Power Knot LLC

Toronto Hospital Biodigests Leftovers, Turns Food Scraps into Drain-safe Grey Water

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Source: Power Knot LLC

Toronto, On -- Runnymede Healthcare Centre turns food scraps into environmentally-safe grey water by dumping the waste into a biodigester instead of a dumpster. Located in the hospital’s main kitchen, the machine enables the hospital to cut food waste hauling costs in half, eliminate odors, cut carbon and methane emissions, and stay ahead of Ontario’s plans to divert more food waste from landfills.


The LFC-100 biodigester at Runnymede Healthcare Centre decomposes about 110 kg (242 lb) of waste food a day into drain-safe ‘grey water’.

In 2015, the hospital launched a five-year strategic plan declaring it would “implement strategies and technologies to lessen environmental impact, cut operating costs, and improve the health of our community.” As a result, Runnymede has won five consecutive Greening Healthcare 5% Club Awards for reducing energy consumption by 5% relative to the previous year. In the past five years, the hospital has reduced energy consumption by 25 percent, earning it a Greening Healthcare Rising Star Award.

Food waste disposal then and now

Food waste was previously disposed of in two ways: through the kitchen sink garburator that shreds waste into particles that can pass through piping or in garbage bins that were hauled to landfills. After exploring options to improve its food waste disposal, Runnymede decided on a model LFC-100 biodigester from Power Knot of San Jose, California. “Our food service staff puts food waste into the unit from eight in the morning until 7:45 in the evening,” explains Westwater, adding, “The machine works around the clock.”

Rotating paddles inside the unit’s U-shaped vessel slowly churn waste food with infusions of hot and cold water, oxygen, and porous plastic Powerchips™ media that distribute microorganisms and Powerzyme™ enzymes that accelerate the decomposition of solid food waste. After 24 hours, the nutrient-rich grey water is routed harmlessly down the drain. The entire procedure is odor-free.

Biodigestion of anything edible

“The unit can convert anything that is edible into drain-safe grey water,” says Westwater, adding, “It cannot digest soup bones and a few other things, but these are not in our food stream for patients anyway.”

Daily biodigester consumption varies depending on the number and type of meals served, but the Runnymede kitchen staff has determined its machine has an effective capacity of about 110 kg (240 lb) of waste food a day.

Using a touch screen, the staff can display information on digestion rates, updates and service alerts, drum temperature, door openings, water volume, water temperature and weight of the food waste digested by hour, day, week, month, and year.

The LFC-100 is connected to the Cloud, allowing operators to access stored data using a laptop, tablet, or smart phone, as well as to program the biodigester and send emails with performance summaries and service reminders.

Diverting food waste from landfills cuts methane emissions

In landfills, food waste decomposes anaerobically (without oxygen) emitting methane gas (CH4) which is 72 times more harmful to the environment than carbon dioxide (CO2).

By contrast, the LFC biodigester decomposes food aerobically (with oxygen), producing only water, CO2 and heat to 42ºC (108ºF), with no methane. The CO2 created is part of the natural cycle of carbon generation from plants, making the process carbon neutral.

“There is no need for daily maintenance, other than cleaning of the machine’s exterior,” Westwater says. “We don’t put any chemicals in it. It runs on its own. It doesn’t give us any issues.”

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