Can you compost paper cups? The answer is yes, no and depends.
My research into Solo was definitely the most peculiar. I had no idea there was a (terrible) song dedicated to red solo cups, and then within that song saying that "within 14 years they are decomposable"... come on Toby- plastic doesn't decompose, it just breaks into smaller pieces for the fish to eat. Going further, there's a Facebook fan page sporting over 45,000 likes... for red solo cups.
Anyway, Solo does have an "eco forward" product line called Bare. Rejoice. This cup uses a whopping 20% post consumer recycled plastic in its plastic cups. I was hoping their eco line would have either cups made from PLA or paper cups with a soybean wax liner, but I guess you can't have it all. Avoid this company. Is their competition much better?
I'm getting ahead of myself. My point for doing the research in the first place was because I didn't realize that nearly all paper cups have a thin plastic (polyethylene) lining inside of them, which is to keep the cup from falling apart (think coffee). Surprisingly, even a great deal of the "cold cups" have a liner too.
I know from experience that it's difficult to use a bioplastic cup with hot liquid in it... the cup falls apart pretty quickly. But I also know that it's possible to use a paper cup with a PLA (polylactic acid, a compostable plastic) liner with good results. How about a doubly thick paper cup with wax?
What is the best solution if you have to use a paper cup? Paper cups can go in the compost pile no problem, just don't expect them to come out for a while, and they'll remind you that you put them in there by leaving behind a plastic skeleton. Fat chance this would be recycled, but it's easy to pull these out from finished compost and put them in the blue bin.
The other option is to "recycle" the paper cup, which is more commonly done than composting. In recycled paper processing mills, the slurry from a pulper is screened to remove plastic, ink, clay, dirt, metals, etc from the paper. Therefore, the cup's plastic liner is considered a contaminant. What happens to this sludge from here?
Any better ideas? The coolest example I've ever seen showed itself when I went on vacation to Panama recently. I received a paper coffee cup with a fold-out handle so you don't burn your hands, while eliminating the need for the cardboard sleeve.