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Our Rural Character
Myth Vs Reality

MYTH: “Digesters completely eliminate odors from animal manure.”


REALITY: Digesters have had the most success controlling odors in highly controlled conditions. In the real world, there are many examples of digesters failing to control odors. 


MYTH: “Digesters benefit small farmers.”


REALITY: The farms that use digesters are NOT small IN SIZE. They are typically concentrated animal feeding operations (CAFOs), also known as factory farms, because they need a very large amount of manure to make a profit. 

  • According to the AgSTAR project development handbook, “Successful farm-based AD/biogas systems typically operate with at least 500 cows in dairy operations or at least 2,000 hogs in swine operations.  As economies of scale yield more favorable conditions (e.g., larger number of animals, larger amount of recovered manure, increased amount of salable products produced) the likelihood of successful application and profitability increases. For example, dairy farms having greater than 1,000 animals or hog farms having greater than 5,000 animals increases the likelihood of project success.”

    • AgSTAR partners directly with digester producers like Vanguard to expand digesters on US farms (link to image site).


REALITY: Most small farmers cannot afford digesters because they are so expensive. 

  • Farmers need to cover start up costs up front as well as operating costs. 

    • Digester equipment estimates: $400,000- $5,000,000 (or more) depending on size and biogas production

    • Operating cost estimates: $25,000-$600,000 (or more) depending on size and biogas production


REALITY: The digester and biogas industry is largely being driven by government programs and subsidies on the state and federal levels. 

  • Since digesters are unaffordable, farmers are funding digesters via direct government support or indirect government support from companies who are using digesters/ biogas to make money from government programs/ subsidies.


  • The Inflation Reduction Act (IRA) provided over $2 billion for USDA’s Rural Energy for America (REAP) program to promote rural or agriculture-related renewable energy


  • Companies are investing in digesters to “offset” their emissions in California markets through their offset program.

  • Companies are investing in biogas production to financially benefit from the Low Carbon Fuel Standard program led by California by selling renewable natural gas (RNG) to fuel producers in California.

MYTH: “By utilizing the trapped biogas as a renewable energy source, digesters displace the need for additional fossil fuels.”


REALITY: Biogas adds to, rather than takes the place of fossil fuels and further ‘locks-in’ CAFOs to our fuel system.  

  • MYTH:“RNG will benefit our neighbors by lowering their electricity bills with cheap natural gas.

    REALITY: Renewable natural gas (RNG) is not the same as natural gas. 

    • The cost of purchase of green natural gas is 5 to 6X more than regular natural gas. When this more expensive gas enters the line, the cost to the end consumer must rise.

    • Cost of natural gas via pipeline in WI from the ground: $8 - $14 USD/mmBTU

    • Cost of Anaerobic digestion gas:  $20 - $50 USD/mmBTU

      MYTHBUSTING DIGESTATE (I.E. the stuff that comes out of the digester)

  • MYTH: According to AgSTAR (2018), “Digesters, particularly heated digesters, can destroy more than 90 percent of disease-causing bacteria that might otherwise enter surface waters and pose a risk to human and animal health,” (5).

  • REALITY: Researchers admit that the bulk of research was conducted in laboratories, which are highly controlled environments and only a small number of studies have been conducted on the pathogen content of digestate on CAFOs in the real world. 

    • Burch et al. (2018) addressed these limitations by testing the pathogen levels of digestate from 9 different facilities in southern and eastern Wisconsin over a period of 9 months. They found that after the digestion process, the microbial content of the digestate was lower, but levels of “inactivation” of those microbes varied substantially across different digesters during different seasons. After the completion of the digestion process, the researchers found that “nearly every microbe we could detect” could be identified in the liquid digestate, which is framed as a safe to use fertilizer on fields around people’s homes (342). 

    • On Irish farms, Nag et al. (2020) found that, “Cryptosporidiumparvum, Salmonella spp., norovirus, Streptococcuspyogenes, E. coli enteropathogenic (EPEC), Mycobacterium spp., Salmonellatyphi (followed by S. paratyphi), Clostridiumspp., Listeria monocytogenes and Campylobactercoli were found to be the most relevant (top 10) pathogens in relation to potential risk from spreading anaerobic digestate on agricultural land, specifically in Ireland.”

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