Using local energy sources such as lake water, wood waste or even garbage to heat and cool buildings is one way for communities to cut their greenhouse gas emissions — the goal of this week's UN climate summit.

In district energy systems, instead of having an individual heating and cooling system for each building, multiple buildings are hooked up to a central system — similar to how buildings are connected to the municipal water service instead of each one relying on individual wells. Heat is distributed to buildings via pipes that typically carry hot or chilled water.

It's an idea endorsed by the United Nations Environment Programme, or UNEP, which calls district energy a "key measure for cities/countries that aim to achieve 100 per cent renewable energy or carbon neutral targets."

Once the distribution is set up, almost any energy source can be plugged in, depending on what's available locally and what will benefit the community.

Here's a look at what six communities across Canada have done.

Location: Charlottetown, P.E.I.

Technology: Waste-to-energy/biomass

Year: 1986 

The wood waste used to come from a sawmill, but that shut down so now the wood is from forestry and land clearing. It was originally built to address a shortage of landfill space.

The local landfill doesn't have systems to collect methane, a powerful greenhouse gas produced by decomposing organic waste. So by sending garbage to be burned in this system, it both prevents the methane from going into the atmosphere (burning generates carbon dioxide, a less potent greenhouse gas, instead) and displaces natural gas that would otherwise be burned to generate electricity, says Carlyle Coutinho, president and chief operating officer for the Canadian region for Enwave Energy Corp.

Because P.E.I. relies heavily on power imported from New Brunswick, the availability of a local source of power and heat also makes the island more resilient in case of natural disasters.

The company plans to expand to take more of the province's waste and generate more electricity.

Deep Lake Water Cooling System

Location: Toronto

Source: Deep lake water cooling

Year: 2004

Toronto sits on the edge of Lake Ontario, allowing this system, also run by Enwave Energy, to draw cold water from its depths to cool 150 buildings in downtown Toronto, including hospitals, educational campuses, government buildings, commercial and residential buildings. In January 2019, the federal government announced an expansion to an additional two million square metres of floor space – the equivalent of 40 to 50 buildings.

Coutinho says the system saves electricity that would have been used for air conditioning and water that would have evaporated from cooling towers.

He admits working in a built-up environment like Toronto, where distribution pipes need to be installed deeply in order to avoid other underground infrastructure and many buildings need to be retrofitted, is more difficult than installing in a new building. But the high density makes it easier to reach many customers.

Read the full article on CBC's News Site 

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