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Use of Chemical Amendments in Swine Manure

Livestock Update, November 2001

Dustie Taylor and C. M. Wood, Animal & Poultry Sciences, VA Tech

Swine waste is often used as fertilizer for agricultural land. However, producers in regions with intensive animal production must pay particular attention to the nutrient content in manure because of negative environmental impacts due to the buildup of nutrients. Phosphorus, in particular, is of concern due to its propensity to build up in the soil and run off into surrounding water sources. This leaching leads to a high phosphorus content and low nitrogen content. Leaching also results in poor soil for crop production and can lead to improper mineral content of water for human and animal consumption. The opposite, a high nitrogen to phosphorus ratio, is ideal for manure fertilizer to contribute the greatest benefit to the soil.

A number of studies designed to reduce the phosphorus in swine manure by means of chemical amendments have been conducted recently. Two of these, Toth et al. (2001); and Worley and Das (2000), were very similar in procedure. Worley and Das (2000) used a settling basin to separate solid waste from flushed swine manure both with and without chemical amendments. The settling basin alone allowed for removal of 38% of the phosphorus with the solids fraction. Combining the settling basin with 2900 mg/L of alum (aluminum sulfate) resulted in 75% removal of phosphorus.

A laboratory experiment conducted by Toth et al. (2001) was based upon reducing the water solubility of phosphorus. Several chemical amendments were used to determine their effects on reducing phosphorus solubility of fresh swine manure. The amendments in this study consisted of alum or coal combustion by-products: fluidized bed combustion flyash (FBC), flue gas desulfurization product (FGD), or anthracite refuse flyash (ANT). Preliminary results indicated that alum, FBC, and FGD allowed significant reduction of water soluble inorganic phosphorus. ANT, however, was determined to be ineffective in reducing the solubility of phosphorus. A second extraction trial was performed which resulted in a reduced concentration of water soluble phosphorus and an increase in acid soluble phosphorus. This study is still being conducted and refined to produce more accurate results before starting field trials.

Producers today not only are faced with the problem of what to do with the manure produced, but also the environmental issues that are caused by traditional methods of spreading manure for fertilization. Studies such as these have the potential to impact the management of swine waste all over the world. Chemical amendments may result in an environmentally safe way to manage and utilize swine waste. The producer may also have a more balanced fertilizer for land used in other aspects of the agricultural industry.

Literature Cited

Toth, J. D., G. Zhang, Z. Dou, and J. D. Ferguson. 2001. Reducing phosphorus solubility in animal manures using chemical amendments. J. Anim. Sci. 79 (Suppl 1):255.

Worley, J. W. and K. C. Das. 2000. Swine manure solids separation and composting using alum. Appl. Eng. Agric. 16:555-561.

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