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Bicomposites based on Polyhydroxy-butyrate (PHB) |
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A synthetic wood substitute that may one day save trees, reduce greenhouse gas emissions and shrink landfills has been developed by Stanford University. The faux lumber is made from a new biodegradable plastic that could be used in a variety of building materials. The research team focused on a new class of construction material called biodegradable composites, or "biocomposites"-glue-like material reinforced with natural fibers that are made from plants and recyclable polymers. After testing a number of promising materials, the best turned out to be natural hemp fibers fused with a biodegradable plastic resin called Polyhydroxy-butyrate (PHB). The hemp-PHB biocomposites are stable enough to use in furniture, floors and a variety of other building materials, he added. To degrade, it must be kept away from air- e.g., buried in a landfill-because its decomposition depends on microorganisms that live in anaerobic environments.
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 reused to make more biocomposites. Microbes are used to break down PHB plastics and release methane gas, and different organisms that consume methane and produce PHB as a byproduct. Capturing methane has the added benefit of combating climate change because 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 are not widely used is cost. Most bioplastics are made using sugar from corn and other relatively expensive materials. This 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.
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