Worldwide, a staggering four to five trillion plastic shopping bags are used every year. Most are discarded after a single use. Like all other plastics, the bags too are made from fossil fuels and are popular because they are durable, cheap, strong and lightweight. But these very characteristics are also what make them a problem. Plastic bags take extremely long to degrade: estimates range from 100 to 1000 years. Which means that all the plastic bags ever manufactured are potentially still around in the environment. And that is a problem.

‘Biodegradable’ plastic bags have been adopted by a local retail chain (pic: Meera Iyer)

When improperly discarded, plastic bags are more than just eyesores. They wreak havoc. Bangalore’s flooding problems are exacerbated by plastic bags choking our storm water drains. They can be fatal to animals if ingested. They provide a breeding ground for mosquitoes. They accumulate in the soil, and potentially release toxins that can eventually pollute groundwater. When properly discarded, they overwhelm garbage dumps with their sheer volumes.

Reducing the plastic footprint

The desire to be environment-friendly prompted Nilgiri’s Dairy Farm to provide biodegradable plastic bags to participants at the Tour of Nilgiris (TFN) event that it recently sponsored. Pragyata Ranjan, Brand Manager at Nilgiri’s and the person behind the TFN, says though they would like to introduce these bags in their stores, as of now, Nilgiri’s has no concrete plans to do so.

Another Bangalore chain, Total Hypermarket, introduced degradable bags in their stores in January this year. A senior official at Total explains, “We introduced the degradable bags because we wanted to reduce our plastic footprint and did not want to contribute to killing the planet.” The bags come in two sizes and Total charges its customers a nominal fee of Re 1 for either size. Each bag proudly proclaims that it is “100% biodegradable”. Large posters about the bags are put up at the entrances to the stores, and inside, little flyers advertise that you can “save the planet” for a rupee. Frequent announcements are also made about how you can return the used bags, in any form, and get a new bag for no charge the next time you shop.

Both, officials and tellers, at Total say the bags have been very popular. A smiling Devraj N, teller at the Total store in Madivala, recounts how some customers ‘shouted’ at the idea of having to pay for the shopping bag, but adds, “90% accept it because they know it is good. Only 10% shout.” Devraj and other store employees were also quite enthusiastic about the bags, explaining how it could be composted by mixing it with soil. One young shopper, Anurag Gogoi, a software engineer, exemplified the attitude to the new item when he said he was quite willing to pay a rupee for the bags because “although they are plastic bags, in one way, they are good. They are not polluting.”

Unfortunately, both Devraj and Gogoi may be wrong.

Biodegradablity

There are biodegradable bags and there are biodegradable bags. Ordinary plastic bags are made of polyethylene, a polymer. To make the plastic durable, anti-oxidants are added to the polyethylene, which prevent oxidation and so keep the polymer chains from breaking down. But for the bag to degrade, the polymer needs to break down. So additives are added to the polyethylene to promote oxidation. Theoretically, the polyethylene chains in biodegradable bags should break down into smaller fragments which are then consumed by soil micro-organisms, leaving only carbon dioxide, water and biomass.

The bags distributed at the TFN, branded Biotec bags, are manufactured by Ravi Plastics in Chennai. PS Shankker, partner at Biotec, says the bags have a hefty dose of enzymes added to promote degradation. Those distributed at Total are oxodegradable or oxo-biodegradable, which means they have pro-oxidants (the opposite of anti-oxidants) added to allow oxidation of the polyethylene.

The true test of biodegradability is to see if the bags are eventually consumed by microbial activity. India currently does not have standards or tests specified for determining biodegradability. Standards specified by the American Standards for Testing and Materials (ASTM) and the European Committee for Normalisation specify the requirements to determine the biodegradability of plastic. The most stringent standard is the European EN13432, according to which, for a material to be labelled biodegradable, more than 90% of it must be converted to carbon dioxide, water and biomass in 6 months.

CV Krishnamurthy, shop owner, Kusum General Stores with the sign board requesting shoppers not to ask for plastic covers (pic: Meera Iyer)

Biotec bags are certified biodegradable by the Bangalore centre of the Shriram Institute for Industrial Research. According to institute scientist Nagendra Kumar KM, the bags were put through the specified tests for biodegradability according to both ASTM and European standards. Kumar says the testing took over 7 months and included measuring carbon dioxide evolution, the only foolproof method of determining microbial activity.

Total’s bags are certified by Pune-based National Toxicology Centre (NTC). NTC scientist Mandavi Gargi also claims to have followed ASTM tests, though she did not specify which particular standard they used. NTC says the bags went through three tests, one lasting 200 hours, and two of which lasted 30 days, at the end of which the bags showed “good biodegradation (10%)”, which means there was 10% degradation at the end of the tests. According to Mandavi, NTC did not measure microbial activity but evaluated the tensile strength of the material only. This means the NTC measured physical degradation only rather than microbial degradation.

In fact, one problem with oxodegradable plastics is that they are thought to undergo some physical degradation but then persist in the environment. Experiments have shown that even after almost four years, microbial activity only damages the surface of oxodegradable plastic, leaving behind very small pieces of plastic that are invisible to the naked eye.

Isn’t it enough that plastic bags break down till when they cannot be seen anymore? No, according to Ramani Narayan, a professor at Michigan State University and an authority on biodegradable plastics. “Out of sight does not make the problem go away,” he writes. Degraded pieces of plastic that remain in the environment for long can be particularly dangerous because they tend to attract and hold toxic residues like DDT and its breakdown products. If these fragments migrate to the water table, they can end up transporting concentrated forms of toxins to other environments.

Simple solution

Biotec bags are currently not available in Bangalore. Shankker says there has been an interest in Biotec carry bags despite higher costs, and adds that Biotec garbage bags will “soon be available” in shops in Bangalore.

But meanwhile, at least one local trader has a low-tech, foolproof, effective solution to the problem of plastic bags. Since the year 2000, Kusum General Stores on Avenue Road has not been giving its shoppers plastic carry bags. A sign just behind the counter announces “We are plastic free,” adding the admonition: “Please do not ask for carry bags.” Most customers who throng this popular provision store bring their own jute or cloth bags. For those who don’t, Kusum offers a woven plastic carry bag costing Rs 4. Those who return the bags are refunded the money. Says shop owner, CV Krishnamurthy, “It is good for the environment, it is cheaper for us, and so much less of a hassle, too.”

Sometimes, the simplest solutions are the most effective.
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