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Odor Control for Liquid Manure Storage Practices - Anaerobic Digestion
Anaerobic digestion enhances a naturally occurring process by
providing conditions suitable for complete decomposition of organic
matter to low-odor end products. During the process, manure is
contained in a closed system, preventing release of odorous emissions
to the atmosphere. The use of anaerobic digestion has proven very
effective in reducing manure odors both during storage and during
land application. As much as a 50 percent reduction in dairy manure
odor intensity was observed using a 20-day retention time of material
in the digesters. Although generally thought to be a capital-intensive
system, some estimates illustrate that Extension Publications
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anaerobic digestion is economically
feasible for larger operations. An example of a budget shows that
a positive net income per cow of $31 per year can be realized if
methane is captured and used as an energy source. The following
economic information, based on a 3,000-head swine finishing facility
is provided: $1.10 (20-year life) to $4 per head (10-year life)
for initial construction, minus gas harvesting equipment; $40 per
head to install and purchase gas harvesting equipment; $3 per head
capacity recaptured as income from energy produced. However, return
on investment is largely related to investment costs and resale
value of the energy generated. Typically, the operation must be
able to utilize the energy it generates for anaerobic digestion
to be affordable. This limits its use, largely, to dairy operations
and some larger breeding and gestation facilities.
