Manure happens, how do you deal with it?
By Shannon Finnell
|Photo by Eric Vaterlaus|
When life hands you lemons, you make lemonade. That sounds all right, but what do you do when life hands you poop?
Livestock farmers in Lane County have to answer this question every day because their animals produce tons of the smelly stuff. According to the Natural Resources Conservation Service, every thousand pounds of dairy cow produces 80 pounds of manure each day. Just ten 1,100-pound dairy cows produce more than three tons of manure each week! That would fill up those downtown pits in no time.
Since their livestock ensure that poop is an abundant resource, farmers have traditionally found ways to reuse the refuse. “There’s a variety of ways of accomplishing that,” says Ross Penhallegon, an associate professor of horticulture from the now sadly defunct Lane County Extension Service. Typically, farmers in Lane County apply manure to crops or compost it to make fertilizer. “They take the manure, take the sawdust and return it to berries, vegetables and trees,” he says.
Penhallegon cites Winter Green Farm, an organic farm in Noti, as one of the best muck managers in the area, because of their management goal to generate and consume their own manure products without waste.
Wali Via, an owner and manager of Winter Green Farm, says that looking at the big picture is key to proper management. “The aim is to have the right balance of animals and crops to make a sustainable rotation or sustain the most fertility cycling as possible. That’s done through good rotation, proper tillage, proper fertility applications, that sort of thing.”
At Winter Green Farm, the manure comes from calves sheltered in barns during the winter. Farmers stack clean layers of hay on top of a hay and manure mixture, keeping the calves in clean hay and protecting the precious poop from the elements and preventing leeching. In the late spring they start composting by mixing the manure, grass clippings and moisture. When the compost ripens in the fall, it fertilizes produce on the same farm.
“As a biodynamic farm, one of the principle concepts is looking at your farm as a living organism; and to do that you have to be aware of how the different aspects or parts of the farm interrelate with each other,” Via says.
According to Via, larger farms have become more specialized in the last 75 years, raising only plants or animals. “The result of that is that you have some farms that are in need of fertility and some farms or ranches that are producing more fertility than they know what to do with, so it becomes a waste problem,” Via says. “As a model, that specialization really hasn’t worked out too well.”
Via acknowledges that managing a farm that uses its own excretions can be complex. Winter Green has some “creative relationships” that enable it take in some wayward feces, but Via says that keeping the fertilization process on-site is ideal.
Some farmers dispose of dung using less traditional methods. Vermiculture, a special method of composting, generates vermicompost, or worm humus, as its final product. Worms eat manure, plus most types of food scraps, and worms can be used on a farm with a diverse range of wastes.
The horrifyingly named “manure tea,” a cousin to the equally icky sounding but useful “compost tea” is a process in which manure steeps in water and the solids are strained out before it’s sprayed onto soil, is usually produced in buckets and is used as a complement to other methods of manure disposal.
To some dairy farmers, a whiff of cow manure smells like energy. Cal-Gon Dairy Farms near Salem has an on-site dairy digester that uses the manure from its 350 cows to generate electricity. Its 30-40 kilowatts are sold to PGE. Solids leftover from the digested manure are still used in compost. Liquid is diverted to waste lagoons, as usual, but with less of the bacteria that can pollute rivers.
Composting manure is an aerobic process (it uses oxygen), while the dairy digester process is anaerobic (does not rely on oxygen). Once manure is placed in the digester, bacteria begin breaking it down in a series of reactions that eventually result in methane and carbon dioxide. Digester operators refer to this mixture of gases as biogas. An internal combustion engine and generator then convert the gas into electricity.
Groups with varied interests can find a lot of reasons to like dairy digesters. Communities tend to support the projects because they cut down on the odor of manure emanating from farms. Dairy farmers like them because they don’t have to use their land for composting and manure storage. Environmentalists appreciate that less methane (a significant greenhouse gas) is released into the atmosphere.
When life hands you lemons, you make lemonade. When life hands you manure, you’ve got options.