LESS CEMENT



It is in the nature of cement to be hard. It is in the nature of cement to be durable. It is in the nature of cement to be destructive through its production. Cement production accounts for around 8% of global CO2 emissions.1 Cement is made from heating limestone to 1450°C to separate carbon dioxide from calcium carbonate. Calcium carbonate is used to form clinker, the binding component of cement. 3% of global emissions can be attributed to the energy needed to power cement kilns, with another 5% from the CO2 byproduct.

Cement is roughly 10% of concrete. Concrete is an enormous component of contemporary life. It is the bones of buildings, the flesh of roads, of runways, of bridges, and the skin of sidewalks. This has increased in recent years: in China alone, more cement was used in the three years between 2008 and 2010 than in the entire 20th century in the United States.2 Hurricane Maria decimated the built environment in Puerto Rico, sweeping away lives and livelihoods. What was rebuilt was constructed out of concrete. Superstorm Sandy inundated large parts of New York, and Build It Back built it back with concrete, from the boardwalks of the Rockaways to the foundations of Staten Island homes. When planners conceive of ways to protect lower Manhattan from sea level rise, they imagine building a big concrete “U.”

Is it possible to change the nature and energy appetite of cement itself? Kilns might be converted. A majority still use fossil fuels, but some consume waste oils and shredded tires. Retrofitting old kilns to improve thermal efficiency might lower the industry’s energy needs by two-fifths, says the Carbon Disclosure Project, a step that would also cut the industry’s overall expenditure.3 Other emissions reductions could come through transformations in the production process, such as replacing limestone clinker with other binding materials including fly ash (a byproduct of burning coal). Power plant emissions could be injected into concrete, with this sequestering of carbon potentially also improving concrete’s strength and durability.4 Reusing concrete from demolished buildings could also reduce carbon emissions by diminishing the need for aggregate, a major component of concrete


Design for less concrete, use less in concrete
construction. Less concrete, less cement.

1. Andrew, R, ‘Global CO2 emissions from cement production’. Earth Syst. Sci. Data, 10 (195-217), 2018.
2. Vaclav Smil, ‘Making the Modern World Materials and Dematerialization,’ Chichester: Wiley, 2014.
3. ‘Cement manufacturers Cracks in the surface: Why grey firms will have to go green,’ The Economist, 25 August 2016.
4. Timperley, Jocelyn, ‘Why cement matters for climate change,’ Carbon Brief, 13 September 2018.

Image: Gabriela Salazar, Matters in Shelter (and Place, Puerto Rico), 2018.  

As citizens commemorated the one-year anniversary of Hurricane Maria, the extent of the storm’s slow violence was finally being acknowledged. When the storm hit on 29 September 2017, a dozen people were reported killed. The Puerto Rican Government’s official count eventually grew to 641 but as deaths from related causes such as bacterial diseases, lack of access to health care in general, and suicides driven by Maria’s destruction of livelihoods begin to be factored in, the government has now ‘quietly’ acknowledged that the cumulative death toll is closer to 3000.2

Gabriela Salazar’s work Matters in Shelter (and Place, Puerto Rico), part of the exhibition Indicators; Artists on climate change (2018), at Storm King Sculpture park in New York, presented a vaulted space of reflection, a memorial of sorts both to the ongoing impact of Hurricane Maria, and also to the economic crisis which was already crippling Puerto Rico as the storm struck. Through material and olfactory effect, Matters in Shelter (and Place, Puerto Rico) probes the history of colonial relations between Puerto Rico and the United States, including the draconian policies that tipped the island into financial crisis and have made recovery from Maria so difficult.

The cobalt gossamer mesh which comprises the shelter’s skin is a material which echoes the blue FEMA tarps used for temporary shelters in Maria’s immediate aftermath. The material also references the semilleros or hothouse structures used to protect young coffee seedlings. Inside Salazar’s installation concrete breeze blocks in various arrangements act simultaneously as floor, seating, and display apparatus—as rough plinths for another set of blocks made from compressed coffee grounds. These coffee bricks point both towards an element of Salazar’s heritage—her mother grew up on a coffee farm in Puerto Rico—and also to the precarity of the island’s present. In recent years coffee has been a resurgent crop in Puerto Rican agriculture, but the industry was decimated by Maria’s impact. While the smell of coffee-ground blocks evoke the Puerto Rican agricultural industry, the concrete blocks speak to a broader global irony: in re-building efforts that follow the devastation of climate-amplified extreme weather events, concrete is used because of its ubiquity and relatively low cost, yet at the same time the production of the material contributes to the climate crisis.

1. Frances Robles, ‘Puerto Rican Government Acknowledges Hurricane Death Toll of 1,427,’ The New York Times, 9 August 2018.
2. Sheri Fink, ‘Nearly a Year After Hurricane Maria, Puerto Rico Revises Death Toll to 2,975’, The New York Times, 28 August 2018.

Image: Gabriela Salazar, Matters in Shelter (and Place, Puerto Rico), 2018. Coffee clay (used coffee grounds, flour, salt), concrete block, wood, and polypropylene mesh tarp, 12 x 16 x 20 ft. Courtesy the artist. 
Mark