I was dismayed to learn from Boing Boing about our TreeHugger Community Liason Alan Graham's "Cat Jet" litter box ventilator- he didn't think it was green enough for TreeHugger. He is right; what self-respecting TreeHugger would use a 90 watt bathroom exhaust fan? It is serious electrical and mechanical overkill- they usually move about 150 cubic feet per minute, which would evacuate the box in about three quarters of a second. He did hooked it up to his computerized home automation system and a motion detector so that it is not constantly exhausting, but still, there is room for improvement...
the offending cat
"I already have a home automation system running off of a Mac Mini. This system allows me a little more control over how the fan works. In front of the litter box sits a motion detector. When the detector "sees" the cat, it tells the computer to start a timer. After 5 minutes (hopefully enough time for the cat, unless he's reading), the fan kicks on and vents the box for 15 minutes. That's just about enough time to take care of any major business that occurred. However, cat pee has that ammonia smell, so it doesn't take long for that to build up and overpower anything else. Because it releases over time during the day, it isn't enough to just vent when the cat uses the box. I wanted to keep the box venting. My system turns the cat fan on every hour for 5-10 minutes. This keeps the scent from building up, and since I run it only a short time, it really shouldn't affect the neighbors. However, as a safety precaution I placed a dryer sheet over the outside of the vent to perfume it up a bit. I do think a charcoal filter might work best in the near future."
Others in the forum suggested using a computer fans totalling five watts, which could easily run off a small solar panel. I would also suggest another approach:
Every house should have a heat recovery ventilator to bring in fresh air and recover the energy from the stale air being exhausted. If you hooked the cat box up to a small HRV like the Purifresh, you would have a constant exhaust of 40 CFM, HEPA filtered incoming air for your home, and 80 watts is put to a lot better use. See more in TreeHugger Forum
More on Heat Recovery and clean air in TreeHugger:
Indoor Flueless fireplaces: Are They Safe?
Vancouver Office Building Goes "Off-Pipe"
Village Energy at the National Home Show