February 20, 2014 – Did you know that concrete is the third largest source of human produced greenhouse gases (GHGs) on Earth? Concrete ranks second only to water as a human consumable. The average rate of consumption amounts to 3 tons per person today. Manufacturing of it contributes to 5% of all GHGs annually. That contributions is equal to half of what all automobiles and trucks in the world produce and only trails the fossil fuel industry itself as the largest emitter.
With the Developing World experiencing significant urbanization the need for concrete structures is expected to double globally over the next decade. That means concrete, the most versatile building material we humans ever invented, poses a significant problem for a planet dealing with human-derived climate change from increasing levels of CO2.
Concrete is derived from limestone and clay. And making concrete produces CO2 two ways. The first is called calcination. That’s when you heat limestone to 1,450 Celsius degrees. This leads to the release of calcium oxide and CO2. The second source of CO2 is in the burning of fuels to heat the kilns where the process of manufacturing is conducted. The ratio of CO2 contribution from the former is 50%. The latter is about 40%. The remaining 10% comes from transporting the finished product.
Since manufacturing is the biggest GHG producer it is the best place to start looking at ways to reduce the CO2 from the process. A Halifax, Nova Scotia company, CarbonCure Technologies, is attempting to address this challenge and have come up with a recipe for concrete that can turn the building material into a carbon sink.
CarbonCure’s solution is to sequester CO2 from industrial sources and inject it into the concrete as it is being mixed to create finished products – concrete blocks, and concrete pavers. The injected CO2 gets permanently locked with the limestone producing a stronger material. Every concrete block CarbonCure produces sequesters 30 grams of Co2. The company states that 3,000 of its concrete blocks can sequester as much CO2 as a mature tree does in a single year. Considering we globally produce 12 billion tons of concrete annually, if all of it were CarbonCure we would sequester a significant amount of carbon.
Today CarbonCure is being used for construction of many of the building and sport venues for the upcoming 2015 PanAm/ParaPan Games to be held in Toronto and surroundings next summer. Most recently it has been used in the United States at UC Davis for construction of the Jesse Jackson Sustainable Winery (see image below).
The low-carbon concrete represents a critical innovation that if applied globally could turn concrete from a net emitter to an effective tool for carbon sequestration. Considering we produce 12 billion tons of the stuff every year, our atmosphere could sure use this technology. It couldn’t arrive at a better time.
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