Documents, Tools and Resources
Making Methane-Recovery Work Methane from Animal By-Products
is Feasible Energy Source
From March 1997 DQA Quest
This is a first! Rarely does DQA Quest feature stories that
follow the philosophy of the pork industry, but this exception
is important.
For years the pork industry has been proud to claim it can
use every part of the pig but the squeal. Using everything
includes using animal by-products (manure). The pork industry
can do this, and this is the competition that the dairy industry
is facing. While we may not have any more use for the "moo" than
the pork industry has for the "squeal," the dairy
industry certainly needs the attitude that no part of dairy
production should be treated as a waste.
Methane recovery from animal by-products can be an important
part of this. A preliminary analysis indicates that it is economically
feasible for larger dairies to utilize the by-products from
livestock to produce methane. This works best for dairies with
300 or more cows.
Dairy producers must be aware that the biological process
of breaking down dairy cattle by-products into methane will
work. This is important to remember, because consumer concerns
about odor and about ground water contamination are real. It
is also important to approach the use of by-products with a
commitment to make the process work.
Methane is generated through a biological process called "anaerobic
digestion." Methane, the primary component of natural
gas, is produced by the anaerobic digestion of manure in liquid
and slurry storage systems.
To utilize a by-product, it must be collected in an effective
manner so that it can be utilized as a profitable part of the
dairy. This may or may not mean any changes in how the by-products
are currently collected.
The next step may be taking place at your dairy right now.
You must make provisions to let the by-products be digested,
which means bacteria break down the animal by-products into
basic components like methane (carbon and hydrogen).
Next the methane must be captured as it rises to the surface.
This is done by floating a plastic or rubber membrane across
the top of the by-product storage area to trap the gas. The
sides extend perpendicularly down toward the earth walls and/or
floor. As the animals by-products are produced, these are piped
underneath the membrane for bacterial digestion.
This membrane captures the methane so it can be drawn off
and pumped to other locations on the farm. Normally this takes
a very small pump and a relatively simple piping system.
Dairy producers can then use the methane to reduce milk production
costs. Thanks to methane, mechanical energy can be created
by an engine which turns a generator to produce electricity.
This electricity can then be used to replace many or all of
a dairies electrical needs. In some cases the excess power
can be sold to an area electrical supplier.
Another use of the methane fuel might be to burn it in a boiler
and use the hot water for cleaning. In some cases, where the
dairy is located in northern climates, the hot water can aid
the process of by-product digestion in the collection area
by maintaining an adequate temperature.
Methane generation works. Methane generation can replace electricity
and/or gas for heat. Though it works best for dairies which
have at least 300 cows and relatively warm climates, it can
work anywhere in the U.S.
Systems like methane recovery demonstrate that "waste" is
potentially useful, and there really is no such thing as waste
in dairy production unless you count the "moo."
This animal by-product storage area on a North Carolina farm
is covered by a vinyl/plastic membrane which floats on the
surface and traps the methane gas. The gas is produced as bacteria
break down the by-products.
These PVC pipes transfer the methane from the animal by-product
storage area. The pipes are attached to the floating membrane,
and the methane can be pumped a considerable distance, if necessary.
This generator is attached to a methane-burning engine, which
is similar to a diesel engine. The energy that is produced
can run a boiler which heats all the water needed for cleaning
and heating livestock buildings.
Photos by Paul Miller
Converting animal by-products into an energy source can help
agri-businesses increase bottom-line profits while meeting
or exceeding environmental regulatory guidelines.
For more detailed information on this subject, please contact
the Dairy Quality Assurance (DQA) Center, Inc. at 1-800-55-DAIRY,
and we will provide you with additional information, including
software, to help perform a specific analysis for your dairy.
Learn about DQA's certification program for dairy farmers here. 
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