The issue of latex paint disposal can be the most difficult debris removal task for the property preservation specialist. Here's what can make it so troublesome: it is not a hazardous substance, yet it cannot be disposed of at your local transfer dump. Why, you ask?
Although latex (acrylic) is not hazardous, it cannot be taken to the dump in a liquid form. Therefore it must be dried up before your dump will accept it. Now, drying up half a gallon of is not a difficult or expensive process. But drying up 40, or more, gallons of paint can be both time-consuming and costly.
The website of your local landfill probably has some suggestions, but here's two that we've used. If you have a room in your garage that is insulated and can be heated, the process can be hurried along in a warm environment. Just open the cans and let them air dry.
Usually, however, you need to do it more quickly. We buy 40 lb. bags of kitty litter at our local warehouse store, and take one or two with us to a debris removal job. Find the latex paint right away, and take it outside, open up all the can, pour some off of the fullest ones, and then pour kitty litter into each can. Get a sturdy stick (at least 1" x 2" x 3'), because the paint will get stiff. With a little experimentation, you'll discover how much kitty litter it takes. When you're ready to make your trip to the dump, the paint will be dry.
We know of two communities that have services which take in latex paint for recycling. One has a paint barn where people can drop off paint for free, and others can pick some up for free. It seems to work!
In a metropolitan area we've enjoyed a municipal service that takes in latex paint for no charge, and then remixes it and sells it. Unfortunately for us, this is in another state, 150 miles from where we do most of our work.
Look for a free latex paint disposal service like one of these near you. If you find one, it'll be well worth the time it takes you to find it!