This Data Digest takes a look at the swine sector of the biogas industry, which accounts for 8% of farm-based biogas output in the U.S. Although the sector is dwarfed by the dairy sector, growth in the volume of biogas produced from swine manure, coupled with a huge untapped potential, suggests the swine sector could play an important role in both US methane emission reductions and renewable energy production in the future.

The ABC currently lists 87 swine biogas systems in its Biogas Projects Database, up by 43% since 2019 when only 50 swine farms had biogas systems. The increase is even greater when measured in terms of digesters, with the number rising by 166% from 62 in 2019 (1.2 digesters/project) to today's (July 2024) running total of 165 operating digesters (1.9 digesters/project).

This dramatic growth has been enabled by investment in cluster projects which involve multiple farms, to achieve efficiencies in methane abatement and capture. The clusters either collect biogas from multiple farms to supply a centralized gas upgrading system or collect feedstock (manure, in this case) to be recycled in a centralized biogas system. Both versions make participation by small farms more economically viable. These multi-farm/multi-digester clusters, such as those implemented by Align RNG (Dominion Energy and Smithfield Foods) and Monarch Bioenergy (Roeslein Alternative Energy and Smithfield Foods), have become the main driver of growth in the swine sector, making it more appropriate to talk in terms of digester numbers rather than ‘projects’ or ’sites’.

That's some impressive growth - and the huge potential for continued expansion makes the outlook even more interesting. According to the USDA National Agricultural Statistics Service's recently released 2022 Census of Agriculture, in total, the U.S. has 9,739 farms in the 1,000+ herd size category, with an inventory of over 72 million animals. We estimate that currently, only about 2% of these pigs' manure is being recycled to produce biogas and reduce methane emissions.

If there were no obstacles to converting the manure from these pigs, we estimate biogas output could reach 81 million cubic feet per year. However, as swine manure is largely handled as a liquid and flushed into ambient temperature lagoons, biogas production is likely to be higher in warmer, southerly states unless heating is added when the lagoons are covered to produce biogas. This can be seen so far in the fact that while Iowa, Minnesota and North Carolina have the largest swine populations, North Carolina ranks the highest in biogas production.



The following chart highlights the vast untapped biogas potential of the swine sector. Only three of the top 16 states that have swine farms with over 1,000 animals have any discernible number of pigs contributing to biogas production. In the key pork producing state of Iowa, which is home to over 23 million pigs, the manure from less than 1% of the inventory is fed to anaerobic digesters.

One final take away on how the biogas is used by swine farm biogas systems: like other biogas sectors, new biogas projects using swine manure as feedstock have swung away from using biogas for generating power in favor of renewable natural gas (RNG). This trend is particularly stark with swine farms. Every swine project that has come online since 2019 upgrades its biogas to RNG for injection into the natural gas network.

Thanks for reading! Stay tuned for next month's data from ABC's Data Analysis Team, led by Ian Taylor, ABC Data & Analysis Manager