Photo by Ayotunde Oguntoyinbo on Unsplash
Plastic pollution is a reality we can no longer ignore. From plastic containers to microplastic particles, plastic waste is rapidly accumulating in our environments, where they can remain for hundreds of years. The rate at which we are consuming and disposing plastics is equivalent to dumping a garbage truck full of plastic waste into the ocean every minute.
To reduce the amounts of plastic waste, single-use plastics will be banned in the European Parliament by 2021. In Canada, major cities like Montreal and Vancouver have already taken action against single-use plastics, and the conversation has already started in Toronto too.
As promising as these regulations are for the reduction of plastic waste, the success of this motion will require the involvement of every resident. In April of last year the federal government launched a consultation where Canadians could “…share their views on the topic ‘Moving Canada Toward Zero Plastic Waste.’” The consultation received 1,900 comments and 12,000 campaign letters, which is by no means an extensive pool of participation. Nonetheless, it produced a series of potential solutions and certainly got the conversation going.
The three R’s: Reduce, Reuse, Recycle
One of the comments resulting from this consultation touched on how there is plenty of information available for recycling, but not so much in terms of reducing and reusing plastics. This statement is alarming considering that, according to the Canadian Council of Ministers of the Environment (CCME), Canada only recycles about 10% of plastics.
Sadly, this low percentage of recycled plastics is not exclusive to Canada. According to a study published in 2017 in the journal of Science Advances, it is estimated that only 9% of the plastic waste generated by 2015 has been recycled (out of which only 10% is recycled multiple times), 12% has been incinerated, and 79% has been sent to landfills. Further, the authors estimate that only 30% of plastics produced between 1950 and 2015 are in use.
It is not clear why recycling rates are so low, but Plastics for Change provides an interesting list of examples that make it much easier to use virgin material as opposed to recycled plastics in developing countries.
Perhaps the easiest way in which we as consumers can contribute to the reduction of plastic waste is to use less plastic. Sounds quite obvious, but when we actively look into how to consume less plastic it is shocking how much we’ve grown accustomed to using plastic products. Fortunately, there is plenty of information online about how we can limit our consumption of plastics to have a positive impact in our society, such as this example I really like.
Photo by Paweł Czerwiński on Unsplash
Recirculate… the fourth R?
When talking about plastics, we should be careful of lumping all plastics in the same category. Synthetic plastics, those derived from petroleum, are the most widely available types of plastics. Amongst these you are probably familiar with polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET) and polyurethane (PUR).
One should keep in mind that we have now started to integrate bioplastics and biodegradable plastics in our industry. Bioplastics are made with polymers derived from renewable materials, such as polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB) and starch blends. Biodegradable plastics, on the other hand, can be either synthetic or bio-based, but can be degraded by microorganisms and enzymes.
The rate of degradation in biodegradable plastics, however, occurs at a very slow rate. It would be unreasonable to assume that plastic degradation could keep up with plastic consumption rates. Additionally, researchers from the University of Basel suggest that microplastic particles derived from biodegradable plastics provoke similar digestive constraints on freshwater invertebrates. So whether you are using synthetic, bio- or biodegradable plastics, the use of plastics should be avoided where possible.
Over the last decade, there have been several studies aimed to discover microorganisms and enzymes capable of degrading plastics that are considered non-biodegradable. A review published in 2017 provides a recollection of research efforts with the purpose of identifying enzymes that contribute to the biodegradation of recalcitrant plastics for the recovery of chemical feedstocks. Some examples include cutinases that hydrolase ester bonds in PET; hydroquinone peroxidase for the degradation of PS; and laccases, manganese peroxidase, and lignin peroxidase, for the degradation of PE.
It is important not to confuse bioplastics with biodegradable plastics; while some biodegradable plastics are bioplastics, not all bioplastics are biodegradable (e.g. bio-based PET and PE). This becomes particularly important when recycling systems are in place. If biodegradable plastic is mixed in the recycling bin, it could ruin the entire batch.
Re-refining plastics
The quality that makes plastics so useful in our industry, durability, is the same reason why we are having such a worrying problem with plastic waste in the first place. The only way to destroy plastics is by burning them, which produces large quantities of CO2, along with many toxic gases. A study comparing two plastic treatment options in The Netherlands, incineration and recycling, concluded that, even though the incineration of plastic waste generates energy, it is not enough to offset the large amounts of CO2 released in the atmosphere.
However, advances in thermochemical processes make it possible to have more control over the emissions and products obtained. Pyrolysis is a thermochemical treatment in which degradation occurs at temperatures between 500˚C and 900˚C in total absence of oxygen. Pyrolysis produces a liquid product (pyrolysis oil), a gaseous product (syngas), and a solid product (char), and the composition of products is highly dependent on the feedstock used.
A study from the University of Surrey looked at the conversion of plastic waste into a diesel-like oil through pyrolysis. The authors of the study used a mix of waste products as a feedstock, including styrene butadiene, polyester, PE and PP, and showed that the pyrolysis oil produced could potentially be used in diesel engines, although more work is needed to optimize performance.
Similar conclusions were discussed in another study, where half of the energy required by the pyrolysis reactor was provided by a sola photovoltaic system. In this study the authors looked at PS, PE and PP independently, and showed that PS had a yield of 90% pyrolysis oil, PE had a yield of 51% syngas, and PP had a yield of 65% syngas.
Even though thermochemical treatments like pyrolysis are not developed to a point were it is realistic to convert all the plastic waste we have in a responsible way, the technology is getting better and better. We just need to stop making it worse for now.
As in most issues affecting our environment, the solution to plastic pollution requires that we take action from many angles. By consuming fewer plastic products, recycling our waste properly, and sourcing biodegradable alternatives to plastic, we can stop throwing more plastic waste to our environment. However, this has to be an active choice by individuals, governments, and our industry.