Characterization of pig slurry with reference to flocculation and separation

Pig production is concentrated in large farms, increasing the need to export excess nutrients, so manure separation would be useful to concentrate the nutrients. We examined the physicochemical properties of pig manure pertinent to flocculation and separation. Manures from three farms were stored for 3 months at 13 °C. The organic pools in the manure did not vary significantly during storage, so microbial metabolism was low and storage was of minor importance to separation. The manure contained highly charged particles and surface charges did not vary between the manures. This implies that the polymer doses required for flocculation can be determined directly from the manure dry matter content and that highly charged, high-molecular-weight cationic polymers can be used. Phosphorus was mainly found in the particulate fraction as struvite and was retained in the solids fraction at high pH. Thus, pH adjustment can control the amount of dissolved phosphorus in manure.     

Phosphorus leaching through intact soil cores as influenced by type and duration of manure application

Leaching of phosphorus (P) in manure-amended soils has received increased attention as a significant source of non-point source P pollution. Intact soil cores were collected from fields on a farm in Southern New York to test the effects of long-term dairy or poultry manure application on P leaching. Nine fields were selected (four poultry, four dairy, and one unamended) to represent a broad range of P saturation levels (5.3 to 62.4%) in the topsoil (0–7.5 cm). Water was applied weekly at a rate matching a 1-year return period storm for the study area (230 mm h⁻¹). Dissolved reactive P (DRP) losses in leachate from all soil cores ranged from 0.007 to 0.055 kg P ha⁻¹, except in two fields with long-term histories of dairy and poultry manure application, where losses averaged 0.21 and 0.45 kg P ha⁻¹, respectively. Hydrographs of the field with the dairy manure history suggested preferential flow as an explanation of leachate P enrichment. In the poultry manure amended field, high levels of soil P saturation throughout the profile suggested subsoil P desorption as a factor controlling leachate P. Surface application of dairy manure to the soil cores (167 kg total P ha⁻¹) increased the mean leachate DRP concentration from 1.5 to 10.5 fold. After five leaching events spanning 22 days, DRP concentrations remained 2.0 to 13.4 fold above pre-manure application levels. This study points to saturation of P in subsoils by long-term manure application as a key concern to P loss in leachate and highlights the role of annual manure additions on subsurface P loss potential.     

The economics of reburning with cattle manure-based biomass in existing coal-fired power plants for NOx and CO2 emissions control

Coal plants that reburn with catttle biomass (CB) can reduce CO₂ emissions and save on coal purchasing costs while reducing NO_x emissions by 60–90% beyond levels achieved by primary NO_x controllers. Reductions from reburning coal with CB are comparable to those obtained by other secondary NO_x technologies such as selective catalytic reduction (SCR). The objective of this study is to model potential emission and economic savings from reburning coal with CB and compare those savings against competing technologies. A spreadsheet computer program was developed to model capital, operation, and maintenance costs for CB reburning, SCR, and selective non-catalytic reduction (SNCR). A base case run of the economics model, showed that a CB reburn system retrofitted on an existing 500 MW_e coal plant would have a net present worth of −$80.8 million. Comparatively, an SCR system under the same base case input parameters would have a net present worth of +$3.87 million. The greatest increase in overall cost for CB reburning was found to come from biomass drying and processing operations. The profitability of a CB reburning system retrofit on an existing coal-fired plant improved with higher coal prices and higher valued NO_x emission credits. Future CO₂ taxes of $25 tonne⁻¹ could make CB reburning as economically feasible as SCR. Biomass transport distances and the unavailability of suitable, low-ash CB may require future research to concentrate on smaller capacity coal-fired units between 50 and 300 MW_e.     

THERMAL DEWATERING OF DILUTED ORGANIC SUSPENSIONS: PROCESS MECHANISM AND DRYING KINETICS

Drying of raw hog manure, a highly diluted suspension of organic and inorganic matter was studied experimentally in the multistage screw-in-trough dryer. Laboratory tests included material characteristics (rheological properties, thermodynamic equilibrium, critical settling point), boiling pattern, and kinetics of convective drying at temperatures from 90 to 120°C and air velocity from 0.5 to 1.5 m/s. Three phases of manure drying were identified, namely boiling and release of volatile compounds, evaporation from viscous liquid, followed by drying of a soft paste, and finish drying of semi-dry granular product. Drying kinetics were quantified in terms of reduced moisture content and a generalized drying curve using the characteristic drying time concept. Field tests were carried out in the pilot multistage screw-in-trough dryer to validate design calculations.     

Association of manganese effluent with the application of fertilizer and manure on tea field

Manganese (Mn) concentrations in the tea field effluent were 1.1-3.5 mg/l over a 2 year period from June 1997 to May 1998 (first water year) and June 1998 to May 1999 (second water year). The annual Mn loads were 38,000 g/ha in the first water year and 19,000 g/ha in the second. The highest Mn loads were observed, respectively, in July 1997 (10,000 g/ha) in the first water year and in June 1998 (4100 g/ha) in the second. The water-soluble Mn content of soil of the tea field increased abruptly with decreasing soil pH in the pH region below 4.5. The large Mn load from the tea field during the rainy season is likely due to application of excess fertilizer and manure before the rainy season, which may lead to acidification of the soil.     

Semi-continuous co-digestion of solid slaughterhouse waste, manure, and fruit and vegetable waste

The potential of semi-continuous mesophilic anaerobic digestion (AD) for the treatment of solid slaughterhouse waste, fruit-vegetable wastes, and manure in a co-digestion process has been experimentally evaluated. A study was made at laboratory scale using four 2 L reactors working semi-continuously at 35 °C. The effect of the organic loading rate (OLR) was initially examined (using equal proportion of the three components on a volatile solids, VS, basis). Anaerobic co-digestion with OLRs in the range 0.3–1.3 kg VS m⁻³ d⁻¹ resulted in methane yields of 0.3 m³ kg⁻¹ VS added, with a methane content in the biogas of 54–56%. However, at a further increased loading, the biogas production decreased and there was a reduction in the methane yield indicating organic overload or insufficient buffering capacity in the digester.In the second part of the investigation, co-digestion was studied in a mixture experiment using 10 different feed compositions. The digestion of mixed substrates was in all cases better than that of the pure substrates, with the exception of the mixture of equal amounts of (VS/VS) solid cattle–swine slaughterhouse waste (SCSSW) with fruit and vegetable waste (FVW). For all other mixtures, the steady-state biogas production for the mixture was in the range 1.1–1.6 L d⁻¹, with a methane content of 50–57% after 60 days of operation. The methane yields were in the range 0.27–0.35 m³ kg⁻¹ VS added and VS reductions of more than 50% and up to 67% were obtained.     

Overview analysis of bioenergy from livestock manure management in Taiwan

The emissions of greenhouse gases (GHGs) from the livestock manure are becoming significant energy and environmental issues in Taiwan. However, the waste management (i.e., anaerobic digestion) can produce the biogas associated with its composition mostly consisting of methane (CH₄), which is now considered as a renewable energy with emphasis on electricity generation and other energy uses. The objective of this paper was to present an overview analysis of biogas-to-bioenergy in Taiwan, which included five elements: current status of biogas sources and their energy utilizations, potential of biogas (methane) generation from livestock manure management, governmental regulations and policies for promoting biogas, benefits of GHGs (i.e., methane) emission reduction, and research and development status of utilizing livestock manure for biofuel production. In the study, using the livestock population data surveyed by the Council of Agriculture (Taiwan) and the emission factors recommended by the Intergovernmental Panel on Climate Change (IPCC), the potential of methane generation from livestock manure management in Taiwan during the period of 1995–2007 has been estimated to range from 36 to 56 Gg year⁻¹, indicating that the biogas (methane) from swine and dairy cattle is abundant. Based on the characteristics of swine manure, the maximum potential of methane generation could reach to around 400 Gg year⁻¹. With a practical basis of the total swine population (around 4300 thousand heads) from the farm scale of over 1000 heads, a preliminary analysis showed the following benefits: methane reduction of 21.5 Gg year⁻¹, electricity generation of 7.2 × 10⁷ kW-h year⁻¹, equivalent electricity charge saving of 7.2 × 10⁶ US$ year⁻¹, and equivalent carbon dioxide mitigation of 500 Gg year⁻¹.     

Investigation of the tetracycline, sulfonamide, and fluoroquinolone antimicrobial compounds in animal manure and agricultural soils in Turkey

Occurrence of antimicrobial residuals in the environment is of concern because of the emergence and development of antimicrobial-resistance in pathogen bacteria, and the ecotoxicological behaviour of these compounds. Investigation of antimicrobial pollution in animal manure has special importance since they constitute the major source for the dissemination of these chemicals into the environment. Hence, eight animal manure and nine agricultural soil samples from the North part of Marmara Region (Turkey) were collected and analyzed for two tetracyclines (TCs), four sulfonamides (SAs), and two fluoroquinolones (FQs). At least one antimicrobial compound was detected in all the agricultural soil and animal manure samples. The highest antimicrobial concentrations were in general detected in the fresh poultry manure samples. Mean recoveries from spiked soil and manure samples ranged from 60 to 86% and 62 to 77% for TCs, 69 to 101% and 14 to 82% for SAs, and 46 to 55% and 24 to 42% for FQs, respectively. Relationship between the recovery rates of the antimicrobial compounds and sample characteristics was statistically evaluated by means of hierarchical cluster analysis (HCA), and principal component analysis (PCA) followed by multiple stepwise regression (MSR). HCA showed agricultural soil samples with higher di- and trivalent metal contents resulted in higher TC and lower FQ recoveries. TC recoveries from manure were highest in the samples with lowest K, Mg, and Ca content, while FQs were more efficiently extracted from the manure samples with less % organic carbon (OC) content. The findings of HCA for TCs were supported by those of MSR analysis, giving comparable results. In addition, MSR of SA recoveries revealed that the increasing amounts of manure % OC led to lower recoveries.     

Influence of organic amendments on growth, yield and quality of wheat and on soil properties during transition to organic production

A transition period of at least 2 years is required for annual crops before the produce may be certified as organically grown. The purpose of this study was to evaluate the effects of three organic amendments on the yield and quality of wheat (Triticum aestivum L.) and on soil properties during transition to organic production. The organic amendments were composted farmyard manure (FYMC), vermicompost and lantana (Lantana spp. L.) compost applied to soil at four application rates (60 kg N ha⁻¹, 90 kg N ha⁻¹, 120 kg N ha⁻¹ and 150 kg N ha⁻¹). The grain yield of wheat in all the treatments involving organic amendments was markedly lower (36–65% and 23–54% less in the first and second year of transition, respectively) than with the mineral fertilizer treatment. For the organic treatments applied at equivalent N rates, grain yield was higher for FYMC treatment, closely followed by vermicompost. In the first year of transition, protein content of wheat grain was higher (85.9 g kg⁻¹) for mineral fertilizer treatment, whereas, in the second year, there were no significant differences among the mineral fertilizer treatment and the highest application rate (150 kg N ha⁻¹) of three organic amendments. The grain P and K contents were, however, significantly higher for the treatments involving organic amendments than their mineral fertilizer counterpart in both years. Application of organic amendments, irrespective of source and rate, greatly lowered bulk density (1.14–1.25 Mg m⁻³) and enhanced pH (6.0–6.5) and oxidizable organic carbon (13–18.8 g kg⁻¹) of soil compared with mineral fertilizer treatment after a 2-year transition period. Mineral fertilized plots, however, had higher levels of available N and P than plots with organic amendments. All the treatments involving organic amendments, particularly at higher application rates, enhanced soil microbial activities of dehydrogenase, β-glucosidase, urease and phosphatase compared with the mineral fertilizer and unamended check treatments. We conclude that the application rate of 120 kg N ha⁻¹ and 150 kg N ha⁻¹ of all the three sources of organic amendments improved soil properties. There was, however, a 23–65% reduction in wheat yield during the 2 years of transition to organic production.