Patent Application
20070272609
The invention is best understood from the following detailed description when read in connection with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following figures:
The materials that combine to form the stabilizing manure additive according to the present invention are chosen on the bases, among others, of their binding properties, availability, and economy. These materials do not alter any of the major useful characteristics of the manure. Each material is used to address one or more of the specific problems and drawbacks inherent in conventional manure additives.
In a first embodiment, the present invention is directed to a composition that can be added to bio-solids (including without limitation, livestock manure), mushroom compost, and other waste materials to give the waste materials useful characteristics. An important parameter of the composition is the proportion of ingredients included in the composition. Preferably, the composition includes: (1) gypsum obtained either as commercial product or as waste wallboard; (2) lime (CaO); (3) silica or fly ash; (4) optionally water; (5) optionally iron slag; and (6) optionally portland cement. Still more preferably, the composition includes gypsum in a weight ratio of about 15-40%, lime in a weight ratio of about 9-40%, silica or fly ash in a weight ratio of about 15-40%, optionally water in a weight ratio of about 0-40%, optionally iron slag in a weight ratio of about 20-25%, and optionally portland cement in a weight ratio of about 30-50%. When portland cement is included in the additive for manure applications, the manure is no longer suitable as fertilizer because it becomes a hard, rock-like product; the rock-like characteristic of the product is useful, however, for disposal purposes or for use in the construction industry.
Gypsum is hydrated calcium sulfate or CaSO4-2(H2O). Gypsum is one of the more common minerals in sedimentary environments. It is a major rock-forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Because it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water. Gypsum has a very low thermal conductivity, prompting its use in drywall or wall board as an insulating filler.
Wall board gypsum is commonly used to cover the interior walls of homes, offices, and other structures. It is composed of gypsum and a paper backing that makes up approximately 2-4% of the total wallboard weight. Other uses for gypsum include plaster, some cements, paint filler, and ornamental stone. Gypsum is also used in agriculture as a fertilizer and as a soil amendment. Gypsum is not a liming material and will not increase soil pH.
Limestone is rock that is composed of calcium carbonate (CaCO3), magnesium carbonate (MgCO3), and small amounts of other minerals. Lime is made by heating limestone (calcium carbonate) to high temperatures. This process, known as calcining, results in quicklime, or calcium oxide. As used in the context of the present invention, the term “lime” refers to calcium oxide (CaO).
Industrial sand and gravel, often called “silica,” “silica sand,” and “quartz sand,” includes sands and gravels with high silicon dioxide (SiO2) content. These sands are used in glassmaking; for foundry, abrasive, and hydraulic fracturing applications; and for many other industrial uses. The specifications for each use vary, but silica resources for most uses are abundant. In almost all cases, silica mining uses open pit or dredging mining methods with standard mining equipment. Except for temporarily disturbing the immediate area while mining operations are active, sand and gravel mining usually has limited environmental impact.
Fly ash is a fine, glass-like powder recovered from gases created by coal-fired electric power generation. Thus, fly ash is a coal combustion product and is considered a difficult solid waste. U.S. power plants produce millions of tons of fly ash annually, which is usually dumped in landfills. The compositions of fly ash are highly variable, and commonly consist of oxides of Si, Al, Fe, and Ca, and of the elements Na, P, K, and S. Fly ash is an inexpensive replacement for portland cement used in concrete, while it actually improves strength, segregation, and ease of pumping of the concrete. Fly ash is also used as an ingredient in brick, block, paving, and structural fills. Weathered fly ash, after equilibrating with atmospheric CO2, is called lagoon ash, which has an alkaline pH and provides a good fixing agent to suppress the availability of heavy metals in manure compost.
Iron is typically manufactured by putting iron sand and charcoal together in a furnace, heating it, and reducing the iron sand. At this point, the impurities contained in the iron sand are melted at high temperature and drained out as slag. In iron manufacturing, about half of the iron sand will be reduced and turned into iron through smelting. The remainder will react at a high temperature (1,200° C. or higher) with the clay in the furnace walls to create a fused silicate mass and melt out into iron slag. Chemical analysis of the iron slag reveals it to be composed of SiO2 (silicate), Al2O3 (alumina), FeO, Fe2O3 (oxided iron), and TiO2 (titanium dioxide).
ASTM C 150 defines portland cement as “hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) produced by pulverizing clinkers consisting essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulfate as an inter ground addition.” Clinkers are nodules (diameters of 0.2-1.0 inch or 5-25 mm) of a sintered material that is produced when a raw mixture of predetermined composition is heated to high temperature. The phase compositions in portland cement are denoted by ASTM as tricalcium silicate (Ca3S), dicalcium silicate (Ca2S), tricalcium aluminate (Ca3Al), and tetracalcium aluminoferrite (Ca4AlF). The low cost and widespread availability of the limestone, shales, and other naturally occurring materials make portland cement one of the lowest-cost materials widely used over the last century throughout the world.
The useful characteristics of the manure achieved via addition of the composition according to the present invention are many. First, the manure is stabilized (i.e., the odor emanating from the treated manure is minimized or eliminated). The manure odor decreases to such a significant extent that the treated manure approaches an odorless material. Second, the additive changes the texture of the manure composition so that it can be formed into pellets or coarse powder, which facilitates bagging, storage, transportation, sale, and application. The pellets can be crushed.
The combination of gypsum, silica or fly ash, and lime in certain proportions, perhaps in combination with certain other optional ingredients according to the present invention, has not been previously used for manure stabilization. Known materials that are used as manure additives fail to stabilize the manure; are relatively expensive; do not prevent nutrient leaching into surface water; and do not reduce the burden on land fills. The method and composition of the present invention achieve all of these advantages left unfulfilled by conventional manure additives.
More specifically, the method and composition of the present invention offer several advantages. At least two of the materials used to form the manure additive are discarded materials, inexpensive, and readily available. Fly ash is a discarded material. Gypsum can be obtained from waste wallboard otherwise discarded. Thus, reuse or recycling of discarded materials is achieved—an environmentally favorable result. Two source materials each having negative characteristics, untreated manure and discarded materials, are combined to produce an excellent fertilizer.
Manure has nutrients such as phosphorous and nitrogen. Government regulations define how much manure can be applied as fertilizer per specified area because phosphorous and nitrogen leach out of the manure and can contaminate water reservoirs. In addition, phosphorous and nitrogen foster algae growth and can cause pollution, which is a major problem, for example, in Chesapeake Bay watersheds. The phosphorous in the manure does not leach, once the manure is treated with the additive of the present invention, from the manure into surface water resources when the manure is stored outside or spread on agricultural fields. As discussed in more detail below, the method and composition of the present invention reduce phosphorous leaching by about 87%. Similar results are expected for the nitrogen in the manure.
Another embodiment of the present invention is the development of an analytical method for odor detection. Several components of odors are relevant to research: (1) odor quality, measured by comparing the odor with a known odor; (2) odor strength, measured by the amount of fresh air needed to dilute the odorous air to the threshold odor level; and (3) odor occurrence, measured by the frequency and total length of time the odor persists. There are two general approaches to measuring odor: (1) measure the concentration of specific gases in an air sample, and (2) use the human nose to perceive odor. The embodiments of the present invention illustrated in
The main odor-causing compounds in manure are ammonia and hydrogen sulfide, which are generated by the decomposition of manure. The wastes are in an anaerobic state when excreted and remain anaerobic unless oxygen is introduced into the system. There are two forms of ammonia solution: NH3, which is a non-ionized gas, and NH4, which is the ionized form. The relative proportion of each depends upon the pH. Manure normally has a pH of 6.5 to 7.0. Reducing pH in manure with an acid (hydrochloric, sulfuric, phosphoric or nitric) to about 5 increases nitrogen fixation thus reducing ammonia emissions. Unfortunately, addition of some of these acids increases the nitrogen or phosphorous content of the manure, and can increase the release of hydrogen sulfide. At a pH of 4 to 5, amino acid decarboxylation occurs, leading to the release of odorous amines and sulfur compounds.
Virtually all of the ammonia in animal waste has the potential to be lost as NH3 gas. In addition to being an odor problem, ammonia gas release is increasingly being considered an environmental problem, because it tends to be oxidized by various oxidants in the air to produce nitrous oxides, which are considered major contributors to acid rain.
Hydrogen sulfide (H2S), which is produced by anaerobic microorganisms that convert sulfate in manures to sulfide, is considered the characteristic odor of livestock urine. It is a highly toxic and malodorous gas that can reach levels that are threatening to livestock and humans. Exposure to a few minutes of hydrogen sulfide concentrations of 2000 ppm has proven fatal to humans. In addition, animals exposed to sub-lethal doses may become more susceptible to pneumonia and respiratory diseases.
At relatively high pH levels, hydrogen sulfide release is minimized, but the release of ammonia and organic acids is enhanced. At a pH of 9.5, almost no hydrogen sulfide will escape the manure. A pH of about 12 allows solids to settle and reduces the moisture content and odor production. The generation of most odor components also is increased at higher temperatures.
The most critical point in controlling odor emissions is regulating the volatilization rate of the ammonia and hydrogen sulfide. Among the factors that influence the volatilization rate are source concentration, surface area, net radiation, air temperature, wind velocity, and relative humidity. The present invention seeks to control the microbial formation of the volatile organic compounds, the best way to successfully control the volatilization rate. The manure additive of the present invention slows down or stops the microbial fermentation of the organic matter in waste before the hydrolytic and acetogenic bacteria become active. Thus, the additive prevents the formation of volatile organic compounds, which represent odor. The use of the additive inhibits the fermentation and, in turn, reduces the odor produced. In addition, nutrients are retained in the manure (although it is desirable to remove H2S from the manure, the nutrients present in ammonia desirably remain in the manure) and the production of greenhouse gases is inhibited. The additive is environmentally safe, relatively inexpensive, and easy to apply.
In order to evaluate the amount of odor reduction achieved by the additive composition of the invention, a method for measuring the presence of these odor-causing compounds in the manure was achieved. This method can be computerized. The odor is measured by determining the concentrations of the odorous compounds (i.e., ammonia and hydrogen sulfide) present in the manure and the results are compared for the fresh and stabilized (with the additive) manure.
The concentrations of the ammonia and hydrogen sulfide gases, in both fresh manure and in manure stabilized using the additive according to the present invention, were measured using the apparatus of
The following examples are included to more clearly demonstrate the overall nature of the invention. These examples are exemplary, not restrictive, of the invention. As the sample numbers indicate, a large number of samples were prepared. A brief summary of some of the stabilized samples, omitting those samples for which test results were not as good, is as follows:
Sample No. 1: Portland cement and manure were mixed in a 1:1 ratio and left for a day. The resultant mixture had some cement which had no water to blend with the manure. The mixture had a moderate strength and could be crushed by hand with significant force.
Sample No. 6: Manure, portland cement, gypsum, CaO, and water were combined in equal ratios and mixed well. The material was formed into a coarse paste. After a day of setting time, a powdery substance with no lumps was formed.
Sample No. 9: Manure, gypsum, and water were combined in equal ratios and mixed well. The material was formed into a paste and, after a day of setting time, formed into a lump which was very easy to break. When crushed, however, the lump compressed and then broke into granulates.
Sample No. 11: Manure, CaO, and water were combined in equal ratios and mixed well. The material was formed into a paste and, after a day of setting time, formed into a very fragile lump. The lump broke easily into powder and had a yellow color.
Sample No. 16: Manure, CaO, and water were combined in the ratio 2:1:2 and mixed well. The material was formed into a paste and, after a day of setting time, turned into a soft lump. When crushed, the lump broke into a powder and had, comparatively, much less smell.
Sample No. 23: Equal ratios of manure, silica (200 mesh and finer), gypsum, CaO, and water were mixed well. The material was formed into a paste, brown in color. After a day of setting time, the mixture had a smooth texture and could be crushed by hand. The smell was reduced.
Sample No. 24: Equal ratios of manure, silica (40 to 100 mesh), gypsum, CaO, and water were mixed well. The material was formed into a paste, brown in color. After a day of setting time, a smooth-textured mixture resulted. The mixture broke easily.
Sample No. 25: Equal ratios of manure, silica (fine granular), gypsum, CaO, and water were mixed well. The material was formed into a paste, brown in color. After a day of setting time, the result was similar to the mixture of Sample No. 24 but the color was light brown when compared and the smell was less.
Sample No. 29: Manure, CaO, gypsum, fly ash, and water were combined in equal ratios and mixed well. After a day of setting time, the mixture was soft and could be easily crushed by hand.
Sample No. 30: Manure, fly ash, gypsum, CaO, and water were combined in the ratio 2:1:1:1:1. The sample was found to be hard, but crushable. The odor was reduced significantly in two days.
Sample No. 31: Manure, fly ash, gypsum, CaO, and water in the ratio 1:1:1:1:2 were combined and mixed well. This sample was hard and crushable. The odor was reduced significantly in a week.
Sample No. 32: Manure, gypsum, fly ash, CaO, and water in the ratio 3:2:3:1:2 were combined. This sample was soft and could be crushed easily into powder. The odor was reduced significantly in a week.
Sample No. 31 for poultry manure was determined to offer the best combination of desirable characteristics of the samples tested. Thus, the test results provided below were obtained using Sample No. 31.
The tests performed to obtain the data reflected on the graphs of
For comparison purposes,
The tests performed to obtain the data reflected on the graphs of
A common use of livestock manure is as fertilizer on farms. The important nutrients of the manure are phosphorous and nitrogen, among some other micronutrients. These nutrients are easily leached, however, from the fresh manure during storage or after application. The leaching undermines the effectiveness of the manure as fertilizer and causes heavy pollution problems to natural ecosystems. The phosphorous runoff from the agricultural land contributes to eutrophication of surface waters. In the areas with intensive animal farming, phosphorous loss from manure fields may be elevated due to high concentrations of phosphorous in manure.
Since the 1970's, phosphorus removal from wastewater has been recognized as one of the basic processes necessary to be done at all wastewater treatment plants. Continuous development of knowledge concerning phosphorus occurrence, mechanism of its removal, and evolution of process technologies has led to modern technical solutions which allow efficient removal of this wastewater constituent.
In our study, the leaching of phosphorous was controlled by stabilization of the fresh manure by the addition of the composition according to the present invention. The fresh and stabilized manures were mixed with 30 ml of distilled water and shaken for 1 hour to simulate raining or flashing conditions. Then, the amount of phosphorous leached into the water was tested with the standard total phosphorous methods. The results are shown in Table 1.
Second, the Toxicity Characteristic Leaching Procedure (TCLP; Standard Method) was done to conduct the tests for the manure samples. Extraction fluid of 20 times the weight of the percentage of dry solids in the manure was prepared. 100 g of the fresh and stabilized samples were taken along with extraction fluid and were tumbled for 18 hours at room temperature. The extraction fluid was prepared by adding 5.7 ml of glacial acetic acid to 500 ml of reagent water, adding 64.3 ml of 1 N sodium hydroxide solution, and then diluting it to a volume of 1 liter. The pH of the extraction fluid prepared was 4.91.
After 18 hours extraction, the sample in the bottle was filtered through a new glass fiber filter. The filtrate was again tested with the standard total phosphorous methods. The results are shown in Table 2.
Table 1 shows that, after stabilization, the dry solid content was increased. This will be helpful for storage, transport, and use of the manure. Furthermore, the leaching amount of phosphorous was largely reduced after stabilization, as shown in Tables 1 and 2. The data of Table 1 show that 2.14 mg of phosphate (PO4) was leached from 1 g of fresh manure under the simulated conditions. This value decreases to 0.26 mg, by a factor of 8 (or about 88%), after manure stabilization (Table 2). And, 1.57 mg of phosphate (PO4) was leached per gram of fresh manure and 0.25 mg was leached per gram of fresh manure in stabilized manure in the TCLP test reflected in Table 2. This result means that phosphorous leaching in manure is reduced by 85-90% by using the stabilization methods completed in the laboratory.
Although illustrated and described above with reference to certain specific embodiments and examples, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention. It is expressly intended, for example, that all ranges broadly recited in this document include within their scope all narrower ranges which fall within the broader ranges.
