US is flushing 350TWh of energy down the drain every year. Here's why?

As the temperatures dip during winter months, one cranks up the heating to stay comfortable indoors. Not just humans, even our devices like washing machines and dishwashers work with hot water. Put together with hot showers, Americans are flushing 350 terawatt hours (TWh) of energy down the drain every year.

350 TWh is the amount of energy that could heat 30 million homes while helping reduce . As countries race to reduce their fossil fuel dependence, there is a demand for renewable sources of energy that can meet our energy requirements without spewing carbon dioxide and methane into the atmosphere. While these technologies need time to be scaled up, there is a huge untapped source of energy available right beneath our feet, and solutions to tap into it already exist, says from global engineering firm– Donfass.

What is excess heat? Excess heat is the terminology used to describe heat generated during the operation of a device which then has to be let out since there is no use for it. An internal combustion engine, a refrigerator, or data centers all produce excess heat that is usually let into the atmosphere.

However, heat generated from showers, washing machines, and dishwashers enters the sewage system where it can be recovered and repurposed. This isn't something that municipalities in the US are doing. According to a from the London South Bank University, the heated water discharge is leading to a loss of 350TWh of energy every year.

How can this be avoided? The unused heat from the sewage can be recovered using heat pumps before it reaches the treatment plants. At 68 Fahrenheit (20 degrees Celsius) sewage water is only mildly warm but heat pumps can capture and concentrate this to produce water that reaches 176 Fahrenheit (80 degrees Celsius).

Such a facility has been currently operational in False Creek, Vancouver since 2010, a said. "What's exciting is that our heat recovery system operates at efficiencies of over 300 percent," Derek Pope, facility manager told the . "For every unit of electricity that we put in to run the heat pump, we get over three units of thermal energy or heat out of it." More than 6k residents in the neighborhood warm up their homes using recovered heat through a system that works well even in frigid winters when the demand is highest.

Buildings in Vancouver are responsible for 50 percent of greenhouse emissions since they use natural gas for heating. This approach of recovering heat, if adopted widely, can help reduce the consumption of fossil fuels, thereby leading to emission improvements. Not just a neighborhood in Vancouver but even densely populated areas in Stockholm, Sweden have adopted this approach and now provide heating to 800,000 residents.

The system is completely underground and further uses digested sludge to produce biogas to fuel the city's buses. In the Danish city of Aarhus, the facility treating sewage water ends up producing 600 700MW of energy, the equivalent of a large power plant from the . Experts told the , that tapping into this continuous resource could help the US reach half of its targets for carbon reduction..