Darin Mann, of M&M Feedlot in Idaho, discusses his operation. Manure from livestock operations can have a negative perception by the general public – it can smell, attract flies and, if not handled properly, can cause environmental concerns. But one family in Idaho is working hard to change that perception through environmental stewardship and an innovative approach to manure management, and by all accounts they are succeeding.

Darin Mann and his father, Kent, manage M & M Feedlot, located in Parma, Idaho, about an hour west of Boise. The family operation got its start back in 1947 when Darin’s grandfather settled in this area.

The area was covered in sagebrush, but he cleared and leveled the land and installed an infrastructure of irrigation systems. He later diversified the farm and started raising beef cattle.

Darin’s father joined the operation in the early ’70s and in 1982, they diversified again and began raising dairy replacement heifers. Today, the Mann operation has a one-time capacity of 10,000 head and supplies replacement heifers to six large dairy operations in the Northwest.

“Many of the dairies we work with can only have a specified number of cattle on the premises,” Darin says. “If a dairy is limited to only 3,000 head on the site, then they want to make sure that every one of those cows is producing milk. That’s why they outsource their heifer replacement programs to us.”


Darin joined the Mann family operation in 2002 after earning a degree in Chinese from Brigham Young University and spending a year in China and Taiwan. When he joined the operation, one of the ideas he had was to change the way the family managed manure.

“Because manure contains a high percentage of water, it was becoming cost-prohibitive to spread it on crop ground more than three miles from our feedlot,” Darin says. “We could only spread manure two times per year – after the crops had been harvested in the fall and before the crops were planted in the spring. That meant we had to stockpile manure for basically six months, and that could potentially lead to odor and fly issues down the road. With 10,000 head of cattle, we had to come up with a new plan.”

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Another reason for the change was good land stewardship. If the soil in a field tested high for phosphorus or nitrogen, manure could not be applied to that field and would need to be transported to a field further away. The cost to transport manure an additional two to three miles was becoming cost-prohibitive. Darin and his father wanted to make sure the nitrates in the soil surrounding their operation were not at excessive levels, so they needed a cost-effective strategy to move the manure further away from the farm.

In addition, state and federal regulations are limiting the amount of manure that can be applied annually to crop ground. Every load of manure needs to be weighed and applied at a specific rate to each field, depending on nutrient levels. Compost, on the other hand, is a more stable product, not as odorous, is easily transported and readily available in the soil, whereas manure first needs to break down before its nutrients can be used. The nutrient value is still there; it’s just more condensed.

After completing some research, Mann concluded the concept of composting would allow the family operation to better manage the handling and storage of manure, plus make transportation more cost effective by expanding their distribution radius up to 30 miles, reducing the possibility of excessive nutrient buildup in fields near the feedlot. So he introduced composting to the family operation.

The composting program results in corrals getting cleaned year-round and the concrete pads around the feedbunks and water troughs being cleaned weekly. The area around the feedbunks is where approximately 50 percent of the manure accumulates in a feedlot setting. Plus cleaning these pads more often makes for a more comfortable area for the cattle.

Darin and his father poured concrete pads along the feedbunk lines and around the water troughs. A tractor and a box scraper are used to clean the pads weekly and deposit the manure into concrete holding areas. Once the holding area is full, the manure is transported to one of two composting areas located on either side of the feedlot.

The two composting areas comprise about 30 acres of land and are constructed of packed natural clay. At the bottom of each composting site is a large collection pond designed to catch any runoff. The runoff water is then used to add moisture to the compost windrows during the first stage of the composting process.

Once the manure reaches one of the composting sites, it’s placed into a 6-foot-tall by 16-foot-wide windrow. The windrows average 800 feet in length, and Darin says they currently have a total of 40 windrows of manure under management. Once the windrows are constructed, it takes approximately 120 days for the composting process to be completed, depending on temperatures.

“Producing compost is part science and art,” he says. “We are working to achieve an optimal balance of nitrogen, carbon, water and oxygen. I’ve learned a lot over the years through trial and error, and we finally have a solid process in place. We typically turn the windrows twice a week, and as we move through the process it decreases to once a week. If water needs to be added, we drizzle it over the top of the windrow.”

Within the first 30 to 40 days, they typically attain the desired internal windrow temperature of 131 degrees over a 15-consecutive-day period required to kill the E. coli, salmonella, weed seed and pathogens present in the manure. Windrow temperatures are monitored with a 4-foot-long temperature probe that is inserted in the windrows every 200 feet on a daily basis during the first 15 days of the composting process. The temperature readings will help determine if the windrow needs to be turned to add more oxygen or if water should be applied to the compost to help further activate the process. Water is applied using a 4,000-gallon honey wagon equipped with an arm that hovers over the windrow and disperses the water.

“We started composting shortly after I returned to the operation,” Darin says. “Every year our composting has grown, and today we have the capacity to compost almost 100 percent of the manure produced in the feedlot.”

M & M Feedlot uses a towable straddle compost turner. It has the capacity to process up to 3,000 tons of compost per hour.

“Upgrading to a Wildcat turner has allowed us to build larger windrows and helps us produce more compost per square foot,” Darin says. “Plus we’re able to completely turn all of the windrows in our composting operation within one day. Before ... we spent up to three days trying to turn all of the windrows.”

Once the composting process has been completed, the material is cured and then processed in a trommel screen. They screen according to their customers’ specifications; however, the majority of the compost is sold to area farmers.

“It’s really just a continual cycle of the farmer raising corn for us, we feed the cattle, cattle produce manure and we turn it into compost,” Darin says. “The final step is spreading the compost back onto the land in a more usable form.”

Word is spreading. Farmers who have been using the compost for the past few years have seen great results, and the operation is getting calls from farmers up to 20 miles away interested in purchasing the compost for their crop ground.

Ninety-five percent of the compost is sold to area farmers and is screened using a 3/4-inch screen. The remaining compost is sold to landscapers, nurseries and garden centers and is processed using a 3/8-inch screen.

Mann currently sells the compost for $12.50 per ton; much cheaper than the true nutrient value.

“We never intended for the composting operation to be a revenue generator for our feedlot – it was because it made environmental sense for our feedlot,” Mann says. “However, we’ve been surprised with the demand and that has allowed us to turn a small margin. Our cost of production is around $10.50 per ton, so we are making enough to help cover future expansion needs. Composting is a way for our operation to more effectively dispose of the manure produced by the 10,000 head of cattle.”

The biggest beneficiaries are most likely the area farmers. Once the manure is converted to compost, M & M Feedlot can cost-effectively ship the product up to 30 miles away since compost contains less water content than manure. Plus it also helps reduce the potential for overapplication near the feedlot.

“Manure has a bad perception – right or wrong,” Mann says. “Compost is more accepted by the general public, and to our customers the end product still contains an exceptional nutrient structure. It’s just more concentrated.”

One trip to this feedlot reveals a lot – planting of more than 600 trees, five acres of groomed lawns and clean and clear ponds. In fact, the feedlot encompasses 150 acres and right in the middle lies a one-acre landscaped park area with trees, boulders and plants, as well as a windmill and gazebo. Visitors to M & M Feedlot remember the trees, groomed grounds and lack of the typical odors associated with a cattle operation of this size. Darin and Kent routinely host school group tours, and the Idaho governor and many members of the Idaho state legislature came out this summer for a barbecue.

“We operate a feedlot, and one of the byproducts is manure, and with that comes odors and flies,” Darin says. “Visitors to our operation typically have a negative perception before they arrive. But it’s exactly the opposite when they leave, and it’s all due to our environmental and composting efforts.” PD

Ehm is a writer from Des Moines, Iowa, who received special access to Manns’ farm from Vermeer, which provides equipment to the farm.

“Compost is more accepted by the general public, and to our customers the end product still contains an exceptional nutrient structure. It’s just more concentrated,” says Darin Mann. Photos courtesy M&M Feedlot.