Building materials and climate change
Traditional masonry has a number of environmentally friendly characteristics, such as durability and thermal mass. However, as our collective understanding of environmental science—and especially of climate change—advances, we’ve had to revise our definition of green building. The manufacturing of building materials (cement, brick, gypsum wallboard, steel, etc.) accounts for about 12% of all emissions of carbon dioxide (CO2)—a greenhouse gas with an immediate and direct impact on climate change.
CO2 and embodied energy
One increasingly useful way to measure a product’s environmental impact is to audit its ‘embodied energy’ and ‘embodied CO2’—the amount of energy consumed and CO2 released to extract, transport, and process raw materials and manufacture the finished product. One focus of materials research and development is finding ways to reduce those levels without sacrificing other product benefits.
Why firing brick emits lots of CO2
Clay brick is fairly high in both ‘embodied energy’ and ‘embodied CO2’. Clay brick manufacturing is energy-intensive because clay requires firing for up to three days to become hard and durable. Brick kilns operate at about 2000 F and are generally kept hot even when not in use. The heat for most kilns is generated by burning natural gas, while some brick producers use fuels such as coal and petroleum coke that are not as clean-burning as gas. All of these fuel sources emit significant CO2 during combustion.
Sustainability: The numbers that matter
The National Institute of Standards and Technology (NIST) Building for Environmental and Economic Sustainability (BEES) database lists the average embodied energy for a common fired clay brick at 8800 Btus. A state-of-the-art fired clay brick plant operating at optimal efficiency might reduce this figure to slightly below 5000 Btus. CO2 emission is often a by-product of energy consumption; each clay brick fired with fossil fuel releases about 1.3 lbs of carbon dioxide into the atmosphere.
Sustainability: The CalStar brick solution
Producing fly ash brick consumes less energy and emits less CO2 because it does not require firing to harden the masonry units. Fly ash bricks and pavers are composed mainly of silicon dioxide, aluminum dioxide, and calcium dioxide—the same elements found in clay, though in different proportions. While the base elemental composition is more like clay, the addition of water and proprietary additives generates a chemical reaction between these compounds similar to cement hydration. The brick is compacted in molds and gains strength through this chemical reaction, without the need for firing. This is why FAB technology is truly a new, hybrid masonry category, distinct from both clay and concrete masonry, but exhibiting elements of both. The CalStar green brick solution represents 85% lower embodied energy and 85% lower CO2 than fired clay brick.