Separated Liquid Manure Research Articles

Surface Covers Affect Liquid Manure Temperature, Albedo, and Evaporation

HighlightsEvaporation from clear water, manure, and separated liquid manure was 4.6 mm d-1 on average.Straw, foam, geotextile, and roof covers decreased evaporation by 54%, 53%, 31%, and 21%, respectively.Albedo was highest for floating foam covers and lowest for metal roof covers.Straw, foam, and geotextile increased manure temperature compared to uncovered manure. ABSTRACT. Evaporation is a key component of the surface energy budget of liquid manure. Models rely on accurate energy budgets to predict manure temperature, which in turn is used to model temperature-dependent greenhouse gas emissions from liquid manure storages. Due to lack of data, it has been assumed that liquid manure has similar evaporative properties to water; however, this assumption may be inaccurate. Many factors, including manure crusting, covers, and turbidity, are all likely to affect the surface energy budget and the evaporation rate. This experiment investigated the differences in evaporation between eight treatments, including water, dyed water, raw and separated liquid manure, and four commonly used covers (straw, geotextile, foam, and roof), by measuring weekly evaporation. Albedo, surface temperatures, and internal temperatures were also measured to determine treatment effects. Over the 10-week study, no significant difference was found between the evaporation rates of water, raw manure, and separated liquid manure, with an average rate of 4.6 mm d-1. Notably, the raw manure did not form a consistent surface crust, which may explain the similarities in evaporation rates in this study and is unlikely to represent manure with a crust. Overall, covers significantly decreased evaporative losses by between 21% and 54% compared to uncovered raw manure. Average evaporation rates of the covered treatments were 1.9 mm d-1 for straw cover, 2.0 mm d-1 for foam cover, 2.9 mm d-1 for geotextile cover, and 3.4 mm d-1 under a roof cover. Similarities between each treatment and water as well as between the four covered treatments and the uncovered raw manure were found using linear regression on weekly evaporation. Generally, the uncovered treatments were more similar and could be predicted (high R2) by multiple linear regression with environmental variables, while the covered treatments differed more and were not as well predicted (lower R2). Results from this study can help adjust evaporation rates in biophysical models to improve estimates of manure temperature, tank holding capacity, and emission predictions. Keywords: Evaporation, Dairy manure, Liquid manure, Manure covers, Manure management.

Effect of Climatic Conditions on Differences in Thermo-Technical Properties of Organic Bedding in Laboratory Testing

Abstract The aim of this experiment was to analyse the influence of climatic factors on the thermal performance of separated liquid manure. The samples of organic bedding were collected from the lying area of dairy housing and preparatory store. The measurement of properties of recycled manure solids (RMS) was carried out in laboratory conditions. Samples were examined with determining the temperature effect on the thermal conductivity λ of ’dry‘ separated liquid manure (with a dry matter content of 60%) and ’wet‘ liquid manure (with a dry matter content of 26%), in air temperatures ranging from 0 °C to 40 °C. Subsequently, the thermal resistance of three selected types of cows lying structures was calculated for winter and summer boundary values. Based on the results of thermal conductivity and thermal resistance, it was observed that dry separated liquid manure as an alternative bedding has, in low temperature (up to 5 °C), the most suitable thermal performance if it is maintained in a dry condition (with a dry matter content of 60%). With increasing temperature (above 20 °C) and increasing humidity of bedding (below 26%), thermo-technical properties get worse; however, when comparing the thermal resistance of the cow bed structure with sandwich mattresses with a 50 mm layer of organic bedding and the deep cubicle filled with 200 mm of organic bedding, the thermal resistance of floor structure decreases by 7.6% or 18.4%, respectively. With a proper handling of the recycled organic bedding, it is possible to use its economic advantages.

Can Phosphate Salts Recovered from Manure Replace Conventional Phosphate Fertilizer?

Pig farming produces more manure than can reasonably be spread onto surrounding fields, particularly in regions with high livestock densities and limited land availability. Nutrient recycling offers an attractive solution for dealing with manure excesses and is one main objective of the European commission-funded project “BioEcoSIM”. Phosphate salts (“P-Salt”) were recovered from the separated liquid manure fraction. The solid fraction was dried and carbonized to biochar. This study compared the fertilizing performance of P-Salt and conventional phosphate fertilizer and determined whether additional biochar application further increased biomass yields. The fertilizers and biochar were tested in pot experiments with spring barley and faba beans using two nutrient-poor soils. The crops were fertilized with P-Salt at three levels and biochar in two concentrations. Biomass yield was determined after six weeks. Plant and soil samples were analysed for nitrogen, phosphorus and potassium contents. The P-Salt had similar or even better effects than mineral fertilizer on growth in both crops and soils. Slow release of nutrients can prevent leaching, rendering P-Salt a particularly suitable fertilizer for light sandy soils. Biochar can enhance its fertilizing effect, but the underlying mechanisms need further investigation. These novel products are concluded to be promising candidates for efficient fertilization strategies.

Design and Validation of Field-Scale Anaerobic Digesters Treating Dairy Manure for Small Farms

<abstract> <b><sc>Abstract.</sc></b> Six field-scale (FS) digesters designed using a plug-flow design used by millions of farmers in developing countries and reconfigured for a temperate climate were tested over an 18-week period. Digester efficiency was analyzed based on methane (CH₄) production, volatile solids (VS) reduction, cost-benefit analysis, and energy production efficiency. Results were compared to the literature and a full-scale on-site anaerobic digestion system (BARC) that uses the same manure source. The average CH₄ yield of the replicate FS digesters was 0.31 m³ CH₄ kg^-1 VS added, resulting in 0.34 m³ CH₄ m^-3 digester^-1 d^-1, with 67.2% CH₄ and 4310 ppm H₂S in the biogas. The digesters reduced VS in the solid-separated dairy manure by 43.3%. Weekly CH₄ production values between the six replicate digesters varied <18%. The results were comparable to the on-site BARC digestion system (0.31 m³ CH₄ kg^-1 VS). Both systems used separated liquid manure and operated in the lower mesophilic range (25°C to 30°C), yet functioned at the higher range of literature values. The total energy produced by the FS digesters was three times the energy needed to counteract heat loss from the digesters, but the heating kettle system was inefficient. The material cost of the system ($16,800) was much higher than in developing countries ($150 to $400) but lower than traditional U.S. digestion systems, illustrating the impact of the heating and insulation infrastructure on sustainability at the small-scale. The FS design presents an alternative for smaller-scale farmers in temperate climates without anaerobic digestion systems. However, while the design and insulation appeared to be sufficient, the heating efficiency should be improved and/or use of waste heat from an engine generator set should be explored.

SOLIDS SEPARATION ENHANCES REDUCTION OF ORGANIC STRENGTH OF SWINE MANURE SUBJECTED TO AERATION TREATMENTS

To reduce overloading lagoons used for treating/holding animal manures, some form of pretreatment to reduceorganic strength of the manure is necessary. Aerobic treatment is one such pretreatment, but the associated aeration costsmost often limit use of this process. Reducing these associated aeration costs, therefore, would make this fast pretreatmentmethod more feasible. In this study, a combination of solids/liquid separation and low-level aeration treatment processes wereexamined for stabilization of the swine slurry and on their effect on pertinent manure nutrients. Results indicate thatsolids/liquid separation and low-level aerobic treatments of swine manure enhance bio-stabilization of the separated liquidmanure. In this study, 0.164 day-1 and 0.061 day-1 bio-stabilization rates were observed in the separated liquid manure andin the control (unseparated) manure, respectively. By day nine, 40% and 76% reductions in COD were achieved in the controland the treatment, respectively, i.e., the strength of the influent into the anaerobic lagoons can be reduced by as much as 76%using this combined treatment approach within nine days. The faster bio-stabilization in the separated manure liquid isbelieved to be a result of improved aeration efficiency and better contact between the microbial biomass and the dissolvedsubstrate. Although aeration treatment did not result in considerable change in both TKN and TAN, effluent liquid after anovernight sedimentation process from the unprocessed manure (control) was found to retain approximately 90% of TKN, 34%of TP, and 73% of TS, while effluents from the treatment after the same overnight sedimentation retained approximately 67%of TKN, 30% of TP, and 54% of TS. The treatment, therefore, not only resulted in higher reduction of organic strength but alsoin substantial reductions of TKN, TP, and TS than the control in the liquid effluent after an overnight sedimentation process.

Solids Separation Coupled with Batch‐Aeration Treatment for Odor Control from Liquid Swine Manure

Previous studies on solids/liquid (S‐L) separation for odor control from swine manure indicated that the practice might not technically be feasible because of the complexity of removing the fine particles, which are usually the major source of the odor problems. This study coupled S‐L separation by sedimentation with an aeration treatment to quickly break down the fine as well as dissolved solids. Results showed that S‐L separation of manure prior to aeration, at the same level of aeration, took only 1.5 days compared to 3 days needed for the control, to bring down volatile fatty acids (VFAs) to the “threshold of unacceptable level”. In addition, it took 2.3 and 5 aeration‐days for VFAs to reach the “acceptable level” for the separated liquid manure and the control, respectively. Results also showed that within the three weeks of post‐aeration storage, the VFAs in the separated liquid manure consistently stayed 13.5 folds below the acceptable level. In the unseparated manure, the VFAs gradually increased upwards from 2.2 folds below acceptable level achieved at the end of aeration treatment, to 1.38 folds below the acceptable level at the end of the third week of storage and looked poised to definitely rise above the acceptable level in a matter of days. A strong relationship (R = 0.99) between pH and the VFAs in the manure suggested that; degradation of VFAs rendered manure more basic as shown by the increase in pH. After only three days of aeration, the oxidation reduction potential (ORP) in the separated liquid manure stabilized at a much higher level of − 15 mV, while the ORP in unseparated manure stabilized at a much lower level of − 200 mV. The S‐L separation treatment thus significantly improves the oxygen transfer efficiency, which in turn significantly reduces the aeration power needed to maintain adequate ORP if prolonged aeration is desired.

ENHANCED PHOSPHORUS REMOVAL FROM SWINE–NURSERY MANURE IN AERATED BATCH REACTORS

Phosphorusbased land application of swine manure slurry results in underapplication of nitrogen (N), whilenitrogenbased application leads to overapplication of phosphorus (P). Significant amounts of P must be removed fromswine manure to reduce P overapplication, and at the same time, safely apply targeted amounts of N. This study comparedthree schemes of soluble orthophosphate (orthoP) reduction from liquid swine nursery manure during batch aeration:(1) solidsliquid separation before aeration (preaeration solidsliquid, or PASL, separation), (2) solidsliquid separationin the middle of aeration (midaeration solidsliquid, or MASL, separation) and (3) no solidsliquid separation (control).Significantly more orthoP was converted to nonsoluble species with MASL separation (92%) than with either PASLseparation (87%) or the control (84%). MASL separation also significantly improved the removal of total phosphorus (TP)in the sludge from the liquid after an overnight sedimentation process: 80%, 70%, and 66% for MASL separation, PASLseparation, and control, respectively. Solidsliquid separation enhanced the maintenance of higher oxidation potentials(depicted by higher values of ORP in the separated manures than in the control) in the manure during the latter days ofaeration, implying that substantial energy saving is possible for prolonged aeration of separated liquid manure. This is animportant element in the postaeration treatment for ensuring that P removed from the solution stays in the sludge and is notreleased back into solution, if removal of the sludge does not immediately follow scheduled aeration treatment.