Garbage as a Renewable Resource

Cheap alternative energy may be no farther than your nearest landfill.

Mark Redwood has a keen appreciation for garbage.

As a research fellow with the University of Birmingham’s Unit of Functional Bionanomaterials, Redwood has helped develop a process that uses bacteria cultures to convert food waste into hydrogen fuel.

“There are special and yet prevalent circumstances under which microorganisms have no better way of gaining energy than to release hydrogen into their environment," wrote Redwood in a Microbiology Today article. "Microbes such as heterotrophs, cyanobacteria, microalgae, and purple bacteria all produce biohydrogen in different ways."

Redwood and his fellow researchers are hopeful that “waste to energy” processes might give consumers around the world a clean and affordable energy source while reducing the flow of garbage into landfills.

“The world today faces a triple threat of growing waste volumes, declining disposal options, and limited energy resources,” reads the Web site of Biowaste2Energy Ltd., a firm co-founded early 2008 by Redwood’s university research unit and outside agencies to further develop and promote waste-to-energy technology. The site touts the method as one that “dramatically reduces the waste volume, while providing clean energy.”

The Biowaste2Energy process involves two storage tanks, one that houses cultures of fermentative bacteria and another that teems with photosynthetic bacteria. Machines churn the food waste up and pour it into the fermentative-bacteria tank, whose micro-residents munch away and burp quantities of hydrogen for use as fuel.

The fermentative bacteria also emit acid compounds that drain into a photosynthetic bacteria tank, where other bacteria convert the compounds into even more hydrogen for fuel use.
Garry Golden, a futurist and energy consultant, says the process is so simple and involves equipment so portable that homeowners might someday buy waste-to-energy disposal units for their homes and produce their own electricity. Golden estimates that a household with a lot of biodegradable trash might save as much as 20% to 30% on its monthly energy bills.

“People can start extracting energy from their own sources on site,” he says. “You’re looking at more localized production and storage.”

Many villages in Costa Rica already practice a form of waste-to-energy scheme, according to Rachel Tubman, University of Houston future-studies graduate assistant. Tubman has researched villages in which residents truck their homes’ food waste and animals’ excrement into a community tank unit; bacteria and enzymes break it all down into a natural gas that villagers use for heating and cooking. The leftover solid compounds make for a highly nutrient-rich fertilizer.

“It amounts to taking something that is considered the bane of our existence and making it a positive thing,” says Tubman. “In an energy-constrained society, every piece of biomass becomes valuable.”

Golden notes that the United States currently consumes 3.8 trillion kilowatts of electricity a year. He calculates that if the United States converted all 170 million tons of the garbage it currently incinerates or sends to landfills, it would get a yield of 93.9 billion kilowatts of energy a year—2.4% of the current energy need. But even 2.4% could prove to be a substantial saving for many consumers who worry about energy expenses.

“It doesn’t save the world,” he says. “But if GE or some company can design a bioenergy appliance and sell it to homes in America, that is a great way to reduce waste, a great way to reduce the cost of energy, and a great way to improve the environment. There are a lot of positives.” —Rick Docksai

Sources: “Life’s a Gas…and it’s Hydrogen,” by Mark Redwood and Lynne Macaskie. Microbiology Today. Society for General Microbiology. Web site www.sgm.ac.uk.

Biowaste2energy Ltd. Web site www.bw2e.com.

Garry Golden. The Energy Road Map. Web site www.garrygolden.net.

Rachel Tubman, University of Houston. Web site www.uh.edu.