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Grow your own wallboard

Posted: 27/06/2007

Mushrooms are not a common building material, but Eben Bayer, who grew up on a mushroom farm in Vermont, and is now a young engineering graduate, thought they might be pressed into service when given the job of creating a sustainable insulation. Bayer combined his agricultural knowledge with colleague Gavin McIntyre's interest in sustainable technology, and the pair created their patented "Greensulate" formula, an organic, fire-retardant board made of water, flour, oyster mushroom spores and perlite, a mineral blend found in potting soil.

A mixture of water, mineral particles, starch and hydrogen peroxide are poured into 7-by-7-inch molds and then injected with living mushroom cells. The hydrogen peroxide is used to prevent the growth of other specimens within the material.

Placed in a dark environment, the cells start to grow, digesting the starch as food and sprouting thousands of root-like cellular strands. A week to two weeks later, a 1-inch-thick panel of insulation is fully grown. It's then dried to prevent fungal growth, making it unlikely to trigger mold and fungus allergies. The finished product resembles a giant cracker in texture.They're hoping the invention will soon become commonplace among eco friendly products.

Bringing the insulation to market is still at least a year away though, and will require much more research and work, as well as better facilities. McIntyre and Bayer have applied for a grant - up until now they've been growing the product under their beds.

"It's sustainable, and environmentally friendly, it's not based on petrochemicals and doesn't require much energy or cost to make it."

The two say recent tests at the National Institute of Standards and Technology have shown it to be competitive with most insulation brands on the market. A 1-inch-thick sample of the perlite-mushroom composite had a 2.9 R-value, the measure of a substance's ability to resist heat flow. Commercially produced fiberglass insulation typically has an R-value between 2.7 and 3.7 per inch of thickness, according to the Oak Ridge National Laboratory in Tennessee.

McIntyre said they had envisioned modifying the product to make structural panels that could be grown and assembled onsite to produce sustainable homes.

Green building materials should be evaluated on the idea of cradle to cradle, according to the Natural Resources Defense Council. In the cradle-to-cradle industrial model, goods should either be fully biodegradable or reusable, limiting waste and pollution.

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