Is PLA Biodegradable? Can You Compost PLA?

by Mike Brooks | Last Updated: January 31, 2022

Polylactic Acid (PLA) is a thermoplastic monomer manufactured from renewable organic sources like corn starch or sugarcane.

More importantly, its production remains different from most plastics produced using fossil fuel through distillation and polymerization.

Notably, despite the raw material difference, you can produce PLA using the same equipment as fossil-based plastics. Meaning the PLA manufacturing process remains cost-effective.

Also, PLA is considered the second most-produced bio-plastic after thermoplastic starch. It enjoys similar mechanical properties to polypropylene (PP), polyethylene (PE), or polystyrene (PS).

So, Is PLA Biodegradable?

PLA remains a bioplastic derived from renewable material, and as such, it should be biodegradable. However, its biodegradability remains a hotly contested topic among 3D printing professionals and hobbyists.

3D printing professionals believe that PLA is degradable but not biodegradable. The conditions required for PLA to biodegrade effectively are not found in the natural environment.

PLA is not a biodegradable material in most environments. However, it remains a compostable material only in industrial environments.

Is PLA Environmentally Friendly?

Polylactic Acid Production

Polylactic Acid (PLA) production uses 65% less energy than producing petroleum-based polymers. Also, it produces fewer greenhouse gases and contains no toxins at all; as such, PLA remains one of the most environmentally friendly plastic materials.

Plastics or polymers retain a reputation of not being environmentally friendly. This reputation remains because polymers/plastics take many years or even centuries to decay.

Different PLA Types Decomposition Time

However, plastic bags and materials made of PLA take five years to decompose. Also, PLA’s drinking bottles and food containers take longer to decompose as they are manufactured from thicker material.

More significantly, PLA will remain environmentally friendly if you learn to follow its correct end-of-life handling scenarios. This end-of-life option includes:

• Recycling
• Composting
• Incineration
• Landfills

How Long Does PLA Take to Biodegrade in Landfill?

Many manufacturers in the food industry are switching their food packaging to corn-based plastic made from PLA plastic. PLA is a degradable thermoplastic polyester made from renewable plant resources such as fermented plant starch.

PLA Biodegradable Time

Research shows that PLA decomposes into water and carbon dioxide in 47 t0 90 days. Thus, it decomposes four times faster than a PET-based bag floating in an ocean.

PLA decomposition needs certain conditions to need to be right. PLA breaks down effectively in industrial composting plants at a high temperature.

The industrial composting plant heats PLA to temperatures above 50 degrees celsius and feeds a steady diet of digestive microbes.

Is PLA Bad for the Environment?

However, if you put your PLA plastic product into a landfill, the scenario changes completely. Landfills are known to have little or no light or oxygen. A condition that is not good for polylactic acid to degrade.

A plastic cup or a salad box made from renewable resources such as PLA filament (check at Amazon) could take between 100-1000 years to decompose.

It may not be what you thought when you saw the word “biodegradable” on your PLA plastic food packaging. That remains the main reason why many people contest the biodegradability of PLA, especially in landfills.

So next time you buy food and beverage in PLA packaging thinking you are a responsible person, bear in mind that it may not be the case. The PLA plastic container needs to get to an industrial composting plant and not landfills.

Most countries lack the infrastructure to handle PLA properly. So, most of the PLA does not find its way to the industrial composter but goes directly into landfills, where it takes between 100-1000 years to decompose.

What Makes PLA Biodegradable?

Biodegradable Material

PLA filament remains one of the most used plastic filaments in the 3D printing industry.

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Other plastics made of fossil fuels may have a higher tensile strength than PLA, but PLA retains the advantages of being easy to use, and you will experience minimum warping with it.

PLA is a bioplastic, meaning it is composed of renewable materials, which theoretically should be biodegradable.

PLA remains a unique plastic filament as it comprises lactic acid units. The lactic acid units are small organic acids similar to those found in the most readily available foodstuff.

More importantly, anything or food that contains glucose to lactic acid molecules.

Also, you need to note that lactic acid remains the basis of PLA material, and it accounts for PLA’s weak thermal properties, such as its melting temperature and molecular weights.

Additives

PLA material contains other chemical components it acquires during its manufacturing. You can refer to this material as additives.

Additives dilute the purity of PLA, but in return, make the material more practical for 3D printing.

The presence of the additives in PLA makes it difficult to decompose and therefore not biodegradable in normal environments.

Extraction and Creation of PLA Material

One of the most common plants producing lactic acid for PLA filament remains corn. Cornstarch contains enough glucose that enables the extraction of lactic acid required to manufacture PLA.

The process known as wet milling allows for starch extraction from organisms. Starch is combined with chemicals in the wet milling process and then heated to isolate sugar. Then, the sugar is fermented to produce lactic acid monomers.

Finally, lactic acid is used to manufacture PLA through condensation or polymerization.

Therefore, the material and process used to produce PLA determine its biodegradability to a large extent.

Is PLA Packaging Compostable?

What Is a Compostable Material?

A compostable material degrades as a result of natural biological processes but also produces carbon dioxide, water, inorganic compounds, and biomass. Also, it leaves no visible or toxic residue in the process.

PLA and not other plastics are compostable and biodegradable but only in very specific types of environments. These environments need very specific levels of oxygen and temperature that are well above 140 degrees Fahrenheit.

You can discover these conditions in controlled environments like industrial composting plants.

PLA packing is compostable but only in industrial composting conditions. Also, PLA remains a unique plastic and can contaminate other plastics if not properly recycled.

The main reason PLA is not compostable in standard environments is that it is fragile. PLA remains less durable, crystalline, and heat resistant than petroleum-based plastics.

To strengthen its mechanical properties, you need to blend PLA with fossil-based polymers. It means that while PLA in itself is compostable, the chemical additives it’s blended with may significantly minimize its composting properties.

What Is Better for PLA: Compositing or Recycling?

PLA Waste

Plastic that is thrown away after a single use has contributed immensely to the problem of world environmental pollution. For that reason, governments worldwide are pushing for the use of biodegradable plastic instead.

The major area of concern remains in food packing, where significant effort is directed. Most governments are pushing for PLA to serve as an alternative bio-based plastic.

The aim is to replace the use of artificial petroleum-based plastic with PLA that is derived from renewable resources. Due to the material used in its manufacture PLA enjoys compostable and biodegradable properties under certain specific conditions.

Composting PLA

PLA material can only be considered composted if you meet the following three conditions:

• The material must breakdown into carbon dioxide, waste, and biomass
• The PLA needs to disintegrate completely
• No toxic residues should be left, and the compost should support plant growth

PLA takes between 1-6 months to complete the composting process in an industrial composting environment fully. However, composting is dependable on material type and temperature.

Notably, the rate of composting PLA in industrial composting plants remains significantly higher than composting PLA at home. In an industrial environment composting disposed of PLA boxes or containers and cups takes 1-3 months.

Contrastingly, composting the same at home will take you up to six months to complete.

Most PLA products or wastes end up in landfills and not industrial composting facilities. Transfer stations that sort municipal waste have problems sorting mixed PLA and PET plastic. Both PET and PLA plastics are transparent plastic materials.

Also, buyers tend to offer lower prices or may not be interested in buying recycled material in the first place.

Equally, the compost needs to be compliant with (OMRI) regulations in the USA.

Remember, PLA is not 100% compostable, and many composters see it as a contaminant.

Recycling PLA

3D printing offers accessible manufacturing options and the ability for you to experiment with new designs. Additionally, it drives innovation and creativity. In the process, many mistakes occur, occasioning piles of useless 3D prints.

Most 3D printing professionals believe that the best end-of-life option for PLA material is recycling it.

A European study showed that the environmental impact of recycling PLA is over fifty times better than composting the same.

Besides, the same studies view that recycling PLA has 16 times better environmental impact than combustion.

So, as a 3D maker, you may want to recycle your own PLA material. You can use instant home plastic recycling machines such as the “Filabot” to recycle plastic. It is best used for recycling plastics in small businesses.

The machine collects printed waste and extrudes re-usable filaments. Also, it would help if you were cautious not to mix contaminated plastic in a home recycling machine. It will help you avoid ending up with recycled plastic of inferior quality.

Conclusion

PLA material remains a popular plastic filament used in the 3D printing industry. The issue of whether PLA is biodegradable material remains a highly contested topic.

However, many 3D printing professionals agree that PLA is not readily biodegradable in standard environmental conditions. It remains biodegradable in specifically controlled environments such as industrial composting plants.

Also, PLA is compostable in specific environments.

Michael Brooks is the founder of M3DZone.com. He sees a very bright future for 3D printing that's why his mission is to try and make this easy for everyone. Discover your hidden talent and creativity. You can follow here: Facebook, Twitter & Pinterest.