Colorado Public Works Journal, Spring 2019

14 Colorado Public Works Journal Biogas Treatment & Renewable Natural Gas City of Longmont Takes the Lead in Sustainable Fuel Production Fueling a fleet is one of the largest costs associated with managing vehicles in a Public Works department. From the environmental standpoint, fueling vehicles also contributes significantly to environmental pollution, and environmental degradation. A fleet of municipally owned vehicles is essen- tial for city operations, and is often one function that doesn’t get much press. But what if there was a way to fuel a fleet of vehicles, decrease environmental impacts with a renewable resource, AND create a fiscally and operationally sustainable option instead? Sounds too good to be true, but the future has arrived, and the City of Longmont has taken the lead. In late 2018, Longmont began construction on its Biogas treatment sys- tem and Renewable Natural Gas (RNG) fueling center. A first of its kind in the Front Range, this process leads the way in what the future holds for municipal fleet operations in Col- orado. Sustainability – A Plan for the Future In 2016, the City of Longmont published its first Sustainabil- ity Plan. This document, created under the vision of multiple city departments, provided direction for the city in sustain- able operations and future decision making. The goal of the sustainability plan was to create a Longmont that was a vi- brant and community where every resident could thrive. The sustainability plan not only focused on environmental sustainability, but also looked at sustainability from the fiscal, planning and operational functions of the city. Ten areas were addressed in the City’s sustainability plan including Air Quality, Economic Vitality, Energy, the Natural Environment and Transportation. The RNG project impacts all of these factors within the plan for sustainability, by providing a fuel source that is renew- able, cost effective and better for the environment. In one small step, Longmont is already creating a better place to live for its residents. What is Biogas and Renewable Natural Gas and Why it’s Great! Biogas is a natural byproduct of the decomposition of natu- ral materials. Biogas has, for many years, been harnessed in livestock operations as a fuel source for heating barns and fueling equipment. So long as there are operations that have an organic, natural waste source, the production of biogas is possible. Renewable natural gas, is a treated form of biogas. Identical in chemical composition to fossil natural gas (the same natu- ral gas used in your home), RNG is a man-made product with unlimited production potential. When combined with existing processes and infrastructure, RNG and biogas treatment are a great option for helping municipal fleet services save money and be better stewards to the environment. RNG Production at Longmont’s WWTP In 2018, following the City’s first greenhouse gas inventory, it became clear that there were ways that Longmont could take steps to reduce greenhouse gas emissions, and start the process of creating environmentally sustainable processes within the city. The greenhouse gas inventory gave the city an opportunity to evaluate strategies for reducing greenhouse gasses. RNG was one of a number of strategies identified. Anaerobic digestion is a typical process in waste water treat- ment. The process uses bacteria to decompose the solids and sludge produced during treatment. This process creates a significant amount of biogas. In many waste water plants including Longmont’s, this biogas is used to heat the plant and the rest is “flared” or wasted by burning off. Because of the abundance of biogas produced in anaerobic digestion, it is an ideal source for generating RNG. Longmont contracted with the team of CGRS and Carollo En- gineers to design and construct the project. CGRS, based in Fort Collins, is the project lead and responsible for design of the RNG fueling system and construction of the entire proj- ect. Carollo Engineers, with offices in Broomfield and Little- ton, designed the RGN system. Both firms have broad portfolios of work relating to waste water treatment and RNG treatment systems. Construction of the biogas treatment system and RNG fuel- ing infrastructure began in late 2018. The Longmont biogas treatment and RNG delivery project, has three components: • Biogas treatment • RNG Pipeline and Fueling Center • Ad- ministration Building The Biogas treatment system will remove impurities from the biogas such as water, hydrogen sulfide, and other organic compounds, resulting in a product that is a minimum of 90 percent methane, and will be chemically identical to the natu- ral gas that is used to heat homes and businesses. The end product is Renewable Natural Gas. The biogas treatment process will also pressurize the RNG to 4,000 psi, allowing it to be stored and distributed to vehicles. by Tamara Moon Image © CRGS

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