Manitowoc Public Utilities (MPU) initiated the Manitowoc Refuel Renewable Project in 2021. This project entails refueling two existing circulating fluidized bed boilers – Boilers 8 & 9 – from burning primarily fossil fuels, such as coal and petroleum coke, to burning 100% Wisconsin-recognized renewable fuel pellets. MPU has been burning this fuel since 1996, but only at a small percentage. Refueling to renewable fuel pellets is beneficial to the City of Manitowoc, and MPU customers, for several reasons, including: cost control, maintaining grid resiliency, providing local control, and increasing sustainability. Listed below are more details on each benefit of this project.
Cost Control
Renewable fuel pellets are made from local non-economically-recyclable industrial paper and plastic waste that would otherwise be landfill-bound. Costs of fossil fuels like coal and petroleum coke have drastically increased. Renewable fuel pellets are significantly cheaper allowing MPU to maintain competitive electric rates for our customers.
Sustainability
By refueling our boilers to burn these pellets, approximately 18,000 tons per month of non-economically-recyclable industrial paper and plastic waste is diverted from the landfill. Additionally, the pellet burning process recognizes a reduced need for limestone addition to the boiler, which results in a reduction of about 7,500 tons per month of limestone and subsequent equivalent reduction in need for landfill disposal as limestone/ash. This project also recognizes that comparing to our 2005 baseline, our net greenhouse gas emissions would be reduced by approximately 55%.
Local Control
Without this project, MPU’s power plant would no longer be considered economical and therefore would not be called on to run by the Midcontinent Independent System Operator (MISO), who is the power grid operating authority for Wisconsin and other nearby states. MPU’s power plant asset is valuable for several reasons, but primarily because of retaining local power plant jobs and the Payment In Lieu of Taxes (PILOT) to the City of Manitowoc. Along with maintaining jobs and PILOT, staff is researching ways to increase supply of renewable fuel pellets that would end up adding jobs and potentially increasing the PILOT payment to the City of Manitowoc.
Grid Resiliency
Generating power with renewable fuel pellets creates dispatchable energy to the grid, meaning the generation is consistent and continues generating as long as there is fuel supply. Non-dispatchable energy sources, such as solar and wind, can only be utilized when the conditions are right. This project enables more non-dispatchable energy sources to be utilized while this baseload generation, also deemed renewable by the State of Wisconsin, allows for those peaks and valleys when non-dispatchable energy sources cannot produce. This creates a stable power grid that can accommodate low, and high, demand.
Project Outcomes & Initiatives
2021 – 2023 Outcomes
- First Unit (23MW) – Refueled and operational since December, 2021. Resulted in a 6% increase in Generator Verification Test Capacity (GVTC), 50% reduction in average production cost ($/MW) and regularly dispatched based
on economics. - Second Unit (63MW) – Successfully completed extended run at max output exclusively on pellets in Spring of 2023.
- Facilitated expansion at existing pelletizing facility to increase pellet production by 33% in late 2023.
- Secured dry storage capable of holding one month’s worth of fuel needed to operate both units.
2024 Initiatives
- Execute contract for local construction of additional pelletizing facility with production in late 2025.
- Explore wet raw material (sludge) drying facility to increase raw material options for pellets.
- Explore fuel handling automation to improve efficiencies with transition to pellets.