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Farmers look to alternative energy: science converts cow manure to profit for dairies

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Posted on August 17, 2009 |
By Kathryn Flagg



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THE ALGEPOWER PROJECT hopes to extract oil from manure-fed algae for biodiesel, which could be used to power farm equipment. Photo Courtesy Mark Hoffman

ADDISON COUNTY — Light streamed in through the paper-thin walls of the temporary shed, a small, greenhouse-like structure plunked down on a Bridport dairy farm. Here, Mark Hoffman is dabbling in alchemy.

Hoffman, a project manager for Montpelier-based Algepower, peered into shallow, plastic troughs stacked one above the other. He was between experiments, and the troughs were mostly empty, but when the system is in full swing the plastic slings are filled with murky green water and hungry algae.

It’s in this small shed on the Audet family's Blue Spruce Farm in Bridport that Hoffman and Algepower are trying to manufacture biodiesel fuel from algae. It’s the pilot project for a new photobioreactor that the company has developed and patented to cultivate algae as a fuel source.

“People are looking at algae all over the country,” Hoffman said. “It’s a really hot topic. Everybody’s looking at algae, because it grows so fast and captures energy really well.”

This is just that latest effort that some Addison County farms are making to convert the byproducts of dairy farming into profitable alternative energies — a lifeline for some dairy farms struggling to get by in tough financial times.

So far, there’s no other system quite like the one Algepower is testing in Bridport, which is partially funded by Central Vermont Public Service Corp.

Here’s how it works. Hoffman pointed to the first of two 300-gallon tanks in the greenhouse. This is the media tank, he explained, where liquid manure is mixed with water.

That mixture is then piped up to the top of a four-story system of plastic troughs, linked by tubes. Algae is introduced into the system in the top trough, feeds on the liquid manure mixture, and slowly descends through the four levels.

The manure is rich in ammonia, a mixture of nitrogen and hydrogen that helps the algae grow and multiply. For roughly half the amount of time the algae is in the system, it is pumped full of nitrogen. Then, Hoffman explained, the goal is to “starve” the algae, forcing them to begin storing energy instead of multiplying and growing.

That means oil begins to build up in the algae’s cells. In fact, half of algae’s composition, by weight, is lipid oil. Then, finally, that oil can be extracted from the algae’s cells. This could be done by pressing the algae, much like olives are pressed to create olive oil. Another possible method for extracting the oil uses a solvent to break up the algae. Hoffman hopes that, by the end of the summer, the pilot project will be ready to start experimenting with different extraction techniques.

All in all, it takes four to eight days for algae to trickle down from the top of the four-tier system to the bottom, where it collects in a small tank. The algae grow darker in color over the course of the run as it soaks up light and nutrients.

After algae is pulled out of the system and harvested for oil, the leftover water is pumped into another 300-gallon tub. It’s later mixed with more liquid manure. Hoffman’s goal is to create a closed loop system where no additional water needs to be pumped into the project.

For farmers, these new technologies offer more than the promise of renewable energy: if cost-effective, they could add up to dollars and cents savings.

Take Blue Spruce Farm. When fuel prices were high, Hoffman said, the Audets were spending more than $20,000 a month on diesel fuel for the farm.

Just imagine, he said, if that fuel could instead be generated in a facility like this one, in tanks filled with green algae.

“If we could have a one-acre facility, and be producing a substantial amount of diesel fuel every month, between the carbon credits and the fuel savings, it would probably pay for itself pretty quickly,” he said.

COW POWER
As it turns out, algae power is just the latest of many on-farm efforts to generate renewable energy. In Vermont, the best-known project so far is the CVPS “Cow Power” initiative, which uses manure to generate electricity.

Again, the Audets paved the way.

In 2006, the Audets were the first farmers in the state to start selling electricity generated by an anaerobic digester. Every day, the Audets process more than 30,000 gallons of manure in their digester. The manure is pumped into a large concrete holding tank, where it is then heated up to produce methane gas. The methane is collected and used to fuel a generator, which in turn creates electricity.

That electricity is then sold to CVPS and marketed as “cow power.” CVPS customers can in turn pay a premium to power their home or business using renewable energy.

What’s left after all of this — a manure byproduct — contains no pathogens and little odor. Farmers can spread that byproduct on fields as fertilizer, or use the dry solids as bedding for their animals in place of sawdust.

A hop, skip and a jump from the Audet farm in Bridport, Bernard DuBois and his brothers in Addison are also hoping to install an anaerobic digester, with the project possibly hinging on a major grant.

For the DuBoises, it turns out, the promise of dry solid byproducts is one of the reasons installing an anaerobic digester is so attractive.

“It’s very hard to get sawdust for animals right now,” said Bernard DuBois. “A lot of the sawdust is being used for pellets (for pellet stoves), and the supply is drying up.”

That in turn means the price of sawdust has gone up. Right now, the DuBois farm requires 70 loads of sawdust a year to keep their 1,200 cows in fresh bedding. They hope that installing a digester would mean they could cut that amount down to 15 or 20 loads annually.

Plus, they estimate they’d be able to generate enough electricity to power 350 to 400 homes.
Right now, the DuBoises are in the permitting stage for their digester. They’ve applied for some grants, and earlier this summer learned they’d been approved for $500,000 in financing through the Vermont Economic Development Authority.

But they’re still waiting to hear from the United States Agriculture Department about grant funding for the $2.4 million project.

“Until we find out what we get for grants … it’s pretty much in limbo,” DuBois said.
If the project moves forward, the DuBois farm would become the state’s seventh agricultural facility to produce its own electricity with an anaerobic digester.

That’s good news for CVPS, which hopes to be generating five percent of the utility’s energy on farms within 10 years. With six farms online now, the amount of energy CVPS is bringing in from Cow Power is just a hair under one percent of the utility’s total amount of electricity, according to CVPS spokesman Steve Costello.

Back when CVPS first began exploring options for fully renewable energy products, Cow Power outshone wind-based or solar energy. It was something no one else was doing, Costello said, and it was a shot in the arm for Vermont’s struggling dairy farmers, who were significant customers for the Vermont public utility. Once a farm transitions to a Cow Power system, their herds bring in two streams of revenue: the first from their milk, and the second from their manure.

Now, 4,000 CVPS customers are paying a premium to be part of the Cow Power program. The economy has “slowed the march” toward digesters for a lot of farms, but Costello said that CVPS is working with around a dozen in the state who are moving toward installing generators.

So far, the Cow Power program is only cost-effective for farms with at least 500 cows, but CVPS is beginning to toy with a plan to build digesters on smaller farms and truck methane gas to a central location, making Cow Power a possibility for smaller operations.

THE ALGAE EXPERIMENT
Back at Blue Spruce Farm, Hoffman thinks algae could be another way for farms to turn natural waste into profits. One of the best ways to do that may be to link an algae-growing facility to an existing waste treatment plant, much like the digester already in place on the farm.

But there are still a lot of unanswered questions about the project, and that’s why Hoffman is manning this small shed. It’s a feasibility study, he explained.

“A lot of the information we have comes from people using vials in laboratories,” Hoffman said. “Just by scaling up to the 1,000-gallon system we have here, we learn a lot.”

There are plenty of variables to sort through: What is the best strain of algae to use in a project like this? What is the most efficient way to extract oil?

And along the way, the project is hitting its fair share of bumps in the road.

“We run into problems every day,” Hoffman said. He noted the skin of the greenhouse is spotted with mold, and that Algepower is uncertain of how effective the project will be during the winter, when less daylight means the algae will be exposed to less light.

But Hoffman sees great potential for linking algae projects like his with the anaerobic digesters that farmers like the Audets have already installed. The digester captures more methane than the generator can convert into electricity, Hoffman said, which means the Audets have to “burn off” the extra.

Maybe, in the future, that methane could be diverted and stored to power a system like the algae project through the winter.

Eventually, Algepower envisions installing much larger projects — as large as one-acre facilities. Even then, Hoffman said, he didn’t think the algae project would be using all of the liquid manure a farm like Blue Spruce produces each day.

And the company is taking the long view. That’s exactly what CVPS did a few years ago, Costello said.

“When we first started talking about Cow Power, a lot of people were scratching their heads. But we tried to be really visionary,” he said.

That may be the case now with algae power, but Costello thinks it could pay off.

“We think there’s a tremendous amount of potential,” he said.

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