Carbon-Storing Building Materials

Buildings Can Become Carbon Sinks

Carbon-sequestering building materials | Credit: Courtesy

Since my recent article on constructing carbon-storing buildings, many have asked for specifics on carbon-sequestering building materials. Here is a partial list:

• Cross-laminated timber (CLT) panels of varying dimensions made up of alternating layers of perpendicular boards. Because small-diameter trees, pest-damaged trees, and even trees killed by wildfires are used in fabricating these members, forest resources are more fully utilized. In addition to being strong, stiff, stable, and relatively lightweight, CLT panels are highly fire resistant and hinder fire spread. CLT can often be substituted for steel, even in high-rise construction.

• All bamboo building materials. Bamboo is a fast-growing wild grass that takes carbon out of the air faster than other plants. When laminated into posts, beams, glue-lams, and trusses (trade name Lamboo), it rivals the strength ratio of steel yet is more fire resistant without the use of ecologically unfriendly fire retardants. 

• Cal Star bricks and pavers. These are manufactured from fly ash, a waste product, using a small fraction of the energy needed to fabricate other masonry products. Another technology, on the cusp of commercialization, is growing bricks at ambient temperatures using bacteria and biomass. Absorbing pollution and carbon is part of the process.

• Hemp lightweight composite (building) blocks. Developed by JustBioFiber Structural Solutions, these blocks are highly resistant to fire, mold, and insect damage. Hemp products are top performers in the negative carbon materials classification.

• Calplant MDF rice straw panels. These panels utilize a carbon-sequestering waste material that normally is disposed of by farmers flooding their fields using large amounts of valuable water.

• Low-carbon insulating materials: cellulose, fiberboard (Gutex Multitherm), hemp board, recycled denim, and mushroom insulation. Ecovation is the brand name for mushroom insulation. It can be sprayed into wall cavities or seeded, filling the cavity in three days.

• Ecosmart drywall. This product uses less energy, resources, and water to manufacture and is fire resistant and lighter in weight, thus requiring less energy to transport.

• Green concrete. Cement accounts for around 6 percent of greenhouse-gas emissions (GHG). Green concrete focuses on three strategies: cutting GHG emissions; reducing inputs of natural resources, mostly by substituting recycled materials; and lessening air, land, and water pollution related to its production. Ceratech, a U.S. company, has created a feed mixture for cement that is 95 percent recycled fly ash and 5 percent renewable liquid additives, yielding an almost zero-carbon footprint. Its concrete mixes reduce virgin resource inputs by 95 percent and water by half. This hydrated cement has superior properties to Portland cement, the industry standard. Another innovation is a cement that cures by absorbing CO2.

Incorporating these and other low- or negative-carbon materials in new and remodeled construction can substitute for many traditional building materials. Traditional materials like steel, concrete, aluminum, and glass account for 11 percent of global CO2 emissions, according to a report from the UN Environmental Program. All materials listed above, except the bacteria grown bricks, are currently available and fit standard construction practices.

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