Register Tuesday | April 16 | 2024
Waste Not

Waste Not

Don’t call it bullshit—manure can power farms, heat homes and run engines. Presenting the twenty-first century’s most undervalued hope for renewable energy.

Photograph by Emmanuel Lattes

As you drive north from Minneapolis toward Dennis Haubenschild’s dairy farm, the passage from city to country is signaled by a gradual transition from suburban outlet malls to forests, fields and some of the state’s eponymous lakes—and by a hand-painted sign you pass after about half an hour, nailed to a roadside tree. Instead of another update on how many miles lie between you and the Mall of America, it’s a very different consumer come-on: “Manure for Sale.”

As fertilizer, manure is valuable here. But Haubenschild, a sturdy sixty-one-year-old clad in jeans and a baseball cap, thinks it’s dramatically undervalued, and a growing number of entrepreneurs and environmentalists agree with him. Since 1999, he has been running a 135-kilowatt generator on the biogas he harvests from the fifteen thousand gallons of manure his 1,100 cows produce each day. He powers his farm and seventy surrounding homes, heats his barns, sells the resulting carbon offsets, and has big plans to fuel his pick-up trucks, run fuel cells and produce ammonia for fertilizer. A natural aphorist, Haubenschild sums up his credo as follows: “The back end of the cow has much more potential than the front end.”

Manure power, of course, has a long and distinguished history. It was the abundance of yak dung, according to some theories, that fuelled the migration of the first North Americans through the frigid, treeless expanse of Siberia fourteen thousand years ago. It remains a crucial source of fuel for millions of people in the developing world, but burning it over an open fire is a dirty and inefficient way of getting at the energy inside. Moreover, with a global population of over four billion cows, sheep, pigs and goats—not to mention seventeen billion chickens—manure now accounts for 18 percent of the planet’s greenhouse gas emissions, and in many places there’s far too much to safely spread on fields.

All of this has been true for decades, but soaring energy prices and heightened fears about climate change have sparked a new push to establish manure as the “other” carbon-friendly renewable energy source. A key advantage, proponents say, is that the use of manure skirts the “food vs. fuel” debate that dogs other biomass proposals. But it’s not without controversy. Like solar power, manure power experienced a mini-boom and subsequent bust in the 1970s, leaving a bad smell in some nostrils. And the best way to capture that energy remains unclear.

A few hours west of Haubenschild’s single-farm operation, a sprawling new industrial-scale power plant consumes five hundred thousand tons of poultry litter a year trucked in from surrounding farms. The success or failure of these Minnesota projects will play a big role in determining the most efficient—and economical—way of harnessing that back-end power.

The basic technology at Haubenschild’s farm couldn’t be simpler: a 150-foot-long, fourteen-foot-deep pit, covered by a white canopy held aloft by gases escaping from the manure within. This is a simple “anaerobic digester,” in which microorganisms break down the organic materials to release a biogas containing about 60 percent methane (natural gas, essentially), with the remainder mostly carbon dioxide. This gas is piped out from under the canopy and used to fuel a Caterpillar engine that generates 135 kilowatts of electricity around the clock—enough to power the entire farm and then some. The pit is kept at a carefully controlled 100 Fahrenheit—like any other living thing. “It’s like a baby calf,” Haubenschild explains. “You have to feed it the same thing at the same time every day.” This is accomplished by automatic scrapers that inch steadily and continuously along the floor of the dairy barns, pushing the efflux into the pit. From the far end of the digester, a nutrient-rich sludge emerges, bubbling like a thick, carbonated milkshake. With the gas removed, this digestate is still perfectly suited for use as fertilizer.

Next to one of the barns, a pair of slightly battered solar panels serves as a reminder of an earlier era of energy panic, and offers a testament to Haubenschild’s long commitment to greening his farm. He installed them in 1979, and they’re still working nearly three decades later, pre-heating fifteen tons of rock that serve as a thermal sink to help keep the barn at a comfortable temperature. That he’s managed to keep them going for so long hints at why he’s succeeded with his digester where many others have failed. “Dennis is a unique individual,” says Phil Goodrich, a professor of agricultural engineering at the University of Minnesota and a longtime collaborator. In addition to practical know-how and a certain idealism, Goodrich says, Haubenschild has a laser-like attention to detail. Showing a visitor around his farm, Haubenschild spouts an endless stream of precise figures. Every 110 cows can produce the equivalent of a barrel of oil a day. It takes twenty-three cubic feet of biogas to make a kilowatt of electricity. And his favourite, a simple equation of sustainability: each acre of land produces enough forage for one cow; each cow produces enough manure to fertilize one acre.

There’s only a faint, slightly sweet scent in the air to remind you that you’re standing next to a four hundred thousand-gallon pit of manure, since the anaerobic digestion process eliminates most of the foul-smelling compounds in the mixture. Indeed, odour control was one of the primary motivators cited in a recent survey of sixty-four farmers who received US Farm Bill funding to build digesters in 2003 and 2004. But the warm feeling of being a good neighbour isn’t enough, on its own, to defray the capital costs of building and running a digester. To construct his system in 1999, Haubenschild spent $355,000 on materials alone; about a third of that was covered by grants and in-kind assistance, and the Minnesota Department of Agriculture provided a further $150,000 interest-free loan. The return on his investment comes primarily from producing power and selling some of it back to the utility, and saving on heating costs thanks to co-generation from the generator. Still, according to a 2007 analysis by University of Minnesota economists William Lazarus and Margaretha Rudstrom, the system would have been a money-loser without those grants.

The main financial obstacle, Lazarus says, is the system under which excess power is sold back to the utility—a hurdle also faced by solar and wind projects. While state targets for minimum use of renewable energy have encouraged utilities to buy “green” energy, that approach has been much less successful than the European model of legislating a minimum sale price for renewables—which is why Germany, for example, has about four thousand digesters that provide nearly 1 percent of its total electricity needs. Most utilities in North America remain distinctly unenthusiastic about paying anywhere near the retail rate for excess power, or even permitting the “net metering” that would make it possible. The survey of digester builders found that negotiating with the local utility was the most significant obstacle encountered, resulting in more than half the projects being delayed or abandoned. Lazarus cites the case of a California dairy that simply flares off half the gas it produces, since generating more power than it uses would force it into a different administrative category with the local utility.

“Under the current situation,” Goodrich says, “generating electricity is not what you want to do.” So he and Haubenschild are looking for better options. In the metal-walled shed that serves as Haubenschild’s lab, an assortment of machines connect to pipes running in every direction, linked to a computer that sends real-time data to the university. Pride of place goes to a five-kilowatt fuel cell that made headlines in 2005. “It’s the first time a fuel cell has ever run off cow power,” Haubenschild says proudly. But extracting pure enough methane from the biogas to run this fuel cell requires too much energy and effort to be practical, so they’re now pursuing a different kind of fuel cell being developed by a Connecticut start-up. This high-temperature “molten carbonate” design should allow them to feed raw biogas straight into the fuel cell system, without having to scrub the carbon dioxide and hydrogen sulphide out.

Haubenschild also has two compressed natural gas fueling tanks, picked up recently as surplus from the Minnesota Arboretum, and he plans to use some of the gas to run his vehicles. He has already added an extra carburetor to one of his pick-ups to allow it to run on natural gas. This is only a partial solution, though: the low density of natural gas means that it takes too much room and energy to store it in large quantities for long periods of time. For a farm, where energy use is heavily concentrated at planting and harvest times, that’s crucial. Instead, Haubenschild and Goodrich are hoping that the new molten carbonate fuel cell will allow them to produce anhydrous ammonia, a valuable fertilizer that can also power internal combustion engines, and serves as a denser and more efficient way of storing the energy produced.

The road west from Haubenschild’s farm leads out of deciduous woodlands into the vast, rolling prairie of west-central Minnesota. This is turkey country, a high-density region that makes Minnesota the nation’s top turkey state. While most of Haubenschild’s schemes suffer from issues of scale—he’s not big enough to negotiate effectively with utilities, or to justify the capital costs associated with currently feasible ways of upgrading biogas or producing ammonia—this region faces the opposite problem: it has way too much turkey manure. It’s in this context that, in 2007, a company called Fibrowatt opened its Fibrominn plant in Benson, a town of 3,376 situated just up the road from the headquarters of the country’s largest turkey processing operation. From the small main drag, you can peer up the train tracks that cut through the heart of the town and see, looming over its northern outskirts, the plant’s three hundred-foot smokestack.

“This plant is basically the same as any other power plant,” explains Fibrominn’s operations manager, Aaron Larson. “Except the fuel.” Instead of coal or natural gas, the plant burns five hundred thousand tons of poultry litter a year, mixed with small amounts of wood chips, sunflower hulls and other biomass, making steam to spin a turbine. Its fifty-five-megawatt output, enough to power about forty thousand homes, makes it one of the biggest biomass plants in the world. The litter—a mix of droppings, wood shavings, feathers and straw—arrives in giant tractor-trailers, mostly from nearby farmers who have signed multi-year agreements to supply the plant. (In addition, some is purchased on short notice: “Most people wouldn’t realize there’s a spot market for turkey litter,” Larson notes.) To prevent odour from escaping, air from the fuel hall where the litter is received is sucked at negative pressure through a long shiny tube that looks like a gently sloping waterslide, into the neighbouring generator building, where it is fed straight into the furnace and combusted.

Like Haubenschild’s much smaller operation, Fibrominn takes in animal waste and puts out electricity and fertilizer—in this case, the ash from the furnace, which has lost its nitrogen in the combustion process but retains its potassium and phosphorus. That makes it suitable for crops like soy beans and potatoes, but not for corn, says Larson, a former navy and nuclear plant engineer who has farmed on the side since returning to his native Minnesota for this job. Fibrominn’s centralized approach requires a significant quantity of additional fuel to haul the litter in trucks, but, because of the high density of turkey farms in the area, that litter would have had to be hauled away anyway to avoid damaging the soil.

A more pointed criticism comes from David Morris of the Institute for Local Self-Reliance. “Fibrominn is getting paid some $150 to $200 million in subsidies to destroy most of the nitrogen available in our state’s poultry manure,” he points out. That wasted resource is all the more frustrating given that the price of nitrogen fertilizers more than tripled between 2000, when the plant was approved, and 2008. In that respect, he says, digester technologies are far superior to “primitive” incinerators like Fibrominn’s.

Since late 2008, about two billion BTUs a day of cow-derived natural gas have been flowing through a pipeline from Texas to California’s Pacific Gas & Electric Company, which pays a 10 to 15 percent premium on the market rate since the gas is considered “renewable.” The company behind the project, New York-based Environmental Power Corporation (EPC), believes it has struck a hybrid approach that combines the best aspects of centralized projects like Fibrominn with the advantages of farm-based manure processing. The key is upgrading biogas produced by anaerobic digesters to pipeline-quality natural gas, so that it can be fed into the existing pipeline infrastructure—thus avoiding the hassles of dealing separately with electric utilities.

Currently, the company has projects at both ends of the size spectrum: single-farm digesters in Wisconsin that generate electricity just like Haubenschild’s set-up, and large facilities like Huckabay Ridge in Texas, which has eight digesters accepting manure trucked in from surrounding dairies with a total of ten thousand cows. The size of Huckabay Ridge, which began operations last year, made it possible to build a state-of-the-art scrubber to upgrade the biogas for the Pacific Gas & Electric contract. Like Fibrominn, the facility is in a high-density livestock area where farmers are forced to haul their manure away. “Generally speaking, though,” says Mark Hall, EPC’s senior vice president, “it’s better to avoid trucking manure around.”

The company’s newest projects, both in California, take a different approach. Each one consists of a cluster of three dairies located close to each other. The farms will each have their own digester, so the manure doesn’t need to hauled; but the gas produced will be piped a short distance to a shared gas upgrading facility, which will then feed into the existing natural gas pipeline network. The company is convinced that it has a model that can be profitable with no subsidies except the permission to issue tax-free bonds to fund the initial capital costs—a concession it has been granted already in Texas and California. “We have a business development team out there, actively looking for new locations,” Hall says.

In addition to the gas revenue, the company sells carbon offsets. EPC sold its first offsets in a bilateral agreement with another company in 2007, and started selling them on the Chicago Climate Exchange in 2008. A ten thousand-cow facility like Huckabay Ridge produces between seventy-five thousand and 250,000 tons of carbon dioxide-equivalent offsets annually, which at 2008 prices represented a windfall of over $1 million a year. (Haubenschild, in contrast, was earning about $360 a week selling his credits on the exchange.) Carbon prices have crashed since then due to regulatory uncertainty, but could rise again with the right legislation.

While single-farm digesters are very different from the massive Fibrominn plant, it’s still a stretch to call them “small.” EPC is looking, at least initially, for dairies with at least five thousand cows. There are examples of smaller operations: a two hundred-cow dairy belonging to Jerry Jennison in Brooten, Minnesota, for example, has a newly operational digester. But the system cost half a million dollars, was 80 percent grant-funded, and doesn’t even produce enough electricity to power the farm, so it’s not a model that is likely to spread. In fact, as Nicolette Hahn Niman of Niman Ranch argued in a 2006 New York Times op-ed, government support of manure power provides an incentive for farms to expand—Haubenschild, for instance, doubled the size of his herd to nine hundred when he first installed his digester.

In a world that increasingly values small-scale, local food initiatives, this may become a potent criticism. “If we don’t pay ranches who grass-feed their cattle and thus use the manure directly, we shouldn’t pay feedlots who grain-feed their cattle and end up with a potential hazard,” Morris says. “It should be a cost of concentration.” But in the short term, at least, we won’t be able to wish away high-density farming, so it seems foolish to ignore a technology that could mitigate the damage done by these farms, while reducing greenhouse gases and producing renewable energy in the process. US Department of Agriculture funding for anaerobic digesters reached $12.9 million in 2003, but decreased steadily after that, to $1.8 million in 2007. Still, that investment has yielded tangible gains: in 2007, more than two hundred million kilowatt-hours of energy were generated by over one hundred digesters. While that remains an infinitesimal fraction of the US’s total energy use, it’s still nearly triple the 2003 figure.

Ultimately, for manure power to fulfill its potential, either the technology or the economics needs to improve. If Haubenschild and his collaborators can figure out an effective way to convert biogas to anhydrous ammonia on a small scale, that could tip the balance. Alternatively, a binding national cap-and-trade scheme for carbon emissions would drive up the price of offsets dramatically (in Europe, for instance, they still trade at over one hundred times the current American price), making digesters significantly more attractive. And the simplest, most immediate change would be to smooth out the patchwork of regulations governing the terms under which small producers can sell electricity back to the grid.

In December, dairy industry leaders signed a memorandum of understanding with the US Department of Agriculture to work together toward these changes, with the goal of reducing the sector’s greenhouse gas emissions by 25 percent over the next decade. A month later, Haubenschild was anointed Innovative Dairy Farmer of the Year by the International Dairy Foods Association at a ceremony in Phoenix. Slowly, other farmers are awakening to the value hidden in their most malodorous by-product—a mental rotation that Haubenschild has been advocating for thirty years. “Manure is not waste,” he insisted in a presentation after receiving the award. “Animal manure on our dairy has as much value as the milk does.”

Related on

—The Green Gospel
—Hong Kong's Air Conditioning Addiction
—The Happiness Project

SubscribeFollow Maisy on TwitterLike Maisy on Facebook