Every year cement production contributes about 5% of the global emissions generated by humans. Any improvement around cement production will have a good impact on lowering carbon entering our atmosphere. In Sweden there’s one company using algae to lower its emissions. The country has carbon emission rates that are likely increasing in the next few years, which has inspired the cement company to figure out how to avoid paying more for producing the same amount of cement. Their solution: pumping the carbon output from their cement factory onto algae which then inhales all that delicious carbon, once the algae dies it becomes food.
It’s elegant: Take water from the Baltic Sea’s Kalmar Strait next to the plant, pump it about 100 meters (330 feet, about the length of a soccer field) into bags that can hold about 3,000 liters (800 gallons) of liquid. Add key nutrients to multiply the naturally occurring algae, and then let them soak in the gases piped to it from the cement plant (what would otherwise be the factory’s waste product) while the sun shines.
What’s more is the algae are rich in proteins and fats. After drying, they can be used as an additive for chicken- and fish-food. Heidelberg is in talks to sell the algae additives to major agricultural companies like Cargill. At its current size, the Algoland system in Degerhamn can only produce about a few kilograms of algae a day. But the plant has all it needs to scale up to make many metric tons of algae daily—light, water, fresh algae, and lots of space—and thus capture many metric tons of carbon dioxide in the process.
The science underlying Algoland is not novel, but what is new is how well it integrates the many parts entailed into an economically feasible carbon-capture plant. The used-up limestone quarry can provide the space; a greenhouse built on it ensures the right temperature and light is available even when the sun’s not shining; and the Baltic Sea is a source for both water and fresh algae.
Cement is a very popular building material for a lot of good reasons, the problem though is that the process of making it requires a ton of energy. This problem has led to a growing number of people looking into ways to make cement less damaging to the planet. We’ve covered cement on here before.
The Smithsonian has a good round-up of the current world of greening the cement industry. In some ways these solutions can work together.
Though still refining its procedures, Novacem is racing with at least five other companies and university centers to come up with a greener cement. “Given all the attention to carbon these days, a lot of entrepreneurs have popped up,” said MIT’s Jennings. “They see the opportunity side.” With cement a $170 billion-a-year industry, investment money is pouring in.
A California company called Calera has perhaps the most unusual approach: It harnesses carbon dioxide emitted from a power plant and mixes it with seawater or brine to create carbonates that are used to make cement. They can be added to Portland cement to replace some or all of the limestone. Calera is backed by a $50 million investment from Vinod Khosla, a computer engineer who is perhaps Silicon Valley’s most respected and deep-pocketed investor in green technologies. “We are actually making our cement out of CO2,” said company founder Brent Constantz. “We are taking CO2 that would have gone into the atmosphere and turning it into cement.” The technology is still in development, with a demonstration plant in Moss Landing, California, and a partnership with a Chinese group to build a plant next to a coal mine in Inner Mongolia, where they plan to use carbon dioxide emissions to make cement.
Calix, an Australian company, makes cement using superheated steam, which modifies the cement particles and makes them purer and more chemically reactive. The process also separates out carbon dioxide, making it easier to capture the gas and keep it out of the atmosphere.
Louisiana Tech University, like Novacem and Calera, is doing away with limestone altogether; it’s using a paste called geopolymer, which is made of fly ash, sodium hydroxide and potassium hydroxide.
A mixture of hot gas rises out of a flue stack at the St. Marys Cement plant about 50 kilometres west of Waterloo. But not all the CO2-rich exhaust is vented to the open air.
Some is redirected through a 15-centimetre thick pipe connected to the side of the stack. The pipe carries the gas into a high-tech facility where a species of algae from the neighbouring Thames River uses photosynthesis to absorb the carbon dioxide and release oxygen in return.
“It’s a small model of what a big full-scale facility could be,” says Martin Vroegh, environment manager with St. Marys Cement Inc., headquartered in Toronto. The algae project, which went live last fall, is believed to be the first in the world to demonstrate the capture of CO2 from a cement plant.
The idea, Vroegh explained, is to turn CO2 into a commodity rather than treat it as a liability. The CO2-consuming algae will be continually harvested, dried using waste heat from the plant, and then burned as a fuel inside the plant’s cement kilns. Alternatively, the green goop can be processed into biofuels for the company’s truck fleet.