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Monday, 21 July 2014

Composting toilets: Every flush turns your waste to fertiliser

Eco-toilet: The composting toilets empty into a tank where the waste is mixed with wood shavings. Starter microbes break down the waste and turn it into rich compost. - MCT

Eco-toilet: The composting toilets empty into a tank where the waste is mixed with wood shavings. Starter microbes break down the waste and turn it into rich compost. - MCT

The most radical “green” features of the City Of San Jose’s new Environmental Innovation Centre are concealed behind two doors marked “Women” and “Men”. There, plopped between the other conventional stalls, are two “composting toilets”, the first ever installed in a California office building.

“You assume you get an outhouse on a trail,” says Nora Cibrian, an environmental services specialist with the city. “But you just don’t think you can do it indoors, too.”

These two toilets resemble every other commode, but at a total cost of approximately US$20,000 (RM64,000), they aren’t your great-grandmother’s latrines. They skip the sewage system entirely, funnelling waste into a tank in the basement the size of a commercial trash bin.

Unlike an old-fashioned outhouse, where the waste goes straight into a hole in the ground, the composting toilets use the magic of chemistry to convert it to fertiliser. Just as in a backyard compost pile full of leaves and fruit rinds, the nutrient-rich waste mixes with carbon from wood shavings in the tank. Hungry bacteria then break down the material into tiny pieces, generating heat and carbon dioxide.

A fan circulates air, reducing odour and ensuring the bacteria have plenty of oxygen. It takes some additional work to complete the year-long composting process. You have to toss in some earthworms, sift occasionally, and add about five litres of water per day.

When it’s all done, the city will have access to mature compost, according to toilet manufacturer Don Mills, a sales director for Clivus Multrum, a Massachusetts company founded in the 1970s by environmentalist Rockefeller scion, Abby Rockefeller. “It’s not a highly complex device,” Mills says. “It’s a consciousness-raiser as well as an actual technology.”

The design team saw the toilets as a natural fit for the city’s new Environmental Innovation Centre, a facility that includes a variety of Earth-friendly innovations, says city spokeswoman Cheryl Wessling. The toilets use less than a litre of water per flush – just enough to moisten a biodegradable foam solution that coats the tanks before and after each use, and much less than the five to 20 litres guzzled by average toilets.

“This is definitely a learning process,” Cibrian says. “We’ll see what works and what doesn’t work and whether it can be applied elsewhere.”

The Bay Area is home to two other composting toilet installations, both outdoors. One is at the Presidio’s El Polin Spring in San Francisco and the other at Crystal Springs Golf Course in Burlingame. The Presidio Trust installed the composting toilets near the spring in 2011 to preserve a unique watershed with a rich archaeological history, says Allison Stone, the organisation’s director of trails and philanthropy.

She admits they were a bit nervous at first, but are now quite happy with their off-the-grid choice. “It’s been a great experience,” Stone says. “We have not had any major problems.”

But despite the water-saving benefits, the composting toilets have one big drawback apart from the steep upfront cost that has limited their use: governments still see the resulting compost as sewage, sharply limiting disposal options. Though San Jose expects to approve permits soon for the unconventional toilets at the Environmental Innovation Centre, city officials haven’t decided how they will dispose of the resulting compost. Wessling says it might be used on-site to fertilise the landscaping, or the city could have Clivus haul it away for US$350 (RM1,250) a month.

The Innovation Centre’s new tenants are expected to pay the maintenance costs. They include: ReStore, Habitat for Humanity’s building materials store and donation centre; a household hazardous waste drop-off facility; and Prospect Silicon Valley, which will run a programme to help develop clean technology. The Presidio Trust hired a contractor to regularly sift and care for the toilets and that contractor removed the waste, Stone says.

Vermont Law School installed composting toilets indoors in 1998 and gets numerous requests to see them, says Lori Campbell, the school’s facilities manager. “People are fascinated,” she says.

But the compost disposal poses a big drawback that advocates face coast to coast. “It is presently the case in nearly every state that you must regard this material as sewage,” Mills says.

Vermont state law still precludes the school from using the compost on its grounds, Campbell says, calling the restriction “unfortunate”. “It’s beautiful compost,” she says. “It’s so rich, it’s unbelievable.”

Peter Scott, an emeritus professor of physics at University Of California Santa Cruz and California’s foremost expert on the commodes, believes the steep upfront cost chiefly dissuades many potential buyers. He first learned about the toilets while visiting the Vermont Law School in the early 2000s and he has been advocating their use ever since. “It’s an interesting problem and an interesting puzzle as to why there aren’t more of them,” Scott says. “It seems like we have a lot of opportunities.” – San Jose Mercury News/McClatchy Tribune Information Services

Tags / Keywords: Environment , composting toilet


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