By: Yvonne Ho
Last month I had the opportunity to go on a field trip to Woodward Wastewater Treatment Plant in Hamilton with a group called Women in Renewable Energy (WiRE). WiRE is group that focuses on advancing women’s role in the renewable energy sector through monthly networking meetings, educational field trips, mentoring programs, and other engagement initiatives. As a newer professional entering the renewable energy space, I have been a member of WiRE for almost one year, and have found all of their programs to be immensely rewarding and enriching.
When we arrived at the plant, we were warmly welcomed by Tom Chessman, Manager of Energy Initiatives at City of Hamilton Public Works Department. He gave us a brief introduction into the origins of the plant and oriented us to the present day operations of this plant.
What’s so special about Woodward?
Woodward Wastewater Treatment Plant is not your typical treatment plant—the methane from the wastewater treatment process is fed into a cogeneration digester plant on site. Cogeneration, or “Combined Heat and Power (CHP)”, is a process that produces electricity and useful heat from a common fuel source on site, and represents a highly efficient method of generating electricity. Typically, it can achieve primary energy savings of approximately 40% compared to the separate purchase of electricity from the national electricity grid and a gas boiler for onsite heating. Other benefits include lower energy costs and reduction in carbon emissions.
This cogeneration plant is owned by Hamilton Renewable Power Inc., and contracted to Ontario Power Authority (OPA) under a 20-year agreement. In terms of energy generation capacity, the cogeneration unit at Woodward has a nameplate capacity of 1.6MW— along with two identically sized units at a nearby landfill site also owned by Hamilton Renewable Power Inc.— making a total capacity of 4.8MW.
The cogeneration process allows this facility to kill two birds with one stone. On top of electricity generation, Woodward produces thermal energy in the form of hot water that is distributed back to the facility for use in its wastewater digester process, which offsets the purchase of natural gas. The raw biogas is stored in a large gas-storage sphere resembling a globe that is visible from the Burlington Skyway, also known to be one of Hamilton’s most iconic landmarks.
How does a typical biogas system work?
- Organic waste from the plant is inputted into a large anaerobic (oxygen-free) digester tank, where microorganisms break down the waste to produce methane gas (biogas) consisting of approximately 65% methane and 35% carbon dioxide –Woodward’s operations produces approximately 17,000 cubic meters of digester gas everyday.
- The leftover liquid product is called “digestate”, which can be used as high quality fertilizer on farm fields; the dry solid product can be used as animal bedding for cattle or as potting soil supplement.
- The raw biogas is fed into the cogeneration plant to be burned and converted into both heat and electricity.
- The heat is used on site while the electricity is sold to the power grid.
- In the case of Woodward’s facility, the raw biogas can also be directed to their biogas purification unit as “renewable natural gas” that is then injected into the Union Gas Distribution system.
What are the environmental and financial benefits of such a system?
In conventional wastewater treatment plants, biogas is “flared off” and the energy content wasted. In the case of Woodward’s plant, the cogeneration system uses up this biogas as a source of green renewable electricity, directly reducing the plant’s energy needs and greenhouse gas emissions. Financially, biogas cogeneration can be an effective way to cut costs and potentially generate extra revenue for the municipality— Woodward generates between $1.7 to $2 million in revenues and overall benefits each year.
In addition to selling electricity to the grid, the plant has decreased its operating costs by using waste heat to offset natural gas usage. Biogas has the same attributes as conventional natural gas— as of 2012, a purifying unit has been added at Woodward to clean and upgrade the raw biogas for it to be injected to Union Gas’s distribution system as Renewable Natural Gas (RNG). RNG is essentially biogas that has been processed to purity standards. Like conventional natural gas, RNG can be used in the form of compressed natural gas (CNG) or liquefied natural gas (LNG) as a transportation fuel. Hamilton was the first municipality in North America to build a wastewater treatment plant that feeds its gas into a biogas purification unit.
With ample environmental benefits and a guaranteed positive, long-term return on investment, there is no reason why other Canadian regional municipalities shouldn’t look into the addition of such renewable energy generation systems, and maximize the energy potential of their own wastewater facilities!
For more information:
To learn more about the Woodward Biogas Cogeneration Facility, contact Tom Chessman, Manager of Energy Initiatives at the City of Hamilton Public Works Department: Tom.Chessman@hamilton.ca.
Hamilton’s Woodward Wastewater Treatment and Cogeneration Plant was part of the 5th annual Green Energy Doors Open sustainable energy showcase weekend September 9-11, 2016. Local community members were invited to tour the facility to learn about energy efficiency and innovative technologies.
To learn about a similar biogas system operating right here in Toronto, check out ZooShare, a non-profit that is turning poo from zoo animals into energy. ZooShare was also part of the Green Energy Doors Open showcase weekend, highlighting the ‘pootential’ of animal waste for sustainable energy.
Yvonne is an environmental professional with an educational background in environmental science and sustainability. She has several years of work experience in the environmental non-profit sector— carrying out research on key environmental issues, writing reports and educational articles, executing membership development and outreach initiatives, as well as implementing marketing and communications plans for campaigns. She has a keen interest in renewable energy, impact investing, sustainable development, and environmental laws and policies. Prominent environmental organizations she has volunteered at and worked for include Sierra Club, Environmental Defence, Ontario Sustainable Energy Association, Toronto Environmental Alliance, and Pollution Probe. Yvonne is motivated to work together with like-minded people and organizations towards greater environmental justice and climate action.