Above: Image © anek suwannaphoom, iStockphoto.com

Have you ever visited a large animal enclosure at a zoo? If you have, you probably noticed just how much poo is produced by animals like rhinos, pandas, and elephants. At the time, you may have giggled or held your nose. But you probably didn’t think about the potential to use animal waste to power your home. Yet the Toronto Zoo and the non-profit organization ZooShare Biogas Co-operative are working together to change these steaming piles of potential into electricity. They plan to open North America’s first biogas plant. This plant will convert animal poo and grocery store food waste into useable energy.

Did you know? If the plant is a success, there are plans to expand the project to other zoos across North America.

Biogas refers to the gases produced when bacteria break down waste in the absence of oxygen and light. The process by which biogas is created is known as anaerobic digestion. This is similar to how a cow breaks down food in its many stomach compartments. At the Toronto Zoo biogas plant, zoo poo will be combined with food waste from local grocery stores and then added to a concrete digester tank. This will lead to a steady supply of biogas (made up of methane and carbon dioxide) and digestate (odor-free fertilizer).

So how exactly does the concrete digester take food and animal waste and turn it into fuel? It’s more chemistry than magic. The food waste and zoo poo are added to the digester. Then it is heated and mixed for a period of about 60 days. During this time, anaerobic digestion occurs. The proteins, carbohydrates, and fats in the food and poo waste are converted into a mixture of methane and carbon dioxide. This happens through a four-step process:

The biogas that is produced will be used as fuel for an engine that will transform the chemical energy into electricity and heat. ZooShare plans to sell the electricity generated to the Ontario power grid. They will recycle the heat that is created for use in the digester tank.

Large animals produce a lot of manure. This means that there is always plenty of poo at the zoo. It also means that biogas can be considered a renewable source of energy. For example, an adult African elephant can leave behind about 150 kilograms of poo in one day. The Toronto biogas plant will have the capacity to handle 3,000 tonnes of animal waste and 14,000 tonnes of food waste each year. This is enough to produce electricity to power 250 homes.

Did you know? Community bonds are being sold to raise capital for the Toronto Zoo biogas project. If you believe in poo power, you can purchase bonds on the ZooShare website.

Providing renewable energy won’t be the only way that the biogas plant will be helping the environment. The food and animal waste used as fuel at the biogas plant would normally be sent to landfills. There, it would naturally decay. As it decays, it will release methane and carbon dioxide into the environment. These greenhouse gases trap heat in the atmosphere and contribute to global warming. By trapping these gases in a concrete digester and using them to produce electricity, ZooShare estimates that the plant will annually reduce emissions by the same amount as produced by 2,100 cars.

So if there is so much pootential to create energy from animal waste, what about all the human poo that is created every day? Are you flushing away a valuable source of energy? It turns out you are! Cities across the globe have already begun tapping into their sanitary sewage systems to reduce their reliance on fossil fuels and lower their greenhouse gas emissions.

For example, the city of Olso in Norway has converted 80 city buses to run entirely on biogas collected from sewage treatment plants. In Canada, the city of Hamilton has been using biogas from wastewater treatment plant digesters to generate electricity and heat since 2006. Larger North American cities, such as New York, also see biogas production as a possible energy option.

So it turns out that our stinkiest everyday waste can be recycled into green and renewable energy. And it will be helping to lower greenhouse gas emissions in the process. From heating buildings to powering gadgets, poo power can go a long way!

This article was updated by Let's Talk Science staff on 2016-09-12 to improve readability by reducing the reading grade level.


General information

About Biogas (Biogas Association)
Biomethane Production at Ontario Wastewater Treatment Plant (Peter Gorrie, BioCycle)
Greenhouse Gases, Climate Change, and Energy (US Energy Information Administration)
Norway or the Highway: Poo Powers Oslo Buses (Dave Demerjian, Wired)
The Scoop on Poop! (San Francisco Zoo and Gardens)
Toronto Zoo project (ZooShare Biogas Co-operative)
What is Biogas? (ZooShare Biogas Co-operative)

Scholarly publications

Weiland P. 2010. Biogas production: current state and perspectives. Applied Microbiology and Biotechnology. 85(4):849–860.

Emily Nichol

Emily Nichol is a wildlife biologist based in Yellowknife, NT.

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