The recyclable plastic bags you get at the green grocer are not biodegradable. But product life-cycle assessments, which are about to become more prominent in the marketplace, fail to consider whether those bags will break down in landfills or just end up as litter.
On a visit to India a while back I came upon a fenced empty field that was practically buried in flimsy white throwaway plastic bags, the kind you carry your purchases home in from the store. The locals joked that this was “the garden where plastic bags grew.”
But when I returned to India last month, I was pleasantly surprised to find that now when you shop in New Delhi, no store will give you a plastic bag for your purchases. They’re illegal there, as well as in many other Indian cities and states.
That puts India well ahead of most of the world when it comes to this particular ecological issue. Most everywhere in the U.S., for instance, the throwaway plastic bag remains the ubiquitous way people haul their stuff home from the local store. But those bags never biodegrade into anything that nature can use again.
Worse, the vast majority of such single-use plastic items never get recycled, and even “degradable” plastics may not degrade all that well. On top of that, product life-cycle assessments, which are on the verge of becoming more commonly available and used in the marketplace, do not include either litter or biodegradability as factors.
The news on some once-promising plastic alternatives is not so encouraging. A review published last month in Environmental Science and Technology by a group of scientists — one at the polymer science division of the Indian Institute of Technology — finds that “degradable polyethylenes,“ used in one type of “recyclable” plastic bags, do not really disintegrate back into nature. The polyethylenes in the plastic bags studied are made by adding metals like iron and cobalt to the mix of ethylene polymers, to speed up their oxidation. But while such hybrid plastic bags once discarded do, indeed, break into fragments relatively quickly, those shreds seem to persist for a long time. No one knows just how long — the number of long-term studies is zero.
Perhaps the most dramatic example of how oil and water don’t mix can be found in the middle of the planet’s great oceans and seas in the form of litter gyres, rotating currents laden with countless bits of floating debris, mainly plastic and Styrofoam, all of which were pushed to the middle of these great bodies of water by the currents that circle them.
While the so-called Eastern Garbage Patch at the center of the Pacific has received the most media attention, every great sea now has such a gyre, a rotating ring laden with plastics. The plastic in a gyre eventually breaks down into small bits, called nurdles, which never mix with water. Marine life at the heart of a gyre, reportedly, can subsist (or perish) on a diet of many times more nurdles than krill.
Pitcairn Island, in the middle of the Pacific, offers a particularly poignant testimonial to the toxic impacts of the plastic debris whirling about at the center of our seas. Albatrosses from all over come to these islands to breed and raise their babies. Plastic bottle caps, like those atop kids’ juice containers, are plucked out of the water by albatrosses and fed to their fledglings, killing them.
All this has led me to rethink an OpEd I co-authored in the New York Times two years ago, with an industrial ecologist, Gregory Norris. Using the tools and metrics of his craft, we computed the eco-math over their entire life cycles to calculate whether a reusable steel water bottle was better or worse for the planet than single-use plastic water bottles. The computations on trade-offs compared their relative impacts. The steel bottle required seven times as much fossil fuel as a single plastic bottle, released 14 times more greenhouse gases, used hundreds of times more metal resources, and posed far more toxic risk to people and ecosystems.
We compared these to the “costs” of the plastic bottle in fuels, energy and emissions. This led us to determine a tipping point: If you were persistent enough to replace 500 plastic water bottles by instead refilling the steel bottle, the steel was the better choice. But now I feel our life cycle analysis gave too little weight to the end-of-life consequences of plastic bottles.
Steel is infinitely recyclable with a robust market. Most single-use plastic — like those shopping bags as well as water bottles — never gets recycled. The Environmental Protection Agency (EPA) tells us that only about 9 percent of plastic bags are ever recycled in the U.S. And a mere 7 percent of all plastics end up being recycled (which would allow a true “cradle-to-cradle” reuse).
“Litter is a blind spot in the LCA [life cycle assessment] world,” Gregory Norris said, when I recently raised this issue with him. “A few industrial ecologists have talked about the need to make this a standard category in LCAs — there’s no reason it couldn’t be.”
Norris suggests this would require a further step, specifically a working group to do some “fate modeling” of products like plastics, zeroing in on their end-of-life impacts. “If we did fate modeling for plastic bags and bottles,” Norris added, “that might mobilize the plastic industry and their B2B [business-to-business] customers to solve this problem.”
Tim Grant, an industrial ecologist at the Royal Melbourne Institute of Technology (RMIT) in Australia, has been raising the issue for a decade. With Karli James of the Sustainable Products division of RMIT, Grant published a demonstration of life cycle assessments on the varieties of shopping bags — paper, standard, and degradable. The LCA compared bags made with six types of degradable polymers (ranging from those made mainly from corn starch, to those with 30 percent starch from cassava plants) with bags made from materials like cotton and paper, including those made from the materials evaluated in the Environmental Science and Technology article published last month. However, the question of biodegradability was not answered by the RMIT study; the article was simply a theoretical demonstration that such a life-cycle assessment could be done.
Including plastic litter in product life cycle assessments may seem a trivial matter. But given the growing interest in making this assessment data transparent and more readily available in the consumer and business-to-business marketplace, this small step could have major impacts. In a world where transparent LCA comparisons could begin to substantially shift purchasing decisions, the inclusion of a litter metric becomes consequential.
In the meantime, nonprofits like the Plastics Pollution Coalition (PPC) are pursuing other strategies. The coalition is campaigning to inspire individuals to refuse single-use plastics and reduce their overall plastic footprint; to urge manufacturers to own the entire lifecycle of plastic products; and to persuade policy makers to formulate regulations like the legislation in Germany that makes companies responsible for their waste, which has boosted plastic recycling rates to 60 percent.
A fourth strategy: to encourage polymer scientists to develop viable bioplastics. “None of the alternatives are what they should be,” Daniella Russo, the PPC’s executive director, says. “For an alternative plastic to succeed, it should be non-toxic over its entire life cycle, fully biodegradable in all situations, and cost competitive.”
The PPC is one of many environmental groups lobbying for laws like those passed in San Jose and Palo Alto, Calif., that curtail or ban single-use plastic bags, or put a surcharge on them. That strategy makes sense. Laws like India’s have been surprisingly effective. China, the world’s largest user of plastic bags, saw the numbers of bags drop by half with a recent law requiring stores to charge for them. In Ireland, a similar law has seen use of the bags drop from an average of 330 used per person per year, to just 20.
But on my return to the U.S. from Delhi, I stopped on the way from the airport to pick up some groceries for the next day at a “green” branch of a national supermarket chain. Coming directly from the airport, I didn’t have my reusable shopping bags with me — and so ended up lugging groceries home in three single-use plastic bags.
