I have been fiddling with an Airhead composting toilet which we have been using on the road the the last 9 months. A few points that may be of interest:
1. I don't think the carbon filter in this unit will last too long. Composting toilets work by dessicating and composting to poo, so a lot of moisture will go through the carbon filter. Carbon filters in rangehoods don't like moisture and I would expect the same to happen with this loo. The carbon filters you can buy for regular cassette toilets need to be changed regularly. So budget for plenty of spares. Best maybe to duct it outside. There is always some kind of composty smell, which is not offensive.
2. I think you will get sick of emptying the wee bottle. I did, so we had a nipple welded in, added a valve and plumbed it outside. We flush with a 30% solution of white vinegar with a dash of vanilla in it to keep odours down. Stored pee has a smell that you will never forget. So don't let in hang about in a wee bottle.
3. Composting toilets don't like very cold weather or very humid weather.
4. They also don't enjoy too much toilet paper. We fold ours up and put it into a plastic bag which we change every day and is odour free.
Ours lasts a month between emptying with almost continuous use. But we use other loos whenever we can.
Good luck with it. A composting loo is definitely the way to go.
Keith
