Environment

Could Concrete Help Lower Carbon Emissions?

by Geneva B | January 26, 2009 at 03:39 pm

365 views | 1 Recommendation | 2 comments

The production of concrete, a hardened mix of cement powder, aggregate, and water, has increased almost 400 per cent since 1970 and its manufacture is resource-intensive and polluting. The cement industry is responsible for an estimated 6 per cent of human-related carbon emissions. The expression "concrete jungle" has become more than fitting.

Alternatives have emerged this past year, however, that may redefine the future of cement. One company, California-based Calera Corp., claims to have found a way for cement production to absorb more carbon dioxide than it emits, acting as a vehicle for carbon capture and sequestration, or CCS.
Similar to how certain corals produce reefs by excreting dissolved calcium carbonate, or limestone, Calera sends carbon dioxide emissions through seawater to create a chalky carbonate byproduct. This cement substance is then mixed with aggregate and water to create concrete. Its production avoids the need to heat the cement materials in coal-fired kilns, while sequestering carbon throughout the process, the company says.

For every ton of cement produced, two-fifths of a ton of carbon dioxide is stored, according to founder Brent Constantz.

"Calera appears to be the only viable, economically feasible, no CO2-footprint way to capture, separate, and sequester billions of tons of carbon dioxide," said Constantz, a Stanford University biomechanical engineer who developed bone-fracture cement before turning his attention to climate change solutions. "We're converting carbon dioxide into carbonate, and we're putting it into the built environment."

California-based Carbon Sciences plans to mix cement with power-plant emissions and waste material from coal and steel production. Carbon Sense Solutions in Nova Scotia, Canada, redirects emissions from pre-cast concrete plants into new cement. And London-based Novacem says its magnesium silicate cement will absorb enough emissions to make it carbon negative.

While green building designers would like to see more dramatic changes option-wise, the list of alternative blends of concrete could potentially transform the way we see cement. These solutions could also help prevent what recently happened in Tennessee.

Alternative blends have included ash from coal-fired power plants, known as fly ash, and pozzolana, a volcanic ash. Although limited in their supply, these natural materials replace some of the fused minerals used in traditional cement, and therefore avoid the need to heat limestone to 1,450 degrees Celsius. The substitutes are becoming more common, mostly in continental Europe, according to the International Energy Agency.

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Mornixuur

at 23:43 on January 26th, 2009

Radio Kootwijk was built in 1922 and is made almost completely of concrete. Designed by the ducth architect Julius Luthmann after the form of an egyptian sfinx (you are looking at the backside in this picture). The building was used for long and short wave radio communication (mostly to the the dutch indies). A 3 minutes conversation would cost about 14 euros. In ww2 it was used by the germans to keep contact with their submarines. Currently it is a monument and while awaiting a new destination and renovation it is used to stage various events. For example, it was a major set in the movie mindhunters.

Mornixuur has contributed a photo to this story.

cwhite3424

at 08:53 on February 6th, 2009

The construction project pictured here is an Emergency Operations Center being added to a fire station. The construction method was chosen for its relative resistance to damage from weather and its high energy efficiency.

cwhite3424 has contributed a photo to this story.