Region of Waterloo Cogeneration Facilities

Award of Excellence

Jacobs

Ontario’s Regional Municipality of Waterloo operates wastewater treatment plants (WWTPs) that produce digester gas as waste byproduct. Jacobs, CIMA+ and Eramosa Engineering led design and services during construction for the installation of cogeneration facilities at the region’s three largest WWTPs in Waterloo, Kitchener and Galt.

These facilities now combust digester gas to produce electricity and heat. The resulting energy is used on-site, thereby reducing greenhouse gas (GHG) emissions and the cost of externally provided electricity and natural gas.

Jacobs’ design offered economic and environmental benefits, including offsetting electricity costs for the sites and reducing emissions. By way of example, if digester gas production at a site is low or unavailable, the cogeneration facilities have the capability to run on natural gas or a blend of natural gas and digester gas.

One size does not fit all Jacobs worked with W.A. Stephenson Mechanical Contractors to manage the schedule and budget. The project had a high level of complexity, as the sites entailed different existing conditions that had to be evaluated so the detailed design would provide a constructable and cost-effective solution for all of them. The structures had to be flood-proof, for example, due to their proximity to watercourses; and the gas quality and quantity varied, which needed to be considered from a process perspective to size the generator engines appropriately.

Construction management was also complicated. Each of the three sites had its own operational staff, natural gas authority and electrical local distribution company (LDC).

Enhancing efficiency The Galt and Waterloo facilities each generate 600 kilowatt-electric (kWe) capacity, which delivers more than 33% of their electrical loads, while the Kitchener facility generates 800 kWe, more than 70% of its load. The generated heat is transferred to the plants’ hot water systems. It is then used to heat the buildings and digester sludge, reducing the natural gas load to the boilers.

Before, digester gas was inefficiently used in boilers, with excess sent to flare. The complete combustion of digester gas releases carbon dioxide (CO bustion results in the emission of methane, a GHG with 25 times greater global warming potential (GWP).

When the cogeneration facilities are running 100% on biogas, the reduction of GHG emissions compared to pre-construction levels is equivalent to 934 tonnes of CO2 for Waterloo, 425 tonnes for Kitchener and 554 tonnes for Galt, annually.

Before the blend of digester gas and natural gas is combusted in the engine generator, it is dried, filtered and cooled by the gas conditioning system to remove constituents that may hinder the efficiency or reliability of the combustion process. Similarly, exhaust from the generator engine is treated with urea to lower the concentration of harmful constituents emitted to the atmosphere.

Typical energy recovery of the cogeneration facilities is 70% of digester gas energy value, with 35% as electricity and 35% as heat.

Region of Waterloo Cogeneration Facilities, Kitchener, Ont. Award-winning firm (prime consultant): Jacobs, Kitchener, Ont. (Ryan Connor, MBA, P.Eng.; Mitch Jewson, EIT; Frank Absi, P.Eng.; Taryn Davis, P.Eng.; Faiz Lawand, P. Eng.; Thomas Kowpak, M.Sc., P.Eng.; Brian Sudic, P.Eng.; Maggy Au, P.Eng.; Derek Murray, CET). Owner: Regional Municipality of Waterloo. Other key players: CIMA+ (sub-consultant), Eramosa (sub-consultant), WA Stephenson Mechanical Contractors (mechanical), Selectra Contracting (electrical), GAL/2G (cogeneration units), Thomson Power Systems (switchgear), Toromont Caterpillar (switchgear), Biospark Clean Energy (gas conditioning equipment).