日本語
Causes and reasons for plastic waste
Basic knowledge of biodegradable plastics
When the topic of plastic waste in the sea is reported, you may hear of the term “biodegradable plastic” at the same time. Then, what mean does this term “biodegradable plastic” have?
It is said “biodegradable plastic” is plastic which has the same durability as normal plastic, and is decomposed completely into carbon dioxide and water after using it by working of microbes living in the natural world.
Also, though you may imagine it is decomposed in the environment, there’re cases in which it isn’t. Actually, biodegradable plastic has a different nature depends on the type of it. PHBH (Polyhydroxybutyrate hexanoate), PLA(polylactic acid), BioPBS (bio-based PBS) are sort of representative “biodegradable plastic”, and each of them has the different environment in which they can be decomposed.
According to this graph, PHBH(polyhydroxybutyrate-hexanoate) is decomposed in the water environment, and the number of it is small fraction. Though PLA(polylactic acid) is decomposed in the hot and humid environment in the compost, it’s hard to be decomposed in the normal soil environment or the water environment. Also, BioPBS(bio-based PBS) can be decomposed in the compost and the normal soil environment, but it isn’t well in the water environment. Therefore, not all the biodegradable plastic can be decomposed in the sea. It may be possible all the cases to say “We can solve the problems of plastic pollution in the sea by using biodegradable plastic”.
The logo of GreenPla
There is an effort to keep the standards for biodegradable plastics that can be clear out in hot and humid environments. It is the "GreenPla" defined by JBPA (Japan Bioplastics Association). Organic compounds that can mark “Greenpla” are limited to "natural organic substances such as paper and trees, or those with a biodegradability of 60% or more at a biodegradation rate based on international standard analytical methods". This rate of biodegradability means that it is resolved in the compost facility at the same rate as paper or trees. The background of this movement is the outflow of “biodegradable plastics” which haven’t unified biodegradation rates. There are some plastics in the world that don’t eventually decompose into water and carbon dioxide. It is the problem that consumers think like “We‘re using biodegradable plastics, so we’re taking eco-friendly action.” Of course, it is important to change consumers’ awareness, but it would be nice to spread biodegradable plastics with guaranteed quality.
Issues revealed by the survey
1． Biodegradable plastics are more expensive than normal plastics, so it’s hard to penetrate into society.
2． It is hard to produce unified biodegradable plastics because there is no specific law on processing and recycling.
3． We need to think of a new separation method because recycling together normal plastics and biodegradable plastics degrades the quality.
