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Biogas Treatment & Renewable Natural Gas Production

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Overview

In 2018, the City of Longmont will begin construction of a project at its Waste Water Treatment Plant (WWTP) to make fuel from gas produced in the treatment of Longmont's sewage. The project will convert biogas (generated through anaerobic digestion) into clean Renewable Natural Gas (RNG). The RNG produced will then be used to power the City’s trash trucks.

Upon completion of the RNG fueling station in 2019, 11 of the City’s 16 diesel trash trucks will be replaced with trucks capable of using RNG fuel (this change-out aligns with the existing replacement schedule for those trucks). The remaining five diesel trucks will be replaced in 2021.

The RNG fueling station is an example of the City pursuing an innovative project that provides economic value to the community while also aligning with multiple goals in the Envision Longmont & Sustainability plans.

Learn more about the project by following along with the blog run by CGRS, a Fort Collins-based environmental services and construction company partnering with the city.

Why is this project so exciting?

  • Renewable Vehicle Fuel – A renewable resource is a resource which can be used repeatedly and replaced naturally. This project will create a renewable vehicle fuel for the City’s Sanitation fleet which is composed mainly of refuse collection trucks.
  • Reduce Carbon Emissions – On average, the Sanitation Department uses over 90,000 gallons of diesel fuel per year. By switching to renewable vehicle fuel, this project will eliminate over 1,000 metric tons of CO2!
  • Innovative & Sustainable – Longmont is dedicated to fulfilling the goals set forth in the Sustainability Plan. This project is a collaboration between two different City departments (Wastewater and Sanitation) to improve local air quality and sustainably recover energy in waste.
  • Expandable – The Sanitation department will use 50-70% of the biogas produced at the Wastewater Treatment Plant (WWTP). The infrastructure in this project can be easily expanded to serve other types of fleet vehicles.
  • Front Range Leader – Longmont will be the first city on the front range to implement a renewable vehicle fuel project. Other utilities have been looking at Longmont as a model for their operations.

So how does the City produce this “renewable vehicle fuel”?

It all starts with Anaerobic Digestion. The City’s Wastewater Treatment Plant (WWTP) uses this biological process to break down organic material. One of the produces of Anaerobic Digestion is biogas. Approximately 60% of the biogas is composed of methane (the combustible compound found in natural gas that you use at your home).

What does the City do with that biogas right now?""

Currently, 75% of the biogas produced is flared (wasted) because only a portion is needed for heat at the WWTP. In addition, the biogas contains contaminants (H2S, Siloxanes, Moisture) which prevent it from being used directly in engines.

So how do we go from producing biogas to using “renewable vehicle fuel”?

New infrastructure will allow the City to clean, compress, and utilize the biogas as a “renewable vehicle fuel"


""Cleaning Biogas

A biogas treatment skid will be installed to remove all the contaminants in the biogas. This will make the biogas the same as the natural gas at your home!

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Compressing Biogas

The pressure of the clean biogas is about 100 psi. To use the fuel in vehicles, compressors will boost the pressure of the biogas to over 4,000 psi!

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Utilizing Biogas

New Sanitation trucks are outfitted with engines capable of using compressed natural gas instead of diesel. With a new fueling system, the cleaned & compressed biogas can now be used as vehicle fuel!

 

But does the project provide financial benefit?

  • Fuel Savings - After the project is complete, the Sanitation department will no longer pay for diesel fuel. As we all know, fuel prices at the pump are variable. If diesel fuel is $3.00/gal, and we are no longer using 90,000 gallons per year of diesel, that’s $270,000 saved per year!
  • Renewable Fuel Credits - In addition to fuel savings, the City will also be earning credits through the EPA’s renewable fuel standard program. The annual benefit associated with these credits is $150,000-$250,000 per year!
  • Grant Funding - The Colorado Department of Local Affairs awarded the City with a $1,000,000 grant to contribute to the project!

Contact

For more information on this project, please contact Environmental Services.

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