Developing an Energy Neutrality Plan for the Metropolitan Water Reclamation District of Greater Chicago

The Metropolitan Water Reclamation District of Greater Chicago (MWRD) treats an average of 1.4 billion gallons of wastewater per day collected from the City of Chicago and over 128 suburban communities throughout Cook County. Wastewater is conveyed into a combined sewer system from gravity sewers as well as 23 pump stations and directed to 7 water reclamation plants (WRPs). The 7 WRPs can treat maximum flows ranging from 4.0 to over 1,440 MGD. The magnitude of the District's system requires significant energy for treatment, using 1,090,041 MWh/yr of electricity, biogas, and natural gas in 2020 (Figure 1). As an environmental steward, the MWRD has established a Strategic Plan and a Climate Action Plan to set forth its path to reduce their GHG emissions and impart a positive environmental impact. In alignment with the agency's vision and values, the MWRD investigated the feasibility of achieving energy neutrality (EN) at one WRP by 2030 and as an organization by 2035. The conceptual energy neutrality plan (ENP) included estimated capital costs and net present value of the preferred technical solutions to achieve EN. To develop the plan (Figure 2), the project team:
- Reviewed MWRD facilities and set baselines for current performance;
- Set goals and definitions for EN;
- Developed an evaluation methodology with multiple screening steps to right-size the detailed analysis for the options available;
- Organized remaining technologies into categories for implementation;
- Determined viability, benefit, and present value of options that passed screening;
- Created an implementation plan with prioritized projects with incremental benchmarks towards full EN;
- Ran 'what if' scenarios to increase adaptability and flexibility of the ENP into an actionable roadmap.

Building the ENP required a detailed dive into the complexity of the MWRD's operations. This effort established the ENP baseline, forming the foundation of the plan. A universe of technologies and methods that covered all feasible options inside and outside of the wastewater sector was used to understand all possible approaches to meaningfully impact energy reduction or generation. An alternatives analysis, employing an iterative approach, led to the continued refinement of options using the power of solids and energy modelling tools combined with process calculations, life cycle assessments, and the collective expertise of the MWRD and the project team. This included collaborative workshops through which continued investigation led to a potential ENP for the MWRD that was technically feasible. An expert panel, reflecting a diverse group of independent experts with a wide range of knowledge from the utility sector, private sector, and national laboratories, helped to advise and guide the plan.

The ENP separates the desired improvements into categories for implementation (Table 1). The plan focuses on building the program systematically, one component at a time, to adaptively achieve EN. Category 1 and 2 projects represent what level of EN can be achieved through treatment of the water and waste the MWRD receives at its WRPs. Category 3 and 4 projects involve importing energy to provide the remainder of the energy difference to achieve overall EN with enhanced generation. The plan builds on existing EN progress of ongoing efforts by the MWRD and assumes over 50% reduction after implementation of Category 1 improvements. The proposed roadmap shows that using solely the energy from the water and waste the MWRD WRPs treat, the District can only achieve approximately 70% EN, which includes all of the Category 1 and 2 improvements. The remaining 30% of the District's energy use must be offset by importing other sources of energy (Figure 3).

The overall cost of the improvements to achieve EN is approximately $1.2B in 2024 dollars. The plan was designed to be adaptable and be broken down into manageable parts. Also, many of the Categories 1 and 2 projects have synergies with other aspects of the MWRD's CIP that can help further justify proceeding. The projects implemented initially lay the foundation for continuing to improve operations at each of the plants while providing incremental progress to EN. This is critical as the MWRD must balance competing priorities that utilize both capital and staffing resources. These competing priorities include increasingly stringent nutrient and treatment limits, treatment reliability, modernization of a combined sewer system, managing aging infrastructure and affordability while fostering sustainability and resilience in the face of intensifying climate challenges. The ENP helps to deliver a feasible and financially sound pathway to EN while meeting other core District priorities. This approach to developing a plan to achieve energy neutrality across a district of facilities varying in size and infrastructure could be implemented by any organization seeking to improve the operation of their facilities in an environmentally and financially responsible manner.