it with steel slag. Solidia has patented technology to cure cement with CO2 instead of water, sequestering that carbon within the final product and reducing fresh water use.
Like the product itself, concrete as an industry doesn’t easily budge. Sustainability pioneers in the space are up against a great deal of capital and infrastructural investment sunk into the way things have been done for decades. But as regulations tighten and both policies and public opinion reflect the urgency of to mitigating carbon emissions, these ventures will only gain in viability. Energy Impact Partners, for example, is a firm that invests specifically in companies creating and implementing low-carbon and carbon negative technologies.
At Farm, we invest in land stewardship. This means we’re committed not only to the sustainable management of the lands we invest in, but that the systems we implement actively benefit the natural ecosystem. While concrete destroys natural infrastructure, we work to strengthen and rebuilt ecosystem services on every parcel of land we manage.
