How does technology improve ordinary plastic?

Energy from plastic incineration - (not) a good idea?

What should we do with the ever-growing mountains of plastic waste if we don't want it to get stuck in branches, drift in great ocean eddies or clog the stomachs of birds and whales?

According to a report by the World Economic Forum, plastic production is set to double in the next 20 years. Meanwhile, the recycling rate for plastics in Europe is 30 percent, in the US it is 9 percent and in most of the developing countries it is almost zero.

Last January, a consortium of oil and consumer goods companies - including Exxon, Dow, Total, Shell, Chevron Phillips, and Procter & Gamble - decided to invest $ 1.5 billion over the next five years in solving this problem. The money will be used to support alternative materials and delivery systems, improve recycling programs and - a controversial decision - promote technologies that convert plastic into fuel or energy.

Sophisticated incinerators that burn plastic and other municipal waste can generate enough heat and steam to power turbines and generate electricity. Almost 42 percent of the waste generated is already incinerated in the EU, and 12.5 percent in the USA. According to the World Energy Council, the garbage energy sector is likely to see steady growth in the coming years, particularly in the Asian Pacific region. In China, 300 such substitute fuel power plants are already in operation and hundreds more are being planned.

"When countries like China no longer accept garbage from abroad and the overwhelmed recycling industry can no longer keep up with the plastic pollution, incineration will increasingly be touted as a simple alternative," says John Hocevar of Greenpeace.

The pros and cons

Burning plastic waste to generate energy sounds like a good idea at first glance. After all, just like petroleum, plastics consist of hydrocarbons and have a higher energy density than coal. However, there are some obstacles in the way of the widespread use of alternative fuel power plants.

On the one hand, finding a location would be as difficult as with garbage dumps. Nobody would like to live next to a power plant that is driven by hundreds of trucks full of rubbish every day. Usually such power plants end up near low-income communities. Only one substitute fuel power plant has been built in the United States since 1997.

In addition, their construction and operation are costly, which is why dumping garbage in power plants is more expensive than in dumps. Since the plants also run most efficiently when they are constantly supplied with supplies, the combustion material is often imported from great distances.

Large power plants generate enough energy to supply tens of thousands of households. However, studies have shown that an even greater amount of energy can be saved if the plastic is not produced in the first place. This would mean that the extraction of fossil fuels from the ground would also be eliminated, as would the processes used to manufacture plastics.

In addition, substitute fuel power plants can also emit small amounts of toxins, including dioxins, acid gases and heavy metals. Modern power plants have sophisticated gas scrubbers, separators and filters to collect these components. The World Energy Council cautiously commented on the subject in a 2017 report: "These technologies are useful as long as combustion power plants are operated correctly and emissions are controlled."

Some experts fear that countries without appropriate environmental legislation could try to save money on emissions protection. Not to be forgotten are the greenhouse gases produced by incineration plants. In the USA alone, incinerators generated the equivalent of twelve million tons of CO in 20162more than half of which was caused by burning plastic.

Burn better?

Another way of converting waste into energy is gasification. In this process, plastics are melted at high temperatures in a low-oxygen atmosphere so that no toxins such as dioxin or furan are produced. The synthetic gas produced in this way is used to drive turbines. However, gasification plants on the market cannot keep up with the much cheaper natural gas.

The more attractive process is currently pyrolysis, in which plastics are shredded and then burned at high temperatures (which are, however, lower than with gasification) and even less oxygen. The heat breaks down the plastic polymers into shorter hydrocarbons, which in turn can be refined into diesel fuel or processed into other petrochemical products.