1980 - Volume #4, Issue #2, Page #10[ Sample Stories From This Issue | List of All Stories In This Issue | Print this story | Read this issue]
Dairy Farm Turns Cow Manure Into Electricity
Eight years ago, the Waybrights began their search for a way to make the best use of all the resources on their farm - including the manure produced by their large dairy herd. At the present time they are milking just under 700 head of Holstein cows with a herd average of around 13,000 lbs. per cow. After much studying and searching, an agreement was reached with Scheaffer-Roland of Chicago to engineer the construction of a PlugFlow Digester which could extract "Bio-Gas" from cow manure.
To date, the technology surrounding "Bio-Gas" production and use is still in an experimental stage. Richard Waybright related that their digester was constructed on a very experimental basis, with as little initial investment as possible until the project appeared feasible. Even at this, the total cost of this "experimental" electrical power source was $85,000.
The Plug-Flow Digester works by keeping 12 percent solid, slurry cow manure heated to a minimum temperature of 95 degrees for a period of 15 days. The digester, which looks like a large, long black balloon, can hold 195,000 gallons of manure. Each day 13,000 gallons of fresh manure are pumped into the digester, and 13,000 gallons of spent manure are removed. A heat exchanger, operating in conjunction with the generator, is used to heat the manure. Heat pipes running the length of the center of the digester cause the manure to rise and move towards the outside of the digester. This forces the manure on the outside to move along the bottom of the digester towards the center, and the heat pipes. Thus, a continuous motion is maintained, and the bacterial action promoting the formation of "Bio-Gas" occurs. At present, one million, two hundred thousand cubic feet of "Bio-Gas" are being produced monthly.
There ,are two interesting byproducts of the production of "BioGas". One is the production of a 40% washed solid material suitable for use as bedding in free stall barns. The bedding is a result of squeezing the liquid out of the manure removed from the digester. The material is free of pathogenic bacteria, practically odorless since the ammonium nitrate has been stabilized, and spongy, which keeps it underfoot longer. The second by-product is the liquid squeezed from the solids. This liquid emerges as a neutralized fertilizer containing a higher concentration of nitrogen, phosphorus, and potash than fresh cow manure.
At this time only a portion of the available manure can be processed through the digester. However, if the new system continues to operate on its current level or better, there are projected plans for the construction of another digester which will be able to process the remaining manure available from Waybright's herd. When the second unit goes into operation Mason Dixon will be able to produce all the electricity they need, and then some!
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