Agriculture Reference
In-Depth Information
high levels of excess N, P and potassium (K).
In Europe, de Walle and Sevenster (1988) deter-
mined N balances for 11 EU countries and
reported that all countries had a surplus of N
(22-320 kg ha
−1
) with five having a surplus
greater than 100 kg ha
−1
. A national nutrient
balance for Korea, in 1995, showed that excess
nutrients were in the order of 331, 386 and
406 thousand kg for N, P and K, respectively
(Richard and Choi, 1999). In the USA, the
number of confined livestock farms declined
50% from 1982 to 1997, while the number of
confined animal units increased 10% (Gollehon
et al
., 2001). This shift in production led to
more excess on-farm nutrients (734,000 t N
and 462,000 t P in 1997) and the separation
of land from livestock. Approximately 20% of
farm-level excess N and 23% of farm excess P
exceeded the land assimilative capacity at the
county level. To solve these nutrient distribution
problems, substantial amounts of manure may
need to be transported off farm and in some cases
out of the region in which they are produced.
For many livestock producers, manure has
become one of the most problematic areas of
management under a growing litany of off-farm
concerns. Concerns over long-term self-sufficiency
related to inefficient recycling of manure nutri-
ents are mounting. More acute are nuisance,
environmental and health concerns associated
with environmental emissions and runoff. Both
large and small operations face these issues.
Current major strategies for sustainable manure
management include: (i) on-farm; and (ii) off-
farm recycling of nutrients for crop production;
(iii) recycling of nutrients as an animal feed
ingredient; and (iv) export to non-agricultural uses
(energy production, fibreboard, plastics).
Sustainable manure management
implies
more than improved use of manure nutrients in
crop production, ranging from the effective use
of the energy potential associated with manures,
to the minimization of off-site transport of
potential contaminants. How manure is han-
dled, stored and land-applied affect its quality,
including nutrient value and potential to pollute
the environment. Manure treatment can also
play a central role in changing manure quality
to enhance its beneficial properties and mini-
mize its potentially adverse properties. Therefore
choosing the appropriate manure management
system is essential in order to continue to have
large-scale animal production that balances
food production priorities with negative environ-
mental and social consequences.
On-farm Manure
Management Systems
Manure collection and handling systems enable
livestock producers to utilize all the components
in their manure management system efficiently.
Unconfined livestock operations, i.e. grazing
operations where dung is excreted on pastures
or rangeland, are not included in this discus-
sion. A typical manure management system will
include some or all of the following components:
(i) area where manure is produced (i.e. feedlot/
dry lots, barns, other confinement buildings);
(ii) manure treatment area including recycling
of useable manure by-products (i.e. solids sepa-
rator, digester, composting); (iii) manure trans-
port (i.e. transfer of manure from collection to
storage or treatments areas); and (iv) manure
storage facility (i.e. manure tank, holding pond,
stackhouse or other storage area). The purpose
of manure collection and handling systems is
to gather and move manure among the com-
ponents of a manure management system effi-
ciently and safely. This system can also incorporate
technologies to fractionate the manure to improve
its utilization and derive more value from it.
The type of equipment and procedures used
to collect and handle manure depends primarily
on the solids content of the manure, with the
quantity of solids in manure varying with spe-
cies and production system. Classification of
manures on the basis of solids content varies,
but most conventional definitions classify 'solid
manures' as those with greater than 20% solids,
including 'litters', which are predominantly
generated by poultry operations and tend to
contain greater than 70% solids, 'semi-solid
manures' that contain 12-20% solids, 'slurries'
that contain 4-12% solids and 'liquid manures'
that contain less than 4% solids. The solids con-
tent of excreted manure is often changed by pro-
cesses such as adding bedding, drying manure
on a lot surface, adding washwater or dewater-
ing the manure by solids separation.
Solid and semi-solid manures are usually
collected using scrapers, box scrapers, blades,
front-end or skid-steer loaders, or similar devices.
