Economic Potential of Grass2Gas Swine Anaerobic Digestion in Iowa

Abstract

We assess the potential economic impact of a complete-mix anaerobic digester (AD) in Iowa by coupling an AD model with an economic impact (also known as an input-output) model. We augment IMPLAN’s input-output (IO) model to account for aspects of ADs in Iowa. We consider the production of renewable natural gas (RNG) using swine manure as the primary feedstock and corn stover, winter rye, and switchgrass as secondary feedstock. The calculations include revenue from energy sales, carbon payments, and Renewable Identification Number (RIN) generation. Scenarios regarding cost shares and equity/interest payments are included as well. Only the corn stover scenarios are profitable under current technology, assumed market conditions, and policy. We also execute various scenarios based upon these profitable formulations with assumptions about the number of farms that would adapt the technology. We find that construction—across various scenarios related to adoption and feedstock usage—generates a one-time economic output multiplier of approximately 1.57 (for every dollar spent on the construction of a digester, an additional 57 cents is generated outside the construction industry) across Iowa, which could contribute between 200 million and 400 million dollars in added value to the Iowa economy. Across scenarios, the one-time employment in constructing digesters in Iowa would range from 1,351 to 2,776 jobs with additional onetime jobs created in other industries ranging from 683 to 1,373. For the continuing operations of the digester, we find annual economic multipliers of 1.5–1.8, and roughly 22 million to 68 million dollars per year in value added throughout the economy, depending on the scenario studied. Annual employment from continuing operations of digesters ranges from 166 to 199 direct jobs needed for the digester industry itself and an additional 106 to 242 other jobs added in Iowa, depending on the scenario examined. Like the case of construction, these are not full-time equivalent jobs, but rather reflect the job needs of the economy if the given digesters are built on swine farms. We also assess the tax revenue impacts from the construction and operations of the digesters. We conclude by discussing the potential for grasses-only digesters.