Sequestering carbon in building materials
The main binding element of traditional concrete is cement, made in a process that releases significant amounts of carbon dioxide into the atmosphere, contributing to climate warming. Cement production alone is responsible for about 8% of global carbon dioxide emissions, according to the U.S. Department of Energy.
Using plants in concrete could not just reduce its carbon footprint, but negate it. Plants absorb CO2, and binding plants into concrete would trap that CO2 into the building material where it would not burn, biodegrade or otherwise release it back into the atmosphere.
For many applications flaxcrete would not work. It is unlikely a highway overpass will be built out of flax. Even if there were ways to utilize flax, it is hard to get locally. Once plentiful in Pennsylvania, flax is no longer grown here as a commodity crop. Richards sourced shive for his flaxcrete blocks from Nova Scotia, Canada.
A strip of flax grows along the Benjamin Franklin Parkway, part of an installation sponsored by the Association for Public Art called ”Franklin Thread.” (Emma Lee/WHYY)
The PA Flax Project is trying to bring flax back into Pennsylvania agriculture, a little bit at a time. The cooperative’s square yard campaign is asking people to grow a square yard of flax, a challenge that has been taken up by the Betsy Ross House, among others. Flax Project founder Heidi Barr said there are 45 acres of flax being grown in Pennsylvania right now, and she expects to have 300 acres next year. She is shooting for 1,000.
It is a “Catch-22” game between farmers and processors, according to Barr. You need to grow large amounts of flax to justify building a mill, but you need a mill to justify growing large amounts of flax. Once growing and processing flax is established, she said it can be a zero-waste proposition.
“When we visited the mills in Europe, the thing that struck me the most is there are no dumpsters,” Barr said. “The products with commercial value are the long-line fiber, the short fiber, the shive and the dust. Those are all collected and sold.”
The PA Flax Project is primarily focused on growing flax for the textile industry. Could it also be used to launch production of viable building materials?
“That’s a million-dollar question right there. I would not be doing what I’m doing if I didn’t believe that all the products you could produce from flax are going to be viable in the near future,” Barr said. “In particular in the fiber market, there’s a global market that is growing. There’s a huge growing demand. The industrial building trades are a little bit behind the curve.”
A strip of flax grows along the Benjamin Franklin Parkway, part of an installation sponsored by the Association for Public Art called ”Franklin Thread.” (Emma Lee/WHYY)
Flax has taken a back seat to hemp
In the world of alternative building materials, hemp has been getting a lot of attention. The Healthy Materials Lab of Parsons School of Design in New York built a Hemp House in New Castle, Pennsylvania, to showcase the possibilities. Hemp has also entered the commercial building trades. Right Coast Hemp of New Jersey promotes hemp in construction and renovation, often as antimicrobial wall insulation.
Flax has not enjoyed the same popularity as hemp. Richards said he was attracted to flaxcrete’s potential because the plant is already part of the textile industry. Richards believes incorporating flax into design thinking could tie industrial processes to the Earth’s natural processes.
“It’s a part of a biological cycle that’s not disconnected from a human cycle,” he said. “Fifty years ago, a couple miles north of here, we used to make linen in this city. We no longer do. It’s now abroad in places like China. We can bring that back to our city and the way of thinking that builders can be connected to both natural and human processes.”
“Franklin’s Thread” will be on view through October. Public programs onsite are in the planning stages, which could include a harvesting demonstration and flaxcrete molding workshops.