——What’s wrong with plastic?

Nakajima: Why is it bad? There are two points: “It never disappears” and “It becomes a large amount of garbage every year”. For the first point, I think it will easily not disappear for about 100 to 1000 years. 
When we went to investigate the garbage in the deep sea, the garbage we picked up at a depth of 6000 meters in the deep sea had the date “Showa 59” written on it. It was already 35 years old when it was collected. It was very clean and almost undamaged. “This won’t disappear for at least 100 years,” I realized. The fact that a large amount comes out also has an impact. According to the latest estimates, the amount of garbage that flows into the sea and rivers in 2016 is about 20 million tons worldwide. That’s equivalent to 550 Tokyo Sky Trees.

——Why is it called the problem of marine plastic pollution?

Nakajima:  There are still few countries and regions where garbage is properly managed. That’s why it leaks into the sea. It may be small in Japan, but in Southeast Asia and other places, garbage is loaded onto garbage trucks without roofs on the cargo bed, and garbage flies off while driving. Also, in developing countries, many landfills leave garbage exposed. In such places, when an event that brings strong winds and heavy rains like a typhoon comes, a large amount of garbage will fly away.

Also, garbage thrown into drains and rivers also washes up on the sea. For example, if the old man in the neighborhood throws a cigarette butt into the drain, that garbage will flow into the river and eventually reach the sea. Also, in terms of drains, tiny plastic fiber scraps that come out of the laundry at home also end up in the ocean as microplastic waste. These microplastics are not only released into the ocean through laundry; when we wash our faces, the microplastics contained in cosmetics flow into the ocean when we wash our faces, and when we wash dishes, the fibrous pieces of the sponge flow into the ocean, and those that slip through sewage treatment plants also flow into the ocean.

——What kind of problems are currently occurring in the ocean?

Nakajima:  There are thought to be both physical and chemical impacts.

In terms of physical impacts, large pieces of trash, such as plastic fishing gear, have been reported to entangle and kill sea birds and turtles. Small microplastics lead to accidental ingestion. For example, sardines and whales capture their prey by simply opening their mouths and swimming relentlessly, a method known as “filter feeding”. They cannot distinguish between food and plastic. Indigestible microplastics are either excreted as feces or continue to remain in the body. Also, it has been observed that some seabirds feed plastic to their chicks that have not yet fledged. The chicks cannot regurgitate the food they receive from their parents, and the plastic continues to accumulate in their stomachs, leading to death due to malnutrition and other causes.

As for the chemical impacts, the harmful chemicals contained in plastic are a problem. Plastic contains various chemicals, some of which are harmful. If these harmful chemicals are lipophilic, they are said to leach out from the plastic and accumulate in the body’s fat. Indeed, harmful chemicals contained in plastic have been detected at high concentrations in the fat of marine organisms, especially carnivorous animals. Among these harmful chemicals, some are pointed out as having the potential to affect reproductive functions as environmental hormones. It is not yet certain what kind of adverse effects these will bring in the future. The only thing that can be said is that the amount of plastic in the ocean is increasing at a tremendous rate, and there is a possibility that it will bring about unavoidable adverse effects in the future.  

——How much plastic has become waste so far?

Nakajima:  From the 1950s, when mass production of plastic began, to 2016, about 8.6 billion tons of plastic have been produced, of which 6.6 billion tons have become waste. Of the waste, only 9% has been recycled, 12% has been incinerated, and the remaining 79% has leaked into landfills or the natural environment. Even if it is recycled, plastic degrades each time it is recycled, so it can only be recycled at most once or twice. After that, it inevitably becomes waste.

——Will the problem be solved if we pick up the trash in the sea?

Nakajima:  It is basically impossible to pick up the trash that has entered the sea. The project launched by the Dutch venture company “Ocean Cleanup” to collect plastic from the Pacific Garbage Patch is famous. They floated an 800-meter-long ship in the Pacific and spent billions of yen, but in the end, the collected plastic scattered again at sea and the project ended in failure. Collecting trash floating in the vast ocean is like picking up grains of sand on a playground, and even if it can be collected, it is only a fraction of the trash floating in the ocean. Also, every year around the world, hundreds of thousands of volunteers gather to pick up beach trash at once, but the large amount of trash they collect is only 0.1% of the amount that goes out to sea annually. It is much cheaper and more effective to stop it from going out to sea from the river than to pay a lot of money to collect such a small amount. Indeed, the Ocean Cleanup project is focusing on a project to prevent plastic waste from flowing out of rivers into the sea.

So, my idea of reducing marine litter is to “shut off the faucet” of litter entering the sea, reduce the production of plastic, and properly manage the waste that comes out.

Japan is the second largest country in the world in terms of disposable plastic waste per capita. On the other hand, its waste collection and processing technology is among the best in the world, and it is not realistic to further advance its waste collection and processing technology. Rather, in Japan’s case, because the amount of plastic waste generated is extremely large, efforts should be made to reduce plastic waste.

——Will the problem be solved if we eliminate plastic?

Nakajima: Plastic can be reduced, but it will not disappear, it cannot be eliminated. It can be said that our lifespan has been extended thanks to plastic. For example, in the Corona disaster, the fact that the infection is being suppressed was thanks to plastic. Medical devices, masks, vaccines, if they were reused, Corona would have spread more. Plastic is necessary but on the other hand it needs to be reduced. So if there is something that can replace plastic, change it, and if it has to be plastic, leave it, and choose to use plastic that does not rely on oil.

——Will biodegradable plastic be the savior?

Nakajima:  I believe that the demand for biodegradable biomass plastics, including PHA and PLA, will grow in the future. Environmentally friendly plastic is made from renewable materials, is biodegradable, and is non-toxic. PLA and PHA meet these conditions and are recyclable. PLA does not degrade in the sea, but its manufacturing technology has already improved, so it is expected to spread in the future. Why not build a scheme that can be recycled or build a system to collect and compost it? Since it is derived from biomass, it is carbon neutral even if it is burned. If there is a possibility of leaking into the sea, you should use PHA. Currently, the world production of biomass plastic is only 0.3% of the total plastic production. While reducing the use of disposable plastic, it is necessary to promote the spread of biodegradable plastic derived from biomass in the future.