Unlike wood scraps that can sit in landfills for months or years, hemp-PHB biocomposites decompose a few weeks after burial. As they degrade, they release methane gas that can be captured and burned for energy recovery or re-used to make more biocomposites.
"It dawned on us that there are microbes that can make PHB from methane," Criddle said. "So now we're combining two natural processes: We're using microbes that break down PHB plastics and release methane gas, and different organisms that consume methane and produce PHB as a byproduct."
It's the ultimate in recycling, he said: "In our lab, we create conditions where only those organisms that accumulate the most plastic can reproduce. We call the process 'survival of the fattest,' and we have a patent application for it."
Capturing methane has the added benefit of combating climate change, Criddle said, noting that methane gas from landfills and other sources is a powerful global warming agent, 22 times more potent than carbon dioxide gas.
One reason that biodegradable plastics aren't widely used is cost. "We're competing with polypropylene and polyethylene, two really cheap petrochemical products," Criddle said. "Most bioplastics are made using sugar from corn and other relatively expensive materials. But our process uses methane in the biogas from landfills and wastewater treatment plants, which is essentially free."
The potential of producing low-cost, recyclable biocomposites has caught the attention of the private sector. In the next few months, the researchers expect to form a new startup company with venture capital funding.
Interest in the hemp-PHB biocomposites has moved beyond artificial wood products. In 2008, the research team was awarded a three-year, $1.5 million grant from the C
|Contact: Mark Shwartz|