At the Huckabay Ridge biogas facility in Stephenville, Texas, a life preserver and a “No Swimming” sign hangingon the concrete exterior of one chocolate-colored pool are somebody’s idea of a barnyard joke. Early this year, the manure from 10,000 cows from Texas’ Erath County began stoking this facility, which is expected to produce enough pipeline-quality methane to power 11,000 homes. During my visit there, the odor outside is surprisingly mild – comparable to an ordinary stable, even though the operation sits next to an existing commercial composter. Dried manure from local dairies has been trucked in and combined with cooking grease and other food waste to create the soupy brown concoction that now sloshes through open-air vats and into enclosed silos.

 

Inside the air-conditioned office, round-the-clock workers keep tabs on the process and maximize output using a web-based computer system. “We’re borrowing the manure for 20 days, then we give the compost yard the residues,” explains Mark Hall, senior vice president of Environmental Power Corp., which owns and operates the facility.

 

More than 64,000 cows call the windy, rolling pastures of Erath Countyhome. Each of these hard-working beasts delivers thousands of gallons of milk each year, and something else, too – more than 100 pounds of waste, per cow, per day. By any measure, Erath County is knee-deep in manure. To cope with so much excrement, dairy farmers spread some on fields or send it off to composting facilities, but most often they’ll shovel it into noxious lagoons where decomposing manure wafts pungent odors and leaks unwelcome contaminants into watersheds. These days, though, the need for sustainable green energy has given manure new purpose: It’s an increasingly popular source of a type of biofuel.

 

During the natural decomposition process, dung heaps release fumes, typically referred to as “biogas.” More than half of all biogas is methane – the same high-energy fuel traditionally drilled and extracted from underground wells as natural gas. Through a process called anaerobic digestion, bacteria break down manure in the absence of oxygen, releasing methane and other gases like carbon dioxide. Methane extracted from biogas can be used like any other natural gas to heat homes or fuel electric utility plants. Savvy farmers already harness biogas to power their own operations, but with natural gas prices skyrocketing, manure-generated methane has begun to help power the energy grid.

 

By the end of this year, more biogas facilities will come online at dairies across the country. New plants are in construction in Texas and California, joining similar facilities in Wisconsin and elsewhere.

 

When compared to traditional livestock waste management, these biogas operations are a “clear environmental win,” says Nathanael Greene, Director of Renewable Energy Policy at the Natural Resources Defense Council. “These large [livestock] systems in many cases put out more waste than some of our largest cities. It’s really staggering how much poop these systems produce,” he says.

 

State-of-the-art anaerobic digesters reduce the waste’s volume, and their high temperature helps purify it, making it less bio-reactive and better fertilizer. By repurposing biogas as fuel, says Greene: “You’re avoiding raw methane releases, which have 23 times the climate warming potential of CO₂.”

 

Having 1.7 million dairy cows of its own, California views biogas facilities as an opportunity to slash its output of global warming methane by up to 90-percent. Spurred by the state’s mandate to increase renewable green energy, Pacific Gas & Electric Company now buys “cow power” from Vintage Dairy and neighboring Pier Van Der Hoek Dairy in Fresno County. Rather than enclosed silos, these dairies use covered manure lagoons to generate and capture the biogas. The methane is purified at Vintage’s site before getting pumped out to the pipeline. (This facility doesn’t currently add food waste to augment the manure’s methane output.) These Fresno herds total 11,400 cows, and their manure is expected to power 2,500 homes.

 

Manure may be a dirty biz, but thanks to biogas reclamation, the barnyard is now full of four-legged, mooing gas wells.

 

 

 

Copyright Environ Press 2008