Let's talk about plastic recycling / with Michal Babič
The Czech Republic holds an admirable third place in the European Union for sorting plastic waste. But is that enough to resolve the ever increasing amount of this discarded material? Might we be unnecessarily wasting energy, drinking water and other natural resources in the process?
Sometimes our efforts to be ecological lead us to actually harming the environment instead. Sorting waste is seen almost as a no-brainer. And we tend to believe that all material inside yellow containers happily travels along to be recycled into new products. But the reality is not quite that simple.
This time on “Let’s talk about it”, Dr. Michal Babič, a scientist and polymer specialist from the Czech Academy of Science stops by to explain the nuances of plastic waste processing.
ML (Michael Londesborough): Michal, thank you for coming. As a scientist who works with polymers, you have an intimate knowledge of their structure and their properties. In your opinion, how should we manage plastic waste?
MB (Michal Babič): Managing plastic waste can be split into two tiers. The first concerns my behavior as an individual and the second as a citizen of a community. Europeans put in the effort to sort their plastic waste. However, in order for plastic waste management to be prudent and economical, a community needs appropriate infrastructure. This is where we must ask whether our infrastructure investments are sufficient and if we’re using the best available technology.
It’s easy to asses waste management investments in areas with a high population density, such as London, Berlin or Prague. The situation gets much more difficult in places with lower residential concentration, where we transport waste from a much wider area. The infrastructure for effective processing in these areas is insufficient.
ML: I’ve read numerous articles about successful plastic waste reprocessing into primary material or a different, pliable form. But there’s always a catch. It’s too expensive or unfeasible on a large scale. The process works in the laboratory, but not in practice. Is the technology ready?
MB: Let’s look at what we can do with a pile of plastic waste.
First: Nothing- simply throw it away on the ground. That’s the worst option. A second alternative is landfilling- storing waste underground. With the exception of a couple select materials, whose properties rule out all other possibilities, we don’t have to do this.
Third, plastic can be quite efficiently incinerated. Its calorific value is around 45 mega joules per kilogram, which is approx. twice the value of brown coal. In addition, plastics burn on their own- they don’t need special conditions and can even work as fuel to burn other, dangerous materials. This means we could conserve virgin energy, for instance from gas, for much smarter uses. By employing incineration we could fully eliminate plastic waste in landfills.
Then there are recycling options. Most plastic has one fundamental flaw, given by its structure. Polymers, which plastics are made from, are long chains- we can think of them like spaghetti. Polymer material works because the “spaghetti” intertwines like balls of yarn- that’s why they hold shape. When the “spaghetti” is shorter, it’s harder for it to entwine, giving the resulting product inferior mechanical properties. That’s what happens when I recycle plastic into secondary products- the chains get shorter.
So reprocessing often results in products of inferior quality that we have to find suitable use for. Moreover, we can mechanically recycle only one group of plastics- thermoplastics. Thermosets, which are polymer networks, such as polyurethanes, mattresses or various epoxy resin layers, cannot be processed this way.
ML: Roughly what percentage of plastic waste in Czech Republic can be effectively mechanically recycled?
MB: There are two kinds of waste- industrial, produced by companies, and communal, produced by us. Communal waste data shows that around forty percent of it is plastic. We are capable of processing this. Mechanical recycling isn’t the only option. Plastic waste can also be recycled using chemical or thermic methods. Using chemical methods we can effectively reprocess, for example, polyethylene terephthalate and all polymers used for fiber manufacturing, such as polyamides and polyesters. We can chemically break them down into fundamental building units and, after cleaning them, make the same polymer again. Through chemical recycling into primary materials, we can even reprocess some types of polymer networks, such as the polyurethane foams.
ML: Is it energy intensive?
MB: It is. Also, for it to truly work in practice would require significant investment into sufficient infrastructure and into people.
ML: If we add the value of not polluting our environment into the equation then it makes sense.
MB: Yes. And there are two more parameters to determine the expediency of such reprocessing- price of the primary raw material, i.e. petroleum, and the price of energy. If we have a cheap source of energy, petroleum reprocessing will be more profitable than primary petroleum processing. Efficiency will depend on the amount of waste collected from a particular place. Investing into such technology is more rational in large cities than small towns.
The last option involves thermic methods to heat up the plastic and thus shorten polymer chains. The process can be either low or high temperature. The product of low temperature processing is very similar to petroleum- it’s a hydrocarbon liquid which we can either burn for energy or process as primary petroleum.
If we use temperatures around 1300 degrees in the high temperature process, we can “chop up” the plastic material into synthetic gas- carbon monoxide and hydrogen. That’s a valuable chemical resource at the beginning of many chemical processes.
ML: These methods work well in scientific studies under laboratory conditions, with clean polymers being used as feedstock. In reality, however, the incoming plastic will be mixed with other waste. Do they work even in the presence of dirt? Or does the feed material have to be cleaned first?
MB: Definitely. Let’s consider polyethylene terephthalate, or PET bottle, recycling. If the recycled PET is clean and clear, it can undergo a bottle- to- bottle process. That means that we can reprocess the recycled PET once or twice into a new PET bottle which will gain hygienic certification. Prior to undergoing that process, however, the material has to be thoroughly cleaned, which carries costs. Because bottle PET is one of the highest quality PETs in existence, this process makes sense. That’s not the case with all materials. We ought to consider if it makes sense to use drinking water and energy for cleaning foil placed in yellow containers to make a new product with inferior mechanical properties and questionable usage.
ML: How does recycling work in Czech? What needs improvement?
MB: Czech citizens sort their residential waste fairly willingly and effectively. We don’t need to make huge investments into education. There are even enough places for sorted waste collection. One problem is with processing communal waste, where we landfill 40 to 60 percent because we don’t have other options.
ML: Is it due to a lack of options or because it’s much cheaper?
MB: It’s a combination of both. The landfilling fee for one ton of waste is about 550 CZK, which is 20 Euro. In Sweden it’s 140 Euro. The cost of incinerating one ton is around thirty to seventy Euros, depending on transportation distance. In Czech Republic, we have a total of 18 incinerator plants, fourteen of which are for dangerous and hospital waste. There are only four incinerators for communal waste- in Brno, Prague, Liberec and Pilsen.
Let’s look at Germany. They have an ordinance, that starting in 2001 with a transitional period until 2005, unprocessed waste cannot be stored in landfills. And they’ve built the required infrastructure. So we only need to learn from them and invest. In Czech, such an ordinance was supposed to go into effect from the year 2024, but this year in February it got postponed until 2030.
ML: Is it better to invest into finding an alternative to plastics, or into an effective recycling system?
MB: We know that replacing plastics with different materials on the market today would cause a lot of environmental indicators to get worse. It would increase CO2 production, mass and volume of waste and energy consumption during transport. Let’s compare a half-liter PET bottle with a half-liter glass bottle. The energy required for the life cycle of the glass bottle is two and a half times greater than of the PET bottle. Expenditures for the life cycle of a thousand polyethylene bags are five to six times lower than for a thousand paper ones. If we replaced plastics with conventional materials like metal, wood, glass and paper, it would be more expensive, use more energy and take a much greater toll on the environment. Maybe in the future we’ll find a better material to fully replace plastic. We do not have it today.