NCSU Extension Swine Husbandry
A more printable version of Swine News in Adobe Acrobat.
April, 2003 . Volume 26, Number 03
RE-CYCLE: A PROFITABLE SWINE PRODUCTION SYSTEM WITH ZERO WASTE
A description of the first portion of the RE-Cycle project was presented in the March issue of Swine News. In short, conventional swine housing was modified by placing an inclinded belt under the pigs that allowed feces and and urine to be collected separately. The feces were dried and used as an energy source. Ash resulting from this process was used as a feed ingredient for pigs.
Now, processing of urine will be discussed, and the combined system (the business model), including an economic assessment, will be described.
Recycling of nitrogenPigs excrete approximately 70 percent of waste nitrogen in urine, mainly in the form of urea. In conventional swine housing systems, this urea breaks down quickly and results in undersirable ammonia emissions. However, by mimimizing contact between the urine and the feces, and by removing the uring from the house as soon as possible, ammonia emission can be minimized.
Swine urine is a good source of nitrogen fertilizer, but as collected, it is rather dilute, unstable, and smelly (after short-term storage), making land application not an ideal solution except when using an injection system under dry-weather conditions. An alternate method for managing the nitorgen is to nitrify/denitrify it, as is done in many municipal waste-treatment plants. In such as system, bacteria first oxidize the ammonia to form nitrates, and then, in a second step, they reduce the nitrate to N2 gas. Nitrogen gas makes up 80 percent of the of the atmosphere and can be safely released into the atmosphere. Although technically a good option, this process does not produce any value- added products, and it further results in the loss of a valuable resource, fertilizer N.
An alternate solution is to trap the ammonia from urine, using, for example, a reversible chemisorption system, such as the Ammonia Recovery Process (Figure 1). This process consists of a column containing a zinc-based resin that reversibly binds ammonia. When urine passes through this column, nearly all of the ammonia (up to 99.7 percent) binds to the column, and the remaining 'urine' can be used as irrigation water since it is virtually free of nitrogen and phosphorus. Ammonia that is bound to the column is periodically removed by flushing the column with a strong acid solution. The resulting solution of zinc- ammonium-sulfate is transported to a centralized processing facility.
The remaining 30 percent of the waste nitrogen excreted by pigs ends up in the steam-reforming gasifier. There it is also converted to ammonia gas, which is trapped in the gas cleanup. Both the zinc-ammonium sulfate solution and the ammonia from the gasifier are introduced into a furnace (using residual heat from the steam-reforming gasifier), resulting in the production of ammonia gas and zinc sulfate. The zinc sulfate is returned to the farm for generation of the ion-exchange column. Ammonia is trapped in a scrubber column loaded with sulfuric acid, and the resulting solution of ammonium sulfate is dried to form fertilizer- grade ammonium sulfate.
In summary
- Nitrogen in urine can be converted to harmless nitrogen gas
- Nitrogen in urine can be converted to nitrogen fertilizer
The RE-Cycle system in its entirety is designed for an area with a high concentration of pigs. Ideally, at least 500,000 grow-finish pigs would be found within a 9- to 12-mile radius of the centralized processing plant to minimize transportation costs. Other biomass sources of fuel, such as poultry litter, wood, or municipal waste, could be used to provide additional fuel.
From an energy perspective, the outlined system would process approximately 250 tons of dry fecal material per day, equivalent ot an energy input of 58 megawatts. Presuming an efficiency of 40 percent, electricity output would be 23 megawatts, which would yield, based on 8,000 hours of operation, 184 gigawatts per year. This is roughly equivalent to the electricity required of 20,000 households. If the end product were a liquid fuel such as ethanol, instead of electricity, total production would be estimated at 23 million liters per year.
The economics of the RE-Cycle system are still under investigation. In the preceding scenario of 500,000 pigs in a radius of 9- to 12-miles, the preliminary cost, on a yearly basis, would be as follows:
The costs of retrofitting existing barns with a waste conveyer belt are estimated at $7 to $8 (US) per pig place. This assumes individual farms with 4 barns, each holding 1,200 pigs, and includes the costs of urine processing and feces storage. Transportation costs for the feces and zinc-ammonium sulfate is estimated at $11 to $12 per pig place. Revenues from fuel, ash, and fertilizer are estimated at $23 to $28 per pig place.
Thus, in the worst-case scenario, the RE-Cycle system would yield a net profit equivalent
to that of conventional pig production systems. In the best-case scenario, the net profit
would be increased by $8.50 per pig place per year.
This cost picture does not take into consideration any improvement in animal health and
performance that may occur, and it does not take into consideration that waste disposal,
under current conditions, has a cost associated with it that can be avoided. Presuming
that $3 in waste disposal costs per pig place can be avoided with the RE-Cycle System,
the increased revenue for the RE-Cycle System would range from $3 to $11.50 per pig place
per year. Note: Since the RE-Cycle model is not currently operational as a system,
these costs and revenues are estimates.
In regions where the density of pigs is insufficient to support the RE-Cycle system, land
application of manure typically remains a viable option. To facilitate land application
and to reduce air emissions, the belt-housing system provides several benefits: lower
ammonia and odor emissions and a dry, storable fecal waste stream. The fecal waste is high
in phosphorus, while urine is high in nitrogen; thus the belt-housing system allows for
precision application of phosphorus and nitrogen.
—Theo van Kempen
HOUSING OF SOWS AND GILTS IN DENMARK
Political pressure and consumer demands in Denmark during the 1990s led to new legislation
requiring pregnant sows to be loose-housed, reported Niels-Peder Nielsen at the Banff
(Canada) Pork Seminar in January 2003. The National Committe for Pig Production adapted its
research activity to a more welfare-oriented direction, and its research organization, the
Danish Applied Pig Research Scheme, initiated comparative studies og equipment, housing, and
production systems.
Thus, on January 1, 1999, a new act to regulate the housing of gestating sows went into
effect in Denmark. It required that:
These rules were to be implemented on all new or remodeled gestation housing by January,
1, 1999, and all gestation housing must mee these rules by January 1, 2012. An EU commission
has agreed to provide stricter animal welfare legislation, similar to the Danish regulations,
for all its member states and required gestating sows to be group-housed effective January
1, 2003.
Although the regulation in Denmark has been in effect only a few year, Nielsen points out
that studies evaluating group-housing systems for sows had been initiated well before this
legislation came to pass. In the early 1990s, Danish producers focused on simple group-
housing systems. Sows were kept in static groups and either floor-fed using a pellet or
meal diet or liquid-fed in a trough. This system is relatively cheap and requires low
technical inputs and support. Production performance using this group-housing system is
presented in table 1.
Results indicate that sows housed in groups had, overall, 0.3 live pigs per litter fewer
than those housed in stalls. In addition, the study indicated that 15 percent of the sows
housed in groups had to be removed form the study due to poor body condition, leg problems,
and failure to return to estrus. This system did not appear to be effective becasue of
problesm in controlling feed intake and body condition. In addition, aggression was relatively
high, resulting in high culling rates.
Electronic sow-feeding systems provide an opportunity to control individual sow feed intake
and may allow successful housing of pregnant sows in groups. The Danish Applied Pig Research
Scheme has conducted several trials using relatively new versions of electronic sow-feeding
systems, compared to several traditional confinement systems (Table 2).
Table 2. Effect of gestation housing systems on sow production.
Results indicated that productivity was lower with group housing in on of the herds and that
a large number of sows had to be removed form group-housing systems due to fear of the
feeder, leg problems, and abortions. The deep litter system appeared to provide more
opportunity for sows to escape from aggressive encounters that the slotted system. A
transition period of 1 to 1.5 years may be needed for adjustment of the herd and management
to group housing. During this period, production performance may be reduced and culling
rate may increase.
Based on their experience with electronic sow-feeding systems, the Danish Applied Pig Research
Shceme provides the following recommendations:
Nielsen concludes that in 2003 about half of the gestating sows in Denmakr will be group-
housed and that it is possible to be highly efficient using these systems. However, a
number of unresolved issues still need to be addressed, and therefore, these systems will
require continued development in order for them to show improved production and labor
efficiency.
—Eric van Heugten
—Frank Hollowell and David Lee
Breeder
Address
Breeds
Bob Ivey*
314 N.C. 111 S, Goldsboro 27530
L, D, H, Y, CW, X
Wesley Looper*
4695 Petra Mill Rd., Granite Falls 28630
L, D, H, Y, X
Thad Sharp, Jr., & Sons
5171 N.C. 581 Hwy., Sims 2788030
D, Y, X
Tommy Spruill
Rt. 1, Box 149, Columbia 27925
L, X
Thomas Farms
8251 Oxford Rd., Timberlake 27583
X
*Real-Time Ultrasound
Last modified April 04, 2003.