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PartnerWasser & Hygiene

How Sewage Can Be Turned Into Profitable Energy

By Jens Berggren, Communications Director, Stockholm International Water Instititute

Some 10 years ago, in 2007, the British Medical Journal held a poll among its readers on the most important medical breakthrough since the journal was first published in 1840.

The field obviously held some strong contenders, such as the discoveries of antibiotics and anesthesia, but the overall title was claimed by – drumroll – sanitation.

For me, it was wonderful to see the humble toilet placed on a pedestal for once. 

Poo on the podium?

Looking back at the winners of the Stockholm Water Prize and the Stockholm Junior Water Prize, competitions aimed at recognizing excellence in solving the world’s water issues, champions and solutions related to poo and its management are well represented — quite a feat in itself, given the prizes’ prestige and royal glamour.

This year’s Stockholm Water Prize Laureates, Professors Bruce Rittmann and Mark van Loosdrecht, have studied, invented, and constructed new ways of working with our smallest helpers, the microbes, to improve the conversion of sewage into resources such as water, energy, and nutrients. This could mean a significant step toward more — and better — treatment of the world’s waste.

A disgusting 80% of the world’s sewage spews untreated out into our bodies of water. The bacteriological burden of this gross mismanagement is obviously awful in itself, with 1.8 billion people using and consuming water contaminated by feces. To make matters worse, the pollution of our freshwaters inevitably leads to pollution of our seas. Seas become overfed with fertilizing nutrients, causing algal blooms that deprive sea floors of oxygen, resulting in so-called "dead zones" where no fish or crustaceans can live. So, while the toilet has done a lot of good for humanity’s health over the past one-and-half centuries, some of the challenges have been moved, from our cities to our seas, rather than solved.

Solving sanitation

I think that a key to solving sanitation is understanding that pollutants, rather than being something inherently bad, are something potentially valuable that happens to be in the wrong place, in an unsuitable mix or incorrect concentration.  The challenge then is to, firstly, figure out where a compound with these abilities could be of value or how it can be converted and, secondly, understanding how to safely separate, move, and refine it.

Take Action: Urge World Leaders to Take a Stand for Sanitation

Good use for bad gases

Most of the organic material that clogs several of the water bodies of the world uses up the dissolved oxygen in the water when decomposing. The nutrients released create a boom of growth at the surface increasing the amount of decaying organic material. When the oxygen is used up, anaerobic bacteria start converting the remaining organic material to methane gas, a greenhouse gas over 70 times more potent than carbon dioxide. But methane is also an excellent fuel in combustion engines, containing more energy per kilogram than other fuel sources, such as diesel. By burning methane, it is converted to carbon dioxide and water, greatly reducing its global warming potential.

It is estimated that wastewater contains 5 to 10 times the energy required to treat it as well as all the nutrients contained in our food and other compounds from our household items. All of these could be salvaged from sewage or converted into raw materials, creating a circular economy.

The 2018 Stockholm Water Prize Laureates have found ways to improve the output of valuable resources from our treatment plants while at the same time reducing the costs for their construction and operation. And the possibilities for using microbes to clean up our waters by converting it into bioplastics and other polymers are only in their infancy. So, rather than seeing treatment plants as places where dirt is being managed, we should start looking at them as high-tech raw material and energy factories.

When it comes to killing several birds with a single stone, sanitation management seems to have huge potential. It has sometimes been said that water could be the new oil, referring to it as a potential source of regional instability. Could it be so that sanitation instead is the new oil for its ability to provide us with energy and plastics while, protecting us from diseases, dead zones, and climate change?

If it is, I see plenty of glitzy prizes coming sanitation’s way.