Compost loos a long way from a long drop
Composting toilets require a certain amount of work but they could be the way of the future. Mikaela Wilkes meets some ardent advocates of the system.
Put the words compost and toilet together in a sentence and you’re likely to be met with a crinkled nose. Compost toilet educator Lisa Johnston said that was because most people confused a compost loo with the long drop they used on a farm or at camp during their childhood.
Johnston and her partner Greg Inwood formed the Relieve organisation after the Christchurch earthquakes, to provide workshops on how to use and maintain compost toilets as an alternative to the city’s damaged sewage infrastructure.
‘‘People have had bad experiences with long drops and think composting toilets are the same thing. But actually, a long drop could be vastly improved if all you did was add sawdust. It wouldn’t smell or have flies,’’ she said.
The couple have used a bucket-style composting toilet for more than a decade, a setup that is different from some of the hi-tech adaptions available for tiny home owners today.
Tiny houses can be built fully off-grid, or as hybrids with some connections to mains infrastructure and town water. However, many tiny-home owners choose a grey water system with a composting toilet to avoid costs associated with connections.
Hamilton single mum Carol Armstrong uses the $1900 Nature’s Head diving toilet which came with her 26.5 square metre tiny house.
The toilet has separate compartments for liquids and solids and a quiet plug-in motor. She empties the urine cannister, which is diluted with half water, once every three days and the poo compost once every three months.
That’s with Armstrong, her 11-year-old daughter Caitlin, and often a guest using it. ‘‘It doesn’t gross me out whatsoever and it doesn’t smell. But the process is hard work and it’s heavy.
‘‘The inside of the unit is not detachable, so I have to uplift the whole thing and tip it into the soil.’’
Johnston explains that while there are different toilet models, the basic principles of each are the same.
‘‘You do your business, then add sawdust, forest litter, or other home carbon material,’’ she said. ‘‘The aim is to create a carbon balance to the nitrogen in the human waste and aerate it.’’
Armstrong buys $3 coir bricks from Bunnings, which make 9 litres of soil when hydrated. She empties one into the back of the toilet and uses an external crank handle to aerate the soil.
‘‘By keeping the poo relatively dry, it stops it from going anaerobic and starting to smell,’’ said Matt King, a Relieve member who manages Green Earth sustainable construction consultancy.
‘‘The simpler the system, like buckets, the more you have to manage it.’’ Urine comes out as a practically sterile and nonhazardous substance, which is easy to empty onto grass or trees, said King. ‘‘Generally, liquid has an ammonia smell after three to four days, which is when you need to empty.’’
Johnston believes most tiny-home owners compost their poo on site.
‘‘I would say a lot of people would be continuously adding buckets to a pile, filling up a vessel, closing the lid and leaving it for a year before using it anywhere as compost,’’ she said. King uses a sealed wheelie bin.
‘‘It’s ridiculous that we put our poo into water. We’ve taken two valuable resources and turned it into a problem because we’ve contaminated the water.’’
Lisa Johnston Compost toilet educator