Monterey renewable energy and electrical utility reliability study

Monterey One Water (M1W) and ReGen Monterey (ReGen) are public agencies that manage wastewater and non-hazardous solid wastes, respectively. The Agencies serve similar constituencies along the central coast of California and provide essential public services that need reliable and affordable power. As neighbors, they have established a visionary approach for assessing the feasibility of leveraging their co-located infrastructure and resources and secure the energy reliability and resilience their critical public works operations require.

The guiding principles for the vision are centered around three pillars:

• Ensuring energy reliability and resiliency – both agencies have been impacted by severe power grid outages in the past which can affect their ability to provide 24/7 community-critical services.

• Minimizing environmental impacts, such as reducing greenhouse gas emissions, contributing to the health and safety of the community, and supporting California state mandate for diverting organic waste from landfills (Senate Bill 1383).

• Reducing operational energy costs and boosting revenues from biogas.

Our team conducted the Monterey Renewable Energy and Electrical Utility Reliability Study to assess the feasibility of developing a safe and reliable electrical network supporting continuous operations with or without the grid, while minimizing environmental impacts and costs.

The study revolved around four interconnected project components.

Electrical Network

This initial study was focused on an electrical base-case scenario, in which M1W’s and ReGen’s power generation facilities can be interconnected so the Agencies’ electrical networks can support each other’s electrical loads and operate independently of the grid in “island mode” when utility power is not available or is unreliable.

The study identified the infrastructure requirements, including new gensets at ReGen and M1W, medium-voltage interconnections between various ReGen and M1W facilities, potential future battery energy storage systems (BESS) and solar photovoltaic (PV) systems.

Codigestion

Codigestion allows wastewater digesters to process organic waste diverted from landfill, for the purpose of biogas production. M1W has received a CalRecycle grant and procured new mixers for the digesters to enable co-digestion of an organic slurry.

The study discussed the preprocessing requirements that may be needed onsite depending on the source and characteristics of the material used for codigestion. The study also identified additional improvements needed at M1W due to the codigestion upgrades. These enhancements include biogas handling & storage, digester heating system, and side stream ammonia treatment.

The study discussed the preprocessing requirements that may be needed onsite depending on the source and characteristics of the material used for codigestion. The study also identified additional improvements needed at M1W due to the codigestion upgrades. These enhancements include biogas handling & storage, digester heating system, and side stream ammonia treatment.

Biogas Utilization

Biogas from M1W and ReGen is expected to increase in the future. The study evaluated various scenarios to beneficially use the excess biogas after the electrical network requirements are met. Renewable Natural Gas (RNG) production and injection into the utilities pipeline ranked highest.

Biosolids Management

M1W’s wastewater treatment solids are currently managed via anaerobic digestion followed by dewatering, sludge drying beds and ultimately landfill disposal at ReGen. Codigestion of food waste will increase the quantities of biosolids produced and might also increase the concentrations of certain PFAS compounds in the biosolids.

M1W wants to protect its community and address PFAS. Advanced thermal treatment, such as pyrolysis has shown promise in managing PFAS in biosolids. The study thus recommended dewatering improvements as an initial step as it would be required for any future drying and advanced thermal treatment technologies.

The study identified strategic capital improvements that could be implemented over the next 5 to 15 years that will position the Agencies as pioneers in sustainability, poised to deliver renewable energy to power essential community services which are required around the clock, even when grid power is not available.

If implemented, the improvements identified in the studies could reduce greenhouse gas emissions and preserve landfill capacity by re-directing organics, contributing to the health and wellbeing of the surrounding community.