The Ecofest at Red Hill up in the Lincolnshire was on a site with a row of composting toilets. There was a queue for the malodorus, besprinkled chemical loos and I was delighted to use the alternative! But I've no idea how well they coped. FWIW, the ideal for ordinary compost heaps is often held to be loading it all up in one go rather than adding bits now and again. The Centre For Alternative Technology might be able to give more detailed guidance.