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Sewage Heat Recovery: Surprisingly Clean Energy

Sewage heat recovery doesn’t sound like the most sanitary energy efficiency concept out there, but it may prove to be a great renewable resource to reduce energy needed to heat the water that makes it to our homes.  Wastewater consist of sewage from toilets, but also warm and hot water from shower and sink drains.  In fact, most of the water in wastewater pipes comes from showers, sinks, dishwashers, and washing machines.  All of these are sources of hot water that can be used as renewable energy.

A sewage heat recovery system takes advantage of the warmth of this water and uses it to warm up clean water instead of letting that heat get wasted down the drain.  This water usually remains around 60°F – 65°F in temperature.  This may vary a few degrees due to seasonal temperatures and geographical location, but the fact is that it takes much less energy to heat water already at 60°F than it does to heat cold water.  What heat recovery systems do is use heat pumps to capture the warmth from wastewater and transfer it to the clean water.  The system keeps the wastewater separate from clean water at all times; the two never come into contact.  Vancouver, British Columbia is the first major North American city to implement this technology.  The False Creek Energy Centre still provides 70% of the energy needed to power the Olympic Village neighborhood that housed athletes in 2010.

Wastewater heat recovery works the exact same way geothermal heat pumps work, but with one major advantage.  Geothermal heat pumps, which use Earth’s underground temperature to produce energy, require deep digging underground to tap into Earth’s natural heat.  Sewage recovery systems can be installed without major digging beneath a building to find a heat source or install equipment.  All that is needed for sewage heat recovery is access to a building’s wastewater pipes.  Heat recovered from sewers is also about half the cost of a geothermal system, so this process is economically sensible.

North American cities are starting to realize that there is a valuable energy resource flowing right beneath the ground.  Philadelphia and Seattle are just two cities that are experimenting with sewage heat recovery projects.  Currently, most of these recovery systems are designed to work with individual facilities, but the technology is still young, so perhaps cities will soon be able to contribute to large-scale heating and cooling costs by catching heat from the water we send down the drain.

Jessica Kennedy
Energy Curtailment Specialists, Inc.

Jessica can be found on Twitter and Google+.

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