In this issue
		Energy Services Bulletin home page
		Online Key Account Tool Box supports public utility programs
		Fuel cell plant joins Alameda County renewable energy collection
		Revitalized communications promote efficiency, ease rate hikes
		New cooling technology aids South Dakota's pursuit of efficiency
		Fort Mojave tribal casino gets cooling system makeover
		Brigham City bike promotion raises energy efficiency awareness
		Lompoc LED light rebate promotes efficient holiday decorating
		Dairy, utilities learn from South Dakota's first digester
		Outreach programs help busy utilities educate consumers
		Energy Services seeks customer input
		Topics from the Power Line: Radiant heater a good choice for auto repair shop
		Energy shorts
		Technology spotlight: Low-mass, surface-mounted radiant heating panels in homes and offices
		Calendar of events

Dairy, utilities learn from South Dakota's first digester

Midwest Dairy Institute's covered digester, above, collects and processes waste from 1,400 cattle into bedding, fertilizer and biogas to power a fuel cell, below. (Photo by Midwest Dairy Institute)

Minnesota has Haubenschild Farms, Colorado has Colorado Pork Growers, Nebraska has OLean Energy, and now South Dakota joins those states with a biogas generation project of its own.

Like most livestock operations that get into the renewable energy business, the Midwest Dairy Institute near Milbank, S.D., was motivated by odor control issues. The Milbank Community Foundation, which owns the dairy, wanted to expand from 1,400 to 2,400 head and needed an effective way to manage the additional manure. The foundation board decided that a digester project would provide a valuable demonstration for South Dakota's dairy industry. The electricity it generated was a value-added product, explained dairy Energy Maintenance Manager Jeff Loutsch. "This kind of system offers a lot of potential benefits for a dairy but first and foremost, it's an odor control strategy," he said.

Many uses for processed waste

The huge digester—85 feet wide, 163 feet long and 20 feet deep, with a 1.2 million-gallon capacity—began producing methane in January 2006. The gas fires a boiler, which maintains the waste solution at a constant 96-degree temperature, the optimal conditions for the bacteria to break down waste and produce methane.  The boiler also provides hot water for heating more than 5,000 feet of in-floor heat and hot water," Loutsch said. "The gas replaced propane as our heat source, so there was a significant savings right there."

The remaining digested solids are separated into gray water and fiber, which is sterilized and used as bedding for the cows. The farm has cut its bedding costs by $32 per cow or $45,000 a year.

Gray water can be recycled for nonpotable uses, said Loutsch, cutting down on the dairy's consumption of fresh water. There are many such uses in dairy operations, he added. "We use it to flush pipes, thin the contents of the holding pit and, in winter, thaw the pit."

Local farmers buy the excess liquid to use as fertilizer.

Electric generation adds value

In August, the dairy flipped the switch on a generator that turned the digester's surplus methane into another product—electricity. The 375-kW Caterpillar engine is capable of supplying electricity for 250 average homes, about 0.3 kW per cow. Waste heat from the generator supplements the boiler system, heating the digester, the in-floor heating system in the parlor and holding area and some domestic hot water.

The dairy is selling electricity from its grid-connected system to Basin Electric Power Cooperative through its utility, Whetstone Valley Electric Cooperative.  Whetstone Valley was the institute's point of contact for getting approvals from the regional reliability council, helping with interconnection requirements and arranging the power purchase contract.

East River Electric Cooperative, a Basin member co-op, helped with the project on behalf of Western, Basin and Whetstone Valley. "The digester was only a small project compared to other Basin resources, but it touched all three cooperatives and Western, too," said East River Power Supply Specialist Jeff Rud. "Our job was to pull all those parties together and make sure that all requirements were met. We learned a lot about the dairy business, and the dairy learned a lot about the power industry."

"The hardest part was that we were all doing a lot of things for the first time," said Whetstone Valley General Manager Steve Ahles. "East River really helped get the permitting organized."

East River and a company in Florida have also expressed interest in buying green tags from the digester project. The power purchase agreement allows the dairy to reevaluate that possibility in one year.

Experience is biggest benefit

Even with the electricity sales and other benefits, institute engineers have estimated a payback period of five to seven years. Funding for the $5.8-million digester came from a private grant. "The capital investment is probably the biggest obstacle to private dairies," acknowledged Loutsch. 

Ahles pointed out, "The start-up costs are very high for a small resource. Some are the same as they would be for a much larger generator." 

To the Milbank Community Foundation, the digester project's main value is as a demonstration. Part of the institute's mission is to investigate technologies and develop best practices to keep the industry profitable.

Ahles commented that the institute's experience would be valuable to dairies considering digester technology, but warned that some of the lessons learned applied only in South Dakota. "Each state has different regulations, so every project will face unique hurdles," he said.

In South Dakota, regulations covering interconnection and distributed generation are still evolving. "While we were negotiating our agreement, new legislation passed and changed our options," observed Loutsch, "and the debate about net metering is going on."

Still, the digester seems to be fulfilling its educational purpose very well. Loutsch said that large dairy owners and people interested in building dairies have toured the facility. The vendor who built the system also brings groups through. When it comes to increasing the value of agriculture operations, meeting environmental regulations and generating renewable electricity, both the dairy and the power industry may have something to learn from the Midwest Dairy Institute.