Khush Patel

A Solid Argument for Sustainable Cement

By: Khush Patel

Cement is the second-most-used substance in the world after water and cement production is responsible for about 7% of annual global carbon emissions. It is used for plastering, masonry, piping, flooring, roofing, for beams, pillars, stairs, bridges, dams, tunnels, lighthouses, wells, water tanks, lamp posts, houses, roads, and more. The list of uses for cement is never-ending. Cement is the main ingredient in concrete. Over 70% of the world’s population lives in a concrete structure, and that percentage will only grow. As the population increases, there is a need for new infrastructure, which only increases the demand for cement.

Conventional Portland cement involves heating limestone, which causes a large chunk of cement’s emissions (Drawdown). When the limestone, clay and other materials are fired in a kiln, the process releases carbon dioxide. According to the National Ready Mixed Concrete Association, each pound of concrete releases 0.93 pounds of carbon dioxide. This is a significant amount considering that the annual global consumption of concrete is 33 billion tons. It is imperative that the cement and concrete industries are decarbonized for sustainable development. Using alternative clinker in the making of cement would reduce 7.7-15.56 gigatons of carbon dioxide if implemented from 2020 to 2050. Clinker is the nodular material made after heating the limestone and clay in the kiln. Clinker is ground and then mixed with gypsum and water to make cement paste. The average global rate of clinker substitution could realistically reach 40% and avoid up to 440 million tons of carbon dioxide emissions annually (Drawdown). The solution is two tiered: 1.Replace limestone clinker, which is the main ingredient used to make cement. Limestone would be replaced by substances like “ volcanic ash, certain clays, finely ground limestone, ground bottle glass, and industrial waste products- namely blast furnace slag (from manufacturing iron) and fly ash (from burning coal)” (Gartner, Suib). 2.Reduce the energy intensity by “ reducing the thermal and electricity intensity of clinker production by upgrading cement kilns to modern day standards, such as the use of pre-calciners and dry-kiln technologies” (Drawdown).

Implementation of these solutions would initially cost the United States net $61.38 billion, according to the Drawdown Report. There are many companies and startups already producing alternative cement through technological innovations. Some innovations include ashcrete, blast furnace slag concrete, micro silica cement substitution, papercrete/fibrous concrete, ferrock, rammed earth blocks, straw bale blocks, timbercrete and hempcrete. Concrete can also be produced from concrete debris, post-consumer glass, plastic waste, and composite materials. Rutgers University researchers are working with a company called Solidia which produces cement by curing it with CO2 instead of water (a form of carbon sequestration) and by using less energy. As a result of CO2 curing, Solidia concrete is cured in less than 24 hours, as opposed to the 28 days required for traditional concrete.This solution saves time, money, and water. It also both emits less carbon dioxide from the heating process and traps away carbon dioxide from the curing process.While Solidia altered the formula of concrete, other companies have been altering the chemical composition of concrete (Sridharan). NJ Bill S287, also known as NJ Bill A2234, provides corporation business tax (CBT) and gross income tax credits for certain deliveries of low carbon concrete. It also provides this for costs of conducting environmental product declaration analyses of low carbon concrete This bill would incentivize the use of low carbon concrete in New Jersey. The bill has passed the NJ Senate, but has not yet become a law. Support the bill by writing to your State Legislators and Assemblypersons, according to your legislative district.

https://www.solidiatech.com/