Water, Pollution, Electricity Problems? Sewage Could Be the Solution

Earlier this month, Bill Gates made headlines around the world by drinking a glass of water. Five minutes beforehand, it had been human sewage.

The water was made by the OmniProcessor, a self-contained unit supported by the Gates Foundation that is targeted at helping the billions of people in the developing world who have no access to sewage sanitation, and who need clean potable water, electricity, and agricultural fertilizer.

For us in the developed world, it is a great example of how viewing issues as interrelated can turn a whole set of problems into solutions.

Thinking about sewage not as waste but as a resource shifts thinking about four vitally important areas of public concern:

• How to supply enough clean potable water for people to use
• How to generate enough electricity to meet rising demand
• How to handle human sewage as population grows and becomes more dense
• How to reduce pollution from fertilizer and chemical runoff from agricultural facilities

Right now, each of these is a very expensive proposition. But inventors and entrepreneurs are discovering that if addressed together, these problems can help solve each other, dramatically reducing costs, potentially paying for themselves, and possibly even generating a profit.

Producing safe drinking water and treating sewage costs about $7.5 billion a year in the U.S. alone, and the processes requires as much as 2 percent of total national electricity consumption, according to a June 2014 report from the U.S. Department of Energy [PDF].

Many of these treatment systems are wearing out, and need investment to be able to continue handle their existing workloads, much less accommodate future growth. The total cost estimate is nearly $700 billion over the next 20 years, according to that U.S. DOE report, which calls for combining elements of national energy and water policy efforts to promote self-sustaining wastewater treatment plants.

The water in sewage can be separated and purified. Bacteria that digest the waste produce methane that often qualifies as a renewable fuel, and can be burned to produce electricity or replace natural gas from deep underground. Left behind are nutrient-rich solids.

Several companies are trying various methods to do this:

• Improvements to digester designs mean future versions of today’s sewage plants could handle disposal of additional amounts of material, such as food waste from commercial food companies and even sludge from older sewage facilities.
• The OmniProcessor boils sewage, collecting the water vapor for purification, burns the remaining solids to generate electricity, and leaves behind ash that can be used to fertilize crops. See a video of how it works.
• A “microfuel refinery,” as its inventor terms it, microwaves sewage to dry it out, and then runs an electrical current through the dried waste. The vapor that’s produced can be condensed into a diesel fuel substitute.
• Sewage also has latent heat that can be recovered to provide heat and hot water for buildings.

These approaches don’t solve every problem relating to sewage, water or fertilizer. For example, the issue of latent toxics and pharmaceuticals in sewage solid waste remains, as does the potential for sewage-generated fertilizer to be applied in quantities that run off and pollute waterways.

But they make strong starts – and more importantly, encourage people to shift their thinking away from trying to solve individual problems, and toward thinking of the world as an interdependent system. Undoubtedly, new policy tools will be needed to help tap the potential of these silo-busting solutions.