The Pros and Cons of PLA

Table of Contents

What is PLA?

PLA stands for polylactic acid and is the secret ingredient of many “biodegradable” alternatives to petroleum-based plastic.

From bin liners to food containers to toys, PLA mimics much of industrial plastic’s utility, however; PLA’s advantage over the competition lies in its production and its ability to decompose under the right conditions.

Polylactic acid or polylactide is a thermoplastic made from renewable biomass like cassava, sugar cane, sugar beet pulp, and corn starch. The journey from biomass to PLA is a long one that includes fermentation via fungal mush and bacteria, polymerization, and an extensive refinery process.

Out the other end of the scientific jungle gym arrives a plastic-like substance that is non-toxic and suitable for most industries in need of a flexible and durable material.

The Pros of PLA?

Degradable through composting and hydrolysis

Under specific conditions provided by a commercial composting facility, PLA plastics are 100% degradable or compostable due to their organic nature.

Unlike food waste, which is biodegradable from microbial decomposition, PLA plastics will only degrade through hydrolysis. This means that beyond a certain temperature (140ᵒF or 60ᵒC) water molecules may attach to and break off sections of PLA’s polymer chains into combinations of OH(-) and H(+) bonds.

These conditions are attainable at commercial composting facilities, so it is important that any PLA plastic waste is diverted there to keep them out of landfills.

Non-Toxic

Petroleum-based plastic bottles are notorious for leaching the chemical BPA (bisphenol) into drinking water. BPA is an endocrine disruptor commonly found in plastics under the recycling code #3 PVC (polyvinyl chloride). While generally inconsequential to humans, low doses distributed over time into waterways are responsible for disturbing the development of sensitive aquatic species.

PLA degrades into lactic acid which is produced naturally by the body as a byproduct of cellular respiration. This makes polylactic acid bottles much safer to drink from and not-toxic to people.

Doctors even use organic polymers like PLA in the form of surgical screws, mesh, rods, and anchors. Lactic acid implants dissolve under conditions inside the human body as it heals over time, making them ideal over metal and plastic which are infamous for releasing toxic chemicals as they degrade.

Reusable

PLA plastics are versatile and almost just as durable as industrial plastics. PLA is even compatible with existing manufacturing equipment. Being a thermoplastic, PLA does not burn as commercial thermoset plastics do. Instead, PLA melts under temperatures from 152ᵒC to 170ᵒC, making it suitable for 3D printing and cleaner recycling at compatible recycling facilities.

The Cons of PLA

It’s Not Perfect

While PLA is a degradable substitute for plastic it is not without its challenges. PLA plastics will take far longer to decompose than advertised if left outside on their own. Even in a backyard composting bin, biodegradable plastics can take decades to decompose because most household composting systems are unable to provide the conditions necessary for hydrolysis to happen.

Not recyclable with other plastics

Due to the chemical composition of polylactic acid ([C₃H₄O₂]n), plastic recycling plants will not combine them with other PET plastics. Their chemical components don’t play well together and mixing the two negates many of the advantages that polylactic acid has over petroleum-based plastic.

Because PLA and petrol-plastics are Identical in density and buoyancy, recycling plants have trouble distinguishing between the two. Instead, PLA found with PET plastics are separated for incineration or sent off to a landfill to avoid decreasing the quality of the plant’s resealable raw products.

Some recycling plants are specialized to handle PLA plastics, but in America, many are not. This is especially troubling since the goal of this technology is to help divert single-use waste away from landfills.

Does not biodegrade in landfills

Polylactic plastics will NOT effectively decompose under the conditions available in landfills. Landfills are areas of tightly packed garbage with little oxygen and water. Oxygen is a vital component for the aerobic decomposition process required to break down organic material without producing methane, a greenhouse gas 30 times more potent than carbon.

Water is another essential component for breaking down PLA since its polymer chains are only susceptible to hydrolysis, not through a biological attack. That being said, trashing PLA products in the hopes that they will decompose in nature is a counterproductive notion that companies should avoid promoting.

The Takeaway

Degradable plastics are an important feat in eco-friendly technology. While the infrastructure to decompose these products has not yet been normalized as it should, every innovation in waste management paves the way toward a more sustainable future. Incentivizing customers to discard waste products in the hopes that they will decompose is dangerous and promotes a culture of throwing things away for convenience’s sake.

The prospect of degradable plastics is important and exciting for the zero-waste community. Educating consumers on how to dispose of these products is equally important, otherwise, they will end up contributing to the world’s growing landfill problem. Consumers must understand that PLA is not a magic bullet that will dissolve in the ocean. It should never be advertised as such.

If you are interested in making the switch to PLA or other biodegradable plastics, do your research and find a composting facility when you are ready to discard it. If you live in an apartment that doesn’t compost, then PLA bin liners could be a perfect alternative. Using a biodegradable liner, dedicate a bin for any waste you would normally compost. This includes fruits, vegetables, and paper. When it’s full, donate your green waste to a commercial composting facility near you.

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