Focus and Sustainability

From waste to watts

Consumers Energy seeks to buy more green electricity from organic waste material.

April 11, 2014
| By Pete Daly |
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Animal waste is playing a more important role in Consumers Energy’s power production plan. Courtesy Thinkstock

CMS Energy Corp. in Jackson has announced its intention to buy back more electricity generated by anaerobic digestion of farm animal manure, sewage and other types of organic waste material.

The Jackson-based energy company said its Consumers Energy division expects to buy 2.4 megawatts of electrical capacity from generators powered by methane gas collected from anaerobic digesters.

The Experimental Advanced Energy Program is open only to its electric customers. CE is accepting applications through June 2 from existing generators or developers interested in supplying electricity resulting from anaerobic digestion.

In anaerobic digestion, organic material is stored in an air-tight tank where it gradually breaks down in the absence of oxygen, releasing methane gas in the process. The gas is usually burned in turbines that generate electricity, or it could be burned to create steam to power a generator.

Consumers Energy’s Dave Ronk, who directs the utility’s green electricity transactions, said CE is proposing to pay $86 per megawatt hour for 20-year contracts, with delivery of electricity beginning in 2016 at the latest.

Ronk said Consumers currently buys electricity generated at three anaerobic digesters, all in West Michigan. Two are owned by Scenic View Dairy, one in Fennville and the other in Freeport, both using farm waste as fuel. The third is the Fremont Community Digester, which went on line in 2012 and uses food-processing waste from the Nestle Gerber plant there plus waste collected from farms in the region.

Of the existing suppliers, Ronk said the plant in Fennville is rated at a peak capacity of 350,000 watts and produced 2,500 megawatt hours last year, while the Freeport plant is rated at 1 megawatt (1 million watts) of peak capacity and generated 5,800 megawatt hours in 2013. The Fremont digester is rated at 850,000 watts and produced 5,200 megawatt hours.

Ronk said the average home is estimated to use about 9 megawatt hours of electricity per year.

“We are aware of other locations that have this technology available,” said Ronk.

The three existing contracts resulted from competitive bids sought in 2009. Due to confidentiality clauses in the contracts, Ronk is unable to reveal what CE is paying for that electricity, but he noted it is “more than the $86 we’re offering” now.

Since then, he said, CE officials have heard from other anaerobic digester developers who are interested in being suppliers.

“There are a couple of facilities that we are aware of that might fit into this,” he said, including a dairy farm in the Lansing area that has been using a digester for several years and selling the renewable energy credits to another utility. There is also a wastewater treatment facility that has the equipment to produce methane gas for electricity generation, but isn’t currently using it because it hasn’t been worth it. Ronk said at the price Consumers is now offering, that facility was “going to take a look at it again.”

Consumers has been working with Michigan State University, which researched anaerobic digestion facilities to determine which worked well and which did not. MSU also was trying to determine why Wisconsin has “significantly more” digester facilities than Michigan.

Ronk said one thing the research indicates is that a standard price would help developers determine if the investment is worthwhile. There are several factors to consider, not the least of which is the cost of connecting the digester generator to the grid via the nearest transmission lines. Consumers plans to provide potential applicants with a data-crunching tool that will help them make a more informed decision.

One digester that received a great deal of publicity when it went into operation in early 2008 is in Ravenna in eastern Muskegon County. The $2.7 million biogas energy plant on the Timothy den Dulk dairy farm was developed in partnership with Grand Valley State University’s Michigan Alternative and Renewable Energy Center in Muskegon and Reynolds Inc. of Orleans, Ind., with the cost subsidized by a $1 million Michigan Public Service Commission grant. It does not sell energy to Consumers, however, according to Ronk.

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