Green Living

What is polyhydroxybutyrate (PBH) and is it eco-friendly?
Answered by Science Channel
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    Science Channel

  1. The two primary environmental disadvantages of traditional plastics are that they don't decompose quickly and that they're made from petroleum, which is nonrenewable and contributes significantly to global climate change. On the first point, it would be fairer to say that we actually don't know how long it takes commercial plastic to decompose, since plastics have only been ubiquitous in consumer products since around the end of World War II [source: Meikle]. However, since most plastics do not biodegrade -- meaning they're not broken down by bacteria or other organic clean-up crews -- it seems safe to assume that they will be around for a very long time. Discarded plastic bags and bottles may even haunt the earth until they are finally broken down by the process of photodegradation, in which sunlight erodes the material one photon at a time.

    Fortunately, there are many promising eco-plastics on the market; some include various amounts of other recycled, petroleum-based plastics and are non-biodegradable. However, even using these semi-eco-friendly plastics provides a benefit over regular plastic, since they keep the completely non-biodegradable stuff out of landfills for another product lifecycle. In comparison, certified bioplastics are much better for the environment, as they are composed of biological material rather than fossil fuels.

    One particularly promising biodegradable substitute for plastic is not made from petroleum at all. Instead, it is a modified form of polyhydroxybutyrate (PHB). PHB is an energy and carbon source derived from the fermentation processes of several kinds of bacteria, such as Bacillus megaterium. To produce PHB, you can feed corn syrup, beet molasses or any number of other carbon-based energy sources to a culture of bacteria placed under specific stress conditions. In response, the bacteria build the sugars into granules of PHB -- essentially, in an effort to preserve them for later metabolization. This PHB can be used as an effective thermoplastic, and has many characteristics similar to those of standard commercial plastics like polypropylene. While PHB-based plastic substitutes are less flexible than traditional plastics, they are completely biodegradable and leave behind no residue.

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