[an error occurred while processing this directive] ZEPHYR Magazine
                              T H E
                           Z E P H Y R
                  __     M A G A Z I N E
                 Issue #61                12-5-88
            A weekly electronic magazine for users of 
                        THE ZEPHYR II BBS 
                    (Mesa, AZ - 602-894-6526)
                owned and operated by T. H. Smith
                    Editor - Gene B. Williams 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
 . You may share this magazine with your friends under the   .
 . condition that the magazine remain complete and intact,   .
 . with no editing, revisions or modifications of any kind,  . 
 . and including this opening section and statement.         .
 . If you like the magazine, our Sysop and I would appreciate.
 . it if you would let your friends know where they can log  .
 . in to find the magazine (and incidentally one of the      .
 . finest BBSs in the country!).                             .
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
                            (c) 1988

   One of our users, Lyle Knox, is involved in agri-business. One 
day he left me a note in private mail about Arizona Dairy and 
some of the things they were doing. It sounded interesting so I 
made a few contacts to see if any magazines would be interested. 
This resulted in an assignment from one called, DAIRY HERD 
   With the assignment assured, I went to visit the dairy to get 
the information and to take the needed photographs. What I found 
was more than expected.
   I've done articles of this type many times in the past. 
Methane generators have been around for quite a while, but very 
VERY few ever work all that well and often cost more than is 
worth the operation. 
   What Arizona Dairy has managed to do is to build one that does 
indeed work. More, it's the largest of its kind in the entire 
   For those of you unfamiliar with the process:
   In a sense, a methane generator is much like a septic tank. 
The animal waste is "digested" by bacteria. The waste product of 
the bacteria (one of the waste products) is methane. And methane, 
also called natural gase or bio-gas, can be burned as a fuel. 

   Anyway, what follows is the article I wrote for the magazine, 
with thanks to Lyle.

                      From Waste to Profit


                        Gene B. Williams

     With a total herd of 4690 Holstein, Arizona Dairy is the 
largest in the state, but this isn't what makes it unique. On the 
grounds is the world's largest bio-gas (methane) generator of its 
kind. While other dairies are staggering under high electricity 
bills, Arizona Dairy is selling excess power back to the utility 
     Don't let the size throw you off. General manager, Jim 
Tappan, says that he's convinced that the idea can be made to 
work at any dairy with a herd of 100 or more.
     "Actually, we didn't begin with this sort of system in 
mind," says Tappan. "The project began as an attempt to reduce 
the electrical bill. The rest simply evolved from necessity."
     By 1980 they were paying some $15,000 per month, and faced 
the promise of ever higher bills. Owners Kenneth and Marvin 
Morrison and Jim Tappan decided to install a natural gas driven 
generator (Caterpillar G398 NA, producing 475 horsepower and 
generating 320 kw). However, by the time construction was 
complete, the policy of the gas supplier had changed. They wanted 
$100,000 to install the gas line.
     Nearly $250,000 had already been invested in the generator 
and power distribution system. The cost of installing the natural 
gas pipeline caused Tappan and the Morrisons to explore other 
     Conversion of animal wastes into methane gas has been known 
for some time. The problem was that very few have managed to do 
it feasibly on any scale. Even so, it seemed to be a natural 
solution to two problems - supplying the bio-gas to drive the 
generator and handling the manure produced by the cattle.
     Dr. William Jewell of Cornell University in New York had 
been working on a bio-digestion system. His plug-flow design was 
scaled up to meet the needs of the dairy. This would take the 
semi-digested material from the previous tank and feed it to the 
next, resulting in complete and efficient digestion and subse
quent generation of the bio-gas. 
     In 1982 Don Sherman, a graduate of Cornell, came to Arizona 
to oversee the project. The cost came to another $200,000 - about 
twice the cost of installing the gas line - but if the system 
worked, they could greatly reduce or eliminate their staggering 
power bills.
     Five pits were dug. The central three, each 150 feet in 
length, had concrete troughs built around the edges. Large 
plastic tarps were placed over the pits. The plastic was set into 
the troughs and secured with iron bars and rope. When the troughs 
were filled with water, the pits were sealed. 
     Each day 50 tons of manure is introduced into the first pit 
by a manure spreader and then mixed with waste water from the 
milking parlors by a lagoon stirrer attached to the PTO of a 
tractor. The mixture is warmed and fed into the first main pit. 
As digestion continues, the manure is pumped into the second and 
third pits. The total process takes approximately 21 days, and 
creates nearly 200,000 cubic feet of methane per day - more than 
enough to supply the 7500 cu. ft. per hour appetite of the 
generator. Heat from the generator goes back to keep the mixture 
at a nominal 110 for more efficient digestion.
     The remaining effluent (12% solids) at the end of the 
process emerges into the fifth pit. This is then pumped to a 
sprayer system set in an open field on the far side of the dairy. 
As the liquid dries it leaves behind an incredibly rich fertil
izer which Arizona Dairy hopes to one day market commercially.
     The first manure was put into the system in December, 1982. 
Since the system was the largest ever built, testing was needed. 
It began to produce electricity in March of 1983 and about a year 
later reached full capacity.
     There were some initial problems. The original design called 
for the material to be pumped from the top. The heavier sludge 
settled to the bottom, which required that the system be shut 
down occasionally to be cleaned. Cornell suggested that the 
mixture be made thicker to prevent settling. This slowed the 
problem but didn't eliminate it. Output from the system began to 
decline - the symptom that the system has to be shut down and 
     Another suggestion was to bubble the gas back through the 
mixture from the bottom. That also helped, but again didn't solve 
the problem. "It would have been very easy to give up on it," 
Tappan said.
     It was after this that Tappan saw the solution. The next 
time the pits had to be cleaned, he arranged to modify the design 
so that the drains were at the bottom, "like huge bathtubs." Ever 
since, the system has operated flawlessly and nonstop. 
     During the day, when the cost of electricity is higher due 
to public demand, the system produces more power than is needed 
by the dairy. This is sent through a metering system and into the 
power company's lines. The amount is credited to Arizona Dairy's 
power bill. 
     Cost of electricity is lower at night. This is when the 
dairy makes its ice and handles other power consuming tasks. In 
essence, they buy power when it's cheapest and sell it back to 
the utility when it's more expensive.
     "The initial cost was high," says Jim Tappan, "but we hoped 
to make it back in four or five years." 
     They did just that. Five years have passed since the first 
power came from their generator. Despite some earlier problems 
and the need for design modifications, the entire half million 
cost, and all interest on the loan, is now paid off. 
     From here on, the lack of a power bill translates into 
profit for the dairy. "And if we can market the fertilizer, that 
will be an added bonus."

   Seeing it is more fascinating than just reading about it. The 
article will have photos. Since I can't include photos here:
   The building for the generator is on the east end of the field 
and a couple hundred feet away from the pits. 
   The first pit is open. Sitting at the side are the manure 
spreader and tractor with the stirrer. Then comes the first 
working pit. Each of the three is about 35 feet wide and 150 feet 
long. Each has a short concrete wall with the trough filled with 
water to make the seal. Over each is the "balloon" of thick black 
plastic to contain the methane. These bags cover the entire pit 
and rise about 12' upwards when full. On the north side there are 
pipes that connect the bags. This way the methane can be drawn 
from any of the three without depleting the other two. 
   On the west is the fifth pit, filled with a blackish fluid. 
This is what gets pumped about a half-mile to the south. The 
field in use is about 600 feet wide and nearly a half-mile in 
length. The dried fertilizer is now about 3' thick. It's dry but 
feels kinda soft when you step on it.
   A huge reel (orange, with black 6" flexible pipe wound on it) 
connects to one of two pipes. On the reel is a small gasoline 
engine which winds in the sprayer.
   Next time around? 
   Another job I've covered lately is about a couple in Phoenix 
who collect rocks. But not just ordinary rocks. What they have is 
a complete banquet. 
   Yup! Everything in the collection looks just like something 
you'd eat. Hamburger, fries and a pickle. A big "juicy" roast. 
Sirloin steak, chops, fish, rolls, breads, donuts, lemon and 
chocolate pies . . . . 
   Arizona is an amazing state if you just open your eyes and 
ears a bit. Lyle suggested this dairy article. Who knows. Maybe 
another of you knows of something strange, unusual or otherwise 

Zephyr Magazine is © Gene Williams. All rights reserved.