Capture Landfill Gas Electricity Waste Heat
If the electricity project continues to operate, capturing waste heat from the landfill gas (LFG) electricity-generation equipment could offer additional revenue or offset onsite heating costs. Waste heat can be captured from the equipment's exhaust or jacket water and used in applications such as providing hot water or thermal heat, generating additional electricity using organic rankine cycle equipment or evaporating leachate.
Example
Three Rivers Regional Landfill, Mississippi 1, 2, 3, 4
Three Rivers Regional Landfill was paying more than 9 cents per gallon for offsite disposal of 12,000 to 24,000 gallons per day (gpd) of leachate at its local water resource recovery facility (WRRF), including transportation costs. Faced with the possibility that the WRRF could stop accepting leachate and the next-closest location would double their disposal cost, Three Rivers proactively sought an alternative solution.
Since 2012, Three Rivers has operated a reciprocating engine project on site that generates about 0.999 megawatts of electricity. Their search for an onsite leachate solution that would not take LFG from the electricity project led them to the Heartland Concentrator in a 25,000-gpd Hybrid Cogeneration for Industrial Evaporation (CoVAP™) configuration. This configuration combines cogeneration with additional heat from an LFG flare, a design to help those who want to beneficially use thermal energy from cogeneration but the heat is not sufficient to evaporate all the leachate.
The cogeneration expansion of the existing project came online in June 2019. By September 2020, the site had evaporated an average of about 23,000 gpd with a volume reduction of more than 96 percent. Employing the Hybrid CoVAP™ equipment allows Three Rivers to both evaporate leachate at full capacity and still run its energy plant without needing to compromise between the two.
Criteria:
- Onsite or adjacent demand for heat or steam.
- Waste heat can be captured from existing electricity-generating technology.
- For leachate evaporation – leachate disposal is unavailable or expensive.
Pros:
- Cost savings from offset heating or electric demands can be applied to LFG electricity technology operation and maintenance costs.
- Using waste heat does not decrease the amount of LFG available for the electricity project and increases the project's overall efficiency by recovering more energy content from the LFG.
- Regarding leachate evaporation:
- Can help offset costs from leachate treatment/disposal practices, helping the landfill's overall bottom line.
- Landfill owner has full control of its leachate handling.
- Leachate evaporator equipment can be purchased or leased.
Cons:
- Waste heat may not be sufficiently matched to the heat/electricity demand or quantity of leachate needing treatment.
- Savings from avoided leachate treatment may not be the most cost-effective project alternative.
Economic Considerations:
- Cost savings are site-specific but in the example at right, Three Rivers Regional Landfill reduced leachate disposal costs from about 9.5 cents per gallon to 6 cents per gallon.
More Information:
- LFG Energy Project Development Handbook Chapter 3. Project Technology Options, EPA LMOP
- LMOP Webinar "Don't Waste the Heat!", EPA LMOP
- Combined Heat and Power Partnership, EPA
References
1 U.S. EPA. LMOP Landfill and Landfill Gas Energy Project Database. July 2021. https://www.epa.gov/lmop/lmop-landfill-and-project-database.
2 Heartland Water Technology. Case Studies. Three Rivers Regional Landfill. A Cogeneration Solution for Evaporating Landfill Leachate. https://www.heartlandtech.com/case-studies. Accessed December 17, 2021. Filename “Case+Study+-+3+Rivers_final.pdf”.
3 Weigold, John. MSW Management. A Cogeneration Solution for Evaporating Landfill Leachate. March 2, 2021. https://www.mswmanagement.com/landfills/leachate/article/21209790/a-cogeneration-solution-for-evaporating-landfill-leachate. Accessed December 17, 2021.
4 Cammann, Casey. Heartland Water Technology. Email correspondence. June 14, 2021.