Making It With Mushrooms

Sam Harrington stood at the podium at the Plasticity Forum in New York City this summer to preach to the environmentally minded audience about Ecovative Design’s mushroom-based plastics. While Harrington, the firm’s marketing and sales manager, spoke, a basket containing hunks of expanded polystyrene, horseshoe crab shells, and samples of his company’s materials passed from table to table.

The connection between the polystyrene foam and the mushroom plastic wasn’t hard to grasp. They were of similar weight and stiffness. The most obvious difference between the two was texture. The mushroom plastic had a velvety feel, like the moldy skin on a wheel of brie.

Why the crabs were there was more puzzling. But Harrington explained that the horseshoe crab shell and the tiny, interwoven strands of the mycelium—the vegetative tissue of fungi—in Ecovative’s material are made of the same stuff: chitin.

For a more sustainable world, Harrington said, industry will need to exploit processes found in nature. “How could we make a fork the way the horseshoe crab grows its exoskeleton?” he asked.

That’s the goal of a handful of companies developing mushroom plastics. It’s a twist on conventional biobased plastics, where for the most part, development involves perfecting biological pathways to monomers that can be converted chemically into polymers.

The new companies want to go straight to molded “polymers” by growing the mushrooms in cavities of the desired shape. But finding markets for these materials and producing them on a large scale are challenges they still must overcome.

There are a lot of shrimp, crabs, mushrooms, and insects in the world, so much so that, after cellulose, chitin is said to be the most common biopolymer found in nature. Chitin is a polysaccharide. Its structure is similar to cellulose except that it has an acetamide group instead of a hydroxyl group in each repeating unit.

As a material, chitin, especially in the form of the new mushroom-based materials, is relatively unexplored. “It is unclear, exactly, what the best application of this material is going to be,” says Philip Gordon Ross, assistant professor of art at the University of San Francisco. “It is like the early days of plastics, when people knew they had an interesting material but they weren’t sure exactly what it was.”

Ross is also the founder of MycoWorks, one of the firms developing mushroom-based plastics. He learned how to cultivate mushrooms while working as a chef in the 1990s. He would take organic waste such as sawdust or corncobs, pasteurize it, inoculate it with fungal tissue, and let it set in a container to grow. The mixture became a dense material shaped like the container.

With a few refinements, this is how companies manufacture mushroom materials today. The result is analogous to a polymer composite, with the mycelium as the polymer matrix and the organic material akin to fiberglass reinforcement.

Initially, Ross grew reishi mushrooms for food and as an immune system stimulant. After a while, he started using them as a structural material. In 2009, he made a 200-cu-ft building for a German art exhibit. “The entire house was boiled down over the course of the exhibition and served as tea to the visitors,” he recalls.

MycoWorks has put its material through the paces of professional testing. Ross has also tested the material’s limits himself, taking blocks of it down to a shooting range and firing .22, .38, and .45 caliber slugs into them at point-blank range. The .45 penetrated only 5 inches into the material.

The unique physical properties of its materials have prompted MycoWorks to explore applications such as architectural panels. According to Ross, the materials have attracted the attention of the military as well as vehicle makers, who are intrigued by their sound-dampening and structural characteristics. “It blows me away the folks we are talking to,” he says.

Ecovative is mostly pursuing large markets that are traditionally the domain of commodity plastics. Chief among them is protective packaging, where Ecovative’s material competes with polystyrene, polyethylene, and polypropylene foam. The company designs test packs especially for customers and then performs drop testing on the packaging.

“Using approximately the same amount of material, we’re generally able to match g-levels seen in those packs,” says Eben Bayer, the company’s chief executive officer.

Ecovative has enjoyed the most success competing against polyethylene foam, a high-end material used largely for packaging electronic devices. “That has been our sweet spot in the market,” Bayer says, in part because polyethylene foam is more expensive than other plastics, he adds. Ecovative boasts the computer maker Dell as a client.

The company has a big-time partner in the protective packaging giant Sealed Air. The firm, famous for Bubble Wrap, licensed Ecovative’s technology and applied it in a 30,000-sq-ft factory in Cedar Rapids, Iowa. Ecovative supplies the needed agricultural waste feedstock and the mycelium tissue to Sealed Air, which is making standardized protective packaging shapes.

Another deep-pocketed Ecovative backer is 3M, which participated in a $14 million venture capital investment round late last year.

Like MycoWorks, Ecovative is exploring structural uses for its material. One is as a replacement for polyisocyanurate and polystyrene foam insulation. Its mushroom plastic material has an insulation value similar to polystyrene, Harrington tells C&EN, and a class A fire resistance rating, which comes naturally without the need for brominated flame retardants. Another potential application is engineered lumber in which slabs of mushroom material can be pressed into boards.

But the company has more than material properties to worry about: Ecovative’s executives often get questions about processing time. After the agricultural waste material is inoculated with the mycelium, it needs to sit in a shaping mold for 96 hours while it grows into a finished part. Processing time in the plastics industry is generally measured in seconds or minutes.

Harrington coyly responds that mushroom parts can be produced a thousand times faster than cardboard and millions of times faster than plastics. “You have to grow the trees first, or you have to wait for the oil to form over 65 million years,” he says.

“When you do your economic sensitivity analysis, it ends up not being that much of a factor,” Bayer adds, noting that the company has brought the processing time down from 14 days when it was founded in 2007.

Mushroom plastics are an “appealing story,” acknowledges Ramani Narayan, a professor of chemical engineering at Michigan State University who specializes in biobased plastics, but he calls the long processing time a “fatal flaw.” He draws a comparison to polylactic acid, a bioplastic that struggled in its early years in part because it needed minutes of residence times in molds to crystallize. This was subsequently fixed with better nucleating agents.

Narayan doubts the days of process time to make the mushroom plastics can be similarly improved to acceptable levels. “The concept of actually growing stuff into a product, just in terms of the time and capital required to reach large volumes, is not tenable,” he argues.

It’s Ecovative’s intention to be more than an appealing story. The firm is staking its future on high volumes made at competitive prices. “It has become very clear to us that, in general, for mass-market products people are willing to pay very little extra, if anything, for sustainability benefits alone,” Harrington says. “Our goal here is not just to create an econiche product.”