Sewage-to-energy could cut costs as well as reduce greenhouse gas emissions
Most Americans flush the toilet without thinking twice about where the contents end up, but a handful of companies are paying close attention to what goes down the drain. They argue it should be seen as a resource rather than waste.
Dealing with human waste is a tricky business. The wet material typically has to be treated at a sewage plant, dried and turned into a biosolid, then either hauled away to a landfill or turned into mulch and reused as fertilizer.
According to the U.S. Geological Survey, wastewater treatment plants generate about 7 million dry tons of biosolids per year. The conventional methods of dealing with this waste are expensive and energy-intensive. Landfills are also filling up, and sludge that’s turned into fertilizer may still contain chemicals that are potentially harmful to humans and the environment.
Now, some companies are saying this method of dealing with waste is just plain wasteful.
That’s where sewage-to-energy comes in. Industry estimates show that if all biosolids in the United States were converted into biomass energy, they would produce 7 million to 7.6 million megawatts of power. By way of comparison, the current installed capacity of wind power in the United States is around 43,000 MW.
By essentially recycling the waste as electricity or converting it to biodiesel fuel, rather than putting it in a landfill, converting sewage into energy also reduces greenhouse gas emissions. The global warming effect of methane produced by decaying landfills is about 20 times more powerful than that of carbon dioxide. The waste conversion process avoids these emissions by capturing the gas and turning it into a product.
“There are truly not many options for dealing with sewage, but [municipalities] need to address it somehow,” said Dennis Wherrell, CEO of Earth, Wind & Fire Technologies. So why not turn dirty waste into clean energy?
Wherrell’s Florida-based company is one of just a few in the world with the technology to run sludge-to-energy operations on a consistent basis. There is still some distance to go before these companies are fully commercialized, but progress is being made. “This is not a pipe dream on a drawing board for us,” said Wherrell.
Finding the money in sludge
Since the year began, Earth, Wind & Fire has started writing up contracts and engineering plans at over 50 sites around the world, most of which are in the United States, said Wherrell. The company is focused on establishing its new technology in Tennessee, Alabama and Florida, but is already in the process of manufacturing the third unit of a project being sent to Belgium.
Traditional waste disposal is not cheap. For instance, Pasco County, Fla. — where Earth, Wind & Fire recently struck up discussions on a new project — pays $800,000 per year to deal with its sludge. Daytona Beach spends $500,000, and Orlando spends an amount in the millions, said Wherrell.
Eager to pay less, municipalities are turning to other sewage options. Another major sell for his company, said Wherrel, is that cities and homeowners won’t pay a dime for one of his plants. Earth, Wind & Fire will cover all capital expenditures and earn them back by selling the biodiesel or electricity that’s produced in the treatment process.
The company’s income stream starts with taking the waste and microwaving it. The process uses pellets of dried human sludge and carbon-based landfill material, runs an electrical current through it, captures the vapor that’s produced and then condenses it into a No. 2 diesel fuel.
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