Patent Application
20050235715
This invention relates generally to methods of composting animal waste products and, more specifically, to large-scale composting of beef cattle waste.
Cattle feedlots are widely used to efficiently raise high quality beef cattle. Cattle manure is a by-product of the cattle feeding industry that must be disposed of routinely. Manure can provide a good soil enhancement, but has drawbacks that often make it undesirable to crop producers. The most common problems associated with manure as an organic based nutrient source are weed seed content, lack of uniformity, and costly transportation. For these reasons, manure may be considered a liability rather than an asset.
Composting is a microbial process that has been utilized for hundreds of years to decompose various types of organic wastes. Composting large quantities of cattle manure has been a difficult and imprecise endeavor. Typically, manure composting piles are formed after which moisture and carbon amendments are added. Carbon, usually in the form of straw, is added to maintain a carbon-to-nitrogen ratio generally from 25:1 to 30:1. The high carbon ratio provides a favorable microbial environment for composting. However, the carbon amendments also increase the initial volume of the compost pile, decreasing the density and, thus, the amount of cattle manure composted in the pile.
Moisture is also important for microbial action. Moisture levels in the range of 40 to 60 percent are thought to be ideal for composting. However, such levels can be difficult to maintain, especially if a large quantity of straw or other carbon amendment is added. The straw increases the available oxygen for composting but also increases the rate of moisture loss from the pile. Compost that is moisture dense is also heavy and expensive to transport.
According to current methods, the compost piles are turned or mixed on a regular, time-interval basis. For example the piles may be turned biweekly. The pile turning can improve the microbial environment by redistributing the different particle sizes to increase passive air infiltration, and by redistributing the moisture. However, interval pile turning is blind. The composting manure may be experiencing good microbial activity, or such activity may have long since diminished. Thus, resources, such as time and equipment, can be unnecessarily wasted or the composting process unnecessarily delayed using current methods.
A simplified, more effective method of composting cattle manure would be advantageous to increase the value of the large amount of manure requiring removal. The need exists for a more consistent soil enhancement product from a large scale operation that is nutrient rich, uniform, substantially devoid of weed seeds, and easier to transport. The reduction of the costs of composting by minimizing the required man-hours tending to the process of adding moisture and carbon, and turning is also desirable.
The present invention comprises a method of composting cattle waste. The steps include forming a pile of waste in an outdoor environment, monitoring the temperature of the pile, monitoring the moisture content of the pile, mixing the pile, and adding moisture as needed. The pile is mixed after a predetermined temperature drop is sensed. Adding moisture to the pile is carried out as needed to maintain the moisture content within a predetermined range. The steps of monitoring the temperature and moisture, adding moisture, and mixing are repeated until such steps do not create a significant temperature increase following the step of mixing.
In accordance with further preferred aspects of the invention, the method further includes the step of bringing the pile to a predetermined moisture level and mixing the pile after the step of forming the pile and before the step of monitoring the temperature of the pile.
In accordance with one preferred aspect of the invention, the pile is cured and mixed after prior steps do not create a significant temperature increase. A further step includes analyzing samples of the pile to determine pile nutrient moisture, and weed seed content.
Preferably, the step of bringing the pile to predetermined moisture level includes the bringing the moisture content of the pile within the range of 40% to 65% moisture, on a weight basis.
In accordance with yet another preferred aspect of the invention, the waste includes cattle manure. The waste may also include the cattle carcasses. Such a waste pile is formed into at least one windrow. The initial height of the windrow is at least three feet and the width is at least eight feet. Preferably, the step of mixing the windrow is accomplished with a mixer.
In accordance with a further preferred aspect of the invention, a significant carbon amendment is not added to the pile.
In another preferred aspect of the invention, the added moisture is obtained at least partially from pile effluent.
Yet other preferred aspects of the invention include monitoring the temperature at least weekly and monitoring the oxygen level.
In accordance with another preferred aspect of the invention, a soil enhancement is produced by a process including the steps of collecting cattle waste, forming the cattle waste into at least one pile, bringing the moisture level of the pile to within a predetermined range, monitoring the temperature of the pile, and mixing the pile upon a predetermined temperature drop. The steps of monitoring and mixing are repeated until the mixing results in no significant temperature increase.
In accordance with such preferred aspects of the invention, the process further includes the step of checking the moisture content of the pile after a predetermined temperature drop. Moisture is added to the pile as needed to bring the moisture content within a predetermined range. The process may further include a step of curing the waste after mixing results in no significant temperature increase.
As may be appreciated from the foregoing summary and the following description, the process efficiently provides a soil enhancement product through increased temperature monitoring and decreased labor input so as to minimize the time period necessary to create the compost while also minimizing the cost involved. The organic based nutrient source produced also includes good nutrient levels, is easy to transport, and has minimal amounts of undesirable elements, such as weed seeds.
The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.
The preferred processes and product of the present invention will now be described in detail with reference to the figures. Referring first to
Referring to
After windrow 12 is formed, the moisture content of the animal waste is checked and moisture is added such that a preferred initial moisture content by weight of the organic matter fraction of the waste is between 40% to 65%. The moisture content is assessed by obtaining a representative sample of the animal waste or manure 10 and weighing the sample before and after moisture removal. Moisture removal may be accomplished through heating the sample, such as in a microwave. The moisture content of the organic matter is determined using the following equation:
0.40 a/[(c)(b)+a] 0.65
where a is the percent moisture, b is the percent organic matter on a dry matter basis, and c is the percent solids. All percentages are on a weight basis. Most feedlot pen manure, will only be 20% to 40% moisture, as a whole, when the organic matter fraction is at 40-65% moisture. This moisture level contrasts with prior composting methods that recommend an overall moisture content between 40-65%.
The addition of moisture is preferably carried out simultaneously with mixing the waste by using a mixer 22 as illustrated in
After the initial moisture level is set, moisture levels are preferably checked at least weekly.
Besides monitoring moisture, temperature and oxygen levels are also preferably monitored. Temperature levels are preferably monitored at least every other day while oxygen monitoring may be performed less often depending on the equipment available. Alternatively, daily monitoring of temperature and moisture, or any other parameter, may be carried out.
As illustrated in
As mentioned, and as seen in the flowchart of
The continuance of composting is noted by a temperature increase. As seen in the flowchart (
The process is also graphically illustrated in
Two windrows were formed at each feedlot. Each windrow was a minimum of 300 feet long, 8 feet wide, and 3 feet high. Windrow #1 was comprised solely of manure, and Windrow #2 was comprised of manure and straw mixed together. The lack of sufficient moisture in some of the windrows required that moisture be added to create a suitable environment for composting. Feedlot A used both fresh water and run-off holding pond effluent, but primarily effluent, to increase the moisture content. Feedlot B used only fresh water. Feedlot C used only effluent until pathogen kill was achieved and then used only fresh water.
All windrows were monitored for temperature and oxygen content every other day. Moisture content was determined weekly. Temperatures were measured using a 48 inch stem, ReoTemp thermometer. The oxygen content was measured using a Bacharach Oxor II O2Single Gas Analyzer, with a modified probe. The moisture content was determined by taking three discrete core samples from approximately equidistant locations in each windrow. One hundred grams of each sample was then dried in a microwave. The moisture content from each sample was determined by dividing the dry weight by the wet weight. The three samples from each windrow were then averaged, and that average was used to represent the moisture content of the windrow. Weather information including maximum temperature, minimum temperature, and precipitation were recorded daily at each feedlot. Where available, other weather information was also gathered. Variations in the presence of odor and pests were recorded. All staff time and equipment usage time was recorded, as well as any material costs.
The compost was analyzed for macronutrient content, secondary and micronutrient content, electrical conductivity, pH, percent moisture, percent organic matter, percent ash, bulk density, and carbon-to-nitrogen ratio. These analyses were completed three times throughout the process. The first analysis was performed immediately after the windrow was built, the second analysis was performed approximately three months after the windrow was built and the third analysis was completed after the windrow had cured for at least 30 days. The finished compost was also analyzed for the presence of viable weed seeds, CO2 respiration, volatile NH3, phytotoxicity, seedling growth response, and fecal coliform bacteria.
The windrows were turned frequently during the composting process, based on the core temperature of the compost. If the temperature decreased significantly from previous levels, the windrows were turned. This decrease in temperature is an indication that windrow conditions have become less favorable for microbial activity. Turning is an attempt to improve the microbial environment by redistributing the different particle sizes to increase passive air infiltration, and by redistributing the moisture. If the temperature increased or stayed somewhat constant, no action was taken. Occasionally, the windrows were turned more than once during a day, in an effort to add or distribute water, or increase the uniformity of the mix. Each feedlot used different equipment to build and turn the windrows. Feedlot A used a manure spreading truck to build both windrows. The manure spreading truck was also used to break up the straw bales, and mix the straw and manure for Windrow #2. A front-end loader was used to turn both windrows throughout the composting process. Feedlot B used dump-bed manure hauling trucks to build Windrow #1 and haul the manure for Windrow #2. A PTO-driven bale grinder was used to grind up the straw bales and apply the straw to the manure for Windrow #2. A Brown Bear 400 was used to mix the manure and straw together for Windrow #2, and turn both windrows throughout the composting process. Feedlot C used dump-bed semi-trucks to build Windrow #1 and haul the manure for Windrow #2. Front-end loaders were used to place the straw bales in Windrow #2. A front-end loader with a Wildcat turner mounted on the front was used to break up the straw bales and mix the straw and manure together. It was also used to turn both windrows throughout the composting process.
The equipment used to add water and/or storage pond effluent to the windrows varied also. Feedlot A used a 3,000-gallon water truck with a hose to spray water/effluent on the windrows while they were being built, and to pour effluent over the top of the windrows after they were built. Feedlot B used a 4,000-gallon water truck with a side discharge to spray water on the windrows while they were being built and after they were built. Feedlot C used a 2,500-gallon tank that was pulled behind the loader and mixer, and was connected to the mixer. This setup allowed water/effluent to be added while mixing. A 5,000-gallon water truck was also utilized to bring water/effluent to the pull-behind tank.
Referring to the particular windrow that generated the temperature conditions illustrated in
The monitoring process continues with sustained downturns in temperature triggering a need to turn or add moisture and turned (mix) the windrow. Finally, as can be seen from the results of the moisture addition and turning at time period 110 and the turning performed between time intervals 120 and 130, the compost has nearly completed active composting. The compost is then cured by waiting and turning. This curing has the benefit of drying the compost for a lighter weight soil enhancement product. Samples are taken for analyses and the product is removed, packaged, and shipped.
Composting manure, according to the process of the present invention, keeps the microbial environment favorable for efficient composting. The favorable conditions result from turning and mixing the windrow only when the temperature indicates that it is necessary and not simply based on a calendar schedule. Also, by not turning the windrow any more than necessary, the labor and equipment costs are kept low. The system does require additional monitoring of temperature and possibly moisture and oxygen relative to prior-art methods. However, these steps are relatively quick and easy and do not require expensive equipment and fuel. Thus, the savings of equipment and fuel in the reduced turning schedule should more than offset the additional monitoring necessary. The composting carried out according to the method described above creates a more physically uniform product, which should allow it to be applied more evenly and make it easier to handle. The odor, fecal coliform bacteria, and viable weed seeds are drastically reduced. Wet manure is dried during the process, resulting in a lower bulk density. This makes it much cheaper to transport, and can result in less field compaction as a spreading truck full of wet manure will weigh considerably more than a spreading truck full of dry compost. The product is more user friendly and more advantageous to crop producers. Another important characteristic of the compost is its soil enhancing capabilities. The organic matter contained in the compost will improve soil structure, enhance microbial activity, improve available water-holding capacity, and provide many other soil benefits, especially for abused, weathered, or other poor quality soils. This is particularly significant near urban areas where odor can dissuade people from using manure to build the soil quality.
Economic benefits can likely be gained from the increased concentration of phosphorous in the compost created according to the present invention as compared to the original manure. The higher phosphorous concentration allows compost users to apply less product, but receive the same amount of phosphorous fertilization. In essence, less compost needs to be transported and applied, and thus handling and transportation costs may decrease. The small amount of phosphorous that is lost from the windrow during the composting process may be captured in the effluent run-off storage pond and can be recycled as water for increasing the moisture of the compost piles or for direct crop use.
Composting, according to the process of the present invention, allows feedlot a workable option for operations wishing to decrease the volume and weight of manure that must be removed from the facility. The process also allows for the elimination of carbon amendments such as straw to the cattle manure. Although the addition of straw may slightly increase the speed of the composting process and can help decrease nitrogen losses, it is not necessary to the process. The addition of straw increases the overall moisture loss and the speed of the moisture loss, necessitating more moisture additions. It also bulks up the material, thus requiring more space to compost the manure.
While the preferred embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.
