Climate Notes: Methane
Experimenting with a new, “raw” format of sharing notes on what I’m learning in climate. Feel free to use it if it’s helpful and share any feedback, corrections, or additions you come across.
The Problem
For a time horizon of 100 years, CH4 has a Global Warming Potential 28 times larger than CO2. Each molecule is 84x more warming than CO2
Methane is responsible for 23% of the global warming produced by CO2, CH4 and N2O in the 20th century.
The concentration of CH4 in the atmosphere is 2.5x above pre-industrial levels (750ppb —> 1800)
Methane remains in the atmosphere for ~10 years (though exactly how long depends on atmospheric hydroxyl radical levels, of which we don’t have a great way to measure). This makes methane a big lever to reduce warming as reduced emissions —> reduced warming within a decade.
Stock v. Flow: Stock gases are long-lived and build up in the atmosphere (e.g. CO2). Flow gases are naturally removed from atmosphere over time (e.g. CH4). Solve the flow problem for methane and you solve the warming problem within the decade.
Concern that melting permafrost may contain high levels of methane ("methane bomb") that is emitted as planet heats up and ice caps melt.
“Million paper cut” kind of problem: Methane emitters are usually diffuse (manure fields, abandoned mines, municipal landfills) and while the tech isn’t hard (“more plumbing v. rocket science”) requires policy > behavior change > enforcement.
Methane Budget
Each year we emit a net ~16.8 Tg CH4 / yr. Natural + human emissions of ~592 Tg / yr and sink ~571 Tg / yr.
Emissions: Ag, Fossil Fuel production represent anthropogenic sources. Wetlands & Biomass Burn represent natural sources.
Sinks: Soils + Atmospheric Reactions (see below) are the major sinks
Percentage and total Tg/yr of CH4. Based on Global Methane Budget 2008-2017
Opportunities
CH4 warming mitigation represents a potential short-term fix for global warming, as methane traps a lot of heat per molecule but is relatively short-lived. Reducing methane levels can buy us more time to scale up carbon capture. Number of atmospheric molecules you'd need to reduce is much smaller than CO2 (but also far more diffuse)
Methane Emission Reduction strategies
Measuring Methane Leaks: Key ingredient to reducing methane is to be able to detect leaks in industrial process. MethaneSat is launching a satellite + data platform for monitoring methane concentrations globally. CarbonMapper and JPL already provide a public dataset to explore. One of the interesting opportunities is to use this mapping tech to allocate and enforce international policy commitments in ways not previously possible with carbon.
via methane.jpl.nasa.gov/ Natural Gas > Electrification: Stop installing gas cooktops and gas furnaces, and substitute electrical appliances
Warning on alt uses for Natural Gas: Do not start using natural gas to produce hydrogen, even if you’re capturing the carbon emissions from the process. This so-called “blue hydrogen,” beloved by oil and gas companies, and included in the bipartisan infrastructure bill, does not cut global-warming emissions, in large part because of the methane that vents out in the process
Cow Feed Additives: Reduced methane emissions from cattle with (Mootral), e.g. garlic & citrus extract has been shown to reduce methane emissions of cows by ~30%
Flaring: converts methane leaks to CO2 (Frost Methane). Sounds a bit dirty but can reduce equivalent CO2 emissions by 98%
Methane Sink strategies
Enhanced atmospheric methane oxidation: Methane Action is looking into ways to use bunker fuels (emitted from ship stacks) which contain iron. Iron, sunlight + salt-sea spray generates a mix of iron trichloride and chlorine atoms, which may oxidize methane. This is just one of many sources of iron, but you need concentrated FeCl3 concentration to oxidize methane
Methane oxidizing bacteria (e.g. Methylocapsa gorgona, found in soil) can oxidize atmospheric methane. We haven’t been able to successfully cultivate this bacteria to scale CH4 oxidation
Questions
What prevents us from measuring atmospheric hydroxyl radicals levels?
Mystery: Methane is naturally oxidized in the atmosphere by hydroxyl radical (OH). CH4 levels plateaued around the year 2000 before resuming globally in 2007. We are unable to measure presence of OH at scale, making it unclear how long methane remains in the atmosphere
What’s the limiting factor on scaling methane-oxidizing bacteria?
Is there a way to create a realtime dashboard of methane emissions attributed to the source based on satellite data?