What other
manure management systems are being used?
New manure treatment and handling technologies are
being developed. Five alternative treatment methods
discussed here are selected from technologies that have been
implemented.
Broad use of these alternative technologies is
slow because:
• there is no guarantee that alternative technologies
will meet ever changing permit requirements and conditions,
• the failure rate of alternative technologies has been
high, therefore caution is in order,
• the environmental benefits/consequences of these
technologies are not completely known,
• the costs of implementing these technologies may be
prohibitive to the majority of farms, and
• the expertise required for management of the technology is
high.
Solid Separation
Separating solids from liquid manure may be beneficial
in some cases. Manure solids contain a significant portion
of the total manure phosphorus if separated soon after
excretion. Manure solids high in phosphorus can be more
fully used by transporting a nutrient-dense smaller volume
to locations low in phosphorus for crop production. The
separated liquid contains only a reduced amount of nutrients
that are applied on the land. The solids may be composted
and sold or otherwise removed from the livestock production
area.
Constructed Wetlands
Constructed wetlands are another manure management
system. In a constructed wetland, liquid
manure is treated aerobically (with oxygen) while aquatic
plants take up some of the nutrients in the manure.
Constructed wetlands can provide a high |
degree of
treatment to manure. So far, constructed wetlands have not
been used by a lot of farmers. They
require a large area of ground, are expensive to construct
and establish. Vegetation requires more
management after storm events due to more surface area that
collects rain water and they do not work well
during cold weather. Livestock producers are not allowed to
release manure or wastewater into waterways, so land
application is still required for water
from a constructed wetland. Long-term use of wetlands
with swine farms has not been well documented.
Methane Digester
Methane generation through anaerobic digestion of manure
is another treatment being researched. Manure
is put into a closed container, where oxygen is not
present and as the manure is digested, methane gas is
produced. This gas can be collected and burned for heat or
used to generate electricity. The leftover liquid has fewer
odors than the original manure. The cost and
labor needed for digesters has slowed implementation.
High-Rise Swine Housing
A system called “high-rise” provides a living area for
pigs on a slatted upper floor with the manure falling
through the slats onto a lower floor containing sawdust
or other carbon source. With proper mixing, turning
and distribution of the manure and sawdust on the
lower floor, composting takes place. This system has not
found wide acceptance in the swine industry due to
increased cost and lack of need or incentive to manage
manure as a solid.
Lagoon Aeration
Aeration is another alternative process sometimes
considered in managing swine manure in lagoons or
other outside storage structures. In this process, small
bubbles of air are introduced into liquid manure to
stimulate the growth of aerobic bacteria. These bacteria
provide high-rate degradation of organic material in the |
