Polylactic Acid (PLA) is a plastic resin that can be manufactured using only plant-origin raw materials without using any petroleum based or chemical based raw materials, and in addition, it is an ideal environment-friendly plastic that is decomposed completely into water and carbon dioxide by the actions of naturally occurring bacteria after it has been disposed of. However, the following doubts come to mind. Since appropriate information is difficult to obtain regarding these doubts, some people may come to misunderstandings about them. The points of view that are supported by a large number of concerned persons at present are described below.

Q1. Why is that polylactic acid resin is not in widespread use in spite of being an excellent material?

A1. While many reasons can be thought of, the most important reason is that the cost of the raw material is still high compared to the raw materials of polyolefin plastics (polypropylene, polyethylene, etc.) or styrene based plastics (PS, ABS, etc.). It was inevitable that the cost of raw materials was still high because the production volume is still low. However, the cost difference is gradually becoming smaller because of big increases in the cost of petroleum and because of the sudden increase in the production volume of polylactic acid plastics. As a result, the trend is towards the problem of the cost of raw materials becoming smaller.

Q2. Is it not possible to burn off polylactic acid ?

A2. It can also be burnt off similar to fossil fuel based plastics. The amount of carbon dioxide and heat generated at that time is about half that of fossil fuel based plastics, and it has been confirmed that these plastics are superior even when burnt in terms of the effect on global warming.

Q3. Is it not possible to reuse the runner, etc. in the case of polylactic acid?

A3. They can be reused.

Q4. What time period is required for biodegradation?

A4. For biodegradation to start, it is necessary that the environment is suitable, such as the quantity of microorganisms, temperature, humidity, pH, etc. Biodegradation does not start under the normal environment of use in our daily life (such as stationery, container, etc.) just because of touching by hand or by keeping water at room temperature in a container. Biodegradation starts in soil or in compost if the conditions are satisfied. In soil, about one month is required for biodegradation to start. In compost, biodegradation starts after about three days if the temperature inside the compost increases to near 60°C. A film shaped molded item put in compost gets completely decomposed in about two weeks. If a molded item with a wall thickness of about 1 mm is buried in soil, it takes about four to five years for it to get completely decomposed.

Q5. Is there no danger of causing a food shortage problem if corn is used as the raw material?

A5. The corn that is being used at present for the manufacture of polylactic acid plastics is millet that is being produced for use as animal fodder for cows, horses, etc. It is not the sweet corn eaten by people. About 99% of the corn being produced in the world is for fodder, and the corn consumed directly as food by people is estimated to be about 1%. At present, the production volume of polylactic acid is about 0.01% of the world's plastic production including those based on petroleum, and even if it increases to about 10%, it is almost impossible to think of this corn usage ever becoming a problem of food for human consumption considering the production capacity of millet.

Q6. Can polylactic acid plastics be eaten?

A6. Polylactic acid plastic is not edible. However, it is harmless even if consumed accidentally. When using for food containers, it is necessary to use a grade that conforms to safety standards of the industry and laws and regulations.

Q7. Is it possible to add coloring agents to polylactic acid plastics?

A7. Coloring is possible in master batches, etc. Coloring agents that are biodegradable are also being developed.

References: Various newspaper reports and material catalogs