and Expected Outputs
||To evaluate composting techniques suitable for use in
Ontario by commercial livestock and poultry farm operations with emphasis
on carbon, nitrogen and other transformations and losses, the affect on
farm productivity, sustainability, environmental impact, economic viability
and potential for implementation as part of an effective farm manure management
and nutrient recycling program.
||The technical presentation should provide information
on carbon, nitrogen and other nutrient transformations and losses; the
economic and physical limitation of optimizing manure carbon to nitrogen
ratios; the evaporative potential of composting manure; the relative nutrient
leaching potential of manures and compost; a comparison with composting
techniques promoted by the Ecological Farmers of Ontario; the practicality
of recycling finished compost as livestock bedding; the quantification
of greenhouse gas production; and databases to establish labour, energy
and capital requirements in each process.
||Open Bid, Industry
||93-94: $132.8 K, 94-95: $114.0 K,
95-96: $62.1 K, 96-97: $91.0 K,
Total: $399.9 K
||Available February 1998
Conventional as well as ecological on-farm manure composting techniques
were studied in this project using a series of 16 composting trials. The composting
trials examined carbon and nitrogen losses as well as nitrogen, phosphorus
and potassium leaching losses. The effect of composting techniques on off-gas
and pore-space methane (CH4), carbon dioxide (CO2),
ammonia (NH3), and oxygen (O2) concentrations was also
examined. Data were collected to track process temperatures, moisture losses
and, in some experiments, weight changes.
|Germination tests were completed using cress seed to compare seed
germination inhibition levels at the end of the active composting process
determined as the point at which the compost process temperature approaches
ambient temperatures. Germination inhibition of the compost was also
assessed after 30, 60 and 90 days of curing.
Manures were sampled from beef, dairy and poultry operations in Ontario
to asses their suitability for composting in terms of moisture levels
and carbon to nitrogen (C/N) ratio.
|Germination tests to check compost maturity (lack of seed germination
Manures used and composts produced as part of this project were sampled
and analyzed for total nitrogen (N), phosphorus (P), potassium (K), ammoniacal
nitrogen (ammonium and ammonia), nitrate (NO3) nitrogen, nitrite
(NO2) nitrogen, dry matter (DM), organic matter, (OM), total carbon
(TC), pH, and ash.
Solid manures produced on the dairy and beef farms sampled during this
study were found to have moisture levels in the range of 70 to 80%, significantly
above the optimum of 60%. Solid poultry manures were found to average 33%,
significantly below the optimum. All manures had C/N ratios significantly
below the optimum of 30/1 and C/N ratios ranged from 10 for poultry manures
to 16 to 17 for dairy and beef.
Data collected from three different composting processes used by ecological
farm operators did not indicate any advantage to these processes over
conventional farm composting techniques in terms of nitrogen conservation,
reduced leachate losses, or maturity as indicated by seed germination
Comparison of traditional turned-pile, passive-aeration, and forced-aeration
composting processes with similar windrow dimensions of 3 m wide by 1.2
m high, did not indicate that one process was advantageous over the other
in terms of carbon or nitrogen conservation, leaching potential, or degree
of seed germination inhibition.
Outside and inside composting were observed to have similar nitrogen
and carbon losses and nutrient leaching potential.
|A "turned-pile" composting process conducted at the Edwin Sittler Farm
The outside composting manure was observed to form a hard surface
due to the sun's drying, which effectively shedded water. This hard
surface reduces the potential for nitrogen leaching during the process
despite the fact that it is exposed to rainfall. The net moisture loss
was approximately 20% greater for the covered processes compared to
the outside process. The outside process had a net moisture loss of
43.2% compared to 69.6% for the covered control process. Composting
processes, manipulated for nitrogen conservation, were observed to have
insufficient moisture loss to make them suitable for treatment of farm-generated
liquids (e.g. barnyard runoff).
|Composting in bins suspended on load cells for weight-loss monitoring
Composting was found to reduce the potential for N, P and K leaching compared
to raw manure. Fourteen out of sixteen processes studied showed a reduction
in N, P and K leaching losses as a result of composting.
The study indicated that windrows 3 m wide and 1.2 m high have sufficient
natural convection through them to maintain aerobic conditions without aeration
enhancements such as forced-aeration, static aeration tubes or mixing. Mixing,
however, was observed to stimulate bacterial activity (as indicated by a temperature
increase after mixing), even when pore-space oxygen levels were not limiting.
This is believed to be due to the redistribution of bacteria, enzymes, and
Mixing using a tractor loader was found to cause significantly greater
heat losses during mixing than the use of a compost windrow turner for
mixing. This initial heat loss was observed to reduce the rate of natural
convention and create a temporary oxygen deficit, increasing the potential
for CH4 production, until the temperature recovered. Based
on the data collected, mixing is warranted for bacteria, enzyme and
substrate distribution as opposed to aeration and should be carried
out using a compost windrow turner to minimize heat losses.
|Passive aeration composting
process set up for on-line monitoring of pore space and off-gas composition.
The data collected did not indicate that one composting technique was
advantageous over another in reducing the production of CH4.
Anaerobic microsites were found to exist regardless of the technology
used. Establishment of anaerobic microsites is a function of the non-homogenous
nature of manure. Forced-aeration processes without mixing were not observed
to reduce CH4 concentrations in pore-spaces or off-gases. It
is believed that mixing will help reduce the level of anaerobic microsites.
Compost curing for up to 90 days was observed to be insufficient time
for the chemical transformations necessary to eliminate seed germination
inhibition, characteristic of composts at the end of the active heating
cycle of composting processes. There was no evidence from the data collected
that compost curing up to 90 days would reduce the potential for nitrogen
On-Line data acquisition system with CO2/O2
analyzer and computer
The benefit of a 50% reduction in manure volumes due to composting is typically
offset by the value of the nitrogen lost during the composting process. Nitrogen
losses during composting for beef cattle manure were found to be equivalent
in value to the reduced spreading costs. The reduced spreading costs for dairy
cattle manure as a result of composting were found to yield a net benefit
of $0.41/T (wet) manure composted after N losses were accounted for. In the
case of poultry manure, the cost of nitrogen loss exceeds the benefit of reduced
spreading costs by $5.10/T (wet).
May 16, 2011 04:12:05 PM