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Manure turnover

Continued production of compost using their dairy manure was just too good of an opportunity to pass up for the operators of Nebraska’s Prairieland Dairy, even when they switched from organic compost to inorganic sand bedding.

Continued production of compost using their dairy manure was just too good of an opportunity to pass up for the operators of Nebraska’s Prairieland Dairy, even when they switched from organic compost to inorganic sand bedding. Their perseverance has really paid off, proving that either way, composting is still a worthwhile business opportunity for many large farms.

“When we originally started out marketing the compost in 2000, we were doing maybe 1,000 yards per year,” says dairy co-owner, Dan Rice. “Now we have grown to 10,000 yards per year and expect 25 percent growth in the next five years.”

The 1,600-head dairy is located 20 miles from Lincoln, Nebraska. In 2000, four family farms that were each milking between 100 and 200 cows created a partnership to establish a new dairy. A new milking barn was built in the community of Firth, and over time, it has expanded to 1,400 milking cows. In addition to milk products, the dairy began producing compost for bedding until 2004 when it switched to sand. Today, the Prairieland Gold branch of the partnership produces a variety of compost mixes primarily in bulk. It’s been an evolution since the dairy began composting in 2000. Not only is the dairy composting its own manure solids, but it is also being paid to accept organic waste from surrounding municipalities and businesses. That waste consists of grass and leaves from local municipalities, as well as waste from large industrial companies that manufacture products such as dog food and baking products. Prairieland Dairy also accepts organic waste from grocery stores, and restaurants. Growth in food waste recycling programs among businesses is driving growth in the dairy’s composting operations. At present, outside organic waste represents about 25 percent of the dairy’s raw material, but Rice expects that to increase to 75 percent within three years.

“A lot of companies are implementing recycling of organics in our area and we are really excited about that,” he says.

The cows are bedded in deep sand beds. The dairy uses a flush system of recycled water from its lagoons to flush the sand/manure mixture daily from the beds into sand lanes in the barn where the sand settles out from the manure solids. Once a week, the sand is collected from the sand lanes and recycled into the stalls. The manure solids are collected and processed through an Ag-Pro static screen separator, which separates the liquid and solid manure streams.

“What we like about the Ag-Pro static screen separator is that there are no moving parts,” says Rice. “It is just a screen where the solids go off the front and the liquids go out the back. It is a very maintenance-free type of setup.”

The dairy conscientiously designed the entire manure gathering and processing system to use only two pumps.

“We kind of take pride in that from the sustainability and maintenance standpoint,” says Rice. “It really eliminates a lot of maintenance.”

Once separated, the solid manure proceeds to the dairy’s dewatering pad. At this point, it has about 85 percent moisture content. For about two weeks, it is left on the dewatering pad, where the excess water drains off and the bacteria starts to grow.

After two weeks, it has dried to between 75 and 80 percent moisture and it is transported and placed in windrows on the dairy’s compost pad. This is where the solid manure is mixed with the food and yard waste, or sometimes referred to as “carbon sources,” in specific recipes that the dairy has developed primarily through trial and error to develop the specific compost nutrient mixes required by its customers. The windrows are monitored on a daily basis for moisture, temperature and oxygen levels. They are turned as needed to advance the composting process.

“It varies, depending on the weather, how the bacteria is doing, how much oxygen they are using at that time and how much excess moisture we are getting from Mother Nature,” says Rice.

He adds that moisture, temperature, and oxygen levels are three key elements to manufacturing quality compost.

“The way I like to explain it is that our farm is all about bugs,” says Rice. “When we make up a ration for our cows, we don’t think about feeding that cow. We think about feeding the bugs in her rumen. We have to keep them happy and keep them working. Same goes for bugs in the compost pile. The compost bugs basically need feed, oxygen and water, so those are the three things we need to monitor.”

In terms of the mix, Rice says they start the windrow with the end user in mind. For example, greenhouse customers want a final product derived from 100 percent manure.

To turn the windrows, Prairieland Dairy uses a Brown Bear PTO-PA 35C auger aerator attached to a farm tractor. Turning the windrows eventually lowers the moisture content to about 30 percent. The compost ends up with about a 2:1:1 NPK rating and a 95 percent coliform kill rate.

Prairieland Dairy is considering a new compost turner system, driven primarily by the rising cost of fuel. One system being considered is a forced air system.

Once the biological composting process is complete, the compost is screened and mixed with other ingredients to achieve the final product expected by their customers.

The dairy’s liquid waste stream is treated in a four-stage settling lagoon. The treated water is either recycled back to its flush tanks or is used to irrigate the company’s 600 acres. Some of the water is also used to irrigate and fertilize neighboring farmland. The dairy contracts the services of a custom manure drag hose contractor called Googles, headquartered in Columbus, Neb.

Rice says composting its manure has definitely influenced the growth and success of the dairy itself.

“We would need quite a large land base, if we didn’t have our composting operation, to grow our dairy herd to the 1,600 head that we have currently,” he says. “So it has helped us in that respect. Basically, if you compare what it would cost us to get rid of our manure from our 1,600 cows with the cost of our composting operations, yes, it has been a good thing for us to do and it is also the right thing to do environmentally.”

It also has helped the dairy, which generates about 20,000 yards of solid manure annually, to more easily manage its manure.

“We felt that composting was the best way for us to handle manure disposal because it cut our volume by half,” Rice says. “So, if we are going to have to move it off the farm and move it long distances, there is a whole lot less to move after you compost it.” He adds that compost is also much more readily available to plants as a fertilizer than raw manure when land applying.

Prairieland Dairy switched from compost bedding to sand bedding in its barns primarily for business reasons, as staff market their own dairy products through another arm of the partnership called Prairieland Foods. Making the switch has delivered good results, as the somatic cell count in the dairy’s milk has dropped by half.

“When we started marketing our own brand of milk, we really felt it was very important to have the very highest quality possible,” Rice says. Although the somatic cell count wasn’t a major concern when the dairy used compost bedding and it was comfortable for the cows, it was simply a matter of choosing to deal either with an organic material that encouraged growth of bacteria or a non-organic material like sand, which is sterile when it goes into the beds and does not promote bacteria growth. Given the drop in the milk’s somatic cell count, sand has become the preferred option.

Although Prairieland Dairy made the switch to sand in 2004, recycling the sand bedding still generates a significant solid and liquid waste stream that requires management and disposal. So the dairy began developing compost and potting soil mixes to suit particular customer needs from the separated manure solids. One product is manufactured for a chain of nurseries in the Midwest called Earl May Nurseries.

“We have a lot of fun with it,” says Rice. “It’s called the ‘Poo-In-The-Pot’ program. We make a potting soil mix and put it into a compostable pot, which they use to grow the seedlings in the nurseries. Then those nurseries turn around and sell the plants in the Earl May Nurseries stores. It has been a very successful program for us.”

The dairy is preparing to travel further down the green path, having developed a business plan to install an anaerobic digester. Rice says the partners feel that an anaerobic digester would be a great addition to their operation because they could use an existing resource to generate electricity and/or methane gas or heat to use in other parts of their operation.

“Our business plan shows that we can power our dairy, our processing plant, and our town of Firth – which has about 600 people – through the use of our dairy manure and food waste,” says Rice. “So we think that it makes a whole lot of sense from a renewable energy standpoint and brings a great aspect to the dairy. It eliminates some of the odors and helps us be more sustainable.”

However, that plan is currently on hold because of cheap electricity rates currently available in Nebraska.