A digester for the 135-cow dairy: fact or fiction?

Someday soon, small dairies may have an opportunity to create their own energy.

About 95% (that’s roughly 61,650 farms) of dairy farms in the United States have less than 500 cows. In Michigan, the average dairy herd size is 135 cows. According to AgSTAR data, 90% of the anaerobic digesters currently in place in the United States are on farms with 500 cows or more. On average, these digesters cost $1.5 million. Small dairy operators want the benefits that come with a digester without the hefty price tag. To bring the price of a digester down within the reach of a small dairy farmer means implementing changes in policy and creating systems approaches while increasing digester efficiencies.

But economics is the bottom line. If a digester isn’t profitable, a farm isn’t going to install one. It will take a combination of solutions to get digesters on small farms. Some ideas worth considering include:

  • Spreading design, permitting, financing, procurement, construction, commissioning and operation costs over multiple dairies in close proximity to each other. (Native Energy has a good example of this concept.)
  • Increase the price of carbon credits.
  • Design cheaper digester vessels using materials other than concrete or steel.
  • Improve digester performance through methanogenesis manipulation or other means.
  • Using the proven biorefinery model, create greater value for the fiber, filtrate and biogas from a digester.

Today, a digester on a 135-cow dairy is fiction. But advancements in technology, coupled with outside-the-box thinking, could make it fact in the future. The mission of Michigan State University’s Anaerobic Digester Research and Education Center is to design digester systems for smaller livestock operations.  For more information, visit AgStar and the National Sustainable Agriculture Information Service.

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