Dairy aerobic digesters are used in the treatment of cattle manure and urine in efforts to curb methane output from industrial cattle farming. This method involves covering manure lagoons with a plastic sheeting that captures the anaerobically-generated biogas (methane) that is released when the organic waste is broken down by naturally occurring microbes. Once the methane is captured in the digesters, it can be refined into “renewable natural gas” (RNG). It can then be used in place of fossil natural gas [1], to replace more carbon-intensive fuels such as gas and diesel [2]. Globally, countries such as China, Germany, the USA, Italy, UK and France are deemed to be leading in the biogas sector in the world due to long intensive and well funded research, as well as government incentives [4]. As of March 2022, there were about 330 anaerobic digester systems operating at commercial livestock farms in the United States [9]. Due to immense state funding, California is the state in the US with the most dairy digesters. Supporters of the dairy aerobic digester process point to the California Air Resources Board’s study which found that on average vehicles running on RNG reduced CO2 emissions between 49 and 59% less carbon per unit of energy compared to diesel vehicles [1] [2].

So far, the majority of research has been into curbing emissions from enteric fermentation (the methane produced from cattle ‘burps’), yet almost 10% of methane emissions in the US come from manure management practices [3]. In comparison, the practice of using dairy aerobic digesters is seen by critics as a technological “bandaid fix” [18]. Treating the root cause could be changing the cattle's diets or, to go even further, decreasing industrial intensity of cattle farming.

Big Oil investments and joint ventures with industrial agriculture

In the US, Big Oil companies have been heavily supporting the shift towards RNG. BP are buying the upstream portion (the manufacturing and processing part) of Clean Energy Fuels Corporation for $155 million, additionally signing a long term contract agreeing to support Clean Energy in their renewable gas business further down the supply chain [5]. This kind of agreement is not uncommon amongst big oil and RNG companies. In 2021, Total also entered into a new joint venture with Clean Energy, with the initial investment into building renewable gas production facilities set at $100 million [10]. Furthermore, following the success of Shell’s first biomethane plant in the US - New Energies Junction City in Oregon [7] - the company began construction of two more RNG facilities in 2021. Shell’s Downstream Galloway Biomethane facility in Kansas as well as its Downstream Bovarius at the Bettencourt Dairies in Idaho are two more facilities that add to Shell’s expanding biofuels portfolio. Together, these two dairy RNG facilities will be able to produce approximately 900,000 MMBtu a year of "negative carbon intensity RNG" [8] [6]. 

Chevron and Brightmark LLC (a global waste solution company) entered into a joint venture together in 2021, committing to funding the necessary construction of infrastructure and commercial operation of dairy biomethane projects in several states in the USA [11].

These examples indicate that over the past 3 years there has been an increased interest from big oil companies in the production of RNG. As industrial agriculture and Big Oil - two of the world’s largest polluting industries [18] - continue to partner up in these joint ventures, we are subsequently becoming locked into business deals with huge polluting potential. 

Public funding supports the industry and incentivises more dairy farms

Researchers have found that replacing fossil fuels with biomethane from dairy RNG projects is “not likely to be commercially feasible without large subsidies” [12]. However, lavish public funding means that for those who invest and win the publicly funded

contracts, dairy digesters can also paradoxically be very lucrative [13][14][15]. Critics point out that in California specifically, many of these contracts have been awarded to just 2 developers - the research and development programme set up by the state awarded over $180 million [13] to 109 projects, Yet, 95% of these projects are operated, owned and financed by Maas Energy Works and California Bioenergy. These companies have indirectly monopolised this market in California receiving between $82.5 million - $99 million each for the projects they manage [13]. 

This kind of funding ends up acting as monetary incentives for farmers too - who benefit from the profits made possible by the public subsidies. This in turn props up interest in running Concentrated Animal Feeding Operations (CAFOs) and enlarging dairy operations.

Health Impacts

Researchers found that it is exactly these kinds of large CAFOs that have the capacity to operate dairy digesters that can have a detrimental impact for local communities and the environment [14]. There are many negative health issues that burden communities adjacent to industrial agricultural projects such as exposure to ammonia, hydrogen sulphide, methane, and particulate matter contaminating the air, and zinc and nitrates found to contaminate the nearby soil and water [12][15].

Further to this, as more public funding that is meant to promote and enable good public health is committed to these kinds of projects, small scale, comparatively more sustainable agroecology farms will find it increasingly difficult to affordably farm and own land [18]. Small dairy farms do not benefit from the dairy RNG subsidies. Indeed, in 2022, it would cost $4.7 million to build a digester in a farm with less than 5,000 cows, and if you had 14,000 cows, it would cost $9.7 million [20] - the amount a farmer receives in subsidies grows with the number of cows. To this effect, small dairy farmers are left behind, often with financial worries. In Vermont, nearly half the predominantly small dairy farms went out of business between 2012 - 2022 [21]. Without access to large monetary subsidies, small farms cannot keep up with the bigger farms as they diversify their produce by entering into the energy sector. 

Carbon Credits

The California Environmental Protection Agency (EPA) website explicitly states that Cap-and-Trade investments are “aimed at improving public health, quality of life and economic opportunity in California’s most burdened communities, and at the same time, reducing pollution that causes climate change” [17]. In 2019, California brought into force a Cap-and-Trade programme incentivising companies to reduce their emissions below their allocated cap [16]. The programme effectively operates as a carbon credits market, in which dairy RNG's can sell carbon emissions allowances for the carbon they claim to prevent from entering the atmosphere [23].

Offering a carbon credits scheme that rewards the production of otherwise-avoidable methane in turn incentivises the expansion of farms. The director of fuel policy at the Clean Transportation Program, Jeremy Martin, wrote that "the value of LCFS credits (carbon credits) for a large, confined animal feeding operation (CAFO) dairy vastly exceeds the cost of recovering the biomethane". Equating these two things through establishing a "trade off" credits system is ineffective, and misleading in the fight to curb greenhouse gas emissions [25]. Making RNG carbon credit-able is also an example of how heavily polluting fossil fuel-fired hydrogen production facilities—the very facilities that carbon tax credit is trying to incentivize a shift away from—can disguise themselves as “clean” [26].

Greenwashing of PR

Critics of dairy digesters, such as NGO Food & Water Watch, point out the clever name change of “biomethane” to “renewable natural gas” as just one example of how this industry attempts to greenwash RNG, making it more appealing to the public. Misleadingly using the word “renewable” is an attempt to contorte one of the symptoms for climate change as a solution [18]. In order for RNG to provide meaningful change, it relies on the improbable condition that in the conversion of biogas into biomethane, no methane will leak. Yet, studies have shown that these systems are categorically prone to leakage [19].

In 2018, a report was published by the Environmental Protection Agency that detailed the market opportunities for biogas recovery systems at U.S. livestock facilities [20], mentioning the economic and environmental benefits, with no mention of potential issues and dangers that could arise. It is clear that these projects can be lucrative for the few large companies working in the biomethane processing sector. Additionally, the farm to fuel nexus is fortified with the joint ventures and investments being made by big oil companies. Where does the biomethane boom leave the rural communities or ecosystems?

330 dairy digesters in operation on farms across the USA (2022)

- Shell New Energies Junction City in Oregon - 736,000 MMBtu a year of Renewable Natural Gas (RNG)

- Shell’s Downstream Galloway Biomethane - expected to produce more than 500,000 MMBtu a year of RNG

- Shell's Downstream Bovarius at the Bettencourt Dairies in Idaho - expected to produce approximately 400,000 MMBtu per year of RNG