When the partners of Five Star Dairy teamed up to build their 750-cow dairy in 2000, they didn’t know much about manure digesters. But they were intrigued enough by the technology to leave space for a future system during initial construction.

After much research, the Elk Mound, Wis., dairy — and collaborator Microgy Cogeneration Systems — unveiled their digester this summer. Not only does Five Star Dairy partner Lee Jensen believe the unit will become a profit center for the dairy, he believes it will offer long-term benefits for the farm and the surrounding community.

Fortunately, Jensen and his partners saw the writing on the wall. Manure management is one of the largest issues dairies must deal with — thanks to community and regulatory concerns about odor, air and water quality. The era of simple storage and land-application is over. It’s time for more creative manure-management solutions.

Discuss the following four factors with your professional manure-management adviser so you can select the manure technology that’s best suited to the job at your dairy. These factors apply to both new systems and retrofits.

1. Think holistically.

In other words, think of the ways your manure-management system addresses air quality as well as water quality. 

In addition, keep in mind that different agencies now make the rules for and oversee air and water quality. That means your operation can be impacted by regulations from multiple agencies at the local, state and federal levels.

2. Establish a job description for each technology.

To evaluate the components of your manure-management system, and of any technology you might want to employ, you will need to think outside the box. Start by writing a “job description” for each step or technology in the process -— similar to assigning duties to an employee.

For instance, what task(s) will the technology accomplish? Collecting materials? Degrading nutrients? Be realistic in your expectations and determine whether the technology has more than one purpose.

For example, if it is designed to separate liquids from solids, evaluate whether the technology can solve other problems, such as odor. If it cannot, then you will need to select another technology to accomplish that goal.

For Jensen, the digester fulfills the dairy’s objective of providing solids for animal bedding, reducing odor and concentrating phosphorus in the solids. Meeting these goals has led to reduced lagoon agitation and improved water-pumping capacity.

As long as you’re working on job descriptions, create a performance evaluation for your technology, too. You need to be able to monitor results long-term.

And when you install a piece of technology, plan for it to fail, warns Leonard Meador, owner of Global Eco-Tech, an environmental-consulting firm based in Rossville, Ind. Have a contingency plan in place. And, be sure to include expected downtime for regular maintenance.

For Jensen, the digester -— like every good employee — plays a role in the dairy’s ability to complete future expansion plans.

“We have enough land for spreading, and we have a good relationship with our community, says Jensen. “But we knew that if we were proactive, we would have more choices in the future. So now, when we do expand, we will have more options.”

3. Evaluate technologies.

Once you’ve established the job at hand, you need to evaluate your current system to see if it’s getting the job done.

Whether looking at new equipment purchases or evaluating your current system, use the chart on page 68 to help evaluate three commonly available manure-management technologies. Be able to answer the questions and considerations the chart poses against your system’s job description.

Of course, don’t limit yourself to these three technologies, as there are several to choose from. Also look to other industries for ideas that will adapt well to dairy.

Parameter

Technology

Anaerobic-digestion technology

Odor control

Do you currently have a problem? If so,
identify how you will monitor changes in odor after installation and operation begins

Energy use/
production

Will you flare methane or convert it to electricity?

Nutrient content

Similar to that of original material.

Fertilizer value

Conversion of some organic N to ammonium N (plant available form).

Nutrient stability

More stable after digestion.

Total solids

Reduces organic material to some extent.

 

Chemical and biological additives

Odor control

Is there a beneficial result from the use of the product?

Reliability

Does the product work consistently during
different weather conditions and through changes in animal diet and housing?

Nutrient content

Does the product promote ammonia
volatilization (undesirable from an
air-quality point of view)?

Total solids

Is the concentration of total solids reduced?
If so, what air emissions occur?

 

Solid-liquid-separation technology

Total solids

What percent of the total solids in the
liquid stream can be removed? How will you determine if this has been achieved?

Energy use

How will you document energy use? What additional resources (labor, equipment) are necessary to manage solids?

Labor use

How much labor will you need for maintenance? (Daily, weekly monthly?)

Nutrient use

How will you sample solids to achieve credits for nutrient removal if this is necessary?

Liquid-retention pond

Will you overload the retention pond and prevent biological activity if the separation technology is not functioning properly?

Bedding

How much bedding do you use? Can you at least recover the equivalent weight of bedding with the technology?

Source: Proceedings from the 6th Western Dairy Management Conference

4. Select right technology for the job.

Each dairy is unique. So, select your manure-management solution based on your unique situation.

For example, if you are located in an area where odor/nuisance complaints are common, focus on technologies that effectively reduce odor first, then prioritize what other tasks you need your system to do, suggests Wendy Powers, environmental specialist at Iowa StateUniversity

  • Ask for independent science. Beware of miraculous claims from vendors.
  • Stay current with local, state and federal regulations, as well as new research. Several studies are now under way to determine air-emissions output from dairy farms. (See “They’re pulling numbers out of thin air,” September 2004 Dairy Herd Management.)
  • Determine the various consequences involved. For instance, while anaerobic digesters collect and degrade organic material, they do not reduce much of the phosphorus or total nitrogen from the exiting material. You’ll need a different plan to handle this material.
  • Commit to your technology — whether new or old — from a management perspective when deciding on implementation, recommends Meador. Delegate manure-management maintenance to one employee or group of employees. Make sure that somebody on your dairy — or an outside contractor -— understands the ins and outs of the technology you’ve chosen.
  • Finally, evaluate any technology against your five-year and 10-year business plans. Make sure that the technology you select today does not negatively impact your business plans tomorrow.

New technologies at work

Several new manure-management technologies are in the development stage and hold promise.

They include:

  • Hydrogen fuel cells. In use on a dairy in Minnesota, this system features an anaerobic digester that produces biogas — methane, carbon dioxide, water vapor and trace gasses. Once the biogas is cleaned in the next phase of the system, it is converted to hydrogen fuel which produces electricity in the fuel cell.
  • Manure incineration. Proposed for a Wisconsin dairy, similar technology is being tested by TexasA&MUniversity. This technology first dries the manure by heating it to 160 degrees F. The dried manure then enters a biomass boiler. The boiler’s incinerator heats the dried manure to 2,000 degrees F, and the heat runs the unit’s boilers to make steam. In turn, the steam turns electricity-producing turbines. Manure mass is greatly reduced to an ash concentrated with phosphorus and potassium.
  • Manure press. In use on a Michigan dairy, sand is first separated from manure, then a chemical treatment removes nutrients from the liquid manure and concentrates them in the solids. The manure press comes next in the process, which squeezes water out of the manure to form a nutrient-rich “cake” that is more easily stored and handled. Water is recycled. This dairy composts the solid material for commercial sale.

Politics at work

Politicos in state capitals and washington, d.c., may not know much about nutrients produced on a dairy, but they’re not shy about regulating them.

For instance, open lagoons are no longer permitted in North Carolina. California legislators are pushing for in-vessel composting of manure, and Minnesota has set stiff hydrogen-sulfide standards in an attempt to regulate air quality.

Nobody knows for sure what’s coming down the pike next.

The day may come when agriculture is regulated on what is produced rather than what is emitted, says Wendy Powers, environmental specialist at IowaStateUniversity. In other words, you will have to manage for nitrogen and phosphorus excretion and not focus solely on ammonia emissions or phosphorus accumulation in soil.

Additional information

Research is a key part of your evaluation mission. Ask for independent research before investing in products, and check the results to be sure they back the claims by any vendor, recommends Deanne Meyer, associate livestock waste management specialist with the University of California-Davis. Ask the opinions of others who are using the same technology. 

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