Alan Journet, Co-facilitator, Southern Oregon Climate Action Now
April 2021

After years of persuading us that Fossil (Natural) Gas is ‘the clean fossil fuel,’ the gas companies have come up with a new campaign.  This campaign is designed to convince us that they have a new improved replacement for natural gas: just as the misnomer for fossil gas is ‘natural’ gas, creating the impression of a benign, even healthful fuel, so the new term ‘Renewable Natural Gas’ creates the impression of a fuel that is environmentally benign, or even healthful. It is not!

Note that this discussion is not about CNG (Compressed Natural Gas) used as a transportation fuel and for other purposes. CNG is simply gas (whether shale-fracked fossil gas or synthetic RNG or biogas that is transported in and released from high pressure containers for combustion.  CNG suffers from all the drawbacks of the basic fossil gas or RNG.

Fossil Gas Basics in Brief:

  • Fossil (natural) gas is 85 – 95% methane (CH4).
  • When combusted to generate electricity, or heat, or whatever, methane is converted to and emits water (H2O) and the global warming gas carbon dioxide CO2).
  • When fossil gas is burned to generate electricity, the methane emits just over 50% of the carbon dioxide that is emitted by coal so, if assessed only in terms of combustion emissions, it appears cleaner.
  • Methane is 86 times worse as a global warming agent than carbon dioxide on a 20-year basis and 34 times worse on a 100-year basis.
  • From extraction by fracking (hydraulic fracturing in shale deposits) through processing and transmission, leakage (fugitive emissions) occurs.
  • Because of the high Global Warming Potential of methane, only about 2.8% leakage is enough to negate the combustion benefit noted above where burning methane emits about 50% of the carbon dioxide emitted by coal per unit of energy generated.
  • Studies of leakage over the years reveal that this leakage is either close to that critical 2.8% value or above it, meaning fossil gas is potentially as bad as coal.

For a more complete discussion of the drawbacks to fossil (natural) gas visit: Fossil Gas – A Bridge to Nowhere.

Renewable Natural Gas (RNG)

RNG is essentially produced one of two ways:

  • RNG as Synthetic Gas can be produced by an energy intensive process (electrolysis) that splits water (H2O) into Hydrogen (H2) and Oxygen (O2). The Hydrogen can be used directly as a fuel, or then inserted into Carbon dioxide (CO2) with Oxygen released as a by-product to produce methane (CH4). Unfortunately, “The energy value of the hydrogen produced is about 80% of the energy used to split the water molecule…” in the first place (https://www.carboncommentary.com/blog/2017/7/5/hydrogen-made-by-the-electrolysis-of-water-is-now-cost-competitive-and-gives-us-another-building-block-for-the-low-carbon-economy).  This means using fossil fuel to generate Hydrogen releases more greenhouse gases than would be used by just using those fossil fuels directly as an energy source. The catch to this process, then, is that to be effective, the energy used to manufacture the synthetic methane must be a renewable energy source otherwise substantial greenhouse gas emissions will inevitably result. Using fossil fuel to generate Hydrogen would undermine or even negate subsequent transmission and combustion benefits.
  • RNG as Biogas is produced biologically by the process of fermentation or anaerobic (oxygen-free) digestion / decomposition. This is parallel to what happens in the gut of cows (and other ungulates) where enteric fermentation results in their belching methane: CO2 + 4 H2 → CH4 + 2 H2 A second reaction involves Acetic acid: CH3COOH → CH4 + CO2.  The locations where RNG production is undertaken are commonly landfills using the biomass in the fill as the source, and Confined Animal Feedlot Operations (CAFOs) using manure as the feedstock for the anaerobic digestion.

When RNG or biogas is produced the process consumes carbon dioxide from the atmosphere.  When the gas is ultimately combusted to release its energy, the CO2 recently captured is released back into the atmosphere.   Thus the carbon dioxide released was recently extracted from the current atmosphere and is returned to it.  This is different from fossil gas and fossil fuels generally.  In these fuels, the carbon dioxide released when burned was trapped from an atmosphere hundreds of millions of years ago, and is thus transferred from that atmosphere to ours.  This is the reason that RNG has been labelled a Renewable energy source.  This is certainly a benefit over all fossil fuels.  However, as discussed below, there is little possibility that RNG will ever replace fossil gas.

In addition, unlike the process of fracking which results in fugitive emissions (leakage) of methane that potentially negates the combustion benefits of fossil gas versus coal and oil, the manufacture of RNG should not result in the release (leakage) of methane since it necessarily is sealed to exclude oxygen.  However, to reach an end-use the RNG must still be piped under pressure, during which leakage can and will occur.

The disadvantages of RNG, however, are several.

Availability:  The production of RNG relies either on the availability of an abundance of renewable energy to drive the manufacture of synthetic product, or an abundant supply of landfills and CAFOs to produce biogas.  While the abundant supply of renewable energy – especially during non-peak usage times, may arrive, we are not yet there.  Meanwhile, the need for abundant landfills or CAFO operations means that providing our energy need will promote either considerably increased consumption and waste production resulting in landfill proliferation or increasing meat and dairy consumption and the need for CAFOs.  Clearly, both methods of increasing Biogas RNG production should be avoided.

The result of these limitations is that RNG will likely be in limited supply.  Although the number of production facilities has grown three-fold over recent years, the expectation is that in the foreseeable future RNG will still only supply 4 – 7% of current fossil gas usage (https://www.greenbiz.com/article/7-things-know-about-renewable-natural-gas). The consequence is that over 90% of gas needs will still be fossil gas and means that our energy economy will continue to rely on fossil gas into that foreseeable future.  Regrettably, as we know, our timeline for action is short, requiring that we reach net zero emissions by 2050.  Since fossil gas infrastructure has an anticipated lifespan of many decades, (e.g., 50 years –  WILLIAMS TRANSCO CENTRAL PENN LINE SOUTH: A CITIZEN’S GUIDE) the strategy adopted by California, Washington and, apparently, Oregon of promoting RNG means either we are locked into the continued use of fracked fossil gas beyond that deadline making achievement of net zero emissions an impossibility or the gas providers will find themselves with pipelines as stranded assets.

Cost:  It is critical to assess the economics of RNG.  Reports suggest that  the current cost of RNG is between two and five times that of fossil gas. Monthly domestic gas bills could easily climb fivefold promoting a switch to less expensive energy sources. Given this likely outcome, it makes little sense to promote RNG rather than simply focus future energy strategies on the genuinely renewable sources.

Carbon Intensity: On the positive side of the leger, it is suggested  that RNG will likely reduce greenhouse gas emissions somewhat compared to fossil gas with a reduction to 55  – 60% when sourced from a landfill or sewage treatment plant.  However, given that RNG will not replace fossil gas, merely a small proportion of it, we will have to continue using fossil fuel to make up the difference and will continue with the current fossil gas economy.  There may be specific situations where RNG is beneficial, such as industrial processes where no net zero emissions option is possible.  However, generating RNG to provide a small percentage replacement of fossil gas is unlikely to provide much, if any, benefit.

Industry Obfuscation:  In promoting RNG, the gas industry frequently implies that fossil gas is being replaced by, or can be replaced by, RNG. However, as discussed above, the replacement is anticipated to cover only a very small proportion of the fossil gas.  This reflects the consistent focus on obfuscation gas companies have exhibited.  For example, when promoting pipelines (such a Pembina promoting the Pacific Connector Pipeline and Jordan Cove LNG export facility) they claim that the combustion of natural gas is cleaner (i.e., producing less carbon dioxide) than coal.  While correct, this totally ignores the fugitive emissions of methane from extraction through delivery to the end-use of the gas.

For an extended discussion of these drawbacks, please visit: The Four Fatal Flaws of Renewable Natural Gas. Meanwhile, a recent 2020 report revealed: “RNG is not inherently climate friendly. Based on consideration of both the source of methane used to produce RNG and the likely alternative fate of that methane, and using reasonable assumptions about likely system methane leakage, it is unlikely that an RNG system could deliver GHG negative, or even zero GHG, energy at scale.”

Although RNG may be useful in some limited situations, it is absolutely not a Renewable energy source like wind, solar, geothermal and wave sources or even hydroelectric energy.

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