Last February, a study published in the journal Science estimated that in 2010 between 4.8 and 12.7 million tons of plastic rubbish were dumped in the world’s oceans. Although this is a frightening number, it is only a small part of the 275 million tons that were generated that year in 192 coastal countries. World production of plastics has increased some 500% since 1980, and these materials represent between 80% and 90% of maritime pollution. However, most of it stays on land, and it is in developing countries with poorer sanitation and recycling systems where the problem of plastic pollution is of particular importance. In fact, developing and emerging countries are mainly responsible for plastic pollution; according to the study in Science, of the 20 most polluting countries only the twentieth is a western developed nation, the United States.
Is it possible to conceive of a future without plastic? Some predict that the future depletion of fossil fuels will force it and that it will be necessary to develop substitutes. But even if this comes about, the end of plastics would not mean their disappearance from the Earth due to the very slow degradation of these polymers, and thus it will be necessary to also address means of decontamination. This is the background for the efforts toward the goal of achieving a world without plastic.
Living without plastic
Some media campaigns and blogs, such as MyPlasticFreeLife.com, offer hints and tips on how to minimize the consumption of these materials and keep track of one’s personal plastic footprint. Attempts to live without plastic are based mainly on choosing purchase options that are limited to the use of traditional materials such as glass, paper, metal, ceramic or stone.
But it is not easy; synthetic resins are present, one way or another, in most of what we buy, consume and discard. The reason for this is that oil polymers allow for great flexibility and diverse properties, and making the reverse journey toward materials of natural origin does not seem to be a universal solution. In addition, life without plastic is more expensive. Monitoring and reducing the use of plastic is the mission of organizations like Plastic Disclosure Project and Plastic Pollution Coalition. The latter bases its objectives on its motto of the four Rs: refuse, reduce, reuse and recycle.
Beyond the personal or non-governmental initiatives, authorities in some countries have decided to take legal measures to cut the consumption of plastics. In 1990, the island of Nantucket became the first place in the US to ban single-use bags. Other cities and counties then followed suit, and last August California became the first state to pass similar legislation. In China, the decision that stores must charge consumers for disposable bags, introduced in 2008, managed to reduce the amount of this type of plastic by 50%. Some developing countries have banned plastic bags altogether, although the implementation of these measures is sometimes problematic.
The European Union has not yet implemented a general prohibition, but has agreed to impose on member states the obligation to reduce by 80% the use of the lightest bags over the next decade –shifting from over 170 bags used each European per year to just 40 in 2025– or heavily tax their use from 2018. Some countries have already surpassed this: Italy was a pioneer in eliminating non-biodegradable bags in 2011, while France last year passed a law that will ban single-use bags in 2016.
Biodegradable plastics and bioplastics
The first step in attempting to reduce the plastic footprint of the human being is producing biodegradable polymers by using additives. However, this does not solve the problem of its petrochemical origin, which still involves the use of a non-renewable resource. Therefore, the next step is to obtain substitutes that do not depend on oil.
Steady progress is being made in the manufacture of bioplastics based on materials such as starch or cellulose. An example is polylactic acid, a bioplastic similar to polystyrene produced from the same compound that causes tooth decay. But it should be noted that not all bioplastics are biodegradable. Polyethylene, the plastic of bags, has a biological version obtained from the fermentation of cultures, but just like the plastic derived from petroleum, it is not biodegradable.
Among the researchers experimenting with new plastics from a biological source and with easy biodegradation is a team at the Italian Institute of Technology in Genoa, led by Ilker Bayer and Athanassia Athanassiou. These scientists work on the production of plastics from edible vegetable waste, such as parsley, spinach stems and the husks from rice or cocoa pods. The advantage of the method is that it allows for a wide range of cellulose bioplastics, from the most rigid to the soft and bendable. “The comparison of their mechanical properties with those of several synthetic petroleum-based polymers indicates that these bioplastics have mechanical properties that are equivalent to those of the non-degradable type,” the scientists wrote in a study published last year.
Microbes that eat plastic
Even in an ideal situation, with petrochemical plastics limited to those applications where there was no other option and always in durable applications, with all disposable uses covered by biodegradable bioplastics, and with extensive recycling … even then there would still be millions of tons of plastic waste to be eliminated. What to do with it all? Almost all eyes are on biotechnology, the use of microorganisms capable of degrading plastics. There are bacteria, such as the soil microbes of the genus Pseudomonas, and even fungi like those that grow on wood, that can digest plastics naturally. The downside is that the biodegradation of plastics in this way usually requires special conditions, such as high temperatures or ultraviolet light.
Recently, a team of researchers from the Beihang University Beijing (China) has found a route that avoids the need for laboratory conditions. The scientists observed that the caterpillar of a particular type of moth usually feeds on food containers. Upon examining their gut, they found two kinds of bacteria that break down polyethylene without the need for other treatments. According to researchers, it is “promising evidence for the degradation of polyethylene in the environment”.
In developed countries, efforts are focused on increasing recycling rates for plastics. However, experts warn that recycling is not a panacea: contrary to what happens with glass containers, those of plastic are not used to make other similar ones, but rather very different objects that may end up in landfills.
An interesting alternative comes from India. Since plastic is produced from oil, why not turn it back into a liquid fuel? The method designed by the chemist Achyut Kumar Panda of the Centurion University of Technology and Management in Odisha, and chemical engineer Raghubansh Kumar Singh of the National Institute of Technology in Orissa, uses heating to 450 degrees centigrade in the presence of a catalyst to convert polyethylene bags into a liquid fuel similar to gasoline, kerosene and diesel fuel. For each kilo of plastic 700 grams of fuel is produced. In their study, the researchers stress that the procedure would help to “reduce the waste problem”, which would be especially interesting in developing countries.