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What is the difference between degradable, biodegradable and compostable?

Nov. 05, 2019

Bio-based plastics and biodegradable plastics are new materials that are environmentally friendly and sustainable alternatives to traditional plastics that are currently primarily petroleum-based. "Degradable," "biodegradable," and "compostable," etc., are terms that are often referred to when talking about these materials, and are similar but different.

When designing a new product, it is important to consider its ecological behavior, which is related to its final treatment. Of particular concern are the plastics used in disposable packaging and consumer products. These materials are designed to be biodegradable and ensure that they are ultimately properly disposed of in order to be environmentally friendly and ecological. For example, composting biodegradable plastic bag and waste paper with other organic compostable materials, such as yard waste, food, and agricultural waste, can produce large amounts of carbon-rich fertilizer (humic material). Fertilizer-modified soils have a number of benefits that reduce the amount of chemicals and inhibit plant diseases by increasing the levels of organic carbon, water and nutrients. Today, people are increasingly using compost to sustain the sustainable development of agricultural systems. In many countries, food waste and other biological waste are collected separately and composted to produce good, high-value soil-improving materials that return to the field to maintain the carbon cycle.

Biodegradable T-Shirt Bag

Biodegradable T-Shirt Bag

In the past, polymers were designed as materials that are not easily degradable. Today, the challenge is to design polymers that have the required functionality during use but are decomposable after use. More importantly, the degradation products are not toxic, can not exist in the environment for a long time, but can be completely digested by soil microorganisms in a certain period of time like food. In order to ensure that the market can accept biodegradable products, there is no doubt that these materials can be biodegraded in a waste management infrastructure in a shorter period of time.

However, these are not sufficient to clearly explain the difference between "degradable", "biodegradable" and "compostable" plastics. Further explanation will be given below.

(1) Degradable plastic

Degradable plastics include plastics that can be degraded by physical and biological factors (light or heat, or microbial action). So-called aerobic degradation (accelerated degradation by catalyst or activator at elevated temperatures) or photodegradable starch-polyethylene plastic creates some environmental problems. These materials do not degrade faster than compostable plastics and may leave debris. These degraded hydrophobic debris have a large surface area and may migrate to groundwater and soil, adsorbing and retaining some highly toxic substances such as PCB and DDT on the surface, making the toxic content up to 1 in background content. A million times enough to be a delivery system for toxic substances in the environment. Therefore, it must be ensured that the product is fully biodegradable in the shortest time determined by the treatment facility.

(2) Biodegradable plastics

Biodegradable plastics are plastics that can be completely digested by microorganisms in the treatment system as food for energy. This complete microbiological digestion/utilization is determined by testing whether the carbon of the test plastic is fully converted to CO2 by the microbial processes occurring in the cell.

(3) Compostable plastics

In addition to being biodegradable by microorganisms, it is necessary to meet a time requirement to refer to a plastic as a "compostable" plastic. Industrial composting environment means that the specified temperature is about 60 ° C and microorganisms must be present. According to this definition, the compostable plastic does not leave debris in the residue that lasts longer than about 12 weeks, contains no heavy metals or toxic substances, and can sustain the life of the plant.

Research and development of fully biodegradable plastics is an effective way to solve environmental pollution problems.

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