PLA, or polylactic acid, is a biodegradable plastic that is made from renewable resources such as corn starch or sugar cane. However, PLA cannot be recycled in the same way as conventional plastics, because it requires different processing conditions and facilities.
PLA is often marketed as a green alternative to petroleum-based plastics, as it can decompose under certain conditions and reduce greenhouse gas emissions. However, PLA is not without its drawbacks, especially when it comes to recycling. In this article, we will explore why PLA cannot be recycled in the conventional sense, and what are the possible solutions to deal with PLA waste.
One of the main reasons why PLA cannot be recycled is that it is not compatible with other plastics. PLA has a lower melting point than most plastics, which means that it can contaminate the recycling stream and lower the quality of the recycled products. For example, if PLA is mixed with PET (polyethylene terephthalate), which is used for water bottles and food containers, it can cause the PET to become brittle and unusable. Therefore, PLA must be separated from other plastics before recycling, which can be costly and impractical.
Moreover, PLA is not easily identifiable by the current sorting systems, which rely on optical scanners or infrared sensors to detect the type of plastic. PLA can be mistaken for other plastics, such as PS (polystyrene) or PP (polypropylene), and end up in the wrong recycling bin. This can lead to cross-contamination and waste of resources. Therefore, PLA needs to have a clear labeling system, such as a special symbol or color, to help consumers and recyclers distinguish it from other plastics.
PLA requires special processing conditions and facilities
Another reason why PLA cannot be recycled is that it requires special processing conditions and facilities. Unlike conventional plastics, which can be melted and reshaped into new products, PLA needs to be broken down into its original components, such as lactic acid or lactide, through a process called hydrolysis. Hydrolysis involves exposing PLA to high temperatures and humidity, as well as adding chemicals or enzymes to speed up the reaction. However, hydrolysis is not a simple or cheap process, as it requires a lot of energy and water, and produces wastewater and greenhouse gases.
Furthermore, hydrolysis facilities are not widely available or accessible, as they are different from the standard recycling plants. According to a study by the University of Pittsburgh, there are only 113 industrial composting facilities in the US that can accept PLA, compared to over 8,600 recycling facilities that can handle conventional plastics. Therefore, PLA is often not collected or transported to the appropriate facilities, and ends up in landfills or incinerators, where it does not decompose or releases toxic gases.
What are the possible solutions to deal with PLA waste?
Given the challenges of recycling PLA, what are the possible solutions to deal with PLA waste? One option is to improve the design and labeling of PLA products, to make them more recognizable and separable from other plastics. For example, PLA products can have a distinctive shape, color, or symbol, or use a biodegradable additive that changes the appearance of PLA when exposed to light or heat. This can help consumers and recyclers sort PLA more easily and accurately, and reduce the risk of contamination.
Another option is to increase the availability and accessibility of hydrolysis facilities, or develop alternative methods of processing PLA. For example, PLA can be converted into biogas, a renewable energy source, through a process called anaerobic digestion. Anaerobic digestion involves using microorganisms to break down organic matter in the absence of oxygen, and produces methane and carbon dioxide. Anaerobic digestion can be done in existing facilities, such as wastewater treatment plants or landfills, and can reduce the environmental impact of PLA waste.
A third option is to reduce the consumption and production of PLA, and opt for other materials that are more recyclable or reusable. For example, consumers can choose to use reusable or refillable containers, or buy products that have minimal or no packaging. Producers can also use other biodegradable plastics, such as PHA (polyhydroxyalkanoate) or PBS (polybutylene succinate), which can decompose in soil or water, or use recycled or natural materials, such as paper, wood, or bamboo.
Conclusion
PLA is a biodegradable plastic that is made from renewable resources, but it cannot be recycled in the same way as conventional plastics. PLA is not compatible with other plastics, and requires different processing conditions and facilities. Therefore, PLA poses a challenge for the recycling industry and the environment. To address this challenge, we need to improve the design and labeling of PLA products, increase the availability and accessibility of hydrolysis facilities, or reduce the consumption and production of PLA. By doing so, we can make PLA a truly green and sustainable material.
