Satellite Data Promises Truer Accounting for California’s Low Carbon Fuel Standard

In 2025, new satellite data could, for the first time, give a full account of California dairy methane emissions. But it will be too late to influence Low Carbon Fuel Standard revisions happening now.

Image Source: MethaneSAT, <https://www.methanesat.org/satellite>

On October 1, the California Air Resources Board (CARB) issued proposed revisions to its Low Carbon Fuel Standard (LCFS). CARB’s latest 15-day public comment period ended October 16, and revisions will likely be finalized at a hearing on November 8, after the upcoming election. The revision process, which has been underway since last year, has been hotly contested. This is partially due to the difficulty of measuring methane emissions, as reducing those emissions is currently a key component of the program. Two new satellite systems – CarbonMapper’s Tanager series, the first of which, Tanager-1, launched this summer, and MethaneSAT, a satellite launched earlier this year by the Environmental Defense Fund and partners – could be the answer to this challenge, but a full look at this data will not be available until 2025.

The LCFS is a significant component of California’s strategy to reduce greenhouse gas emissions. The program aims to “decrease the carbon intensity of California's transportation fuel pool and provide an increasing range of low-carbon and renewable alternatives, which reduce petroleum dependency and achieve air quality benefits.” One component of the LCFS issues credits for avoided methane emissions. 

Dairy farms, frequently with the help of digester developers like CalBio Energy, install anaerobic digesters to collect these credits in a lucrative double dip. The farms collect the methane they produce from manure storage, sometimes referred to as factory farm gas. In turn, this captured methane produces two sources of revenue: (1) valuable credits through the LCFS avoided methane emissions scheme; and (2) sales of the methane itself, which can be purified and introduced into the gas system. 

Avoided methane credits are one of the most contested elements of the program, and the recent revisions have largely left them in place, at least for the next several decades. They are premised on the principle that anaerobic digesters are collecting methane that would have otherwise been produced and vented to the atmosphere. Because of this assumption and the potency of methane as a greenhouse gas, the program assigns a highly negative carbon intensity to methane from factory farms, whereas solar and wind energy, for example, sit at zero.

Average carbon intensities for different facility types under the LCFS, with dairy manure pathways averaged on the left-hand side of the graph for production of electricity and production of compressed natural gas. Both averages are highly negative. Graph created by Sabina Mahavni.

Environmental justice advocates argue that avoided methane credits further intensify the pollution and associated health risks that factory farms generate. Over the past two decades, California's dairy industry has already seen significant consolidation as small farms have disappeared.¹ Between 2002 and 2022, the percentage of California’s dairies that contained more than 500 animals went from approximately 39% to approximately 75% – in other words, from less than half of California’s dairy farms to three-quarters of them. This consolidation has resulted in larger herds with large quantities of manure. For instance, Phoebe Seaton, co-director of the Leadership Council for Justice and Accountability, points out that “CARB’s current approach…ignores that managing manure in massive manure pits that maximize methane emissions is a choice, not an inevitability, and even encourages and incentivizes that practice.” 

This choice matters - there are other methods of managing manure that could produce less methane. For example, Brandt Cattle Company spreads their manure in fields to ensure it decomposes aerobically.²

Environmental groups also point out that factory farm gas, once cleaned and incorporated into the gas system, will still be distributed through the same leaky pipelines that a recent study estimated emit 690,000 metric tons of methane per year, meaning that it will continue to contribute to and perpetuate this unintentional source of emissions.

One complication in resolving these tensions is that it is hard to tell exactly how effective the LCFS truly is at abating the state’s methane emissions: currently, decision makers lack the ability to truly and fully account for dairy farm methane. For instance, one recent study that used remote sensing to quantify methane emissions from California dairies found that CARB underestimated these emissions by 60%.

There are two sources of dairy farm methane emissions:

• Enteric Methane: Produced during digestion and expelled by cows.

• Manure Methane: Generated from the decomposition of cow manure when stored in anaerobic holding tank environments.

Digesters only collect manure methane, and even so, they suffer from leakage and are not able to capture all emissions in the digestion process. Enteric emissions in dairy farms still persist even in the presence of digesters, and in some cases those emissions can equal or exceed those produced by manure storage.  In short, the efficacy of digesters in reducing emissions - and thus, the accuracy of the highly negative carbon intensity score currently assigned to digester use by the LCFS - is not entirely clear, and can only be fully understood if the total amount of emissions from a given facility or operation is accurately accounted for.

Satellite data may hold the key to characterizing this problem in order to properly assess this policy. MethaneSAT and Tanager-1 are the first satellites led by environmental nonprofits to quantify global methane emissions, and they have complementary capabilities. MethaneSAT has two highly sensitive, custom-built spectrometers offering continuous, real-time, high fidelity data over wide areas that enable it to precisely measure change over time. CarbonMapper, which already has been recording point source methane emissions via plane flyover measurements, will now use Tanager-1 as the first of a coming network of satellites with a narrower field of view to zoom into individual facilities and augment existing point source data that can be accessed now on their data portal. Existing flyover data is currently so sparse that it’s difficult to draw concrete conclusions from emission measurements at a dairy farm before and after digester installation – a problem that these new satellites will largely remedy. And these satellites’ data will not only track dairy farms in California – they will also be used to monitor oil and gas infrastructure and provide valuable data from around the world.

Screenshot from CarbonMapper data portal of a digester-equipped dairy farm.

Although the first tranche of Tanager-1 data has begun to become publicly available, MethaneSAT’s data won’t be available to the public until next year, by which point LCFS revisions are expected to be finalized. CARB should strongly consider incorporating findings from that satellite data in its future decisionmaking on the LCFS – including to evaluate the real-world accuracy of its carbon intensity score – as well as in the context of directly regulating methane emissions and when it evaluates its greenhouse gas inventory and reporting requirements. 

As policy makers, environmental justice groups, and other stakeholders await amendments to the LCFS and the release of MethaneSAT data, it’s clear that precise and accurate methane accounting is essential for making informed policy decisions that measurably achieve California’s ambitious climate goals.

1. This data also shows that between 2002 and 2022, the number of farms with less than 500 milk cows decreased by 77%.

2. Note that due to enteric emissions – meaning methane emitted when cows burp – the Brandt Cattle Company remains one of the state’s largest emitting point sources.