Manure Acidification Research Articles

Greenhouse Gas and Ammonia Emissions from Different Stages of Liquid Manure Management Chains: Abatement Options and Emission Interactions.

Farm livestock manure is an important source of ammonia and greenhouse gases. Concerns over the environmental impact of emissions from manure management have resulted in research efforts focusing on emission abatement. However, questions regarding the successful abatement of manure-related emissions remain. This study uses a meta-analytical approach comprising 89 peer-reviewed studies to quantify emission reduction potentials of abatement options for liquid manure management chains from cattle and pigs. Analyses of emission reductions highlight the importance of accounting for interactions between emissions. Only three out of the eight abatement options considered (frequent removal of manure, anaerobic digesters, and manure acidification) reduced ammonia (3-60%), nitrous oxide (21-55%), and methane (29-74%) emissions simultaneously, whereas in all other cases, tradeoffs were identified. The results demonstrate that a shift from single-stage emission abatement options towards a whole-chain perspective is vital in reducing overall emissions along the manure management chain. The study also identifies some key elements like proper clustering, reporting of influencing factors, and explicitly describing assumptions associated with abatement options that can reduce variability in emission reduction estimates. Prioritization of abatement options according to their functioning can help to determine low-risk emission reduction options, specifically options that alter manure characteristics (e.g., reduced protein diets, anaerobic digestion, or slurry acidification). These insights supported by comprehensive emission measurement studies can help improve the effectiveness of emission abatement and harmonize strategies aimed at reducing air pollution and climate change simultaneously.

Antibiotic degradation and microbial community structures during acidification and methanogenesis of swine manure containing chlortetracycline or oxytetracycline

Anaerobic digestion (AD) has been applied to animal manure stabilization, and antibiotics is frequently found in animal manure. However, antibiotic degradation and microbial community structures during two-stage AD (acidification and methanogenesis) remain poorly understood. This experiments on two-stage anaerobic swine manure digesters were performed to investigate the degradation mechanisms and effects of chlortetracycline (CTC) and oxytetracycline (OTC) on microbial community structures. Results showed that acidification and methanogenesis showed good degradation performance for manure containing CTC and OTC at 60 and 40 mg/kg·TS, respectively. CTC and OTC were degraded by 59.8% and 41.3% in the acidogenic stage and by 76.3% and 78.3% in the methanogenic stage, respectively. CTC and OTC negatively affected bacterial community in methanogenic and acidogenic stages, respectively. They also adversely influenced the archaeal species in the methanogenic stage. Two-stage AD was proposed to treat manure containing antibiotics and to reduce the negative effects of antibiotics on AD.

Transformation of Organic Matter and the Emissions of Methane and Ammonia during Storage of Liquid Manure as Affected by Acidification.

Acidification of livestock manure can reduce emission of the greenhouse gases methane (CH) and nitrous oxide (NO), as well as ammonia (NH). We examined the relation between emission of these gases and transformation of organic matter as affected by acidification. Liquid cattle manure was acidified with sulfuric acid to pH 5.5 at a pilot scale (100 L), and we measured effects on CH, NO, CO and NH emissions and on transformation of pH buffer components and organic matter. Acidification reduced NH emissions by 62% (47 d) and emission of CH by 68% (57 d). Emissions of NO were negligible, probably due to the absence of a surface crust. Reductions in NH and CH emission were highest at the start but declined over time concomitantly with a gradual increase in the stored liquid manure pH. Acidification did not significantly affect CO emissions. Emission of CO was high, five- to ten-fold of CH emissions, until Day 16 of storage, after which the CO emission rate declined to around twice the CH emission rate; consequently, the majority of C loss during the early stages of storage was CO. Cumulative emission of C in CO and CH closely matched depletion of dissolved organic carbon (DOC), suggesting that DOC may be a predictor for CH emission from dilute slurries. volatile fatty acid and total ammoniacal nitrogen concentrations in surface layers were substantially higher than at the center of stored liquid manure, perhaps resulting from microbial activity at the surface. This pattern deserves attention when predicting NH emission from stored slurry.

Manure-pH Management for Mitigating Ammonia Emissions from Dairy Barns and Liquid Manure Storages

Abstract. Concentrated animal feeding operations (CAFOs) are important sources of NH3 emissions. Manure acidification, however, has the potential to significantly mitigate NH3 emissions. This research investigated achievable NH3 emission mitigation in a dairy barn when maintaining a pH

Reduction of ammonia emissions from dairy cattle cubicle houses via improved management- or design-based strategies: A modeling approach

Given the current scarcity of empirical data on ammonia (NH3) emissions from dairy cattle under different management-based mitigation techniques, a modeling approach to assess potential NH3 emission reduction factors is needed. This paper introduces a process-based model that estimates NH3 emission reduction factors for a dairy cattle barn featuring single or multiple management-based NH3 emission mitigation techniques, as compared to another barn, to which no mitigation measure is applied. The model accounts for the following emission mitigation measures: (a) floor scraping, (b) floor type, (c) floor flushing with water and (d) indoor acidification of manure. Model sensitivity analysis indicated that manure acidification was the most efficient NH3 emission reduction technique. A fair agreement was observed between reduction factors from the model and empirical estimates found in the literature. We propose a list of combinations of techniques that achieve the largest reductions. In order of efficiency, they are: (a) floor scraping combined with manure acidification (reduction efficiency 44–49%); (b) solid floor combined with scraping and flushing (reduction efficiency 21–27%); (c) floor scraping combined with flushing and (d) floor scraping alone (reduction efficiency 17–22%). The model is currently being used to advise the Flemish Government (Belgium), on the performance of certain NH3 emission reduction systems for dairy barns in Flanders.

Producing high-strength liquor from mesophilic batch acidification of chicken manure.

This report describes the results from anaerobic batch acidification of chicken manure as a mono-substrate studied under mesophilic conditions. The manure was diluted with tap water to prevent methane formation during acidification and to improve mixing conditions by reducing fluid viscosity; no anaerobic digester sludge has been added as an inoculum. Highest acidification rates were measured at concentrations of 10 gVS L⁻¹ and 20 gVS L⁻¹; the pH value remained high (pH 6.9-7.9) throughout the test duration and unexpected fast methane formation was observed in every single batch. At substrate concentrations of 10 gVS L⁻¹ there was a remarkable methane formation representing a value of 82% of the respective biochemical methane potential of chicken manure. Increasing substrate concentrations did not supress methane formation but impaired acid production. Consequently, the liquor cannot be stored over longer periods but should immediately be used in a digestion process.

Pig slurry characteristics, nutrient balance and biogas production as affected by separation and acidification

SUMMARYAnimal slurry is separated in order to avoid excessive nitrogen, phosphorus and potassium (NPK) fertilization of crops in the field. To enhance fertilizer efficiency further, slurry and its separation products may be acidified, for instance in animal houses. The current study quantified the effects of these treatments, both individually and in combination, on fertilizer efficiency, energy production and heavy metal accumulation as a result of manure management. Acidification increased the availability of N to plants in the manure applied, and provided a better match between plant-available NPK in the manure and separation fraction applied to fields and crop need. Total biogas production was not affected by separation, whereas acidification reduced biogas production because the process was inhibited by a low pH and a high sulphur concentration. The amount of copper applied per hectare in the liquid manure to the wheat field was lower than the amount taken up and more zink and copper was applied in the solid fraction to maize field than taken up. The transportation and field application of solids and liquids did not increase management costs when compared to the transportation of slurry alone, but the investment and running costs of separators and manure acidification increased overall management costs.

Effect of initial pH on mesophilic hydrolysis and acidification of swine manure

Effects of initial pH (3–12) on mesophilic hydrolysis and acidification reactions of swine manure was studied. The initial pH changed the microbial community in the suspension so as to affect hydrolysis and acidification reactions on swine manure. At pH 10–12 the Clostridium alkalicellum and/or Corynebacterium humireducens were enriched and the soluble chemical oxygen demand (SCOD), total volatile fatty acids (VFAs), proteins and carbohydrates from manure were increased in quantities. In particular, at pH 10 the VFA concentration peaked at 13,600mg-COD/L, with acetate and propionate accounting for 71.8% of the total VFAs. Acidic environment facilitates release of ammonium from manure. The Butyricimonas sp. was found existing at initial pH 5 which led to accumulated quantities of butyrate. Initial pH adjustment was revealed to be an effective way to manipulate rates and end products of hydrolysis and acidification of swine manure.

Optimization of cattle manure hydrolysis and acidification for methane production

Although high lignocellulose content decreases acidification rate of anaerobic fermentation of cattle manure,acidification phase is critical in anaerobic fermentation of cattle manure.Cattle manure acidification conditions were investigated with the aim of optimizing methane production in a two-phased anaerobic process of cattle manure.The effects of acidification time,stirring frequency,feed solution concentration and urea addition for cattle manure methane production were studied in a two-phased anaerobic fermentation at 35 ℃.Single factor experiments showed that 96 h of acidification,3 times in every 24 h(60 r?min?1,1 min?time?1) of stirring frequency,8.0% feed solution concentration and 1.28 g?L?1 urea addition were the optimum conditions.Based on single factor experiments,a series of central composite design experiments were conducted for optimum synthesis.Response surface methodology(RSM) with central composite design(CCD) was used to explore optimum conditions for methane production.The effects of three variables(acidification time,feed solution concentration and urea addition) were subsequently appraised.A regression model for methane production under the acidification conditions was established for analysis of interactions and significance in accordance with central composite design.Results showed that methane production was greatly influenced by feed solution concentration,urea addition and acidification time under at 35 ℃ and 3 times per every 24 h(60 r?min?1,1 min?time?1) stirring frequency.The optimum acidification conditions occurred at the acidification time of 93.7 h,feed solution concentration of 8.3% and urea addition of 1.26 g?L?1.Under the optimum condition,methane content and total production increase by 14.3% and 44.7%.Also the removal rates of volatile solid(VS) and chemical oxygen demand(COD) increased by 41.8% and 33.9%,respectively.However,the contents of cellulose,hemicellulose and lignin were not affected by cattle manure acidification.The findings indicated that cattle manure acidification improved methane production,methane content,and VS and COD removal rates.

Microbial population dynamics and changes in main nutrients during the acidification process of pig manures

This study evaluated the impact of pig manure acidification on anaerobic treatment and composition of the fecal microbial community. According to the different chemical oxygen demand (COD) in the anaerobic treatment processes, pig manure was diluted 4 times (×4), 16 times (×16), or 64 times (×64) and subjected to acidification. During the acidification process, pH, soluble chemical oxygen demand (SCOD), volatile fatty acids (VFAs), nitrogen (N), phosphorus (P) and potassium (K) were determined along with microbial population dynamics. The pH of the three dilutions first declined, and then slowly increased. The total VFAs of ×4 and ×16 dilutions peaked on day 15 and 20, respectively. The content of acetic acid, propanoic acid, butanoic acid and valeric acid of the × 4 dilution were 23.6, 11.4, 8.8 and 0.6 g/L respectively, and that of the ×16 dilution was 5.6, 2.3, 0.9 and 0.2 g/L respectively. Only acetic acid was detected in the ×64 dilution, and its level peaked on day 10. The results showed that the liquid pig manure was more suitable to enter the anaerobic methanogenic bioreactors after two weeks of acidification. During the acidification process, total P concentration increased during the first ten days, then dropped sharply, and rose again to a relatively high final concentration, while total N concentration rose initially and then declined. Based on the analysis of denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene clone library, we concluded that the acidification process reduced the number of pathogenic bacteria species in pig manure.

Biogas Production from Anaerobic Co-digestion of Food Waste with Dairy Manure in a Two-Phase Digestion System

Co-digestion of food waste and dairy manure in a two-phase digestion system was conducted in laboratory scale. Four influents of R0, R1, R2, and R3 were tested, which were made by mixing food waste with dairy manure at different ratios of 0:1, 1:1, 3:1, and 6:1, respectively. For each influent, three runs of experiments were performed with the same overall hydraulic retention time (HRT) of 13 days but different HRT for acidification (1, 2, and 3 days) and methanogenesis (12, 11, and 10 days) in two-phase digesters. The results showed that the gas production rate (GPR) of co-digestion of food waste with dairy manure was enhanced by 0.8-5.5 times as compared to the digestion with dairy manure alone. Appropriate HRT for acidification was mainly determined by the biodegradability of the substrate digested. Three-, 2-, and 1-day HRT for acidification were found to be optimal for the digestion of R0, R1, and R2/R3, respectively, when overall HRT of 13 days was used. The highest GPR of 3.97 L/L.day was achieved for R3(6:1) in Run 1 (1 + 12 days), therefore, the mixing ratio of 6:1 and HRT of 1 day for acidification were considered to be the optimal ones and thus recommended for co-digestion of food waste and dairy manure. There were close correlations between degradation of organic matters and GPR. The highest VS removal rate was achieved at the same HRT for acidification and mixing ratio of food waste and dairy manure as GPR in the co-digestion. The two-phase digestion system showed good stability, which was mainly attributed to the strong buffering capacity with two-phase system and the high alkalinity from dairy manure when co-digested with food waste.

Improved Anaerobic Acidification of Unscreened Dairy Manure

Even though several aspects of two-phase configuration might be very significant for efficient anaerobic digestion (AD) of dairy manure, its application has very been limited. Two sets of experiments daily-fed continuously mixed acidogenic anaerobic reactors with no recycle were conducted to investigate the optimum conditions on anaerobic acidification of unscreened dairy manure in terms of maximum acidification and VS reduction. Effect of solids and hydraulic retention time (SRT/HRT), organic loading rate (OLR), and pH control on anaerobic acidification in terms of volatile fatty acid (VFA) formation and volatile solids (VS) reduction were investigated. Results indicated that SRT/HRT and OLR of 2 days and 15 g VS/L · day, respectively, yielded maximum acidification. The pH control was not effective on the acidification of dairy manure. The degree of acidification increases as HRT decreases, and also higher efficiency was determined in an uncontrolled reactor.

Management Strategy Impacts on Ammonia Volatilization from Swine Manure

Ammonia emitted from manure can have detrimental effects on health, environmental quality, and fertilizer value. The objective of this study was to measure the potential for reduction in ammonia volatilization from swine (Sus scrofa domestica) manure by temperature control, stirring, addition of nitrogen binder (Mohave yucca, Yucca schidigera Roezl ex Ortgies) or urease inhibitor [N-(n-butyl) thiophosphoric triamide (NBPT)], segregation of urine from feces, and pH modification. Swine manure [total solids (TS) = 7.6-11.2%, total Kjeldahl nitrogen (TKN) = 3.3-6.2 g/L, ammonium nitrogen NH(+)(4)-N = 1.0-3.3 g/L] was stored for 24, 48, 72, or 96 h in 2-L polyvinyl chloride vessels. The manure was analyzed to determine pre- and post-storage concentrations of TS and volatile solids (VS), TKN, and NH(+)(4)-N. The concentration of accumulated ammonia N in the vessel headspace (HSAN), post-storage, was measured using grab sample tubes. Headspace NH(3) concentrations were reduced 99.3% by segregation of urine from feces (P < 0.0001). Stirring and NBPT (152 microL/L) increased HSAN concentration (119 and 140%, respectively). Headspace NH(3) concentration increased by 2.7 mg/m(3) for every 1 degree C increase in temperature over 35 degrees C. Slurry NH(+)(4)-N concentrations were reduced by segregation (78.3%) and acidification to pH 5.3 (9.4%), and increased with stirring (4.8%) and increasing temperature (0.06 g/L per 1 degree C increase in temperature over 35 degrees C). Temperature control, urine-feces segregation, and acidification of swine manure are strategies with potential to reduce or slow NH(+)(4)-N formation and NH(3) volatilization.

Effect of retention time and organic loading rate on anaerobic acidification and biogasification of dairy manure

AbstractVast amounts of animal manure produced from concentrated animal feeding operations have the potential to be converted into economic gain if the proper processing technology is employed. Anaerobic digestion (AD) is an effective way to convert organic wastes including animal manure into profitable by‐products as well as to reduce the pollution of water, air, and soil caused by these wastes. Two‐phase AD of manure offers several advantages over conventional one‐phase AD. Solids reduction through hydrolysis/acidification might be very significant for animal manure which contains high amounts of solids. However, to date, studies of two‐phase AD of animal manure have been limited to screened manure. Therefore, this study investigated the two‐phase AD of dairy manure with particular emphasis on the effects of retention time and organic loading rate (OLR) on anaerobic acidification and biogasification of unscreened dairy manure. The results indicated that pre‐acidification of dairy manure in daily‐fed continuously‐mixed reactors with no recycle led to significantly high reduction efficiencies of volatile solids and, thus, biogas production in the subsequent methanogenic reactor especially at OLRs of 4–10 g VS dm−3 day−1. However, the extent of the stimulation in the biogas production relative to corresponding feed samples was quite variable (between 6.9 and 64.7%) for different solids retention times and OLR combinations. A relatively lower performance was observed for the high OLRs (20–30 g VS dm−3 day−1) used which was attributed to the possible wash‐out of the acidifiers at the considerably low retention times (1.25–4 days) used. Copyright © 2004 Society of Chemical Industry