For farmers operating on slim margins, the trick to staying afloat could be under their feet.
Holstein No. 2699 gazes warily over Shawn Saylor’s shoulder. The 39 other cows lining the stainless-steel stalls of the milking parlour at Hillcrest Saylor Dairy Farm appear unperturbed – by two strangers or by the vacuum pumps being swiftly attached to their udders. “They’re very particular,” notes Saylor, a fourthgeneration dairy farmer. “Everything has got to be consistent.” No. 2699 gives one last measured look from under long lashes, lifts her tail and ejects a stream of runny, brown energy that, very soon, will help power the farm.
Most people don’t think of manure from 600 cows – 68 000 litres, produced daily – as an asset; Saylor’s neighbours in Rockwood, Pennsylvania, certainly didn’t. Until two years ago, the waste was pumped to a holding pond on the property and spread on the fields every spring and fall. “You’d see a (half-metre) crust floating down there that you could pretty much walk across,” Saylor says matterof- factly. “The odour was unbelievable.”
A lot of people might not see a 200- litre drum of used cooking oil, flecked with bits of fried chicken, as a resource either. That’s why I asked my uncle, Dave Hubbard, to drive me here from West Virginia in his bio-diesel VW Jetta TDI. Uncle Dave converts the waste oil from local taverns into fuel to run his car, a motorcycle and tractors for five farms, so I figured he and Saylor could trade tips.
Saylor, 35, is both practical and inventive – much like Uncle Dave. Above the Leatherman clipped to his belt, the sleeves of a well-worn blue work shirt are rolled up to the elbows; his face dimples from smiling even as he talks shop in the milking parlour. “There’s a recycleflush system here,” Saylor says, activating a pump. Water recovered from other uses cascades across the floor, sweeping manure in murky streams down the length of the barn and into a tank at the mouth of an anaerobic digester.
Using common-sense engineering and some heavy machinery, Saylor has turned his operation’s greatest drawback into its best feature: the digester transforms 30 million litres of manure and wastewater a year into electricity, bedding, fertiliser and heating fuel – saving hefty sums of money while preventing emissions of methane and nitrous oxide, two potent greenhouse gases. As for foetid odours, the farm’s neighbours haven’t complained in two years.
Harnessing bacteria to generate energy from waste is not a new concept. The first farm-based digesters in the United States were introduced during the 1970s. But because they required a large capital investment and energy prices dropped, few farmers pursued the technology. Now, with electricity deregulation, the tables are turned: Saylor is one of an increasing number of farmers taking advantage of government grant money – and a burgeoning private market for renewable energy credits – to develop alternative energy projects that, until recently, seemed out of reach.
Pennsylvania’s Department of Environmental Protection awarded Saylor a R6 million grant, and Native-Energy, a carbon offset company, paid Saylor up front for the greenhouse gases a digester would eliminate over the next 20 years. But after visiting farms throughout the Northeastern US, Saylor wasn’t satisfied with any one of the three most common digester designs.
“There were some things I liked about each of them, but there wasn’t really a company that would build it the way I wanted it built,” Saylor says. So he decided to combine the features that best fitted the needs of his farm and save R2 million by doing all the excavating, plumbing, welding, electrical work and programming himself. Construction began in early 2006 and ended towards the end of that year.
Saylor and Uncle Dave discuss the merits of various fluids for radiant floor heating – Saylor installed pipes in the floor of the barn – as we walk toward the anaerobic digester. I’m standing on it before I realise we’ve reached our destination: a 21 m diameter, 5 m-deep concrete tank, capped by a lid and covered with soil so that it appears to be solid ground. The digester’s influent tank, on the other hand, is impossible to mistake: inside an adjacent outbuilding, a chute laden with cow manure is poised above a 70 000- litre tank holding a thick slurry of wastewater. The smell is so powerful that I involuntarily catch my breath.
The energy content of manure is relatively low – after all, it’s already been digested once – so every week Saylor mixes in higher-energy food waste from the local potato chip factory. (“Sometimes I’ll get, like, a truckload of cheese curls,” he says.) Uncle Dave asks whether Saylor could get waste oil to make bio-diesel. “I asked,” Saylor says. “It all goes out with the chips.”
From the influent tank, the slurry disappears into the digester and begins to make a 16-day, U-shaped journey around a dividing wall. During that time, anaerobic bacteria break down organic matter, producing a biogas that is about 65 per cent methane. “Basically, it’s like a cow’s stomach,” Saylor says. “A big, efficient stomach.” The gas, which fills the 30 cm of airspace under the concrete lid, is piped to another building for storage in a 12 m-diameter rubberised bladder. From there it drives a natural-gas Caterpillar engine, which in turn runs a 130-kilowatt generator.
In designs that don’t provide methane storage, fluctuations in production may sometimes mean the generator is not running at full capacity, while at other times excess gas is wasted. Saylor opted for a bladder with 480 m3 of capacity. “The bubble buffers me for a couple of days,” Saylor says. “I can run the generator at 100 per cent all the time.”
Last year the system produced 1,2 million kilowatt-hours of electricity, enough to power the farm and several nearby homes, as well as their heat and hot water – saving about R600 000. “It’s covering everything, and there’s still some left over,” Saylor says. “We had 100 000 kWh last year that we didn’t use.” The local utility paid him 2,3 US cents per kWh to put the excess into the grid. The digester also produces more gas than Saylor can use; so, with another grant, he plans to install a second 130-kW generator this winter. All of that electricity will go into the grid – and when utility rate caps start to come off this year, it’ll be worth even more.
A recent study from the University of Texas at Austin calculated that the 1 billion tons of manure produced in the US annually could generate about 88 billion kWh of electricity – 2,4 per cent of annual consumption – and eliminate 99 million metric tons of greenhouse gases.
But digesters provide other benefits, too. At Saylor’s farm, waste heat from the engine saves fuel oil by heating the milking parlour and water for the farm, as well as water that runs through pipes inside the digester to maintain its 40,5-degree temperature.
The watery waste that eventually flows out of the digester is pumped to an augerstyle compressor that separates the liquid from the solids. Earthy-smelling and soft to the touch, the solids displace green sawdust as bedding for the cows and, because they harbour less harmful bacteria than mill waste, are safer. Microbes in the digester have converted most of the volatile fatty acids into odourless methane, and so the liquid byproduct is far less potent. It is pumped to the holding pond and spread on the fields as fertiliser, where plants take up the ammonia nitrogen more quickly than the organic nitrogen in straight manure.
Every bit of efficiency helps, Saylor says. “Farming’s a big gamble, from one end to the other. Yeah, we’re still getting a decent milk price, but commodities are through the roof. Fertiliser is up 300 per cent. It doesn’t take long to burn up any money you’ve got coming in.”
Uncle Dave nods. “And the cost of diesel can really add up.” “We buy a lot of fuel in a year,” Saylor says. “A biodiesel system would work well here.” If he can’t get waste oil to make biodiesel like Uncle Dave, Saylor says, he could raise canola and press the oil himself. “Then,” he says, still thinking out loud, “the cows turn the leftover feedstock to manure, the manure runs the digester and the digester makes energy for the process.” Some farms dabbling in biodiesel have got into trouble for dumping the glycerine byproduct, Saylor says, but he could put it in the digester.
“Or feed it to the cows,” Uncle Dave suggests. “They love glycerine.” “They do?” Saylor asks, surprised. “Oh, man. They think it’s candy.” Then he adds: “And you’ll still get the gas out of it anyhow.”