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Overview

published on

September 2021

The U.S. produces almost 70 million tons of waste each year[1], which, over time, generates biogas with the help of bacteria. Biogas is a mixture of methane, carbon dioxide, and other trace gases and is generally released into the atmosphere. However, waste collection plants are now looking at ways to collect the biogas and refine it into pure methane, also known as Renewable Natural Gas (RNG). RNG can be used for injections into existing natural gas pipelines or used as fuel for RNG-dependent transportation vehicles.  In recent years, the number of RNG plants has grown significantly within the U.S.

Despite the many benefits and solutions that RNG provides, hazards are still present, and because RNG is a relatively new technology, these hazards aren’t as commonly known. Most RNG plants are small and not covered under OSHA PSM 1910.119, which is required if a facility contains 10,000 lbs. or more of flammable gas or liquid. However, when dealing with flammable and toxic materials, it is important to recognize the potential hazards and/or risks associated with the process regardless of formal requirements.

Examples of previous incidents and studies conducted by BakerRisk illustrate the significant hazards that are present in RNG plants:

  1. An explosion in the Anaerobic Digester (AD).
  2. An overpressure or vacuum within the Animal Waste AD, causing the release of toxic and flammable material into the atmosphere.
  3. An explosion in an  enclosed Compressor Building.

The White Paper, “Renewable Natural Gas: considerations for the safe design and operation for an innovative process for achieving a sustainable future”, discusses each of the events described above, highlights the potential hazards, and provides examples of potential safeguards and/or mitigations that could be employed to reduce injury or fatality.

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[1] Tanikawa, S., “Fact Sheet | Biogas: Converting Waste to Energy,” Environmental and Energy Study Institute, October 13, 2017, https://www.eesi.org/papers/view/fact-sheet-biogasconverting-waste-to-energy.