Penn State University held its first Digester Day at the Snider Agriculture Arena on July 21, 2021. The event was put together by Daniel Ciolkosz and Siobhan Fathel of Penn State Extension, who wanted to provide a place for people interested in anaerobic digestion to connect.

Holler julianne
Dairy Producer / Freelance Writer
Julianne Holler is a freelance writer in Sharpsville, Pennsylvania.

Digesters are growing in popularity as farmers are trying to do their part to help the environment and the communities around them. The event featured a panel discussion titled, “Can biogas production benefit your farm?” Panel participants were:

  • Will Charlton, president of Digester Doc, a company that provides laboratory testing and consulting services. Charlton’s focus is microbiology and chemistry. He said he likes to focus on the health of digesters and gas production.
  • Daniel Ciolkosz, an associate research professor of agricultural and biological engineering at Penn State. Ciolkosz’s focus is working with poultry manure and the yield and digestion from it.
  • Heather Karsten, an associate professor of crop production and ecology at Penn State. Karsten’s current focus is the Grass-to-Gas project to capture nutrients. She is working with farmers who inject on no-till ground to capture ammonium.
  • Armen Kemanian, a plant scientist and professor of production systems and modeling at Penn State. He specializes in agroecosystems, soil carbon and nitrogen cycling, as well as plant ecophysiology.
  • Tom Richard, a professor of agriculture and biological engineering at Penn State. Richard works with bioprocessing and how to digest crop materials. Two of his main interests are switchgrass and cover crops and how they can be used to address emissions on dairies.
  • John Tyson, a regional extension engineer and educator in Mifflin County, Pennsylvania. Tyson’s main duty is to work with farmers in the field and to help with the daily functionality of digesters.

Q: What conditions make it possible to put a digester on a farm?

Charlton: Having something unique is a good start. Compressed natural gas can be used for vehicles. Diversity and flexibility are also necessary. The economy plays a big role in this, as a digester is not a cheap enterprise. If the market is good, it can be successful, but it’s also a biomechanical process that you must understand to make it work.

Ciolkosz: Looking at it from the human side, there are certain types of farmers who are the right fit for a digester.

Karsten: There are many new markets out there to help create avenues for starting a project like this, such as regenerative milk. Managing all aspects of the system to truly capture methane is a must, and this could help farms cover the cost. Recycling solids for bedding on dairies is also a benefit. There is a challenge in the U.S. in facilitating programs to help make it cost effective, but there are options.


Richard: Finances must be worked out from the start. This works well for livestock operations, and there is funding available to help cover costs. Electricity from biogas can be offered to local utility companies to help offset remaining costs. Premiums from the government or making connections and selling credits are also ways to help get a digester project funded. Larger digesters could take in food waste, which allows non-livestock owners to get involved.

Tyson: Financial planning must be in place foremost. Figure out how a digester fits into your operation. It is only one component, but it affects all aspects of the farm. Something as simple as pH can change how cows respond. Management is different with a digester than without.

Q: Is it more feasible to put a digester on a smaller farm?

Charlton: In the western U.S., they tend to bring in multiple farms within a 25-mile radius to a central facility. This improves the economy, and digester tanks are specific to individual farms, so they get their own product back. A way that a smaller farm can make money off this could be to sell carbon dioxide as a food-grade refrigerant.

Ciolkosz: The goal is to maximize income. Physical and virtual products can be generated and society values these, which could be a way for smaller farms to pay for a digester.

Richard: Creating the opportunity to put a larger digester on a smaller farm lets other farms feed in. Sometimes this is no problem; other times, when food waste is involved, it can be tricky. If these smaller farms have perennial grasses in the winter and these go through the digester, it is harder to decompose, and additional technology may be needed, which can be costly for a small farm. But, on the plus side, these small farms tend to capture every bit of value and use the products on-farm.

Q: What are some co-benefits of having a digester, and which are most important?

Charlton: Solids and liquids are a co-benefit. Solids can be processed for nitrogen short and long term. More carbon can be replenished to their farms, and all of this leads to a more positive look on agriculture.

Ciolkosz: If the next generation on the farm doesn’t want to strictly just milk cows, installing a digester can be a way to get them involved. This aspect of technology may strike interest with them and lead to long-term sustainability.

Karsten: Carbon credits are a good co-benefit. Minimizing the leakage of methane and nutrient reduction with perennials are also pluses.

Kemanian: After the initial push to install, a lot of opportunities are then opened. These are a chain of benefits that keep going.

Richard: This provides a social license to operate; neighbors can get in on a small digester. Not only do they help with livestock’s reputation, but they can also incorporate the next generation on the farm.

Tyson: Odor reduction is big benefit. Capturing a heat source and using this to dry grain or dry udder towels is saving energy that you would normally be buying.

Q: What are top challenges or misconceptions of biogas on-farm?

Charlton: A digester is biological. It will not run like a tractor, but rather like a cow. For example, at a municipal digester, foam was spewing, and a mechanical engineer couldn’t find the problem. There was an upset [with the bacteria], and it was later found that oil being put down a city sewer was the problem. Something as small as trace elements can create a huge problem. A prime example on a dairy is copper sulfate leaking into the digester.

Ciolkosz: There are generations of knowledge on a farm, but digester owners don’t have this knowledge of the new piece yet. This needs to be learned, and groups need to be formed to draw ideas upon.

Karsten: People think digesters are an easy fix, and they are not. They are a complex, rather new piece of technology. You will need tech support and loans to build one. It must be viewed as an investment, not only in research, but in the supply chain too.

Richard: Nutrient excess. Adding more animals without more land does not mean that a digester is the solution, especially in terms of nitrogen. [The] nitrogen and phosphorus balance is better with more nitrogen, but you need to have land to spread [it] on. Acid upsets and cow pH also are a huge part. If an upset occurs, this can take several months to get out of.

Tyson: Digesters appear to be simple but may be so simple that they are complex. Microbes become complex. Treat a digester like a cow. Think of all the things that can influence it. A digester even keeps a nutritionist on their toes. If the gas goes up, milk tends to go down and vice versa.

Q: What are some new, emerging technology to benefit biogas production on-farm?

Charlton: Chemistry for digesters is improving. Things are now being analyzed to test in real time to get total nitrogen and to see more of what’s going on in the digester.

Ciolkosz: Separate carbon dioxide from methane to upgrade biogas. This only worked at a large scale at first but is now becoming more economical on a smaller scale.

Karsten: Injecting liquids to capture more ammonia is becoming more popular. Organic nitrogen is easily lost as a gas.

Kemanian: Keeping a reputation up and avoiding mistakes is key. Nutrient distribution is a new process to learn.

Richard: Universities are making zero-carbon commitments, so we need carbon storage for when there’s no wind or sun. Batteries and alternatives are needed for storing emerging biogas.

Resources for funding a digester project

A separate panel at the Penn State Digester Day focused on funding sources and incentives for biogas production. Here’s a list of resources suggested by the panelists.