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EnvironmentUnraveling LA’s Hydrogen Combustion Experiment

Unraveling LA’s Hydrogen Combustion Experiment

Unraveling LA’s Hydrogen Combustion Experiment

Combusting hydrogen could keep natural gas plants online, but they won’t be “green” for years––if ever.

That is Part II of “Unraveling Hydrogen,” a series covering the fundamentals of hydrogen policy. The primary post, introducing the series and covering how hydrogen is produced, is obtainable here.

Photo from Zeppelin Museum Friedrichstein (CC BY-NC 2.0)

Led Zeppelin’s eponymous 1969 album featured an iconic photo of the Airship Hindenburg going up in flames above Lakewood, Recent Jersey in 1937. By all accounts, it took between 32 and 37 seconds from the primary signs of a hearth for the dirigible to return plummeting to the bottom. The hearth and resulting crash killed 36 people.

While this disaster spelled the tip of the airship era, it also sealed the image of hydrogen as a volatile and dangerous fuel in the general public consciousness for many years. The general public generally blamed the accident on the seven million cubic feet of hydrogen installed at the middle of the ship. In subsequent years, hydrogen was mostly limited to make use of as feedstock for industrial applications­, including the production of fertilizers, synthetic textiles, and drug precursors.

But with the recent influx of presidency incentives for hydrogen production, latest and improving production and storage technologies, and greater political will than ever before, H2’s status is gaining favor. Hydrogen’s supply-side has been buttressed by incentives from state and federal governments, refineries and utilities trying to extend the lifetime of fossil fuel infrastructure, and renewable energy corporations in search of to benefit from the massive amounts of fresh energy needed to supply green hydrogen. But this still leaves questions on the demand-side market. What if––despite the hype and incentives around hydrogen production––it still struggles to beat incumbent technologies and practices like battery storage, demand-response, or electrification of buildings and vehicles? Or, perhaps more realistically, what if hydrogen policy evolves to artificially prop up the marketplace for hydrogen, even where decision-makers could higher serve the climate and the environment by promoting other strategies?

Within the abstract, the use-cases for hydrogen are broad. Hydrogen might be used for medium-to-long-term energy storage, heat and power generation, and transportation. But for a lot of these use-cases, hydrogen doesn’t do the job particularly well, at the very least as in comparison with existing technology. That is partly because hydrogen production is energy inefficient and––when derived from fossil fuels––still a big source of carbon emissions. Inefficient end uses for hydrogen can further exacerbate this problem. Critically, and as we’ll discuss in greater depth shortly, hydrogen combustion (versus its use in fuel cells) also results in greater emissions of nitrogen oxides (NOx), a toxic group of pollutants regulated under the Clean Air Act.

All this shouldn’t be to say there is no such thing as a place for hydrogen in a clean energy future. Green hydrogen––produced with renewable electricity and water­­––is usually described as a tool for decarbonizing the difficult last 10% of greenhouse gas emissions. Then again, cramming hydrogen into roles that it shouldn’t be fitted to will do more harm than good for health and climate outcomes. Subsequently, the following few entries on this series discuss the varied potential uses for hydrogen and their utility in advancing climate goals, starting with the combustion of hydrogen in natural gas plants.

Photo from user Facewizard, Wikimedia Commons (CC BY-SA 4.0)

I originally wanted this entry to cover a broad sampling of essentially the most steadily discussed use-cases for hydrogen. Nevertheless, hydrogen combustion is solely too topical without delay to not devote a complete post to it. Los Angeles City Council voted last month to maneuver forward with an $800 million plan to mix hydrogen with natural gas (“hydrogen mixing”) on the Scattergood Generating Station, which has received significant attention (including from our own Professor Zasloff) and notably been known as a “greenwashing boondoggle.” Much of the media coverage focused on how the goal is to ultimately (eventually, hopefully) burn 100% green hydrogen. What’s far more certain is that this gas plant will probably be burning a mix of methane and hydrogen for years.

The reasoning behind most hydrogen mixing proposals is familiar. It generally follows the identical logical sequence that gas corporations invoke when defending the continued need for natural gas plants: Proponents argue that almost all renewable energy is intermittent, and batteries––while useful in smoothing variation in solar and wind power over each day cycles––cannot yet cost-effectively store power during multi-day storms or other contingency events that will inhibit renewable generation. Because of this, as we transition to carbon-free energy, we still need firm power, and geothermal, nuclear, and hydroelectric are either difficult to scale, expensive, or politically inexpedient. Natural gas plants retrofitted to mix hydrogen, supporters insist, can cheaply and reliably fill this need with infrastructure that already exists.

By combusting hydrogen, these natural gas plants would stay online, but they’d have a somewhat smaller carbon footprint, and will provide firm energy to satisfy demand. Proponents of those projects argue that, if natural gas plants are sticking around anyway, reducing their carbon emissions through mixing is a low-hanging fruit. LADWP has even expressed a long-term––albeit aspirational––interest in further retrofitting these plants to burn only hydrogen by 2035. As straightforward as this sounds, nonetheless, hydrogen mixing shouldn’t be the answer that supporters make it out to be.

As promised previously, let’s begin by talking about NOx. NOx can form when naturally-occurring nitrogen within the air splits and oxidizes under high temperatures. This process doesn’t require any specific fuel; it just needs a hot-enough combustion response. The warmer the response, the more NOx is created. This creates an issue for hydrogen mixing, as hydrogen burns

Chart adapted from Madeleine L. Wright, Alastair C. Lewis, Emissions of NOx from mixing of hydrogen and natural gas in space heating boilers.

about 500º F hotter than natural gas. One group of researchers found that burning pure hydrogen may produce six times as much NOx as burning natural gas.


NOx is a dangerous criteria pollutant. It’s linked to premature death, cardiopulmonary effects, decreased lung function in children, respiratory symptoms, and emergency room visits for asthma. It’s also a precursor to other pollutants, including ozone (a key component of smog).

All this makes NOx a premier example of environmental injustice here in California. It’s emitted by refineries, ports, freeways, and industrial operators, which exist largely in communities of color and low-income communities. Unsurprisingly, natural gas plants are also disproportionately positioned in environmental justice communities; “half of California’s natural gas power plants are positioned in communities that rank among the many 25% most disadvantaged.” Thus, proposals to retrofit existing natural gas plants with technology that will produce more NOx have received widespread criticism from environmental justice advocates. Constructing on these concerns, outgoing Councilmember Mike Bonin issued an open letter stating that increasing NOx emissions near environmental justice communities is “shouldn’t be an appropriate tradeoff to realize carbon reductions.”

But NOx shouldn’t be the one issue with hydrogen mixing. For starters, it is pricey to retrofit natural gas plants with the technology to combust hydrogen. As noted above, LADWP estimates that it should cost $800 million to outfit Scattergood with the technology to burn a 30% hydrogen mix (although some, including former city council members, imagine this price will ultimately balloon to over $1 billion). While many proponents of hydrogen mixing argue that these plants will sooner or later burn 100% green hydrogen, there are currently no commercially available power plant turbines that may burn pure hydrogen. While small-scale demonstration projects burning pure hydrogen are set to turn out to be operational soon, the fee of retrofitting a big gas plant like Scattergood with this technology is unclear. Furthermore, transporting anywhere near that quantity of green hydrogen would require much more significant––and even dearer––investments within the distribution system.

It’s also necessary to notice that––upstream impacts aside––combusting a 30% hydrogen mix doesn’t translate to a 30% drop in carbon emissions. Hydrogen is much less energy-dense than natural gas, meaning that the proportion of hydrogen burned by volume shouldn’t be reminiscent of its share of energy generated. For this reason, a 30% hydrogen mix by volume delivers only a ten% reduction in carbon dioxide emissions. Furthermore, as we’ll discuss in greater detail in later entries, hydrogen leaks may offset any climate profit promised by hydrogen mixing. Hydrogen is an indirect greenhouse gas that’s as much as 100 times stronger than carbon dioxide over a ten-year period.

The entire above creates a reasonably dismal outlook for hydrogen mixing in natural gas plants, however it doesn’t necessarily address the most important talking point that supporters recommend: we still need firm energy, and hydrogen can reduce a few of those carbon emissions.

After all, this argument ignores the chance cost of constructing out the renewable generation needed to produce the green hydrogen underpinning these mixing proposals. Proposals like LADWP’s Scattergood plan are silent on how they’ll source their green hydrogen (although LADWP likely envisions that it should come from SoCalGas’ nascent Angeles Link proposal). Nevertheless, it’s clear that these producers will need dedicated supplies of renewable energy. A few of this may come from contracts for renewables that will otherwise be curtailed, but outside of relatively rare contingency events, that very same energy could possibly be paired more efficiently with battery storage or exported on to the grid.

Ultimately, hydrogen mixing proposals promise little in the way in which of climate advantages, but include a high price tag, uncertainty in each feasibility and advantages, and jeopardize the health of local communities. And that’s to say nothing of the moral hazard of constructing huge investments into fossil fuel infrastructure, which can ultimately be passed along to ratepayers and will justify keeping that infrastructure online for a few years.

In the following installment: A continued dive into hydrogen’s various use as a transportation fuel.


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