The Sweet Smell of Anaerobic Digestion

By Tim Portz
The road from my current home in Minneapolis to my hometown in Eldora, Iowa, includes a 25-mile stretch from U.S. Highway 20 east to Interstate 35. This stretch of road runs through one of the densest hog producing areas of Iowa and, as you can imagine, the pungent smell of manure fills the air.

I am a big fan of pork, and can appreciate the fact that the industry is an important contributor to the state's economy. In 2002, Iowa hog receipts totaled $2.46 billion and the hog industry supported a whopping $2.02 billion in personal income and $3.02 billion in gross state product (Otto and Lawrence, 2002).

Iowa's pork industry is not alone in its struggle to produce a product efficiently and profitably, while minimizing its impact on the environment and its neighbors. The poultry, beef and dairy industries face similar issues. The New York Times recently reported on the growing public outcry in Maryland over runoff from poultry operations finding its way into the Chesapeake Bay.

The reality is that large-scale production has emerged as the most efficient form of operation for livestock producers. That being said, while the total number of livestock operations has declined, the number of animals per farm has risen. As a result, waste streams associated with animals raised in this industrial manner is more concentrated.

I expect that in the near future, energy production from manure will become an olive branch between large-scale livestock producers and environmentalists. Most notably, anaerobic digestion holds incredible promise to mitigate some of the negative aspects of large concentrations of manure, while providing a domestic, renewable energy source. Some of those operations have been profiled in this magazine.

Manure is a reality of the production of meat, eggs, and milk. Manure already serves as a valuable source of nitrogen for many farmers and energy production doesn't have to interfere with that role. The nutritive quality remains in the digested manure stream, so producers can still count on it for fertilizer. If you factor in the environmental benefits of anaerobic digestion and the revenue opportunities for producers, manure smells pretty sweet.

Tim Portz is a business developer with BBI International's Community Initiative to Improve Energy Sustainability. Reach him at or (651) 398-9154.