A project to update plant heat and power infrastructure
The District’s Heat & Power Improvements Facilities Plan is a guide for updating aging infrastructure and improving energy generation. The plan is centered around a large-scale generational project to update biogas and thermal heating systems, which generate renewable heat and electricity to power plant operations.
A facility plan is a statutorily required step before the District can begin designing and constructing specific capital projects. The purpose of facility planning is to conduct a condition assessment, define needs for improvement, evaluate alternatives and then recommend the most reliable, cost-effective and sustainable option.
The Heat & Power Improvements project examined two primary options: 1) continue reusing treatment plant produced biogas and waste heat with new and improved equipment, or 2) invest in technology that would enable the creation of pipeline-quality gas and generate a new income stream for the District. The plan recommends creating market-ready biogas for the local market as the most cost-effective and sustainable option.
Project background
The District’s energy-producing biogas and thermal systems are outdated and beyond their useful life. These systems are also incredibly valuable, as the treatment plant recovers approximately 325 million cubic feet of biogas per year. This biogas, along with waste heat from District processes, helps power assets, offsetting the need to purchase about $1 million in energy from the grid each year.
To develop the Heat and Power Improvements Facilities Plan, specific information and background research were required:
- Decision-making criteria. Criteria include capital costs, life cycle cost, operational complexity, operational risk, future site flexibility, market risk, energy recovery and outside dependence.
- Energy baseline. No significant differences were found between 2020 energy baseline data and current electrical, biogas and natural gas consumption data.
- Biogas production and thermal demand projections. Both biogas production and thermal demand are projected to increase by 2050.
- Existing infrastructure evaluation. Identified issues with the current cogeneration system include system inefficiencies, infrastructure age, gas pressure deficiencies, undersized piping, condition issues and more. A cogeneration system simultaneously produces multiple forms of energy from a single fuel source.
Alternatives evaluation
Two alternative pathways were evaluated for this plan. Pathway 1 was to upgrade the current cogeneration system with newer, higher-efficiency equipment. Pathway 2 involves upgrading the biogas system to produce renewable natural gas (RNG) for pipeline injection.
An option to maintain existing operations with no major changes (Null Pathway) was also evaluated to collect baseline data for comparison with the two alternatives. In addition, the current centralized heating systems were compared to decentralized heating models.
Pathway 1: Cogeneration
Pathway 1 is similar to the plant’s existing system, but upgrades the cogeneration engines to higher-efficiency, higher-output models while decommissioning the engine blower, which becomes unnecessary with the upgraded engines.
Pathway 2: RNG
Pathway 2 would bring significant changes to the system’s operations. The proposed model is a biogas system for RNG. Biogas would still be produced in the digesters, but it would undergo a very sophisticated, multi-phase treatment system before pipeline injection, and would be of equivalent quality to the natural gas we use. The hot water boilers currently supplying the plant would be replaced with natural gas-fired boilers.
Recommendation
Although the Null Pathway (current system) represents the lowest capital cost, it is not recommended due to significant maintenance requirements, increased operational risk and limited capacity. It is unsuitable for long-term planning due to equipment age.
Instead, the Heat & Power Improvements Facilities Plan leans toward Pathway 2: RNG with a decentralized system for these reasons:
- Most cost-effective with lower capital cost
- Significant revenue potential from the sale of RNG to energy utilities
- Expected reduction in maintenance time by using natural gas for on-site equipment
- Simple payback time is lowest
- Highest combined weighted score for decision-making criteria
- Environmentally friendly and positively contributes to the clean energy economy
Revenue from RNG is possible through the Renewable Fuel Standard program, managed by the EPA to offset carbon emissions in the transportation sector.
Next steps
- January 29, 2026: Public Hearing on the Heat & Power Improvements Facilities Plan
- Submit the plan to the Wisconsin Department of Natural Resources (WDNR) for approval.
- Upon receipt of the WDNR’s letter of approval, District staff will request formal acceptance of the plan from the Commission.
- Prior to initiating the design phase, the District will revisit the recommended approach to confirm that the evaluation and assumptions remain valid before proceeding with implementation.
For more information on the Heat and Power Facilities Plan, watch a December 18, 2025 Commission presentation by engineer Ana Uroic Stefanko. You can view all facility plans and master planning documents on our Plans & Reports page.
