Although an extremely useful material, plastic is an environmental disaster. It clogs up landfills, it litters our oceans and it can be harmful to various organisms. Developing biodegradable plastics that can be produced in a viable and sustainable manner has proved difficult in the past. But all may not be lost as scientists at Stanford University have teamed up with a start-up company called Mango Materials in order to develop a technique to produce a biodegradable plastic in an environmentally friendly way; from waste methane.
Polyhydroxyalkanoates (PHAs) are a family of biodegradable plastics that are produced naturally by some species of bacteria as an energy or carbon storage material through the fermentation of sugars. Previous attempts to commercialize this process have involved genetically modified organisms that are typically provided with plant-derived sugars as the input. However, this isn’t particularly sustainable given that it is taking away from the human food supply and requires land to grow the crops.
The new system developed by Mango Materials is incredibly green; it uses non-genetically modified bacteria that are capable of using the greenhouse gas methane and oxygen (plus a few other nutrients) to produce PHAs. Amazingly, the plastics can be degraded anaerobically in a process that produces methane- this methane can then be fed back into the system to produce more PHA. Neat.
The team is currently tweaking the system by adding different compounds into the mix which alter the properties of the plastics produced, which could result in materials with a wide range of industrial applications. “We are currently focused on applications where biodegradability is key,” says Molly Morse, CEO at Mango Materials, in a news-release. “However, we’re open to all sorts of applications and are eager to bring PHA bioplastics to market.”
The system has numerous added benefits over other techniques. Waste methane is dramatically cheaper than sugar, and so is using wild bacteria rather than GM bacteria. The best feature of the system is perhaps the fact that using a greenhouse gas is environmentally friendly. A lot of methane goes to waste, for example from landfills and wastewater treatment plants. This system could encourage methane capture in facilities such as these, which would reduce methane emissions. According to Mango Materials, if the unused, vented methane from landfills in California was used to produce PHA, over 100 million pounds per year of plastic could potentially be generated.
Although the system isn’t ready to be used on a commercial scale yet, laboratory tests have demonstrated impressive yields and other studies have shown that the bacteria grow at similar rates on pure methane and waste biogas.
*Also see http://www.sciencedirect.com/science/article/pii/S0168165613002058
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