WATER GLOBAL PRACTICE Wastewater: From Waste to Resource The Case of Ridgewood, NJ, USA Achieving Energy Neutrality in Wastewater CHALLENGE Treatment Plants Improve the anaerobic digesters and use the biogas to produce enough renewable energy to satisfy the power Summary demand of the plant Ridgewood, in New Jersey (NJ), upgraded its waste- OBJECTIVE water treatment plant (WWTP) in 2005 by installing Improve affordability, resiliency, and sustainability of the two anaerobic digesters to comply with stricter fed- existing WWTP eral and state environmental standards. However, the biogas produced in the process was being burned and Such  high costs can negatively affect the financial released to the environment. The municipality saw health of the plant and impact the sustainability of an opportunity to use the wasted methane and con- the service. Therefore, utilities have high incentives to vert it into energy for the WWTP. Through a success- implement energy efficiency and energy recovery mea- ful public-private partnership (PPP), the Ridgewood sures to reduce operation costs and reduce the carbon WWTP achieved energy neutrality and became a ref- footprint of the plants. For example, biogas generated erent on sustainable municipal wastewater treatment in WWTPs can be used to produce electricity on-site in the region. and therefore reduce electricity costs. This can be especially beneficial in places where the price of elec- Context tricity is high, as it is in many low-income countries. WWTPs are energy intensive with electricity costs However, utilities do not always have the resources, usually between 5 percent to 30 percent of total oper- time, or skills to explore these opportunities. PPPs can ating costs. In low-income countries the share is usu- be a solution to address those issues, allowing for the ally higher, and it can go up to 40 percent or more. benefits and risks to be shared. 1 Solution municipal WWTP has been enhanced so that enough bio- gas is being produced to meet almost the entire plant’s Retrofitting the existing infrastructure through a energy needs. The biogas is collected, cleaned, com- PPP. The WWTP in Ridgewood was the largest energy pressed, and pumped into a biogas engine to produce consumer that the village owned, costing more than electricity. The excess heat from the engine is used to heat $250,000 a year for electricity. Ridgewood saw this as a the sludge entering the digesters, increasing the plant’s big opportunity cost, and explored combined heat and efficiency. Moreover, to increase the plant’s methane power solutions to both reduce the energy costs and production and improve project economics, Ridgewood improve the sustainability of the plant. Moreover, the Green has financed and installed liquid waste hold- village wanted to enhance its WWTP without impact- ing tanks for co-digestion of vegetable and animal fats, ing its taxpayers. The village believed that it could be oil, and grease (FOG) obtained from external sources. done through a PPP without incurring any upfront Figure 1 shows a simplified diagram of the project. capital investment by the village itself. Local govern- ment officials made a “request for proposal” to design and implement a project that would convert the excess Financial and Contractual Agreements methane into usable electricity. Ridgewood Green The project was financed through a 20-year PPP between RME (RGRME) was chosen. the village of Ridgewood and Ridgewood Green RME. Ridgewood Green retrofitted the plant’s two anaerobic Ridgewood Green made the up-front capital investment digesters to optimize the process and installed a bio- ($4 million) needed to retrofit the plant, which implied gas generator. The anaerobic digestion process at the zero investment costs and minimum risk for the Village FIGURE 1. Diagram of the Project Ridgewood Green Village of Ridgewood • Financed and installed liquid waste Owns and operates the waste water treatment plant holding tanks and a biogas generator, buys electricity produced from Ridgewood Green at and retro tted the plant’s two anaerobic $0.12 per kilowatt-hour, cheaper than market rates digesters Value: • Lowers operating costs • Gets revenue from electricity sales and • Reduces sludge hauling costs tipping fees • Reduces carbon footprint Wastewater Sludge treatment plant Waste Vegetable, animal water fats, oil, and grease 20-year agreement Fee ($) Co-digestion by Wh $ 0.12/kWh Ridgewood Green Electricity Note: Treatment plant image is by Tracey Saxby, Integration and Application Network, University of Maryland Center for Environmental Science (ian.umces.edu/imagelibrary/). 2 Wastewater: From Waste to Resource of Ridgewood. In return, Ridgewood purchases the Ridgewood Green expects to recover the full invest- electricity generated by Ridgewood Green at a price of ment and a reasonable return on investment through 12 cents per kilowatt hour (kWh). The power purchase an innovative revenue model that leverages differ- agreement included a fixed increase rate of 3 percent ent revenue streams: (a) selling electricity to the per year for inflation, establishing the village’s price and Village of Ridgewood; (b) selling all the renewable Ridgewood Green’s revenue for the duration of the con- energy certificates (RECs) to 3Degrees, a leader in tract. The plant used to pay about 15 cents per kWh for the renewable energy marketplace under an agree- utility power. Therefore, this agreement benefits both ment of several years; (c) tipping fees assessed when parts. Since Ridgewood Green invested in the new infra- haulers deliver FOG to feed the anaerobic digest- structure, it owns the new equipment and the Village of ers. Proximity incentivizes haulers to dump FOG at Ridgewood owns and operates the plant with technical Ridgewood’s water plant rather than the traditional support from Ridgewood Green. destinations. Benefits For the Village of Ridgewood For Ridgewood Green • Renewed infrastructure (state-of-the-art) • Showcase solution as an example of sustainability in WWTP (won • No capital cost to taxpayers the Biogas Project of the Year by the American Biogas Council and Environmental Achievement Award) • Savings: lower operating costs for the WWTP • Risk mitigation: power purchase agreement set a fixed increase – Lower sludge hauling costs rate, ensuring Ridgewood Green’s revenue for duration of the – Lower electricity costs contract • More resilient: not affected by electricity price surges (locked price for 20 years) • Lowers the village carbon footprint For the environment • Reduction of greenhouse gas (GHG) emissions Lessons Learned Systems Utilities (NSU), Middlesex Water Co. (MSU), Several key success factors can be highlighted from and American Refining and Biochemical this case study: Technical innovation Stakeholder engagement • Reuse of existing infrastructure • 20-year partnership, lowering risks and ensuring revenue for the capital investor (Ridgewood Green) • Optimization of the anaerobic digestion process with and continues involvement of key stakeholders (see the addition of an enzyme product that increases figure 2) biogas production and reduces odors • Right mix of expertise: Ridgewood Green was • Co-digestion: the production of electricity is formed to leverage each organization’s respective enhanced when food wastes (e.g., FOG) are intro- financial capacities and technical expertise: Natural duced into the process. Wastewater: From Waste to Resource 3 FIGURE 2. Key Stakeholders • Use  of solar panels to achieve 100 percent renew- Municipal utility able energy use in the plant (Village of Ridgewood Dept. of Public Works) Creative and diversify new reve- nue streams for the investor Vegetable, $ Power purchase Agreement for 3Degrees Renewable •  Revenue from electricity Haulers animal fats, oil, 20 years energy sales to WWTP, fees from and grease $ provider haulers, and RECs to $ 3Degrees Agreement Ridgewood Green renewable RME energy Natural Systems Utilities certi cates Conclusion (NSU), Middlesex Water Company (MWC), and The case of Ridgewood shows American Re ning and Biochemical (ARB) that resource recovery in WWTPs can be cost-effective even in Capital investment smaller scale plants if the right stakeholders are involved and if there are the right incentives in PROFILE place. Retrofitting existing plants in an innovative way NAME can be a solution toward sustainable wastewater man- Village of Ridgewood Wastewater agement instead of building new infrastructure with Treatment Plant the latest technology. LOCATION Ridgewood, NJ, USA References SIZE Cleary, J. G. 2014. “Powering the Plant.” Water and Wastes Digest, Nov 10. • 19,000 m3/day design flow https://www.wwdmag.com/smart-resilient-cities/powering-plant. • 8,500 m3/day average flow Corbin, C. 2014. “Value Added.” Water and Wastes Digest, Feb 13. https:// MAIN INNOVATION www.wwdmag.com/energy-efficiency/value-added. • Energy neutrality by retrofitting existing plant Day, D. 2014. “Nice Reward, No Risk.” Treatment Plant Operator Magazine, May. http://www.tpomag.com/editorial/2014/05/nice_reward_no_risk. • Creative alternative revenue streams TECHNOLOGY Greenhouse, M. 2012. “New Jersey Village Turns Heat into Power.” Government Technology, July 25. http://www.govtech.com/dc/articles​ Bar screens, liquid waste screens, liquid waste storage tank, /­New-Jersey-Village-Turns-Heat-into-Power.html. primary clarifiers, aeration tanks, secondary clarifiers with chlorination, conventional anaerobic digesters, biogas engine Middlesex Water Company. 2013. “Photo Release—Village of Ridgewood Wastewater Treatment Plant Now Fully Operational and Producing • Biogas production: 2,600 m /day; 100 percent used for 3 Renewable Energy.” GlobeNewswire, October 18. http://globenewswire​ energy generation .com/news-release/2013/10/18/581619/10053248/en/Photo-Release​ • Feedstock: co-digestion: municipal wastewater biosolids, -Village-of-Ridgewood-Wastewater-Treatment-Plant-Now-Fully​ brown grease (FOG) and septage -Operational-and-Producing-Renewable-Energy.html. • End use: CHP: 240 kW electric and 440 kW thermal energy World Bank. 2012. “A Primer on Energy Efficiency for Municipal Water and Wastewater Utilities.” ESMAP Paper 68280, World Bank, Washington, DC. 4 Wastewater: From Waste to Resource © 2018 International Bank for Reconstruction and Development / The World Bank. 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