C2-Lancaster Farming, Saturday, June 25, 1994
iuli
Pbi
s
Penn State
Poultry ]
Pointers
SMELL OR
ENERGY FROM
CHICKENS?
Robert E. (Graves, Professor Of
Ag Engineering
Poultry manure is full of smell
and energy. Under uncontrolled
conditions, poultry manure will
break down, releasing odor,
ammonia gas, and a little heat.
Under controlled, anaerobic
conditions, there will be little odor
and the break down of poultry
manure can produce energy in the
form of biogas. The residue from
anaerobic digestion and biogas
production is a stable, low smell
ing liquid that still contains the fer
tilizer value of the original
manure.
Biogas is the burnable mixture
of methane, carbon dioxide, and
other trace gases that results from
anaerobic digestion of organic
material. It is similar to natural gas
but with only 60-80 percent of the
heat content
A biogas production unit or
“digester,” is a large, heated closed
tank or container that excludes air.
PENNSYLVANIA
\
Liquid manure is held in the tank
for 20 to 2S days at temperatures of
95 to 105 degrees F. These condi
tions promote the growth of two
types of microorganisms. One
group, called acid formers, break
down manure into simple organic
acids. This is called the liquefac
tion phase. These acids are then
converted to biogas by methane
forming bacteria during the gasifi
cation phase.
Proper temperatures, pH, and
organic loading rate are necessary
for growth of the methane formers.
If these bugs are not working, there
will be little methane gas produc
tion and the result will be a sour,
smelly, nonfunctioning digester.
A biogas digester can be com
pared to a living animal; in fact the
rumen of a cow is a large digestion
or fomentation unit Just like a
cow, a digester needs to be fed and
cared for in a consistent manner for
best results. Failure to do this will
result in a “sick,” malfunctioning
digester.
Recently there has been a
renewed interest in biogas produc
tion as a method to help control
odor when large quantities of man
ure must be handled and stored as
part of nutrient management plan
ning. Pennsylvania has digesters
operating on large dairy, swine,
and poultry farms. The gas from
these units is used to fuel engine
powered generators that produce
electricity and engine heat. Engine
heat is used to maintain the desired
digester temperature. Extra engine
heat may also be used to provide
hot water for space heating or
direct use.
On a recent trip to China, spon
sored in part by the Center for Rur
al Pennsylvania, Penn State and
USDA, a group of agriculturalists
witnessed the use of very small
scale “mini-digesters” to provide
biogas for cooking and lighting in
rural homes. With our cheap and
easily available energy, these
small-scale systems are of little
interest to Pennsylvania fanners.
However, the possibility of con
trolling odor and obtaining usable
eneigy has rekindled interest in
medium- and large-scale digesters.
Animal manures can make very
good feedstocks for biogas diges
ters. Manure needs to be in a
pumpable form with a moisture
content near 90 percent. Cage lay
er facilities can be managed to pro
duce manure of this moisture
content
Disruption of digester operation
because of floating materials such
as straw, sawdust, and feathers or
settling of heavy materials is often
a problem. Further, manure from
cage layers provides another
unique problem. Limestone or grit
in poultry manure will rapidly
settle out as the manure is heated.
This can quickly build up in the
bottom of the digester, interfering
with heating and general digester
operation. TTie .successful poultry
manure digester in Pennsylvania
utilizes a preheat settling chamber
MARYLAND
to remove this material before the
digester.
A few forward-looking, innova
tive farmers have proven that bio
gas digesters can function on Pen
nsylvania farms. These pioneers
have contributed much to our
knowledge and understanding of
biogas production and utilization.
Digester design, construction, and
operation is still an individual, spe
cialized process that is more easily
implemented on larger farms.
Systems for larger number of
animals have a lower unit cost
Larger farms are more likely to
have the resources required to
AFT Hails
WASHINGTON. D.C.
American Farmland Trust (AFT)
applauded the publication of the
final rules for the Farmland Pro
tection Polilcy Act a measure
adopted 13 years ago to compel
federal agencies to spend lax dol
lars more efficiently and minimize
the taking of farmland for high
way construction and other federal
projects.
The rules will govern how the
act is actually carried out through
out the U.S.
AFT, a national farmland con
servation group based in Wash
ington, has long pressed for the is
suance of the rules with the USDA
and other agencies.
“Secretary Espy and the USDA
deserve credit fra taking the criti
cal step necessary to implement
the Farmland Protection Policy
Act,” said AFT President Ralph
Grossi, a third-generation fanner.
Of Regulations
NEED YOUR .
FARM BUILDINGS
PAINTED?
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Write:
Daniel’s Painting
637-A Georgetown Rd.
Ronks, PA 17572
(or leave message)
■■(7l7) 687-8262
Spray on and Brush
i in Painting i
develop needed skills in design,
construction, and operation.
As more people become
involved with digesters, new ideas
and technology are bound to
improve on today’s methods. Sol
ids separation and use of fixed film
digesters to shorten digestion time
making smaller digesters more
efficient are just two of the ideas
currently being considered.
Perhaps with more interest and
experience, the pioneering work
and investment of these ( leaders
will become a realistic alternative
for many more Pennsylvania
farmers.
Publication
“It is a signal that, finally, the ad
ministration will carry out the will
of Congress and become a partner
in the effort by states, local com
munities. and private organiza
tions to protect our nation’s strate
gic agricultural land.”
The U.S. is losing a consider
able amount of its best and most
productive farmland to permanent
non-farm development. Much of
the loss is occurring on the urban
edge of metropolitan America. In
the six-county Chicago area, for
example. 450 square miles, or
288,000 acres, of farmland were
permanently converted to other
uses between 1970 and 1990. By
the year 2010, the Northeastern Il
linois Planning Commission esti
mates another 220 square miles of
farmland may be lost, a land mass
equal in size to the city of Chicago
today.
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