Human waste as an alternative energy source

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With all the recent news buzz about renewables like solar and wind and even harnessing the power of ocean waves, an often overlooked source of energy is right under our noses, so to speak: human waste. It may not be as attractive or enjoyable as other alternatives, but generating energy from human waste may be the most important. With the demand for energy and resources, the world population is increasing every day and resources are becoming more scarce and coveted. The only potential resource growing in proportion to the population is our own waste. Feces and urine are readily available wherever there are people. Currently, large amounts of energy and (often drinking water) from the combustion of fossil fuels are used to dispose of the above-mentioned wastes. New projects in composting toilets, biogas harvesting, biofuel creation and even microbial fuel cells could allow us to turn the cycle around and harness this untapped resource.

While skeptics believe composting toilets will never succeed in the Western world, new and old technologies are being used to solve two problems: what to do with our waste, and how to produce enough food without poisoning us with expensive chemicals Fertilize ourselves and our environment. Next-generation composting toilets, such as those made by Clivus Multrum, are addressing these issues and making the system more attractive to consumers. They make low-flow composting toilets that include basement compost bins, and products that include services. Estamos, an African NGO, is using a much lower-tech composting toilet. While the group’s goal is to improve sanitation and reduce disease, their programs are also helping small farmers earn a living. The organization provided composting toilets for free, greatly improving the quality of life of many poor families. The group’s director, Feliciano dos Santos, has just won the 2008 Goldman Sachs Ecosan Environmental Award for this work.

Many countries have well-established methane capture programs using animal manure, such as pig farms in Australia and cattle farms in the United States. But what about the gas-producing potential of human waste? Developing countries are pioneering the technology as a way to save money and create renewable energy. With the help of Heifer International, farmers in Uganda’s Mukono region are mixing human waste and urine with other biowaste, such as water hyacinth and banana peels, to produce biogas and use the by-products to fertilize their fields. The biogas produced is 60-90% methane and is used for lighting, cooking and some engines, and many residents are improving their quality of life and lifting themselves out of poverty. Likewise, Rwanda’s Cyangugu prison is producing biogas from inmates’ excrement. The Kigali Institute of Science and Technology built biogas digesters for prisons, using the resulting products to cook 50 percent of inmates’ meals, saving $22,000 a year—a huge sum in Rwanda. But developing countries aren’t the only ones using human-generated methane. The Lionsgate Wastewater Treatment Plant in Vancouver, British Columbia, which has been sued for violating federal pollution laws, has piloted a $1.1 million project to capture methane from municipal sewage and send it directly to the natural gas distribution system. The project, expected to be operational in 2009, is expected to reduce greenhouse gas emissions by 500 tons per year and generate enough energy to power 100 homes. A similar project is underway in San Antonio, Texas.

The current debate surrounding plant-based biofuels centers on competition between food crops and biofuel crops, and many experts worry that high demand for biofuels will exacerbate current food shortages. Several projects are addressing this problem by making biofuels from algae grown on human waste. One of these is Aquaflow Bionomic Corporation, which harvests algae for use in sewage treatment ponds in Marlborough, New Zealand. The “green crude oil” they extract from the algae can be used in all crude oil applications such as gasoline, diesel and plastics. In a more direct process, a Canadian company called Dynamotive Energy Systems Corporation is using a “fast pyrolysis process” to feed human waste directly into a biofuel generation system. The system achieves 80% efficiency by recovering exhaust gas and heat generated during the process, and the final product, BioOil®, can be used as a substitute for many petroleum products. The development of microbial fuel cells is one of the highest-tech, cutting-edge technologies for creating energy from human waste. Developed by Dr. Bruce Logan of Penn State’s engineering department, the system has been suggested as a way to take waste treatment plants off the grid. Fuel cells, still being refined to produce acceptable energy output, use waste water to produce hydrogen fuel and produce clean water as a by-product. While the technology is not suitable for other fuel cell applications such as hydrogen-powered vehicles, it could be used anywhere there is a large amount of biological waste.

Many people cringe at the thought of an energy system based on human waste, preferring not to think about what happens in the pipeline, but as humanity’s need for energy grows, we must begin to employ unconventional production methods. With the increasing success of the aforementioned projects, the possibility exists to eliminate global human waste pollution. One day, our sewage may be called “brown gold” and may even be worth more than crude oil.

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