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Manure separation systems: Comparing costs with opportunities

Melissa Hart for Progressive Dairyman Published on 06 January 2017

With the objective to develop novel waste-to-resource technologies capable of converting organic wastes into value-added fuel and chemical products, Dr. Dana Kirk, Ph.D., P.E. in biosystems and agricultural engineering at Michigan State University, had his work cut out for him.

Kirk shared his expertise on manure treatment and nutrient recovery at the recent Dairy Practices Council Conference held on the campus of Michigan State University in East Lansing, Michigan.

“Here at MSU, we take an approach from an energy standpoint that will set us up for the future of manure management,” Kirk said. “And we aren’t just dealing with animal waste – we are dealing with human waste and also any organic waste from industry sources, like from the food industry.”

The objectives of the MSU Anaerobic Digestion Research and Education Center where Kirk works is not only charged with research and development of waste-to-resource technologies, but to fulfill commercialization and technology transfer of new waste-to-resource concepts and to educate the next generation of engineers, scientists and policymakers on waste utilization design and practice.

Kirk said that manure management provides lots of challenges as well as opportunities. And he highlighted the recent headlines of the lawsuits over ground water contamination in Yakima, Washington, involving five dairy farms; the city of Toledo, Ohio, water contamination in 2014; and the blue-green algae outbreaks in Lake Erie that are all challenges in the area of nutrient management.

“From the opportunity standpoint, we know that manure management on the farm is 50 percent of the carbon footprint in a gallon of milk, and so as the dairy industry looks at having a more sustainable product, the low-hanging fruit really is manure management and what we are doing on the farm,” Kirk explained.

“When we look at it from a standpoint of value with nitrogen, phosphorus and potassium being the core products, the raw nutrient value per cow is approximately 300 dollars per year. Are we using it to maximize the agronomic impact of it in addition to its value? These are questions we need to consider,” he said.

The U.S. dairy industry is at a critical juncture with a current state of increasing regulatory and societal pressure about manure management, surface and ground water issues related to nitrogen and phosphorus in the wrong places and an erosion of consumer trust. Kirk explained that we need dairy farms to help resolve societal issues related to water pollution and to realize the economic benefits from voluntary actions as the dairy industry improves social license to operate and increases consumer trust. A nutrient recovery system can aid in this improvement.

In a nutrient recovery system, the process takes out the coarsest material first and then is refined down to usable water. “[Nutrient recovery] is really about how do we get the liquid fraction of manure to look and act as much like water as possible,” he said.

There are four byproducts when taking manure and refining it to usable water. From the coarse solid-liquid separation, the byproduct is coarse fiber. The next step is fine solid-liquid separation and that produces fine solids and phosphorus. The third step in the refining process is taking out the nitrogen, and the fourth step is separating the salt concentrate from the liquid to produce drinkable water.

“Coarse solid-liquid separation is pretty common on most dairy farms today. Probably 30 to 60 percent of dairies around the United States have some sort of coarse-solid separator,” Kirk said. He emphasized from a nutrient standpoint, it’s not as efficient as separating nutrients from water, but it is more cost-effective with a smaller capital investment for a dairy producer with a cost of approximately $5 to $6 per cow per year.

Phosphorus recovery is beginning to gain momentum around the country, and this is from concerns over surface water and phosphorus management.

“If we can remove phosphorus from the liquid fraction, we then can apply manure differently, potentially at a higher rate than if the phosphorus was in that liquid stream,” Kirk said.

When phosphorus can be limited from the liquid, it expands other options for the uses of the liquid, such as irrigation and a nutrient market opportunity. The on-farm cost for this process ranges from $25 to $50 per cow per year.

Nitrogen is the next value in fertilizer, and most processes in nitrogen recovery will go through the nitrification and denitrification processes. Nitrogen recovery is necessary in areas where there are application restrictions.

“If you’re in an area that is sensitive to nitrogen, like sandy soils where nitrogen is moved into the aquifers rather quickly or areas that have had a lot of fertilizer applied to the soil, there will be restrictions on nitrogen,” Kirk explained.

The technology uses air stripping and biological conversion, and there are approximately 20 to 30 systems around the U.S. The cost involved is much more than coarse solid-liquid separation systems and ranges from $100 to $190 per cow per year.

Salt removal is the final step in the process, and the end result is water that is suitable for drinking. “This is a water treatment technology, and the process is very costly, and the systems are very sophisticated, and we don’t see these today because there is not a need for us to get to this quality of water,” Kirk explained. The only areas that would need this kind of technology are where water availability is a challenge. The cost is in the range of $500 to $1,000 per cow per year.

“If we can irrigate a crop without odor and maximize the value of nutrients recovered from manure, then it’s a big opportunity for a lot of dairy farms today,” Kirk said. Europe has developed a business model where farmers take their manure to a central location, and it is made into fertilizer and shipped around the world. Kirk explained, “They have become very effective at containerizing carbon-based fertilizers from manure and sending it all around the world.”

“The problem [in the U.S.] is we have not done a good job at developing the markets for the products we can produce in order to pay for the operations and the capital in making those products,” Kirk said.

To address that challenge, a new company has come on the horizon.

“Newtrient is a company that was formed a year ago by 12 cooperatives around the country, along with Dairy Management Inc. and National Milk Producers Federation to look at the commercialization aspects,” Kirk said. As one of the consultants to Newtrient, Kirk said the company was set up to help dairy producers understand what information is available and what experience the various companies have with this technology specific to dairy farms and dairy manure.

Kirk concluded that this technology is not new; we just have to develop the markets for what the technology can produce. Newtrient is serving as a catalyst advancing new technologies, practices, products and markets, and it helps generate profits for farmers, while at the same time it preserves and enhances the environment.  end mark

Melissa Hart is a freelance writer from North Adams, Michigan.

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