As reported by Time. 

To flush or not to flush. That was the question that designers and ecologists were asking each other this week as hundreds of people — who spend a lot of time thinking about these things — convened for the annual World Toilet Summit and Expo in Macau.

The World Toilet Summit and Expo is like the Star Trek Convention of the waste management and sanitation world. Toilets on show run the gamut from a cardboard box complete with a hole, plastic bag and pouch of waterless magic pathogen-busting dust ($50), to a high-tech 'uber-toilet,' featuring an in-seat warmer/cooler, male and female water jets, an in-bowl light (why? why?) and a USB port so you can connect your mp3 player for your soothing tune of choice ($1,200).

But figuring out how to wean the world off the flush handle took center stage. Though the common flush toilet has remained largely the same since it's invention in 1596, the world it inhabits has changed drastically. City populations have mushroomed, sewers have become overburdened and water has become scarcer. Now, the flushing loo — that human innovation that lifted the industrialized world out of its own dirt, cholera and dysentery — is quickly becoming one of the more egregious instruments of waste in this time of acutely finite resources. "The world can't sustain this toilet," says Jack Sim, the founder of the World Toilet Organization — the other WTO — an organization that advocates for sustainable sanitation solutions for all. "This 'flush and forget' attitude creates a new problem which we have to revisit."

If you are, as Sim's said, one of the millions who tends to 'flush and forget' on a regular basis, chances are you're dumping up to 22 liters of drinkable water every day, one three- to six-liter flush at a time. But the problem doesn't stop there. What follows — the 'forget' part of the toilet experience — is the long and costly process of sanitizing the water that was clean before you answered nature's call. In the developed world, the flush toilet is our only direct link to the enormous — and exorbitant — engineering feat that is the modern urban sanitation system: the sewers, filtration plants, water treatment facilities, and finally, treated water disposal channels that send the scrubbed water into our rivers and lakes.

Using so much water per flush unnecessarily increases the volume of our waste and the cost of its transportation and treatment, ecologists say. If you don't put waste in water in the first place, then you don't have to spend money to remove it at the back end. The process also leaves a huge carbon footprint, says Rose George, author of The Big Necessity: The Unmentionable World of Human Waste and Why it Matters. In the UK, she says, "the sewage system uses as much energy as what the largest coal fire station in the [country] produces" — about 28.8 million tones of carbon dioxide a year.

But the fundamental shift in how we think about our waste, and by extension, dispose of it, needs to be to stop mixing liquids and solids, says the WTO's Sim. "The human body is designed to separate solids from liquid waste," and we should follow suit, he says. By separating fecal matter from urine at the source in what's called a "urine diversion toilet," a wider ecological system of waste disposal becomes possible. Solids can be composted for fertilizer and harvested for methane gas. Urine can be used to produce phosphorous and nitrogen and clean, drinkable water. (The question is, will people bring themselves to drink it?)

Ecological sanitation, as this call to arms is known in toilet circles, is already up and running in many spots around the world. In rural China, 15.4 million homes convert methane into power from what normally went down the pit behind the house. Household waste is stored in a state-subsidized "digester," a kind of metal stomach that breaks down the matter and releases methane gas which is trapped for reuse. In the French city of Lille, a small fleet of ten buses are also using methane, gleaned from the city's poop. And in some Indian villages, simple latrines have been built that separate waste and use it to produce compost and fertilizer at a per capita cost infinitesimally lower than any waste management budget in the West.

In a reversal of the traditional one-way innovation highway — from the West to the rest of the world — many of the best ideas in sanitation are coming from the developing world. And for now, the gap between these initiatives and the large-scale urban sanitary solutions of tomorrow is being filled by inventors and dreamers like Jack Sim and others who gathered this week in Macau. Among their larger visions for collective waste disposal and treatment on display was a network of low-water toilets that separated solids from liquids and assigned them to reservoirs shared by an apartment building or block of houses. Those resevoirs would then produce fertilizer, soil conditioner and energy producing methane — and dramatically cut the cost to the public of waste disposal.

But for many people, this is just hot air. "We have the luxury of flushing the toilet and just seeing it disappear," says George. The industry is stalled not only by that convenience, but by taboo. "People are uncomfortable talking about their own waste." It may have been quite some time since relating the adventures of your most recent bowel movement has constituted acceptable fodder for conversation, but nevertheless, says George, our 'bodily products' have to come back into the conversation somehow, if we are ever going to flush away the flush.