Poultry litter is often used as an organic nutrient source in forage, cereal and fiber crop production. The addition of poultry litter to tall fescue, orchard grass, bermudagrass has been shown to increase dry matter production. In some cases the amount of N applied was in excess of the amount recommended for forage production, resulting in groundwater and surface water contamination through leaching and surface runoff.
Excessive application can cause undesirable effects on forage crops and animals consuming the forage. During a seven-year study in which over 18 tons/ha of broiler manure was applied annually to tall fescue used in a grazing study, Stuedemann et al. (1975) noticed problems with grass tetany and fat necrosis in beef cattle. Increases in corn response to poultry manure addition have been noticed in a number of studies. In most studies, highest corn yields were obtained with the highest rate of manure addition, but the efficiency of manure N recovery by the crop decreased markedly as N rate increased, resulting in N leaching. For example, Sims (1987) obtained three year average efficiencies for N recovery of 50, 37, and 36%, respectively, for poultry manure application rates of 84, 168, and 252 kg potentially available N. The potentially available N from manure was calculated as 80% of (NH4-N + NO3-N) plus 60% of organic N . Similar decreases in N recovery with increasing N rate were observed in the case of fertilizer N application. In some studies, excessive application of fertilizer N or poultry manure has been shown to decrease corn yield, which has been attributed to adverse growing conditions (‘salt injury’) resulting from high salt concentration in the soil.
Continuous cultivation of arable soils results in the deterioration of soil structure leading to reduced crop yield. For example, in the Manawatu region of New Zealand, continuous cultivation of maize has resulted in the deterioration of the physical conditions of the soils. A plant growth experiment was conducted in which the effects of poultry manure on the physical fertility of the cultivated soil and the growth of maize crop were examined. A soil that has undergone continuous cultivation of maize for 34 years and a pasture soil was used in the study. Poultry manure was compared with urea at an application level of 300 kg N/ha. The addition of urea and poultry manure increased the dry matter yields of the maize crop in both cultivated and the pasture soils. In the pasture soil, there was no significant difference in dry matter yields between the poultry manure and the urea treatments. However, in the case of the cultivated soil, poultry manure achieved greater yields than the urea treatment. Addition of poultry manure achieved similar dry matter yields in the pasture and the cultivated soils.
The results indicated that improving the chemical fertility status of the cultivated soil alone through chemical fertilizer input is not enough to achieve the potential maximum yield of maize crop in these soils. These results indicate that the addition of poultry manure improved the physical fertility of the cultivated soil leading to increased maize growth. Compost products, including poultry litter, are used commonly as a mulching material for agricultural and horticultural crops to conserve soil moisture and to protect the surface feeding roots from drying during the summer periods. Similarly, the application of poultry litter has been shown to improve the biological fertility of mine tailings. Organic manures, such as poultry litter, are increasingly being used in the rehabilitation of disturbed land resulting from mining and other industrial activities.
AN ANIMAL FEED
Poultry manure, either on its own or when mixed with feed grains, has been found to be a valuable feed for cattle and fish. Ruminants are able to utilize the urea nitrogen (uric acid) in poultry manure. However, the presence of foreign materials, such as plastic and glass, and feathers affects the digestibility of poultry waste and hence it is important to remove these from the litter before using it as a feed. It is also important to maintain low ash content. When large quantities of soil are removed with the litter, the ash content increased dramatically. It is recommended that poultry litter with ash contents exceeding 28% should not be fed to cattle. From a hygiene perspective, unprocessed poultry waste contains potential pathogenic microorganisms such as Clostridium, Salmonella and Enterobacter spp. Hence proper processing to reduce the number of these microorganisms or render the waste free of pathogens is required.In addition, as noted above, feed additives such as antibiotics, arsenicals, and coccidiostats are added in the poultry diet, which can be excreted as waste by-products. Furthermore, some of the fungal species that are indigenous to the manure or litter can result in the production of mycotoxins. Pathogenic microorganisms can be destroyed by chemical, fermentation,
Although disease problems have not been reported from feeding poultry manures to farm animals under acceptable conditions Cu toxicity has been found to be a problem, especially in sheep. When an excess of Cu is added as a growth promoter to poultry diets, it is excreted in high concentration in the manure since Cu is poorly absorbed in the bird’s digestive system. Sheep are less tolerant than other livestock species to high dietary levels of Cu when fed broiler litter . Processed chicken manure and litter have been used as a feed ingredient for almost 40 years in the U.S. These contain large amounts of protein, fibre, and minerals, and have been deliberately mixed into ruminant feed for these nutrients. Normally, this animal waste is used by small farmers and owners of beef and dairy herds as a winter supplement for cows and weaned calves. While the practice of feeding poultry manure to animals seems unpleasant, the use of this product is safe as long as it meets certain specifications listed in Table 8. For, example, the Association of American Feed Control Officials (AAFCO) has established ‘Standard Names and Definitions’ for three processed poultry waste products used as an animal feed as follows (FDA, 2009):
- Dried Poultry Waste: a processed animal waste product composed primarily of feces from commercial poultry, which has been thermally dehydrated to a moisture content not in excess of 15%. It must contain not less than 18.0% crude protein, and not more than 15% crude fiber, 30% ash, and 1% feathers.
- Dried Poultry Waste-non protein nitrogen (NPN) Extracted: a processed animal waste product composed primarily of faeces from commercial poultry which has been processed to remove part or all of the equivalent crude protein and non protein nitrogen (NPN) as urea and/or uric acid, and which has been thermally dehydrated to a moisture content not in excess of 15%. It must contain not less than 11% crude protein, and not more than 15% crude fiber, 30% ash, and 1% feathers.
- Dried Poultry Litter: a processed animal waste product composed of a processed combination of feces from commercial poultry together with litter that was present in the floor production of poultry, which has been artificially dehydrated to moisture content, not in excess of 15%. It must contain not less than 18% crude protein, and not more than 25% crude fiber, 20% ash, and 4% feathers. The AAFCO specifications require that processed animal waste products do not contain extraneous materials such as metal, glass, nails or other harmful matter. They must be free of pathogenic organisms, pesticide residues, parasites, or drug residues, which could be harmful to animals or could result in residues in human food products or by-products of animals at levels in excess of those allowed by State or Federal statute or regulation .
Although poultry litter has been found to be more valuable as a feedstuff than as a fertilizer, the use of poultry waste as a feed ingredient is becoming a less common practice within the livestock industry. The public perception of the concept of coprophagy (animal consumption of fecal material) contributes to the limited use of this practice as a major means of recycling poultry wastes. It is also likely that concerns about infection by enterohemorrhagic strains of E. coli, and the perception of transmission of neurodegenerative diseases such as scrapie,
Poultry litter can be burnt directly as a fuel source to produce heat energy. One of the problems with using poultry litter as a fuel source is its relatively high moisture content. The moisture content should be less than 15% in order to achieve maximum heat energy during burning. Alternatively, the anaerobic digestion of poultry waste yields biogas, a combustible gas composed of approximately 60% methane, 38% carbon dioxide, and a mixture of water vapor, ammonia, and hydrogen
Poultry litter combustion has received major attention as a method to produce heat and electricity at large centralized facilities. In the search to make electric power from renewable ‘green’ sources, a number of states in the US have turned to thermal conversion of biomass. For example, Minnesota produces over two million tons of turkey and broiler waste — the fuel for ‘poultry power.’ Now some Minnesota turkey farmers are working with a British company (Fibrowatt) that built a manure-fired power plant in central Minnesota in 2007. The plant burns nearly half a million tons of poultry litter every year, generating 50 Megawatts of electricity that will be sufficient enough to supply 40000 households. Similarly, there is a proposal to build a poultry litter-based power plant in Western Australia. On the basis of the Fibrowatt experience, it is possible to produce approximately 0.700 Megawatts of electricity by burning around 7000 tons of poultry litter produced in the proposed broiler plant. This will be sufficient enough to supply around 900 households. However, a limitation to the adoption of this technology is the high capital investment and public concern for potential emission of particulate matter, nitrogen oxides, carbon monoxide, and
IMPROVING THE VALUE OF POULTRY LITTER
Fresh poultry waste is difficult to handle due to its high moisture content and odor. With the introduction of the barn system (confined production), it is now possible to produce relatively dry manure. Another important problem of poultry waste is the loss of N during the storage, drying, handling, and subsequent land application. The loss of N occurs mainly through ammonia volatilization and denitrification during handling and through nitrate leaching after application to land. Gaseous losses of N are of particular concern because they not only reduce the fertilizer value of poultry waste, but also form atmospheric pollutants, and deteriorate the environmental health. Excessive application of fresh poultry manure also results in the accumulation of ammonia in soils causing injury to seedlings and roots. Thus, poor management of this valuable resource could be damaging to crops and also leads to pollution of surface and groundwaters. Appropriate technologies, which are environmentally viable and economically feasible, are needed for efficient management of poultry waste. This can be achieved through proper composting of the manure and the appropriate feed management practices.
Manure by-products undergo a number of treatment processes that include in-situ biological pond treatment, composting, and specific chemical treatment. Aerobic composting is most commonly practiced to overcome some of the problems associated with the handling and disposal of poultry manure. It reduces the bulkiness of the waste and yields a stabilized product suitable for handling and land application. Composting eliminates animal and human pathogens and could reduce the risks of polluting groundwater.
Development of appropriate methods of composting poultry waste with suitable amendments could greatly reduce the nutrient losses and at the same time helps to minimize environmental pollution. Use of amendments, such as straw, peat, woodchip, paper waste, elemental sulphur, and zeolite helps to reduce the N losses during composting of poultry waste. Aerobic composting with cereal straw, which contains readily decomposable carbon, is most effective in reducing the N loss. Nutrient-rich eco-friendly compost can be prepared by composting poultry waste with phosphate rock and elemental sulphur. This can be used as a valuable nutrient source especially for organic farming practices. Addition of a small amount of elemental sulphur reduces the pH of the compost, thereby reducing the volatilization losses of ammonia. It also enhances the dissolution of rock phosphate and enriches the compost with P and S nutrients Use of alum and zeolite to reduce ammonia volatilization, as well as P solubility of poultry litter, has provided encouraging results.
The potential to use such amendments not only addresses environmental concerns but also improves the housing environments for the birds and workers by reducing ammonia concentrations, as well as improving the N:P ratio of the manure for crop utilization. Hence it forms an economically viable option for poultry growers
Although composting is basically aimed at achieving a stable manure product, it may also affect both the total content and the speciation of metals in manure by-products. For example, Sistani et al. (2001) observed that composting decreased Zn content in poultry manure. Moore et al. (1998) observed that treatment of poultry manure with alum [Al2(SO4)3] resulted in the immobilization of Cd, Cu and Zn, thereby decreasing their concentration in soil solution.
Improving feed efficiency and health of animals that minimises the incidence of disease outbreaks is an important consideration in intensive, confined animal production systems . Efficient nutrient utilisation using growth promoters not only reduces the cost of production but also provides a major means of reducing potential contaminants, such as N and P in poultry manure. However, since some of the growth promoters contain metals, this practice is likely to result in elevated concentration of these elements in manure by-products. Precision formulation and feeding of diets to meet but not to exceed the nutritional requirements will likely be a viable component of waste management strategies. Nutrient excretion in poultry manure results mainly from inefficiencies associated with digestion and metabolism. Addition of feed supplements and modifying feeding programme to improve nutrient efficiency can result in significant decreases in the N, P and odour of poultry manures .
Examples of these methods include :
(i) addition of synthetic amino acids and reducing protein contents in the feed have resulted in a decrease in manure N contents by 10 to 27% in the broiler units;
(ii) enzyme supplementation has resulted in a 12 to 15% reduction in the dry weight of broiler manure;
(iii) phytase supplementation has resulted in the reduction of P in poultry manure by 25 to 60%;
(iv) formulation of diet matching the requirements has reduced the N content in manure by 10 to 15%;
(v) phase feeding reduced N and P in the manure by 10-33%; (v) use of highly digestible raw materials in feed has reduced the N and P excretion by 5%;
(vi) certain feed manufacturing techniques (reducing particle size and pelletising) can significantly increase dry matter digestibility, leading to reduced manure production;
(vii) use of alternative coccidiostats, such as ‘ionophores’ (instead of arsenical compounds) can achieve drastic reduction in As level in poultry litter; and
(viii) similarly the use of non-metal containing growth promoters helps to reduce the concentration of metals, metals such as Cu and Zn in poultry litter.
BEST MANAGEMENT PRACTICES FOR BENEFICIAL USE OF POULTRY LITTER
There is an urgent need to formulate strict regulations governing the safe disposal and handling of poultry waste in order to minimize the environmental impact. Management of poultry waste must be integrated into a broader nutrient management programme in agriculture. Guidelines on specific land application, optimal loading rates, and permissible limits of nutrients, heavy metals, antibiotics, and coccidiostats in poultry waste, are needed. Research-based information on the transformation and plant availability of nutrients and heavy metals in poultry wastes is needed for efficient management of this resource as a nutrient resource and soil amendment. Recycling of poultry waste in fish and cattle feed and in power (electricity) generation should also be given consideration for efficient and profitable management of poultry waste. The components of an effective management programme for the agricultural use of poultry litter include (RIRDC, 2009):
(i) site selection;
(ii) production and collection;
(iii) storage, handling and treatment; and
(iv) transport and land application.
Site-specific optimization of each of these components is essential to maximize the beneficial use of litter resources, thereby avoiding the pollution of the nearby environment (Sims and Wolf, 1994). Management programmes for poultry litter must reflect both the potential value of the litter as a resource and a realistic appraisal of the negative effects litter constituents may have on the environment. High transportation costs and lack of distribution infrastructure are some of the reasons why a comprehensive approach to poultry litter management be developed to take advantage of all beneficial end uses for the diverse waste products of this industry.
- Site location for a poultry unit should be based on the facilities for production, storage and treatment of wastes and the suitability of the soils on the site for land application of litter.
- Proximity to streams, ponds, and drainage pathways and an understanding of groundwater hydrology are taken into consideration.
COLLECTION AND STORAGE
- A waste management plan that aims to reduce the volume of waste production will facilitate the ease and efficiency of the operations of the plan.
- Litter collection should be closely linked to storage capacity so that these resources are protected from unfavourable weather conditions and maintained in good physical conditions enabling easy application.
- The unfavorable economics of litter transportation often result in the limited distribution of nutrients throughout the farm, causing a build-up of some nutrients (e.g., P) to excessive levels in the field at short distances from the site of waste generation.
Composting is the most common treatment aimed at achieving a stable organic manure product. It also achieves partial or complete elimination of microbial pathogens.
- Compost areas need to have an impermeable base to avoid leaching and possible groundwater contamination.
- The composting site should be in an elevated area or a bunding may be required in order to prevent extraneous runoff entering the pile and becoming contaminated.
- The compost pile should be protected from rain in order to overcome leaching of nutrients and contaminants, and from wind to overcome the problems associated with odorous gases.
- Nutrient rich runoff from the compost piles should be collected in a sump or dam and may be reused.
- Compost pile
needto be carefully managed to avoid dust and odouremission. If the compost is too dry the process will be slowed and excessive dust may be generated. If the compost becomes too wet, it may become anaerobic and result in excessive odouremissions. Optimum moisture content is around 50 – 55% (wet basis).
- Timing of land application of poultry litter should be aimed at maximising crop recovery of nutrients and closely related to production patterns and storage capacities.
- Poultry compost should be added during the active growth of the crop or immediately before planting. For example, application of poultry manure during fall and winter, when crops have not been able to utilize nutrients is normally not encouraged.
- Application should be based on balanced nutrient requirements of the crop.
- Litter should be incorporated into the soil; this will reduce the gaseous losses of N and the runoff losses of nutrients and contaminants in the litter.
Environmental monitoring is an important component of best management practices to achieve both sustainable production and environmental protection when poultry litter is applied to land. Environmental monitoring includes regular analysis of manure samples, maintaining accurate records of all activities in the farm, and regular soil and drainage water sampling and their analysis for nutrients and other contaminants.
FUTURE LITTER RE-USE
As we show the Application of litter directly onto land provides a convenient mechanism for disposal and is the most commonly used waste management option. Litter acts both as a fertiliser and soil conditioner, unlike inorganic fertilisers that do not supply soil organic matter to soils. It is estimated that in excess of 90% of litter is spread on land that is close to the grower and, if used responsibly, has few environmental impacts. Currently, most Indian growers receive small profits from the sale of litter, or at least trade the litter for sheds to be cleaned and the litter taken away. For some poultry producing regions in India , land application of litter is becoming less cost effective, predominantly due to restrictions on land availability and the cost of transporting litter.
Litter has significant energy value, which is comparable with wood and half that of coal. As a result, power plants overseas have been developed using litter as the primary fuel for heat generation and subsequent electricity production. A host of other value adding technologies are also being developed to capture the energy and nutrients contained in litter while improving waste management for the poultry industry.