Recycling Salvaged Cement Reduces our Carbon Footprint

            Construction is conventionally a carbon-intensive industry – especially in a place like Brooklyn where most medium buildings are built primarily with concrete, mortar, brick and stone. Some degree of greenhouse gas emission is inherent in the production of all construction materials, but none more so than the cement which makes up our foundations and holds our brownstones together. After energy generation, the cement industry is the 2nd-largest CO2 emitting industry in the United States and the world – responsible for about 5% of all man-made carbon dioxide emissions.

           Cement manufacturing entails a chemical process known as calcination in which limestone (i.e. calcium carbonate, CaCO3) is heated with small quantities of other materials, namely clay, in a kiln to 1450° C; this process liberates a molecule of CO2from the calcium carbonate to form calcium oxide (CaO). The clinker – which is the resulting hard end product of calcium dioxide – is then ground up with gypsum into powder form to produce what is commonly known as “Portland cement”.

           From start to finish, roughly 0.9 kilograms of carbon dioxide is produced for every 1 kilogram of cement that is produced – 50% from the end-products of the chemical process itself and 40% from the burning of fuel to heat the limestone to such a scorching temperature, the rest mostly in transportation and administration. More than 70% of all energy consumed by cement kilns is generated by burning coal – the worst of all fossil fuels in terms of greenhouse gas production, about 12% from petroleum coke, 9% from waste fuels, 4% from natural gas and the rest from oil and coke.

           Industry leaders and environmental scientists are trying to devise ways of reducing the environmental impact of cement production. The Environmental Protection Agency, for one, is trying to prod the U.S. cement industry to substitute coal-powered kilns to kilns which run on any fuel other than coal, CO2 capture and sequestration, alternative processes of concocting calcium oxide, etc.  We support these regulatory efforts, but we also believe that New York’s green contractors can do much more than to sit back and wait for change to come from the top down.

            We have devised an even more effective and remarkably simple means of reducing the carbon footprint of our construction and renovation projects:  conservation. Such a large amount of the cement produced in U.S. factories for some reason or another is never actually used to mix the mortar or cement it was intended for. Either contractors estimated too high when they made their bulk purchases and are left with excess cement that they don’t need, or somewhere in transit from the factory to the individual vendor cement bags are ripped or broken and cannot be sold. This surplus is considered trash on the free market – very few contractors make the effort to buy second-hand cement, so every year they take untold tons of perfectly good cement and just throw it in the landfill. If there is any way that NY green builders can cut down on the carbon footprint of construction/renovation jobs, it is by reducing this wholly unnecessary waste of cement; for every 1,000 kg of cement that is thrown out, our air and our oceans are polluted with 900 kg of CO2 for no reason at all!

                 As a green contractor, Eco Brooklyn salvages this otherwise landfill-bound cement from conventional contractors who have overstock and merchants who are stuck with unsellable bags. By recycling salvaged cement, Eco Brooklyn is busy conducting construction projects without there needing to be any additional cement produced, energy consumed and greenhouse gases emitted into the atmosphere. By adhering to our environmentalist mission by this and other practical methods, this green contractor is committed to limiting our carbon footprint to an absolute minimum. 

                Moreover, this NY green contractor is also developing new methods of building and renovation which can cut cement out of the production process as much as possible. Instead of basic concrete which is usually used for foundations, basement walls and floors, Eco Brooklyn is perfecting a rammed earth technology which simply uses the earth and stones dug up from the ground mixed with the most durable and sustainable ratio of cement and water. For the front walkway and steps, we are using natural stones, scrap bluestone and tile – we never use concrete. We don’t need to invest in the costliest and most exotic foreign technologies – in order to turn every brownstone into a greenstone all we can procure most of our materials straight from our own backyards – sometimes quite literally! 

About the author: Zachary Mason

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