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.

 

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, funneling 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 fertilizer. 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 odor 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 liters of water per day.

 

When it’s all done, the city will have access to mature compost.

 

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. The toilets use less than a liter 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 liters guzzled by average toilets.

 

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.
 

 

PHOTO: 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