The Top 6 Ways to Convert Poop Into Electricity

Posted by Trish Riley, July 16, 2009

More on the potential for poop power:

More than half of the 15 trillion gallons of sewage Americans flush annually is processed into sludge that gets spread on farmland, lawns, and home vegetable gardens. In theory, recycling poop is the perfect solution to the one truly unavoidable byproduct of human civilization. But sludge-based as fertilizer can contain anything that goes down the drain—from Prozac flushed down toilets to motor oil hosed from factory floors. That’s why an increasing number of cities have begun to explore an alternative way to dispose of sludge: advanced poop-to-power plants. By one estimate, a single American’s daily sludge output can generate enough electricity to light a 60-watt bulb for more than nine hours. Here are the six most innovative ways that human waste is being converted to watts:

via The Top 6 Ways to Convert Poop Into Electricity | Mother Jones.

Comment on this article in the forums

  1. 1. Ed Brown Says:

    Trish,

    Thanks for posting this.

    The sludge from the GRU wastewater treatment plant gets processed and then driven to Archer where it is spread on a farm that grows food for animals.

    That sludge has a huge amount of embodied energy in it. The process starts when we pump pristine water out of the Floridan aquifer and then pump it long distances to everyone’s house. When the poop is deposited and is flushed down the toilet it again gets pumped long distances to the wastewater treatment plant. We send pristine water to our homes to collect waste, much like we send trucks to our homes to pick up trash and materials to be recycled. Once the water is processed some of it goes to water lawns in the SW and the rest gets injected back into the Floridan.

    GRU is GRU’s biggest customer/user and I was told by the head of the wastewater treatment division that about 20% of the energy GRU uses is used just to pump the water to and from our homes – lots of energy that is produced by burning coal and natural gas from outside Florida. Then more energy is used to process the water and poop.

    By the way, most of the fertilizer we import from around the world that goes into our food is found in that poop.

    Pumps are some of the most energy intensive machines know to man. Can you imagine how much fossil fuel and nuclear energy is required to pump 15 trillion gallons of water/sludge. And what about all the toxic emissions released at the power plants where the electricity to power the pumps is generated?

    Using this method to process our poop is very energy intensive to get it to the point where we will process it into energy for us to burn. Is the energy return greater than the energy used? Does the energy return analysis include the energy used to get the sludge to the plant for processing?

    As clean water and energy supplies decline in the future, this way of processing our waste will become very expensive! It does not make sense to me to invest billions or trillion of dollars in a wastewater treatment process that will not be sustainable in a short time.

    So what do we do with the poop? Use it for fertilizer like over half the population of the world does. Why burn all the nitrogen, potassium and phosphorous in the poop (from the farm that grew our food) that can be used to fertilize our food. When we burn this stuff, we need to take more natural resources from the Earth to fertilize our food. This seems like a very inefficient way of creating energy.

    As you know, I have a composting toilet and use no water in the processing of my poop. No water is taken from the Floridan to process and transport the poop. No energy is needed to pump the water or process the poop. I compost my solid and liquid poop and use the compost on the fruit trees and bushes. The nitrogen, potassium and phosphorous is recycled on site into new food without any energy and water required for processing.

    Systems are available to compost our own waste that are safe and efficient. We should be putting our energy and investments into these processes.

    My belief is we should not create systems that are going to require large energy inputs for them to function. Wastewater treatment is one of the most energy intensive processes we have. We should be reducing our need for this energy, not increasing it.

    I find the thought of injecting sludge into a mile-deep well to be dangerous. There is a saying that goes something like this – “you should not poop or pee in your own water”. This idea will come back to haunt our kids and their kids.

    Ed

  2. 2. Trish Riley Says:

    Agreed again, Ed. I like the composting toilet system you’ve implemented in your home. And the process of spreading sludge on farmland is not only water intensive, but also poses a problem by spreading the petrochemicals and pharmaceuticals in human waste onto our farm fields, impregnating our foods with these synthetic chemicals, some of which are known to be dangerous and many of which pose as yet unknown potential hazards.
    I share your concern about the deep wells, too. Anytime we dig down into the earth, whether to mine minerals or water or to try to bury our wastes out of sight, we are damaging the structure upon which we depend. When we dig into our limestone aquifer, we fracture the stone that filters and protects our pristine water supply, polluting it with waste and opening it up to intrusion from salt water, which makes it unusable for our drinking needs. These kinds of solutions, like carbon sequestration and burying radioactive waste, are not solutions for the future – they are time bombs we’re leaving behind for our kids.
    None the less, I do hope that solar- or wind-powered solutions to managing livestock waste can be found without causing by-product harm to our environment. Perhaps the ideas described in this article will be further developed to meet all of these concerns.

Recent Headlines