Fresh Dairy Manure Research Articles

Condensed and Hydrolyzable Tannins for Reducing Methane and Nitrous Oxide Emissions in Dairy Manure-A Laboratory Incubation Study.

Simple SummaryThis study investigated the mitigation effect of different tannins on greenhouse gas emissions (GHG) from freshly collected dairy cattle manure. Quebracho and chestnut industrial tannin extracts were tested against a fresh cattle manure slurry. The results showed that all tannins added to freshly collected dairy manure could decrease N2O and CH4 emissions over a 14-d incubation period. The objectives of this study were to (1) examine the effects of plant condensed (CT) and hydrolyzable tannin (HT) extracts on CH4 and N2O emissions; (2) identify the reactions responsible for manure-derived GHG emissions, and (3) examine accompanying microbial community changes in fresh dairy manure. Five treatments were applied in triplicate to the freshly collected dairy manure, including 4% CT, 8% CT, 4% HT, 8% HT (V/V), and control (no tannin addition). Fresh dairy manure was placed into 710 mL glass incubation chambers. In vitro composted dairy manure samples were collected at 0, 24, 48, and 336 h after the start of incubation. Fluxes of N2O and CH4 were measured for 5-min/h for 14 d at a constant ambient incubation temperature of 39 °C. The addition of quebracho CT significantly decreased the CH4 flux rates compared to the tannin-free controls (215.9 mg/m2/h), with peaks of 75.6 and 89.6 mg/m2/h for 4 and 8% CT inclusion rates, respectively. Furthermore, CT significantly reduced cumulative CH4 emission by 68.2 and 57.3% at 4 and 8% CT addition, respectively. The HT treatments failed to affect CH4 reduction. However, both CT and HT reduced (p < 0.001) cumulative and flux rates of N2O emissions. The decrease in CH4 flux with CT was associated with a reduction in the abundance of Bacteroidetes and Proteobacteria.

Metagenomics analysis unraveled the influence of sulfate radical-mediated compost nitrogen transformation process.

The mechanism of nitrogen transformation of sulfate radical (SO- 4⋅) in the process of composting is unclear. The objectives of this study were to investigate the influence of SO- 4⋅ on nitrogen biotransformation during composting and to compare the differences in physicochemical parameters and metagenomics analysis between CK (fresh dairy manure and bagasse pith) and PS (the composting raw materials added with potassium persulfate). The results indicated that SO-4⋅ guides electron transfer in the conversion of NH+4-N to NO- 3-N and breaches the extracellular polysaccharide (EPS) structure to promote nitrogen removal. Aminomonooxygenase (AMO) and nitrate reductase (NR) levels displayed an interactive relationship between microorganisms and substrates. Metagenomics analysis revealed distinct microbial community compositions and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways between nitrification and denitrification. Correlation analysis indicated that Methanobrevibacter, Bacillus and Pseudomonas were closely related to these processes. This work demonstrates the effect of SO- 4⋅ on nitrogen cycling and retention, and possible mechanisms of nitrification and denitrification during composting.

Effect of Endogenous Methane Production: A Step Forward in the Validation of Biochemical Methane Potential (BMP) Tests

This work evaluates the influence of the inoculum type, the pre-consumption of the residual substrate and the ratio of blanks’ headspace volume to working volume (Hv Wv−1, 0.6 to 10) on Biochemical Methane Potential (BMP) measurements when methane is monitored by gas chromatography. Different inocula were tested: digested sewage sludge—DSS, granular sludge—GS and fresh dairy manure—DM. Microcrystalline cellulose was used as the substrate. BMP surpassed the maximum theoretical value (BMPmax = 414 L kg−1) when methane produced in the blanks was not discounted, showing that degassing cannot stand alone as an alternative to the procedure of discounting the inoculum’s background production. Still, when the residual substrate concentration is high (e.g., in DM), degassing is mandatory because methane produced from its digestion will conceal the methane produced from the substrate in the BMP determination. For inocula with a low residual substrate (e.g., GS), short degassing periods are recommended in order to avoid detrimental effects on methanogenic activity. For moderate residual substrate concentrations (e.g., DSS), BMP values closer to BMPmax (90–97%) were achieved after degassing and discounting the blanks with lower Hv Wv−1. For higher Hv ∙ Wv−1, less accurate quantification occurred, likely due to error propagation. Proper inoculum pre-incubation time and discounting the methane production from blanks with low Hv Wv−1 (adjusted according to the estimated background methane) are essential for accurate BMP determinations.

Lignocellulosic depolymerization induced by ionic liquids regulating composting habitats based on metagenomics analysis.

The application of ionic liquids with sawdust and fresh dairy manure was studied in composting. The degradation of organic matter (OM), dissolved organic matter (DOM), and lignocellulose was analyzed. The DOM decreased by 14.25mg/g and 11.11mg/g in experimental group (ILs) and control group (CK), respectively. OM decreased by 7.32% (CK) and 8.91% (ILs), respectively. The degradation rates of hemicellulose, lignin, and cellulose in ILs (56.62%, 42.01%, and 23.97%) were higher than in CK (38.39%, 39.82%, and 16.04%). Microbial community and carbohydrate-active enzymes (CAZymes) were analyzed based on metagenomics. Metagenomic analysis results showed that ionic liquids enriched Actinobacteria and Proteobacteria in composting. Compared with CK, the total abundance values of GH11, GH6, AA6, and AA3_2 in ILs increased by 13.98%, 10.12%, 11.21%, and 13.68%, respectively. Ionic liquids can improve the lignocellulosic degradation by regulating the environmental physicochemical parameters (temperature, pH, C/N) to promote the growth of Actinobacteria and Proteobacteria and carbohydrate-active enzymes (CAZymes) abundance. Therefore, ionic liquids are a promising additive in lignocellulosic waste composting.

Degradation of antibiotic resistance genes and mobile gene elements in dairy manure anerobic digestion.

Antibiotic resistance genes (ARGs) are emerging contaminants causing serious global health concern. Interventions to address this concern include improving our understanding of methods for treating waste material of human and animal origin that are known to harbor ARGs. Anaerobic digestion is a commonly used process for treating dairy manure, and although effective in reducing ARGs, its mechanism of action is not clear. In this study, we used three ARGs to conducted a longitudinal bench scale anaerobic digestion experiment with various temperatures (28, 36, 44, and 52°C) in triplicate using fresh dairy manure for 30 days to evaluate the reduction of gene abundance. Three ARGs and two mobile genetic elements (MGEs) were studied: sulfonamide resistance gene (sulII), tetracycline resistance genes (tetW), macrolide-lincosamide-streptogramin B (MLSB) superfamily resistance genes (ermF), class 1 integrase gene (intI1), and transposase gene (tnpA). Genes were quantified by real-time quantitative PCR. Results show that the thermophilic anaerobic digestion (52°C) significantly reduced (p < 0.05) the absolute abundance of sulII (95%), intI1 (95%), tnpA (77%) and 16S rRNA gene (76%) after 30 days of digestion. A modified Collins–Selleck model was used to fit the decay curve, and results suggest that the gene reduction during the startup phase of anaerobic digestion (first 5 days) was faster than the later stage, and reductions in the first five days were more than 50% for most genes.

Efficient decomposition of lignocellulose and improved composting performances driven by thermally activated persulfate based on metagenomics analysis

In this study, fresh dairy manure and bagasse pith were used as raw materials to study the effect of potassium persulfate in the aerobic composting process. The influence of sulfate radical anion (SO4−·) generated by thermally activated persulfate on physicochemical parameters, lignocellulose degradation, humic substance (HS) formation, microbial community succession, and carbohydrate-active enzymes (CAZymes) composition were assessed during composting. Experimental results showed that the degradation rates of cellulose, hemicellulose and lignin in the treatment group with potassium persulfate (PS) (61.47%, 74.63%, 73.1%) were higher than that in blank control group (CK) (59.98%, 71.47%, 70.89%), respectively. Additionally, persulfate additive promoted dynamic variation of dissolved organic matter (DOM) and accelerated the formation of HS. Furthermore, metagenomics analysis revealed that persulfate changed the structure of the microbial community, and the relative abundances of Actinobacteria and Proteobacteria increased by 17.64% and 34.09% in PS, whereas 12.09% and 29.96% in CK. Glycoside hydrolases (GHs) and auxiliary activities (AAs) families were crucial to degrade lignocellulose, and their abundances were more in PS. Redundancy analysis (RDA) manifested that Actinobacteria and Proteobacteria were closely associated with lignocellulosic degradation. In brief, persulfate could accelerate the degradation of organic components, promote the formation of HS, optimize the structure of microbial community, and improve the compost quality.

Monitoring methane and nitrous oxide emissions from digestate storage following manure mono-digestion

Farm-scale anaerobic digestion is increasingly regarded as a greenhouse gas emission reduction measure. To get a full picture of its emission reduction potential, greenhouse gas emissions from digestate storage need to be assessed. This work quantifies methane (CH4) and nitrous oxide (N2O) emissions from farm-scale mono-digested dairy manure by continuous monitoring in an on-site digestate storage for three months, in autumn. A dedicated sampling method coupled with an on-line gas phase analyser was developed to enable continuous measurements over longer time periods. The proposed method was a refinement of existing closed chamber approaches and involved repeated sampling cycles, including a gas accumulation phase from which the emission rate was quantified. Daily average methane emissions per stored digestate volume varied from 4.6 to 14 g m−3 d−1, equivalent to 3.9 to 8.2% of the methane produced in the digester. Daily average nitrous oxide emissions varied from 0.004 to 0.13 g m−3 d−1. The total emission ranged between 170 and 478 g [CO2,eq.] m−3 d−1, up to 10% of which was attributed to nitrous oxide. Both methane and nitrous oxide emissions increased for a larger stored digestate volume and a higher temperature. The system under study was simulated through an anaerobic digestion model, taking into account prevailing operating conditions in the digester and digestate storage. Substrate-specific input values were identified by analysing the fresh dairy manure and digestate. The hydrolysis constant and gas–liquid transfer coefficient were estimated at 0.21 d−1 and 0.003 d−1, respectively, for simulation results to match experimentally observed methane emission values.

Long term crop management effects on soil organic carbon, structure, and water retention in a cropland soil in central Ohio, USA

AbstractThe objective of this study was to determine 13‐year management effects on soil properties between a corn–soybean (Zea mays–Glycine max) cropping system (CSRS) and vegetable production systems (VPS) on a soil in central Ohio. Three treatments included in the VPS were: (1) addition of wood chips, (2) permanent raised beds (PRB) with black polyethylene film (20 μm thick), and (3) bare soil surface (BSS). Additionally, (4) animal manure was applied in all CSRS and VPS treatments except for the wood chips (WCP) added plot in the VPS. Research data from the study show that relatively more soil organic carbon (SOC) stock in the 0–20 cm soil depth of the BSS treatment (100.6 Mg ha−1) was primarily due to differences in the type of soil amendments applied. For example, composted poultry manure was applied in the BSS and PRB plots, compared with input of fresh dairy manure mixed with straw being applied in the CSRS. Furthermore, soil management practices that aided in avoiding or reducing soil compaction (i.e., PRB or application of WCP in the surface) resulted in the overall improvement in soil structure and water retention, compared with that under chisel and disc ploughing done in the CSRS. The highest plant available water capacity (1.79 cm) was observed in the CSRS compared with 0.97 cm under BSS and PRB plots. These trends suggest that the type and amount of animal manure is critical to increasing SOC stocks in intensively cultivated VPS and CSRS in central Ohio, while also improving soil structure and water retention.

Impact of Manure Storage Time and Temperature on Microbial Composition and Stable Fly (Diptera: Muscidae) Development

Samples are often frozen for preservation until needed for use. It has been a common practice to store fresh dairy manure in the freezer until needed for fly development studies. However, conflicting data have suggested that freezer temperature and duration of manure may impact fly development studies, and it is likely due to the change in microbial comminutes due to the freezer conditions. In this study manure storage conditions were assessed to ascertain how temperatures impact stable fly, Stomoxys calcitrans L., survival to pupation and determine which bacterial populations impacted fly development using massively-parallel sequencing and 16S metagenomic analysis. Stable fly survival to pupation was greater in manure that was stored warm (27˚C) or frozen (-20˚C or -80˚C) for 24 days as compared to fresh manure samples. Refrigeration (4˚C) of the manure for 24 days did not affect fly development and slightly decreased the pupal weights. Over 80 bacterial families were detected by sequencing allowing for a more thorough assessment of changes in bacterial populations. Only minor shifts were observed in bacterial family composition in the manure when refrigerated or frozen for 24 days, but significant population changes were observed when the manure was incubated for 24 days at 27˚C. Since it is the temperature and incubation time that yielded the greatest pupation rate, it is hypothesized that the manure microbial community impacts the growth and development of stable flies. This study has determined suggested freezer conditions for the best storage of manure samples to maintain bacterial diversity and retain the closest bacterial populations to freshly collected manure. Although untouched, aged (20 days) manure is best to use to assess fly development, it is not always feasible in laboratory experimentations. This study demonstrates the importance of preservation techniques on manure samples, which could also confer to storage of other biological specimens that contain resident microbes.

Targeting Bacteria and Methanogens To Understand the Role of Residual Slurry as an Inoculant in Stored Liquid Dairy Manure.

Microbial communities in residual slurry left after removal of stored liquid dairy manure have been presumed to increase methane emission during new storage, but these microbes have not been studied. While actual manure storage tanks are filled gradually, pilot- and farm-scale studies on methane emissions from such systems often use a batch approach. In this study, six pilot-scale outdoor storage tanks with (10% and 20%) and without residual slurry were filled (gradually or in batch) with fresh dairy manure, and methane and methanogenic and bacterial communities were studied during 120 days of storage. Regardless of filling type, increased residual slurry levels resulted in higher abundance of methanogens and bacteria after 65 days of storage. However, stronger correlation between methanogen abundance and methane flux was observed in gradually filled tanks. Despite some variations in the diversity of methanogens or bacteria with the presence of residual slurry, core phylotypes were not impacted. In all samples, the phylum Firmicutes predominated (∼57 to 70%) bacteria: >90% were members of ClostridiaMethanocorpusculum dominated (∼57 to 88%) archaeal phylotypes, while Methanosarcina gradually increased with storage time. During peak flux of methane, Methanosarcina was the major player in methane production. The results suggest that increased levels of residual slurry have little impact on the dominant methanogenic or bacterial phylotypes, but large population sizes of these organisms may result in increased methane flux during the initial phases of storage.IMPORTANCE Methane is the major greenhouse gas emitted from stored liquid dairy manure. Residual slurry left after removal of stored manure from tanks has been implicated in increasing methane emissions in new storages, and well-adapted microbial communities in it are the drivers of the increase. Linking methane flux to the abundance, diversity, and activity of microbial communities in stored slurries with different levels of residual slurry can help to improve the mitigation strategy. Mesoscale and lab-scale studies conducted so far on methane flux from manure storage systems used batch-filled tanks, while the actual condition in many farms involves gradual filling. Hence, this study provides important information toward determining levels of residual slurry that result in significant reduction of well-adapted microbial communities prior to storage, thereby reducing methane emissions from manure storage tanks filled under farm conditions.

Management of Warm- and Cool-Season Grasses for Biomass on Marginal Lands: I. Yield and Soil Fertility Status

Switchgrass (Panicum virgatum L.), tall fescue [Lolium arundinaceum (Schreb.)], and reed canarygrass (Phalaris arundinacea L.) are known for high biomass productivity and for various traits that make these species more suitable for marginal environmental growing conditions. The goal of this study was to evaluate the impact of organic vs. inorganic fertilizer application on grass biomass production and soil nutrient status. Switchgrass, tall fescue, and reed canarygrass were established on a sandy soil and a clay soil at the Cornell University Willsboro Research Farm in Willsboro, NY. The experiment was a split-split plot randomized block design with six replicates. Sites were whole plots, grass species were subplots, and fertility treatments were sub-subplots. The six treatments were (1) 168 kg ha−1 of N fertilizer for cool-season grasses, 84 kg ha−1 for switchgrass; (2) 56 kg ha−1 of 0-46-0 P fertilizer plus N (#1); (3) 112 kg ha−1 of 0-0-60 K fertilizer plus N (#1); (4) 89.6 Mg dairy manure ha−1; (5) 44.8 Mg dairy manure compost ha−1; and (6) no fertilizer applied (control plots). Switchgrass with a single harvest per season yielded on average 13.0 Mg ha−1, while tall fescue and reed canarygrass averaged 8.4 and 7.7 Mg ha−1, respectively, under two-cut systems. Switchgrass with no fertilization produced 84% of maximum yield of fertilized treatments. Application of a similar amount of organic N with fresh and composted dairy manure resulted in greater yields for fresh dairy manure. Organic fertilizers strongly impacted the P and K status of soils. Switchgrass is capable of high yields in marginal environments and can provide a land base for environmentally acceptable application of animal manure, although from a yield standpoint it is not very responsive to fertilizer applications.

Decomposition of Dairy Manure Assessed in the Field by Monitoring Natural Abundance of 13C

Decomposition rate constants, k, for organic amendments in soil are generally determined from laboratory incubations. Whether these incubations can be extrapolated to field conditions is an open question. Reliable decay constants are necessary to predict the C sequestration potential of organic soil amendments. We applied fresh dairy manure from corn (Zea mays L. subsp. mays.)‐fed cows to sandy loam soil to characterize the decomposition and retention of manure under dryland field conditions. The δ13C of amended soil was analyzed over 114 d to determine k of the manure. The resulting k was 0.0642 d−1. At this rate, about 1% of the manure C remained in the soil after 10 wk. Literature reports of k for cattle manure from laboratory incubations bracketed our results. The use of native isotope abundance permitted the study of amendment decomposition under field conditions within a growing season and indicated that dairy manure contributed little to long‐term soil C storage.

Effects of amendment of different biochars on soil carbon mineralisation and sequestration

The aim of this study was to determine the impact of addition of different biochars on soil carbon mineralisation and sequestration. Different biochars were produced from two types of feedstock, fresh dairy manure and pine tree woodchip, each of which was pyrolysed at 300, 500, and 700°C. Each biochar was mixed at 5% (w/w) with a forest loamy soil and the mixture was incubated at 25°C for 180 days, during which soil physicochemical properties and soil carbon mineralisation were measured. Results showed that the biochar addition increased soil carbon mineralisation at the early stage (within the first 15 days) because biochar brought available organic carbon to the soil and changed associated soil properties, such increasing soil pH and microbial activity. The largest increase in soil carbon mineralisation at the beginning of incubation was induced by the dairy manure biochar pyrolysed at 300°C. Soil carbon mineralisation was enhanced more significantly by the dairy manure biochars than by the woodchip biochars, and the enhancement effect decreased with increasing pyrolysis temperature. Although the biochar addition induced increased soil carbon mineralisation at the beginning of the incubation, soil carbon mineralisation rates decreased sharply within a short time (within 15 days) and then remained very low afterwards. Carbon mineralisation kinetic modelling indicated that the stable organic matter in biochars could be sequestrated in soil for a long time and resulted in high levels of carbon sequestration, especially for the woodchip biochars pyrolysed from higher temperatures.

Effects of amendment of different biochars on soil enzyme activities related to carbon mineralisation

This study aimed to investigate the effects of different biochars on soil enzyme activities associated with soil carbon (C) mineralisation. Biochars were produced from two types of feedstock (fresh dairy manure and pine tree woodchip) at temperatures of 300°C, 500°C, and 700°C. Each biochar was mixed at a ratio of 5% (w/w) with a forest loamy soil and the mixture was incubated at 25°C for 180 days. Soil mineralisation rates, soil dissolved organic C, soil microbial biomass C, and five soil enzyme activities were measured during different incubation periods. Results showed that biochar addition increased soil enzyme activities at the early stage (mainly within the first 80 days) because biochar brought available nutrients to the soil and increased soil dissolved organic C and microbial activity. Soil enzyme activities were enhanced more by the dairy manure biochars than by the woodchip biochars (P &lt; 0.05). The enhancement effect on enzyme activities (except catalase activity) was greater in the treatments with biochars produced at lower pyrolysis temperature (300°C). Linear relationships between some soil enzymes and C-mineralisation rates might indicate that the increased enzyme activities stimulated soil C mineralisation at the early stage. However, the biochar additions could result in great C sequestration in the long term, especially for the woodchip biochars pyrolysed at higher temperatures.

Mitigation of greenhouse gas emission from the cattle manure composting process by use of a bulking agent

The greenhouse gas (GHG) [methane (CH4) and nitrous oxide (N2O)] mitigation effects of mixing dried grass into passively-aerated manure during the composting process (which accounts for 68.7% of Japanese dairy manure management) were assessed. Gaseous emissions [CH4, N2O, carbon dioxide (CO2) and ammonia (NH3)] from about 4 t of fresh dairy manure with or without 400 kg of dried grass mixed in were measured by the dynamic chamber method. The addition of dried grass contributed to a decrease in GHG emissions from 20.8 ± 1.3 g kg−1 volatile solids (VS) to 5.4 ± 1.4 g kg−1 VS (74.3% mitigation) for CH4 and from 7.4 ± 2.6 g N2O-N kg−1 Ninitial to 2.7 ± 0.4 g N2O-N kg−1 Ninitial (62.8% mitigation) for N2O. By applying this strategy, the expected reduction of GHG emission would be 70,466 t CH4 yr−1 and 1379 t N2O-N yr−1 (1907 Gg CO2 eq. yr−1 in total) in the Japanese dairy sector. On the other hand, it was showed that CO2 and NH3 emissions increase [from 424.4 ± 214.9 g CO2 kg−1 VS to 603.8 ± 99.6 g CO2 kg−1 VS for CO2 and from 16.9 ± 7.1 g ammonium-nitrogen (NH3-N) kg−1 Ninitial to 38.3 ± 3.5 g NH3-N kg−1 Ninitial for NH3] by this method. Moreover, the mechanism of this significant N2O mitigation effect cannot be explained, and a better understanding of this effect could further improve the GHG mitigation strategy.

Fresh dairy manure as a substitute for chemical fertilization in growing wheat forage; effects on soil properties, forage yield and composition, weed contamination, and hay intake and digestibility by sheep

Two experiments were conducted in two consecutive years. Exp. 1 (2008) was aimed at examining the effects of fertilizing three 1-ha fields with fresh dairy manure that was either weed contaminated (CM) or non-contaminated (NCM), as compared to chemical fertilization (CF). Five 10-m2 subplots in each field treatment were analyzed for yield, composition, and in vitro digestibility of forage mass, wheat and weed plants, and changes in soil properties. Higher forage wheat yields were obtained in the CM and NCM treatments (9.45 and 9.41t dry matter (DM)/ha, respectively) than in the CF treatment (7.56tDM/ha, P<0.05). None of the field treatments included herbicide application, and all fields were highly contaminated by weed mass (419–580g/kg DM). Weed profile in the three field treatments was similar to that observed in neighboring fields. Sheep intake of diets containing 900g/kg wheat hay was highest in the NCM treatment, lowest in the CM treatment and intermediate in the CF treatment. Digestibility of dietary DM by the sheep followed an opposite trend, but neutral detergent fiber (aNDFom) digestibility was similar in the three treatments (0.64–0.66). Exp. 2 (2009) measured the cumulative effect of fresh dairy manure fertilization applied at two levels, 60 and 120m3 NCM/ha (designated 60-NCM and 120-NCM, respectively), with CF as the control treatment. The three fields were sprayed with herbicide to reduce weed contamination (<20g/kg). Wheat yield was higher in the 120-NCM treatment (14.5tDM/ha) than in the 60-NCM and CF treatments (12.5 and 12.6tDM/ha, respectively). Sheep intake of rations based on wheat hay from the three treatments was similar (781g DM/d). Digestibility by sheep of DM and crude protein were higher in hays from treatments 60-NCM and 120-NCM than from the CF treatment. Pathogenic bacteria, including Escherichia coli and Salmonella, did not survive in either the soil or the wheat plants during the growing seasons. The increase in wheat yield and digestibility due to dairy manure fertilization was related to the improvement in soil water retention and nutrient availability following this treatment. Adoption of this technology is expected to increase net profits in the dairy industry.

Bioconversion of dairy manure by black soldier fly ( Diptera: Stratiomyidae) for biodiesel and sugar production

Modern dairies cause the accumulation of considerable quantity of dairy manure which is a potential hazard to the environment. Dairy manure can also act as a principal larval resource for many insects such as the black soldier fly, Hermetia illucens. The black soldier fly larvae (BSFL) are considered as a new biotechnology to convert dairy manure into biodiesel and sugar. BSFL are a common colonizer of large variety of decomposing organic material in temperate and tropical areas. Adults do not need to be fed, except to take water, and acquired enough nutrition during larval development for reproduction. Dairy manure treated by BSFL is an economical way in animal facilities. Grease could be extracted from BSFL by petroleum ether, and then be treated with a two-step method to produce biodiesel. The digested dairy manure was hydrolyzed into sugar. In this study, approximately 1248.6 g fresh dairy manure was converted into 273.4 g dry residue by 1200 BSFL in 21 days. Approximately 15.8 g of biodiesel was gained from 70.8 g dry BSFL, and 96.2 g sugar was obtained from the digested dairy manure. The residual dry BSFL after grease extraction can be used as protein feedstuff.

Development and optimization of a culture medium for L-lactic acid production by Rhizopus oryzae using crude protein from dairy manure as a nitrogen source

Experiments were conducted using the crude protein in fresh dairy manure as the nitrogen source in the culture media for Rhizopus oryzae to produce L-lactic acid. Two uniform design experiments were carried out with one for optimizing seed culture while the other for best percent L-lactic acid production. Multiple linear regression and ANOVA analyses were employed to determine the most significant media components. Data from the first uniform design U6 (62× 3), in which the experimental factors involved included nitrogen concentration (crude protein), spore concentration, and treatment duration, showed that the levels of these components in the optimal condition for the seed culture medium were 2.1 g/L nitrogen, 16 hour culture time, and 105 spore concentration. The biomass weight in the seed medium developed in this study reached 1.32 g/L, which was 48.3% higher than that of the control. The combination of culture time and nitrogen concentration was found to be most significant in influencing the biomass yield. In the second uniform design experiment, flask culture with five factors (glucose, nitrogen from dairy manure, ZnSO4, KH2PO4, and MgSO4) at eight levels was examined using the uniform design table U8 (85) with the content of L-lactic acid as the evaluating response Y. The results showed that ZnSO4 had the most influence on L-lactic acid yield, followed by nitrogen and KH2PO4. The optimum culture medium in terms of lactic acid production consisted of 240 g/L glucose, 1.26 g/L crude protein, 1.05 g/L KH2PO4, and 0.25 g/L MnSO4, which could achieve a yield of 59.57% (7.1% higher than the control).

L-Lactic Acid Fermentation by Rhizopus oryzae Using Dairy Manure as a Nitrogen Source

Experiments were conducted to investigate the possibility of using fresh dairy manure as the nitrogen source in a culture medium to produce L-lactic acid by Rhizopus oryzae NRRL 395. The parameters of the culture medium, including glucose (120 vs. 240 g L-1), nitrogen (1.0 vs. 3.0 g L-1, from dairy manure), KH2PO4 (0.65 vs. 1.3 g L-1), MgSO4 (0.25 vs. 0.5 g L-1), ZnSO4 (0.0 vs. 0.05 g L-1), spore culture time (3 vs. 6 h), and the inoculum dosage (6% vs. 12%, v/v), were first examined using the Plackett-Burman design to single out the most important ones to reduce the number of experiments in the optimization stage while still maintaining the statistical validity of the experimental results. In the optimization stage, experiments featuring a two-level, four-factor factorial design (24) for the four most important components, i.e., glucose, nitrogen, KH2PO4, and MgSO4, were carried out, and the results were subjected to ANOVA to determine the optimum levels for each component, within the ranges used in this study, in the culture medium based on the percent L-lactic acid yield. The results showed that glucose, nitrogen, KH2PO4, and MgSO4 concentrations had the strongest impact on percent L-lactic acid yields by Rhizopus oryzae NRRL 395 (degrees of confidence were 93.08%, 96.11%, 89.59%, and 82.2%, respectively). The ANOVA revealed that glucose, nitrogen, and KH2PO4 demonstrated a significant main effect on the yield of L-lactic acid (p < 0.0004). In addition, the interactions of glucose, nitrogen, KH2PO4, and MgSO4 were also found to be significant at p < 0.05. The main effects, as well as the interactions, were summarized by a polynomial regression equation, which was found to be able to sufficiently describe the L-lactic acid production observed in this study (p < 0.0002). The equation was examined against the experimental data, resulting in a coefficient of determination (R2) of 0.9436 for the linear regression relationship between the predicted and observed values. Finally, the optimum culture medium composition with respect to the four major components studied using dairy manure as a base substrate for L-lactic acid generation by Rhizopus oryzae was found to be 3 g L-1 nitrogen, 120 g L-1 glucose, 1.3 g L-1 KH2PO4, and 0.5 g L-1 MgSO4, and the corresponding percent L-lactic acid yield was 29.1% (measured) and 30.76% (predicted), based on the experimental conditions used in this study.

Inhibition of phosphorus sorption to goethite, gibbsite, and kaolin by fresh and decomposed organic matter

The direct effects of dissolved organic matter (DOM) on the sorption of orthophosphate onto gibbsite, goethite, and kaolin were examined using a one-point phosphorus sorption index and the linear Tempkin isotherm model. DOM extracted from fresh and decomposed agricultural residues, as well as model organic and humic acids, were used. Changes in the chemical and sorptive characteristics of the DOM in the absence and presence of added orthophosphate (50 mg l−1) were also determined. For residue-derived materials, DOM sorption to all minerals correlated well with percent hydrophobicity, apparent molecular weight, and phenolic acidity in the absence of added orthophosphate. Sorption of DOM to goethite and gibbsite was significantly decreased in the presence of added P. The correlation coefficient values of percent hydrophobicity, apparent molecular weight, and phenolic acidity to sorption also declined in the presence of added P. Thus, the addition of P substantially lowered fractionation of DOM after sorption to goethite and gibbsite. In contrast, few significant P sorption-induced differences were observed in the kaolin system. According to one-point P sorption results, DOM in the form of Aldrich humic acid, oxalate, and decomposed clover and corn residue, significantly inhibited P sorption to goethite at concentrations of 50 and 200 mg total soluble carbon (CTS l−1). Phosphorus sorption to gibbsite was significantly inhibited by 50 mg CTS l−1 derived from decomposed corn residue, fresh dairy manure residue, and oxalate solution. At 200 mg CTS l−1, all DOM solutions were found to inhibit P sorption to gibbsite. This study suggests that DOM inhibition of P sorption depends on the chemical properties of both the sorbent and the DOM itself. In general, DOM from decomposed organic materials inhibited P sorption to a greater extent than did DOM derived from fresh materials. This stronger inhibition highlights the importance of microbial processes in the release of soluble soil P, a key determinant of P availability to plants.