What are the application fields of biodegradable plastics?Knowledge Science(Part Ⅳ)

Will biodegradable plastic degrade in the air or in use? Can biodegradable plastics only be composted? Knowledge Science(Part III)
2020-07-28

What are the application fields of biodegradable plastics?Knowledge Science(Part Ⅳ)

Q: What is the difference between landfill or incineration of biodegradable plastics and traditional plastics or traditional organic waste?

Some reports believe that biodegradable plastics will produce secondary hazards such as dioxins when burned compared to traditional plastics. However, biodegradable plastic is a kind of traditional plastic, and its polymer structure does not contain chlorine element, etc., and there will be no dioxin waste gas during incineration. In addition, the polyester structure of biodegradable plastics determines that compared with traditional plastics such as polyethylene, the content of organic carbon in the main chain is lower, and it is easier to fully burn when incineration. During incineration, biodegradable plastics do not produce more waste gas than traditional plastics.

In addition, there is concern that biodegradable plastics will release more harmful gases during landfills. At present, many modern landfills use some devices that collect biogas to recover energy during the landfill process. Even if the biogas is not recycled, there are corresponding organic wastes. Measures to release biogas after landfill. The solid content of plastic in landfill waste is less than 7%, and the current amount of biodegradable plastic is less than 1% of traditional plastic. Therefore, even if it is landfilled, there will be no more biogas problems affecting landfills.

 

Q: What are the application fields of biodegradable plastics?

According to the application field, the main applications of biodegradable plastics are textile fiber, packaging, agriculture, forestry, fishery and animal husbandry, automobiles, additives, electronics and electrical appliances, etc. See the table for details:

 

Q: Does the large-scale production and application of biodegradable plastics affect the food crisis?

At present, the global production capacity of biodegradable plastics is about 1 million tons, with an annual growth rate of about 20% to 30%. At present, it is mainly biodegradable plastics such as PBAT from fossil-based sources. Among these plastics, the biodegradable plastics prepared from corn starch as raw materials are mainly polylactic acid. The current global production capacity of polylactic acid is about 280,000 tons/year, and the apparent consumption is about 160,000 tons/year. Even if the polylactic acid production capacity construction in some reports has been realized in recent years, the biodegradable plastics prepared from corn starch as raw materials are only about one million tons, which will not have a fundamental impact on food. In addition, some companies use non-grain raw materials to ferment to produce chemical monomers such as lactic acid. Therefore, the development of biodegradable plastics has a very low impact on the food crisis in the past five years or even longer.

Q: How long does the biodegradable plastic degrade under natural conditions?

The public is particularly concerned about how long biodegradable plastics degrade under natural conditions, which is indeed the case. However, the degradation time and natural conditions and the structure of the plastic are related to the formula, and cannot be generalized. If natural conditions do not provide some suitable conditions for microbial growth or life activities, the degradation of biodegradable plastics and even natural polymers such as paper, straw, wood, etc. will be relatively slow. When we go to suburbs, forests or mountains, we can It is also true that some branches, wood or paper on the sandy soil have not been degraded by the environment for a long time.

Here are some examples to illustrate, it may be better to understand.

According to the demonstration application of biodegradable mulch made of PBAT materials in the country in the past 5 years, it will be completely degraded in 4~5 months in the shortest time. In actual film application, even if the crop is not fully degraded at the time of harvest, it will be degraded after plowing. Can be completely degraded.

Materials like PHA and PBAT can be completely degraded in about 30-60 days in seawater and (25±3)℃.