How to Compost Polylactic Acid

Posted by Robert Bowerman on

We often get asked how to compost the Polylactic Acid that our products are made from.

You might read that to compost PLA requires “industrial” composting facilities. Well that isn’t strictly true.

 The key to composting PLA at home is allowing the temperature of the compost to rise to 60℃ - 70℃ and for that you need an insulated compost bin - some 50 mm of insulation is good. The temperature will rise naturally from the activity of micro-organisms and after a couple of weeks the temperature can drop off again to around 30℃ to 40℃.

Start the compost off with a handful of old compost or soil in order to introduce microorganisms into the mix. Microorganisms are living things that are too small to see, such as bacteria and fungus. It is also helpful to include sawdust or old leaves into the mix to balance out the carbon-nitrogen ratio. And of course, ensure there is enough moisture in the mix so its damp, but not wet.

Every two weeks, turn, rotate or mix the compost and that will get the temperature back up to the 60℃ to 70℃ range. This mixing can either be done by hand with a spade or by using a rotary compost bin.

Keep the amount of PLA to 10% of the mix unless you add things like sawdust and wood-ash to mop up the lactic acid produced during the composting.

One great thing about the composting of PLA is that all of the outputs are good for nature. The material doesn’t just fall apart into smaller and smaller pieces like oil plastic does, but rather decomposes chemically into totally natural simple molecules – basically PLA and water.

There are whole books written about composting and many scholarly articles too!