Think Globally, Act Locally: Net-zero impact development

A bird’s-eye view of the proposed CCR development.
A bird’s-eye view of the proposed CCR development.

Edmonton City Centre Redevelopment
The City of Edmonton held an international competition for a redevelopment plan of its downtown municipal airport. The project was required to be carbon-neutral for 30,000 people in a world-class sustainable neighbourhood. The local coal-fired electrical grid has an emission rate of about 860 kg CO2/MWh, so this posed a significant challenge. Figure 5 shows an overview of the proposed development.

The planned density for the project is about five times as dense as the surrounding residential areas. A large park with lakes is included in the plan with 90 per cent of the development’s residents within a two-minute walk to open park space. The lakes are used for stormwater storage and water reuse for irrigation. Portions of the park extend into the Agrihood on the west side—an area planned to support community-scale urban food production. The existing light rail transit (LRT) system is being extended through the east side of the development with a new tram system to provide local transportation.

To achieve carbon-neutral operation, a district energy system for electricity generation and heat distribution has been planned. Fuelled mainly by waste biomass, boilers will produce heat for organic-rankine-cycle (ORC) generators that send waste heat to the district heating grid. Geothermal options at 6 km (3.7 mi) deep for electrical power generation and 3.5 km (2 mi) deep for district heating will be examined. (The project will be deemed carbon-neutral with or without the deep geothermal. The deep geothermal system is an alternative, carbon-neutral energy source that will need government or other funding to occur). Planned biomass fuel includes waste wood from the forest industries, clean waste wood from the Clover Bar waste-handling facility, and dried sewage sludge from the Gold Bar sewage treatment plant. (Although transportation emissions are not included in the carbon-neutral calculation, emissions are significantly reduced compared to the current case). A significant amount of the biomass fuel for the initial project phases can come from urban waste generated by the City of Edmonton. Flue gas emissions will be cleaned.

Excess electrical power generated will be sold to the grid as green power. The district heating system will be extended offsite to nearby hospitals, colleges, the legislature, and city hall for the initial development of an urban district heating grid. In this way, full use of the electrical and heating output of the District Energy Plant can be realized in a carbon-neutral manner. In fact, the sale of electricity and heat for use offsite will reduce GHG emissions in Edmonton and create a ‘beyond-carbon-neutral’ development.

Greenhouse gas (GHG) emissions from CCR over the potential 20-year development timeframe.
Greenhouse gas (GHG) emissions from CCR over the potential 20-year development timeframe.

Over the potential 20-year development timeframe, this project will actually reduce the overall CO2 emitted in Edmonton by 3.2 million tonnes—a significant savings compared to a business as-usual case (Figure 6). All electrical power used onsite will be generated by the district energy system on an annual-use basis. Some power will be drawn from the grid during the day while more excess power will be supplied over the night, making for a net-positive generation of electricity.

Building energy use requirements have been suggested so developments onsite would comply with the proposed energy target of meeting American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-13, Energy Standard for Buildings Except Low-rise Residential Buildings, minus 20 per cent to present efficient building operation for the first projects opening in late 2015 or 2016. Additionally, it is hoped some projects will meet Germany’s Passivhaus standards. Meeting the proposed performance level would reduce the size of the electrical power generation plant from 24 MW (if current building standards were used) to 18 MW, with a significant capital cost savings in the District Energy Plant.

Potable water use in Edmonton is among the lowest in North America at 209 L (55 gal) per person daily. A purple pipe reclaimed water use facility is planned to provide water for flushing toilets, landscape irrigation, and lake level top-up—this will reduce daily potable water consumption to 139 L (37 gal) per person. Some of the sewage from the site will be mined and reclaimed for non-potable water; the harder-to-treat sewage solids would continue to the Gold Bar sewage plant for a high treatment level. The excess sewage gas from the Gold Bar anaerobic digesters will be scrubbed to natural gas quality and injected into the natural gas line as green gas. This green gas would be used for cooking gas onsite and could fuel a significant number of transit busses serving the site and the city.

The annual carbon footprint for the future residents of the CCR development would be about 4 tonnes per person compared to the estimated current performance in Edmonton of about 24 tonnes.

The business case for the carbon-neutral energy systems was not part of the scope of the planning team. Edmonton is now preparing to seek interest for utilities to develop the energy systems for the project. In any case, a carbon-neutral system will cost more per kWh compared to conventional fossil fuel energy systems—particularly on a small- to medium-sized development. A strategy is to have more efficient buildings that use less energy so the energy bill for the occupant is lower than if he or she stayed in the current home if it were the same size.

Comparing development performance to the global environmental goals outlined previously, one can conclude the following:

  • waste biomass (a carbon-neutral energy source) would be used to generate electrical and heating energy for the site and for sale offsite; deep geothermal, another carbon neutral energy source will also be examined—efficient building performance requirements would reduce energy use below current levels;
  • the project is planned to operate in a ‘beyond-carbon-neutral’ manner so the net GHG emissions from Edmonton would be reduced—the carbon footprint for the CCR residents would be significantly below the city’s average;
  • potable water use onsite would be about 139 L per person per day—possibly the lowest water use in North America for a large community;
  • with the recycling, composting, and waste-to-ethanol facilities at the Clover Bar waste treatment plant, less than 10 per cent of the waste from the CCR site and Edmonton would go to a landfill—this would be among the best on the continent; and
  • the development of the large park areas and lakes will develop the local flora and fauna, and the urban agricultural plots in the Agrihood area will support local food production.

The Edmonton City Centre Redevelopment is an example of how a project of this scale can significantly improve the overall performance of urban fabric.

Both projects demonstrate a whole-systems restorative approach to development, with local solutions addressing global environmental issues. Maximizing local opportunities such as sharing heat energy between buildings, using local waste as fuel, and eliminating demand on municipal potable water can add up to significant positive impacts extending far beyond the limits of one project. 

Blair T. McCarry, P.Eng., PE, ASHRAE Fellow, LEED AP, is a principal and senior engineer with Perkins+Will. He has more than 40 years of experience in engineering and energy systems, especially at a campus and district level. McCarry is a strong proponent of the ‘whole-systems sustainability’ premise and has led the systems planning for multiple projects striving for Leadership in Energy and Environmental Design (LEED) Platinum and beyond. He graduated with a bachelor of science mechanical engineering degree from the University of British Columbia (UBC) in 1971. McCarry is a Fellow of American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE), an honourary member of the Architectural Institute of British Columbia (AIBC), and a member of several other professional organizations. He was also founding chair of the Vancouver Branch of the Cascadia Chapter of the U.S. Green Building Council (USGBC), a member of the Canada Green Building Council (CaGBC) Technical Advisory Group (TAG), and is a current CaGBC board member. McCarry serves as an adjunct professor in the School of Architecture and Landscape Architecture at UBC. He can be reached at

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