We built an aerobic septic at Lakeside Villas. I first learnt about them from the developer of a condominium project here on the island and was quite sceptical. But, after 8 months of trouble free use and absolutely no odours of any sort (and new gardens that are thriving even in the middle of dry season) I think this is a more flexible and more energy efficient system than the composting toilet.
Composting toilets are good when water conservation is a premium. Having said that, the aerobic system's treated water can actually be recycled into the toilets. You never run out of clean flushing water. If you don't plan to recycle water to the toilets you only need one sump pump (for the yard irrigation)...if you plan to recyle you probably need 2 sump pumps...the toilet pump being set lower down than the garden pump.
There's only an airpump and the sump pump(s) to power. The electric bill for the our system doesn't even use the minimum number of allowed KWH per month. The treated water is actually drinkable (after you, though!). And, best of all, it treats grey water as well....literally all of the waste water from your plumbing can go into the septic.
This system doesn't produce any harmful effluent and no raw or partially treated waste seeps into the ground...it's a completely sealed 4 compartment concrete tank.
There is virtually no maintenance. Just add a chlorine tablet every couple of weeks and replace the sump pump and air pump when they finally break down after years of use.
We don't recycle the toilet water as we have city water and rainwater in each house...water conservation wasn't as much of an issue as it might be on remoter parts of the island.