MANURE MANAGEMENT STRATEGIES AND TECHNOLOGIES

Abstract

A number of manure management strategies are used for both open lot and confinement facilitiesin the U.S. The primary control strategies for open lots are solids removal using settling basins andcontainment followed by land application of the liquids. These management strategies are dictatedby federal law for large open lots. Smaller lots may or may not capture and land apply the runoffliquid. Both large and small lot operators must haul and distribute manure solids on the land. Solidmanure spreaders that apply uniform rates is a major research need.<br><br>Confinement facilities rely primarily, but not exclusively, on liquid handling systems. Two generalcategories of liquid systems are pits, or slurry systems, and lagoons, primarily anaerobic lagoons.Anaerobic lagoon design has been researched and is well known to environmental engineers.Anaerobic lagoons work better in warm climates where biological activity continues most ofthe year. Anaerobic digesters with controlled temperatures can be used to produce biogas and reducepathogens, but are difficult to justify due to high capital costs, high management requirementsand a lack of incentives for using the systems. Covered lagoons and anaerobic digesters can significantlyreduce odors and releases of unwanted gases.<br><br>Naturally aerobic lagoons can reduce nitrogen in the liquid significantly, but are impractical becauseof large size requirements. Mechanically aerated lagoons are sometimes used. Autothermalthermophilic aerobic digestion, biofilm reactors, sequencing batch reactors, and combinations ofanoxic and aerobic treatments are being researched, and offer advantages of odor reduction, andwaste degradation and stabilization. Additional research is needed to optimize these systems fornutrient reduction, pathogen destruction, and energy use.<br><br>Solid-liquid separation can be used for both open lots and confinements. Open lots typically usesettling basins. Confinements typically use mechanical separators. The efficiency of a separator dependson the type of waste and the separator. Its difficult to achieve high efficiencies of separationwithout pretreatment with coagulating chemicals. Solids from both separators and from open lotsare sometimes composted.<br><br>Wetland treatment of manure liquids has received some research attention. It has been shown tooffer some nutrient reduction advantages when designed properly. Initial design parameters havebeen determined for animal waste systems, but continued research is needed to adapt wetland systemsto different types of livestock operations.<br><br>Chemical amendments remain a question. Both feed additives and manure additives have beentested by a number of researchers, and have achieved only moderate success at best. Much researchis needed before chemical additives will be major contributors to manure control solutions.Land application systems are well developed, but always need continued work to improve efficienciesand effectiveness. One of the primary areas of research needs currently is for injectionunits that minimize disturbance of the soil and crop residue cover.<br><br>Insect digestion of manure solids has been well researched in laboratory settings. Effective fieldproduction systems need to be devised, and uses for the resultant high protein feedstuffs need to bedeveloped.<br><br>Many of the above technologies can be combined into integrated treatment systems that protectsoil, air, and water quality.<br><br>Manure management strategies are different for manure from a confinement system (used here tomean a totally roofed facility) and from an open lot, or partial open lot system. Because open lotsare subject to hydrologic phenomenon such as rainfall, runoff, sunlight, and evaporation, they arevery different from confinement systems. Although there are some similarities, there are many differences.