Keeping the carbon: Biochar can be added to cement to sequester carbon within concrete. (Courtesy: Sabbie Miller)
Topics: Biomass, Civil Engineering, Environment, Global Warming, Green Tech
Replacing conventional building materials with alternatives that sequester carbon dioxide could allow the world to lock away up to half the CO2 generated by humans each year – about 16 billion tons. This is the finding of researchers at the University of California Davis and Stanford University, both in the US, who studied the sequestration potential of materials such as carbonate-based aggregates and biomass fiber in brick.
Despite efforts to reduce greenhouse gas emissions by decarbonizing industry and switching to renewable energy sources, humans will likely continue to produce significant amounts of CO2 beyond the target “net zero” date of 2050. Carbon storage and sequestration – at source or directly from the atmosphere – are therefore worth exploring as an additional route towards this goal. Researchers have proposed several possible ways of doing this, including injecting carbon underground or deep under the ocean. However, all these scenarios are challenging to implement practically and pose their own environmental risks.
Modifying common building materials
In the present work, a team of civil engineers and earth systems scientists led by Elisabeth van Roijen (then a PhD student at UC Davis) calculated how much carbon could be stored in modified versions of several common building materials. These include concrete (cement) and asphalt containing carbonate-based aggregates; bio-based plastics; wood; biomass-fiber bricks (from waste biomass); and biochar filler in cement.
The researchers obtained the “16 billion tons of CO2” figure by assuming all aggregates currently employed in concrete would be replaced with carbonate-based versions. They also supplemented 15% of cement with biochar and the remainder with carbonatable cement; increased the amount of wood used in all new construction by 20%; and supplemented 15% of bricks with biomass and the remainder with carbonatable calcium hydroxide. A final element in their calculation was to replace all plastics used in construction today with bio-based plastics and all bitumen with bio-oil in asphalt.
“We calculated the carbon storage potential of each material based on the mass ratio of carbon in each material,” explains van Roijen. “These values were then scaled up based on 2016 consumption values for each material.”
“The sheer magnitude of carbon storage is pretty impressive”
While the production of some replacement materials would need to increase to meet the resulting demand, van Roijen and colleagues found that resources readily available today – for example, mineral-rich waste streams – would already let us replace 10% of conventional aggregates with carbonate-based ones. “These alone could store 1 billion tonnes of CO2,” she says. “The sheer magnitude of carbon storage is pretty impressive, especially when you put it in context of the level of carbon dioxide removal needed to stay below the 1.5 and 2 °C targets set by The Intergovernmental Panel on Climate Change (IPCC).”
Indeed, even if the world doesn’t implement these technologies until 2075, we could still store enough carbon between 2075 and 2100 to stay below these targets, she tells Physics World. “This is assuming, of course, that all other decarbonization efforts outlined in the IPCC reports are also implemented to achieve net-zero emissions,” she says.
Alternative building materials could store massive amounts of carbon dioxide, Isabelle Dumé, Physics World
