There are a lot of terms out there and it's sometimes hard to differentiate between them all... Especially at a time when greenwashing is rampant and companies will say just about anything to get your business. More consumers are actively making better choices for the planet, meaning there is more opportunity for them to take advantage of a growing trend.
Here's a super brief (and hopefully helpful!) breakdown of what the difference is between products labeled as compostable versus backyard compostable.
Compostable:
According to the Compost Education Centre, for a product to be certified and labeled as compostable by ASTM standards, it needs to degrade into CO2, water, inorganic compounds and biomass in a commercial facility (an environment with specific aerobic activity and conditions) without leaving any kind of toxic residue and at the same rate as paper.
'Compostable' can apply to animal and plant material, including bioplastics.
Backyard Compostable:
'Backyard compostable' refers to material that can break down easily at home within 6-12 months (although some material might still be visible after this time period).
There are certain things which shouldn't be composted at home, like material that can attract pests or affect the chemical makeup of your finished compost.
Just because something is made of organic material, doesn't mean that it can and will break down in your home compost.
Bioplastics:
Bioplastic is made from corn, sugarcane and other biomass sources. It's a popular choice for takeout containers, bags, cups, and cutlery.
Bioplastic is great in theory, but requires the use of a commercial facility to fully degrade. Light, temperature, and humidity are all controlled to aid in the breakdown process and because of this, bioplastics cannot be composted at home since those conditions are almost impossible to replicate.
Final Thoughts:
If something is labeled as 'compostable', it doesn't necessarily mean it will break down in your backyard. It might actually need a commercial compost facility.
Check with your municipality about their composting programs if they have them! They often have great resources and guides as well as what they accept.
If your area has green bin pick up for organic waste, that doesn't necessarily mean they will accept bioplastics. Green bin programs aren't always the same as commercial compost facilities so please check before tossing away that 'compostable' take out cup.
Sources:
https://www.naturespath.com/en-us/blog/whats-difference-biodegradable-compostable/
https://mamaeco.com/commercially-compostable-definition/
https://www.bbcgoodfood.com/howto/guide/what-biodegradable-really-means
https://www.toronto.ca/services-payments/recycling-organics-garbage/houses/what-goes-in-my-green-bin/
http://www.metrovancouver.org/services/solid-waste/SolidWastePublications/HeresTheDirt.pdf
https://www.compost.bc.ca/wp-content/uploads/2017/07/17-Understanding-Compostable-Plastics.pub_.pdf