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The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
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[Audio clip from The Graduate: One word, plastics.] Two words: biodegradable plastics. For years now, they've been a buzz phrase in the chemicals industry. After all, nobody likes those plastic bags flitting on tree tops or floating in the ocean, essentially forever.
But a new analysis shows that biodegradable plastics, particularly those that break down fast, are contributing to climate change. Because when disposable utensils made from the plastic called PHBO get to landfills, microbes break them down and make methane, a potent greenhouse gas. The research appears in Environmental Science & Technology.
Some landfills have installed systems to capture that methane and make use of it. After all, methane is perhaps better known as natural gas—a fuel used for everything from home heating to electricity generation. But most landfills don't capture the methane. So the potent greenhouse gas finds its way into the atmosphere, trapping the sun's heat to warm global temperatures.
In essence, the analysis is less a call to shift away from biodegradable plastic and more an appeal to take all factors into account when judging the relative environmental merits of a product. In other words, look at the entire life cyle. Because haste literally makes waste.
—David Biello
[The above text is an exact transcript of this podcast.]
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9 Comments
Add CommentThere are always a variety of outcomes to an action - never just one.
Reply | Report Abuse | Link to thisWith governments making decisions over "the commons", rather than individuals for their own private property with strong covenants in place with their neighbors, the range and depth of impacts will rarely be investigated for the longterm. Politicians are interested in getting "the vote" in order to get or remain "in office", the seat of current social power, enabled by the enforcers.
Wouldn't reusable milk jugs and water bottles be both cheaper and less harmful to the environment than the recyclable/disposable option? Back in ancient times glass bottlers offered a financial incentive for bottle returns. A good washing and they were put back into product distribution. Perhaps that'd be too much of an imposition of inconvenience on us modern creatures, though. Maybe this could be implemented as part of the current recycling process, at least...
Reply | Report Abuse | Link to thisTrash dumping in landfill, including garden wastes causes methane to be given off. The solution is to implement biomass pyrolysis which converts carbohydrates or hydrocarbons into charcoal and hydrogen. The hydrogen can be stored in gasometers until it is needed to complement electricity generation when wind or solar power is unavailable. The charcoal can be used as a fertiliser in most climates, and effectively sequesters the carbon that otherwise would have become CO2 greenhouse gas. If governments spent a fraction of the money they give to polluting energy companies biomass pyrolysis would be one of the world's largest industries giving jobs to millions worldwide. See www.eprida.com .
Reply | Report Abuse | Link to thisyes please look at "compostable" bio plastics that actually turn into dirt and not just plastic bits...
Reply | Report Abuse | Link to this"We are running out of landfill space" was a manufactured environmental crisis which preceeded the recent obsession with global warming. Everyone was worried because things weren't decomposing as expected in landfills and therefore that space used for the landfill would never be useful again.
Reply | Report Abuse | Link to thisOf course the reality is that landfill space is not limited, just limited because of politics and regulation. And the perfect material to place in landfills is non-biodegradeable plastics. Just another case of mistaken assumptions and ideas leading to useless solutions.
It is really important not to confuse the two fundamentally different types of biodegradable plastic.
Reply | Report Abuse | Link to thisThe NC State report is about hydro-biodegradable or “compostable”plastic, which is usually made from vegetable matter. This type of plastic is intended for industrial composting, and that is why a rapid rate of degradation is required by ASTM D6400; EN13432; and Australian 4736. It is not designed to degrade in the open environment, and it will emit methane (a more powerful greenhouse gas than CO2)deep in landfill.
By contrast, oxo-biodegradable plastic has a deliberately slower rate of degradation and is inert in landfill in the absence of oxygen.
The fundamental point about oxo-biodegradable technology is that the additive included at manufacture, at very low cost, turns ordinary plastic at the end of its useful life in the presence of oxygen into a material with a different molecular structure. At that stage it is no longer a plastic and has become a material which is inherently biodegradable in the open environment in the same way as a leaf. Approximate timescale for degradation can be set at manufacture as required. For a video of plastic film degrading, go to Symphony’s website.
Disposable anything is the wrong concept to begin with. That being said, any assessment of contribution to GHGs and climate change needs to be a full cycle analysis. What is the emissions intensity of producing non-biodegradable plastics vs. biodegradable? Plasitics are made from oil, which the extraction of has a carbon footprint. Biodegradables are plant based typically. What is their carbon footprint?
Reply | Report Abuse | Link to thisBefore we jump to conclusions like bio-degradables are no good because they emit GHGs in their decomposition, we need to do a real comparison. This study really tells us very little.
@jtdwyer
Reply | Report Abuse | Link to thisThe same advice applies to proposing reusable glass or HDPE for milk bottles. We still have to look at the big picture, including costs for manufacture, sterilization, transport, refilling, replacing lost or broken bottles, and their eventual fate when no longer usable.
After that analysis, it may turn out that they are still better, but one needs to run the numbers first.
Two factories have been opened in Ireland to convert plastics (except PVC) into diesel. So no need for biodegradables that decompose into CO2 and/or methane and no need to open landfill sites.
Reply | Report Abuse | Link to thisThen remove the CO2 from the burnt diesel in the air by biomass pyrolysis.
Think green...