Case Study: Community Digester in Indiana County

Introduction

Anaerobic digestion converts manure or organic waste into biogas, providing a renewable energy source while simultaneously managing waste and generating income (Vasco-Correa et al., 2018; Swindal et al., 2010). Typically, digesters must be large to be financially viable. For dairy farms, the minimum practical size is usually at least 200 cows (leggett, 2023), constructing and maintaining an individual anaerobic digester for a small farm is usually financially unviable and might come with a lot of stress.

Figure 1: Biogas Production  Process Illustration. 

An alternative to small farms having anaerobic digesters is a community digester, which allows multiple farms to share a centrally located digester (Penn State Extension, n.d.), with the help of developers. This collaborative approach reduces costs, enhances efficiency, and optimizes manure for biogas production. Pennsylvania, home to approximately 49,053 farms as of 2022 (Pennsylvania Ag Connection, 2023), with 99% classified as small farms (average herd size of 94 cows) (Center for Dairy Excellence, 2024), presents a strong case for community digesters. This case study explores the community digester currently under construction in Indiana County, Pennsylvania, highlighting its design, benefits, challenges, and role in supporting sustainable agriculture.

Background: Indiana County and the Need for a Community Digester

Indiana County, located in west-central Pennsylvania is home to over 83,000 residents (U.S. Census Bureau, 2023), and known as the "Christmas Tree Capital of the World". The County has a mix of small to medium-scale farms with access to national pipeline infrastructure, making it an ideal location for a community digester.

Overview of the Community Digester in Indiana County

The community digester in Indiana County, PA, currently under construction and developed by Air Liquide, is a multi-stage anaerobic digester system that separates the digestion process of organic matter or manure into multiple distinct phases to improve efficiency and biogas production. The intended feedstock for this digester is manure (they will not accept food waste due to the unfavorable impact on Carbon credit), which will be sourced from 18 farms with a total of about 6,000 cows in the County. The feedstock is to be transported from the farms by truck and pumped into the digester. The digester is designed to produce approximately 280 m3/ min of renewable natural gas (RNG). The produced digestate will be sent back to the farms by trucks (separated into liquid and solid portions). Tests will be conducted on the digestates for early detection of diseases and pathogens, and trucks are cleaned to prevent diseases and pathogen transmission, (digestate overall has reduced pathogen load) (Penn State Extension, 2023).  Before the start of the project, two key factors were considered:

1. End Use of Biogas - Determining whether the produced biogas would be used for electricity generation, direct pipeline injection, or as vehicle fuel.
2. Farm Proximity - Ensuring participating farms were within a reasonable distance to minimize transportation costs and logistical challenges.

Economic and Environmental Benefits

Community digester provides multiple benefits to farmers and the surrounding communities. They include the following:

1. Financial Incentives for Farmers - Farmers will receive payment for their manure, providing an additional revenue stream. Payment for the manure is rated at $1.50 per 1000 gallons.
2. Improved Fertilizer Quality - The digestate offers a potentially more balanced nutrient composition, improving crop growth and soil health.
3. Free Transportation of Manure and Digestate - Unlike many other community digesters where farmers cover transport costs, the management of the Indiana County digester will provide free transportation of manure from the farm and digestate back to the farm.
4. Pathogen Reduction and Air Quality Improvement - The anaerobic digestion process significantly reduces odor and pathogen load, improving air quality on farms.

Typically, digesters are only economically feasible for the largest farms. The community digester concept gives smaller farmers access to the benefits that come from anaerobic digestion.

Challenges Faced in This Project 

Despite its success, the project faced significant hurdles during development:

1. Financing -The total project cost was approximately $20 million, requiring a combination of government grants and private investments. This led to a shortage of financial resources.
2. Permitting - Securing permits involved navigating complex environmental and agricultural regulations. The NPDES permit by the Department of Energy (Pennsylvania) was one of the permits that was particularly challenging to obtain.

Conclusions

The Indiana County community digester serves as a model for sustainable manure management and renewable energy production in small-scale farming communities. Leveraging a cooperative approach demonstrates that anaerobic digestion can be economically viable for smaller farms while providing environmental benefits.

This project highlights the potential for expanding community digesters across Pennsylvania and beyond, particularly in regions with high concentrations of small dairy farms. Future efforts should focus on streamlining permitting processes, increasing financial incentives, and expanding carbon credit opportunities to encourage wider adoption of community digester models.

References

Center for Dairy Excellence. (2024). PA Dairy Overview. 

Encyclopedia Britannica. (n.d.). Indiana County, Pennsylvania. Retrieved [February 8, 2025].

Penn State Extension. (n.d.). Centralized digesters. Pennsylvania State University. Retrieved [January 6, 2025].

Penn State Extension. (2023, March 9). Fate of nutrients and pathogens during anaerobic digestion of dairy manure.

Pennsylvania Ag Connection. (2023). Pennsylvania farm numbers, land in farms unchanged. Retrieved [January 6, 2025].

U.S. Census Bureau. (2023). QuickFacts: Indiana County, Pennsylvania. Retrieved [February 8, 2025].

Klavon, K. H., Lansing, S. A., Mulbry, W., Moss, A. R., & Felton, G. (2013). Economic analysis of small-scale agricultural digesters in the United States. Biomass and Bioenergy, 54, 36-45. doi.org/10.1016/j.biombioe.2013.03.009

Swindal, M. G., Gillespie, G. W., & Welsh, R. J. (2010). Community digester operations and dairy farmer perspectives. Agriculture and Human Values, 27(4), 461-474. doi.org/10.1007/s10460-009-9238-1

Vasco-Correa, J., Khanal, S., Manandhar, A., & Shah, A. (2018). Anaerobic digestion for bioenergy production: Global status, environmental and techno-economic implications, and government policies. In Bioresource Technology (Vol. 247, pp. 1015-1026). Elsevier Ltd. doi.org/10.1016/j.biortech.2017.09.004