[TheThinkTank] Dirty Shop Rags

This is a 'which is worse' question...

Do you clean your dirty shop rags, or bring them to the local hazardous waste facility just like old paint, oil, gasoline, etc.,...?

Our shop rags are actually cut up t-shirts that were extra from a cycling event over a decade ago -- so we have plenty and they cost us nothing. But once they are dirty, they not only produce a fire hazard but a cleaning / disposal issue.

The chemicals required to effectively clean rags aren't good for the water supply / sewers -- since we all live down stream. At the same time throwing something away (even properly) after one use seems like a waste too.

What does everyone else do?