Heat recovery that pays for itself

Summary

The City of Timmins has stepped into new territory: turning organic waste into renewable energy and fertilizer. A feasibility study found that by blending food waste with sewage at the Mattagami Water Pollution Control Plant (WPCP), enough energy could be produced to meet nearly half of the plant’s needs. With benefits such as diverting organic waste from landfill, reducing greenhouse gas emissions, producing renewable energy and fertilizing the land, the City will be helping to protect the outdoor environment its residents are proud of. The results show that even mid‑sized communities can turn waste into reliable energy. By using the infrastructure they already have, the City is creating environmental and economic value for the people of Timmins.

Quick stats

Generate 22,960 GJ of renewable energy per year, approximately 40% of the wastewater treatment plant’s heat and electricity demand

Reduce 2,000,000 tonnes/year of CO2e emissions

Divert 4,140 tonnes/year of food waste from the landfill 

"Diverting waste from landfill is an important objective for the municipality, regardless of whether the material originates from residential or ICI sources. Treating ICI waste supports overall waste diversion goals, extends landfill lifespan, and contributes to broader environmental and sustainability objectives, which benefits the community as a whole."

Background

In 2021, the City completed a feasibility study that quantified residential and industrial/commercial/institutional (ICI) food waste in the local area and compared three waste treatment options:

1. Traditional composting.
2. Anaerobic digestion, which treats organic waste in oxygen-free tanks where microbes break it down to produce fertilizer and biogas that can be used for heating and renewable energy in the form of electricity or renewable natural gas.
3. Co-digestion, in this case a particular type of anaerobic digestion where sewage is blended with food waste at the City’s existing Mattagami WPCP. 

The City worked with the Ontario Clean Water Agency (OCWA) to analyze co-digestion’s feasibility and found that it was the most cost-effective option.

The challenge 

Despite identifying co-digestion as a viable way forward, the City of Timmins is tackling multiple goals at once with this project:

• Increasing organic waste diversion from landfills,  
• Reducing greenhouse gas emissions, and  
• Improving organic waste receiving capacity in the region.  

For medium-sized communities like Timmins, balancing finances with the vision of a circular economy can be more challenging because they benefit less from economies of scale than large cities. 

The solution 

The City analyzed five scenarios in blending food waste with sewage, each along a continuum from adding zero organic waste up to adding the maximum that could be treated at the plant. Each step along the continuum both increased renewable energy production and decreased potential emissions.  

The analysis found that it was more feasible to produce renewable heat and electricity compared to renewable natural gas (RNG). The City required more organic waste and wastewater sludge than what was readily available for RNG production to be feasible. The renewable heat and electricity production scenarios carried the least technical and operational risks. 

Results 

• The most feasible scenario co-digests 4,140 tonnes/year of residential and ICI organic waste that would otherwise go to landfill.
• 2,000,000 tonnes/year of CO2e emissions would be reduced at the landfill with the scenario’s diversion rate.
• The co-digestion of residential and ICI food waste generates enough energy to cover 40% of the heating and 44% of the electricity demand at the plant.
• Using the existing wastewater treatment plant reduces major capital spending and maximizes co-digestion’s cost effectiveness.  
• Using waste as a resource promotes a circular economy.

Lessons learned  

Several practical lessons emerged from the City’s experience that may be useful to other communities considering co‑digestion. Early engagement, trusted partnerships and a strong understanding of local conditions were critical in developing a solution that was both feasible and supported by operators and the community. 

• Prioritize early stakeholder engagement to assess feedstock availability and competition in your area. Developing a relationship with stakeholders takes time and repeated follow-ups, so allocate sufficient schedule and budget from the outset.  
• Work with a partner who has strong ties to feedstock suppliers and gas off-takers: their access to private market data and credibility encourages stakeholder engagement. In this case, OCWA contributed regulatory, technical, operational and project delivery knowledge.
• Rely on in-house operator expertise in order to understand the operational history of your wastewater treatment plant, evaluate system impacts and validate cost-saving assumptions.  
• It is easier to reliably reach expected energy production when there is little competition for organic waste receiving. There are no private organic waste receivers in the City of Timmins, which increases the likelihood of securing the estimated available food waste.  
• When there are neighbouring lands that could benefit from digestate, the project can maximize its environmental benefits. The City is near mining sites where the nutrient-rich digestate could be distributed to help with land rehabilitation.  
• When the community and the operations team see how the changes benefit everyone, projects gain forward momentum. Operators were made aware of the feasibility study and residents were surveyed on their likelihood of participating in an organics collection program.