There are compostable plastic cups made of PLA, such as https://greenpaperproducts.com/biodegradable-cold-cups.aspx https://greenpaperproducts.com/biodegradable

There are compostable plastic cups made of PLA, such as https://greenpaperproducts.com/biodegradable-cold-cups.aspx https://greenpaperproducts.com/biodegradable-cold-cups.aspx. They work fine so long as you're not holding anything hot in them (I've seen them melt when someone tried to serve tea in one).