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Losses of N from livestock operations due to ammonia (NH 3 ) volatilization from animal wastes is a major source of pollution in Europe and North America, and represents a significant economic loss. Paper products have potential as amendments to reduce NH 3 loss because their high carbon (C) and low nitrogen (N) contents would be expected to cause N immobilization. Reduction in NH 3 volatilization from liquid hog manure (LHM) by paper bag (PB), filter paper (FP), newsprint (NP), and pulp sludge (PS) added at 2.5 and 5% (fresh LHM weight) was evaluated in a 56 d incubation study. Cumulative NH 3 volatilization ranged between 28 and 53% of initial manure N. When the rate increased from 2.5 to 5%, NH 3 volatilization was reduced by 47, 40, 37, and 29%, respectively, compared to the control. Increasing the rate increased the amount of C lost from the LHM and reduced the net mineralization of organic N. Hence, the addition of organic amendments appeared to have decreased NH 3 volatilization by increasing microbial activity and N immobilization. Liquid hog manure pH was negatively correlated with C loss, indicating that microbial decomposition of paper amendments lowered manure pH but this effect did not appear to be important in controlling NH 3 volatilization. Paper lignin content was not correlated with the loss of C, manure pH, or NH 3 volatilization, suggesting that the effectiveness of paper products in reducing NH 3 volatilization is not controlled by lignin content but rather by other more labile components.

The contribution of organic wastes to crop yields and soil fertility may be influenced by their composition and the soil type. This 6-yr study (2001―2006) evaluated the effects of repeated additions of mineral fertilizers (MF), mixed paper mill sludges (PMS) (18, 36, and 54 Mg ha ―1 ), dairy cattle manure (DCM) (36 Mg ha ―1 ) alone or with reduced mineral fertilizer (60% NPK) (RMF) and a control, on soil properties and corn (Zea mays L.), barley (Hordeum vulgaris L.), and soybean (Glycine max L. Merr.) yields in a clay loam and sandy loam. The applications of PMS and DCM increased mostly N mineralization and crop yields in the sandy loam than in the clay loam. However, increases of soil C contents, water-stable aggregates and MWD following their application were higher in the clay loam than in the sandy loam. The DCM effects on the soil property changes were of less magnitude than those of PMS. Except in the first year, the PMS applications at rates of 36 and 54 Mg ha ―1 without NPK, and PMS applied at a rate of 18 Mg ha ―1 with 60% NPK, produced highest crop yields in both soils and were comparable to those obtained with MF. The increase in yield following DCM additions (36 Mg ha ―1 ) was lower than that obtained with PMS. Annual MF applications increased crop yields in both soil without significant changes on soil properties. The benefits of PMS and DCM on soil properties and crop yields varied depending on organic wastes and soil type.

Summary Anaerobic digesters produce biogas, a mixture of predominantly CH4 and CO2, which is typically incinerated to recover electrical and/or thermal energy. In a context of circular economy, the CH4 and CO2 could be used as chemical feedstock in combination with ammonium from the digestate. Their combination into protein‐rich bacterial, used as animal feed additive, could contribute to the ever growing global demand for nutritive protein sources and improve the overall nitrogen efficiency of the current agro‐ feed/food chain. In this concept, renewable CH4 and H2 can serve as carbon‐neutral energy sources for the production of protein‐rich cellular biomass, while assimilating and upgrading recovered ammonia from the digestate. This study evaluated the potential of producing sustainable high‐quality protein additives in a decentralized way through coupling anaerobic digestion and microbial protein production using methanotrophic and hydrogenotrophic bacteria in an on‐farm bioreactor. We show that a practical case digester handling liquid piggery manure, of which the energy content is supplemented for 30% with co‐substrates, provides sufficient biogas to allow the subsequent microbial protein as feed production for about 37% of the number of pigs from which the manure was derived. Overall, producing microbial protein on the farm from available methane and ammonia liberated by anaerobic digesters treating manure appears economically and technically feasible within the current range of market prices existing for high‐quality protein. The case of producing biomethane for grid injection and upgrading the CO2 with electrolytic hydrogen to microbial protein by means of hydrogen‐oxidizing bacteria was also examined but found less attractive at the current production prices of renewable hydrogen. Our calculations show that this route is only of commercial interest if the protein value equals the value of high‐value protein additives like fishmeal and if the avoided costs for nutrient removal from the digestate are taken into consideration., Anaerobic digesters are the core engine for a biorefinery producing microbial protein. Either the biogas can be used directly for its production, or via biogas upgrading the separate CO2 can be combined with electrolytic hydrogen to produce more protein.

In this study, the anaerobic performance and stability of coffee husk and pulp with and without trace element (TE) supplement was investigated, using 20 L mesophilic continuous stirred tank reactors for 140 days of experiment (DOE). The TE was cocktail of trace metals composed of Fe, Ni, Zn, Co, Mn, Mo, Se W and B. The organic loading rate (OLR) was increased stepwise from 2.5 (HRT = 40 d) to 6.0 kg VS m(−3) d(− 1)(HRT = 16.7 d). The highest methane productivity from pulp with and without TE was 1.272 and 0.965 m(3) m(−3) d(−1) at an OLR of 6.0 and 5.0 kg VS m(−3) d(−1); while the husks performed 0.895 and 0.795 m(3) m(−3) d(−1) respectively, both at an OLR of 6.0 kg VS m(−3) d(−1). The specific methane yield (SMY) of pulp (at OLR = 5 kg VS m(−3) d(−1)) with and without TEs was 217.9 ± 4.7 and 193.1 ± 8.2 L kg(−1 )VS; while husk yielded 149.2 ± 6.0 and 132.5 ± 4.9 L kg(−1 )VS, respectively. The effect of TEs on SMY was statistically significant (p

Composting of beef cattle manure using sawdust or recycled compost as a bulking agent was investigated for the management of clopyralid risk, such as changes in the clopyralid concentration and the mechanism of clopyralid accumulation caused by recycled compost. These raw materials were composted with laboratory equipment, which was controlled at 60℃ after the temperature peak by autothermal composting. Clopyralid concentration did not changed during composting in the thermophilic phase; on the contrary, it increased because clopyralid accumulated in compost when recycled compost was used repeatedly as a bulking agent. The clopyralid accumulation ratio (ratio of clopyralid concentration to that in the first compost) could be explained by a model using a recurrence formula, and a correlation existed between the calculated (model) accumulation ratios and measured accumulation ratios (R2 = 0.78). Using this model, the excessive accumulation of clopyralid could be controlled when using recycled compost as a bulking agent with lower moisture content or when part of the recycled compost was replaced by another bulking agent, even if recycled compost had high moisture content. In future work, the model and its considerations should be verified in a field test.

Ekinci, Kamil/0000-0002-7083-5199 Composting plants should be operated at a high degradation rate in order to lower their capital and operational costs. Initial C/N ratio is one of the most influential factors on the composting process. This study aimed to determine the impacts of initial C/N ratio on operational composting parameters of two-phase olive mill pomace with separated dairy manure. Five initial C/N ratios ranging from 29.43 to 43.33 were examined using fifteen 100 L cylindrical reactors. The highest decomposition rate was estimated at 0.02 day(-1)with the C/N ratio of 34.49. The maximum relative heat generation was obtained with the C/N ratio of 36.07. The C/N ratio of approximately equal to 33 reduced the composting cost of process-based total airflow supplied per dry matter and organic matter loss. The maximum throughput capacity was obtained when the compost blend had the C/N ratio of approximately equal to 37.24. It was concluded that operating the composting of two-phase olive mill waste, separated dairy manure, and straw with the boundary of the initial C/N ratios between 33 and 37 was recommended. Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [KAMAG111G055/111G149] Scientific and Technological Research Council of Turkey, Grant/Award Number: KAMAG111G055/111G149

Emission of odorous and toxic gases from stored livestock manure is well documented and poses a serious health risk to farmers and livestock. Hydrogen sulfide emissions have been sharply rising with increasingly intensive livestock production and are of particular concern because of the acute toxicity of this gas. Numerous strategies, technologies, and chemical treatments have been used to control hydrogen sulfide emissions, but none have worked particularly well because they are neither cost-effective nor environmentally sustainable, or they are too toxic for animals. The inhibitory effect of the sodium tetraborate decahydrate (i.e., borax) treatment to reduce hydrogen sulfide production using sulfate-reducing bacteria was examined in shallow manure pits in a starter-grower swine facility. Monitoring of air emissions and DNA analysis revealed that treatment of stored swine manure effectively reduced hydrogen sulfide production, and the reduction correlated to a decrease in the sulfate-reducing bacteria population in the stored swine manure.

peer-reviewed Carbon (C) losses from agricultural soils to surface waters can migrate through water treatment plants and result in the formation of disinfection by-products, which are potentially harmful to human health. This study aimed to quantify total organic carbon (TOC) and total inorganic C losses in runoff after application of dairy slurry, pig slurry, or milk house wash water (MWW) to land and to mitigate these losses through coamendment of the slurries with zeolite (2.36 3.35 mm clinoptilolite) and liquid polyaluminum chloride (PAC) (10% Al2O3) for dairy and pig slurries or liquid aluminum sulfate (alum) (8% Al2O3) for MWW. Four treatments under repeated 30-min simulated rainfall events (9.6 mm h-1) were examined in a laboratory study using grassed soil runoff boxes (0.225 m wide, 1 m long; 10% slope): control soil, unamended slurries, PAC-amended dairy and pig slurries (13.3 and 11.7 kg t-1, respectively), alum-amended MWW (3.2 kg t-1), combined zeolite and PAC-amended dairy (160 and 13.3 kg t-1 zeolite and PAC, respectively) and pig slurries (158 and 11.7 kg t-1 zeolite and PAC, respectively), and combined zeolite and alumamended MWW (72 and 3.2 kg t-1 zeolite and alum, respectively). The unamended and amended slurries were applied at net rates of 31, 34, and 50 t ha-1 for pig and dairy slurries and MWW, respectively. Significant reductions of TOC in runoff compared with unamended slurries were measured for PACamended dairy and pig slurries (52 and 56%, respectively) but not for alum-amended MWW. Dual zeolite and alum-amended MWW significantly reduced TOC in runoff compared with alum amendment only. We conclude that use of PAC-amended dairy and pig slurries and dual zeolite and alum-amended MWW, although effective, may not be economically viable to reduce TOC losses from organic slurries given the relatively low amounts of TOC measured in runoff from unamended slurries compared with the amounts applied. ACCEPTED peer-reviewed

Ulgudur, Nilufer/0000-0003-3410-0598 WOS: 000462970500008 PubMed: 30624833 Although anaerobic digestion is a well-established technology, the treatment and disposal of the digestate still presents a challenge due to lack of viable methods for processing. The residual organic matter in digestates also creates a significant residual biogas potential. This fact indicates that the digestates need further processing not only to reduce their organic content for disposal, but also to capture the biogas associated with this residual organic content. This study investigated anaerobic treatment and residual biogas potential of digestates obtained from five full-scale farm-based digesters. The results indicated that it was possible to reduce the total chemical oxygen demand (CODt) of the digestates with an efficiency of 21%-84%. The corresponding biogas yields of digestates ranged between 0.078 and 0.326 L-biogas/g VSadded. This level of biogas production is comparable to the biogas production potential of several commonly used raw substrates.(C) 2019 Water Environment Federation Office of Scientific Research Projects Coordination of Middle East Technical University [BAP-03-11-2016-002] This study was supported by Office of Scientific Research Projects Coordination of Middle East Technical University [BAP-03-11-2016-002].

Composting process parameters such as C/N ratio, moisture content, and temperature are well studied, but limited knowledge exists on energy consumption of the process itself. In this study, co-composting of rose oil-processing wastes (ROPW) with caged layer manure and straw was performed to optimize the system in terms of energy use. Intermittent aeration applied to the five compost mixtures with initial C/N ratios of 12.81, 21.37, 24.66, 29.22, and 37.41 was conducted using fifteen identical cylindrical reactors with volume of 60 L. O2 and CO2 concentrations, compost temperature, dry matter loss, organic matter loss, electrical conductivity, and pH were measured. A first-order kinetic model based on material mass balance was applied to determine kinetic parameters such as decomposition rate and compost equilibrium mass. An equation describing specific energy per initial dry mass of composting as a function of initial C/N ratio was presented and used to optimize initial C/N ratio to maximize composting of ROPW to reach a given level of compost mass ratio. The maximum decomposition, based on dry matter loss, occurred at the initial C/N ratio of 30.18 was 0.032 kg kg−1 day−1. Initial C/N ratio to minimize specific energy use of ROPW composting with caged layer to reach a given level of compost ratio of 0.82 was 29.11. Composting operation can be performed at this initial C/N ratio (29.11) to minimize airflow to keep the power requirement low while still operating the system efficiently. This helps to reduce the energy required for ROPW composting with caged layer to reach a given compost mass ratio. © 2016 American Institute of Chemical Engineers Environ Prog, 2016

Additives applied to animal manure slurries can affect the chemical composition and the biological processes of slurries during storage, with possible improvement of their management and reduction of environmental problems. Some new formulations are marketed claiming a nitrogen (N) removal effect due to denitrification, with the consequence of a reduced N content in the manure after storage. This study evaluated the effects of one of these commercial additives (BACTYcomplex) on slurry characteristics and N losses at a commercial piggery. The additive was applied to four different sectors of the piggery, each with an independent under-floor slurry pit; four other sectors served as controls without treatment. Pits were emptied every 4 wk, and the manure was analyzed for total and ammonia-N and total and volatile solids. Slurry samples from the last month of the on-farm assessment were removed and stored thermostatically in vessels external to the piggery. A subsample of slurry that was treated with the additive at the piggery was treated with an additional dose of additive at the beginning of long-term storage. The additive did not change the composition of the slurry during in-house storage (4 wk duration). During the 155 d of external thermostatic storage, the total solids content of treated slurry was reduced by 18% compared with control slurry, but the N content and composition of treated slurry was unaffected. The additive had a positive effect in accelerating the stabilization of the slurry but did not modify N losses.

Solid-liquid separation is performed to improve slurry management, and acidification of the slurry is used to reduce ammonia emissions. Acidification is known to affect slurry characteristics, and we hypothesized that it may affect mechanical separation. Our objective in this study was to assess the effects of slurry acidification on particle size distribution and separation efficiency. Two types of slurry, aged pig and fresh dairy, and two different acidification additives, sulfuric acid and aluminum sulfate (alum), were studied. We found that acidification with sulfuric acid promoted phosphorus (P) solubilization for both slurries, but no change was observed with alum. More ammonium was found in the acidified dairy slurry compared with raw dairy slurry, but no difference was found in aged pig slurry. Acidification before separation increased the proportion of the solid fraction in the slurries, and the effect was significantly higher with alum. When alum was used to acidify the slurries, the proportion of particles larger than 100 μm increased significantly, as did the P concentration in this particle size range. The efficiency of P separation increased markedly in both slurries when alum was used, with the removal to the solid fraction of the dairy slurry being almost complete (90%). Because the priority in mechanical separation is to increase the P content in the solid fraction, the use of alum before centrifugation may be the most suitable option for enhancing its nutrient content. We conclude that separation efficiency and particle size distribution are significantly affected by acidification, but the extent of the effects depends on slurry type and on the type of additive used for acidification.

BACKGROUND Microbial fuel cells (MFCs) directly convert the chemical energy present in wastewater into electricity. Enriching exoelectrogenic bacteria in the anode biofilm is a current and challenging research target. A multiparametric control strategy, focused on organic loading rate (OLR) and external resistance (Rext) parameters, is here proposed to enhance microbial selection in MFCs. RESULTS The study examines the performance of a swine manure fed MFC working at optimal electrical condition. Maximum power point tracking (MPPT) control was adopted to continuously optimize applied Rext. Subsequent OLR decreases were performed to gradually improve anodic biofilm exoelectrogenic activity. The study demonstrates that high OLRs (11.2 kg COD m−3 d−1) limit MFC electrochemical losses, and increase absolute values of organic removal rate (4.6 kg COD m−3 d−1) and current production (14.9 mA). On the other hand, low OLR adoption (0.7 kg COD m−3 d−1) results in higher organic matter removal (52%) and coulombic efficiency (higher than 70%) of the MFC. CONCLUSION A multiparametric control for MFCs is proposed. Combining MPPT control and low OLR results in rapid improvement of exoelectrogenic activity in MFCs biofilm. The developed strategy may be useful for future MFCs applications, in order to achieve efficient start-up and sustainable operation. © 2015 Society of Chemical Industry

BACKGROUND In 2012, 9.3 million head of dairy cows in the USA produced an estimated 20 million metric tons of manure solids, but little value was gained from this manure. There is a pressing need to enhance manure resource recovery efforts, as dairy manure has potentially significant environmental impacts. This study evaluated components of an integrated suite of biological processes designed to maximize resource recovery from dairy manure, in which algae grown on polyhydroxyalkanoate (PHA) production effluent (PHA-algae) were fermented and anaerobically digested to determine process impacts. RESULTS A 10% PHA-algae supplement produced 11% more volatile fatty acids (VFA) during fermentation and 11% more methane during anaerobic digestion (AD) (vs. dairy manure); the PHA-algae biogas also contained a higher percentage (62.7 vs. 59.1%) of methane than manure biogas. Algal augmentation exhibited no negative effect on fermenter or AD operation. Quantitative polymerase chain reaction (PCR) showed that the ADs contained substantial populations of both acetoclastic and hydrogenotrophic methanogens, which, given the heterogeneous substrate, enhanced process stability. There were significant differences between PHA-algae batches, and large quantities of COD were released during algae freezing. CONCLUSION PHA-algae yielded more VFA during fermentation, and a more methane-rich biogas following AD than dairy manure. A 10% PHA-algae supplement caused no process disturbance in normal manure flora. © 2015 Society of Chemical Industry

Obtaining a reliable estimation of the methane potential of organic waste streams in anaerobic digestion, for which a biochemical methane potential (BMP) test is often used, is of high importance. Standardization of this BMP test is required to ensure inter-laboratory repeatability and accuracy of the BMP results. Therefore, guidelines were set out; yet, these do not provide sufficient information concerning origin of and the microbial community in the test inoculum. Here, the specific contribution of the methanogenic community on the BMP test results was evaluated. The biomethane potential of four different substrates (molasses, bio-refinery waste, liquid manure and high-rate activated sludge) was determined by means of four different inocula from full-scale anaerobic digestion plants. A significant effect of the selected inoculum on the BMP result was observed for two out of four substrates. This inoculum effect could be attributed to the abundance of methanogens and a potential inhibiting effect in the inoculum itself, demonstrating the importance of inoculum selection for BMP testing. We recommend the application of granular sludge as an inoculum, because of its higher methanogenic abundance and activity, and protection from bulk solutions, compared with other inocula.

BACKGROUND The anaerobic–aerobic system is considered an efficient process for simultaneous removal of organic matter and nitrogen from animal manure wastewater. In this work, coupled simultaneous methanogenesis and denitrification (SMD) and shortcut nitrification–denitrification (SND) was investigated to treat animal manure wastewater having high concentrations of nitrogen and organic matter. RESULTS The best COD and NO2−-N removal efficiency was achieved when the influent COD loading rate in the anaerobic reactor was 3 kg m-3 d−1 and the COD/NO2−-N ratio was above 30. It was advantageous to the treatment of high-strength ammonia animal manure wastewater to adopt SND when the pH and free ammonia were about 8.0 and 18 mg L−1, respectively. The average efficiency of of removal COD, NH4+-N, and total nitrogen when adopting the coupling technology was 96.7%, 94.9% and 86.5%, respectively, and the nitrite accumulation rate reached 94.55%. CONCLUSION This study suggested that it was technically feasible to adopt SMD–SND coupling technology of to treat animal manure wastewater with high concentrations of nitrogen and organic matter. © 2013 Society of Chemical Industry © 2013 Society of Chemical Industry

A prerequisite for efficient ammonia removal in air stripping is that the pH of the liquid to be stripped is sufficiently high. Swine manure pH is usually around 7. At pH 7 (at 20°C), only 0.4% of ammonium is in ammonia form, and it is necessary to raise the pH of swine slurry to achieve efficient ammonia removal. Because manure has a very high buffering capacity, large amounts of chemicals are needed to change the slurry pH. The present study showed that efficient air stripping of manure can be achieved with a small amount of chemicals and without strong bases like NaOH. Slurry was subjected to aerobic biological treatment to raise pH before stripping. This facilitated 8 to 32% ammonia removal without chemical treatment. The slurry was further subjected to repeated cycles of stripping with MgO and Ca(OH)(2) additions after the first and second strippings, respectively, to raise slurry pH in between the stripping cycles. After three consecutive stripping cycles, 59 to 86% of the original ammonium had been removed. It was shown that the reduction in buffer capacity of the slurry was due to ammonia and carbonate removal during the stripping cycles.

This study investigates the prevailing microbial communities during the composting of vegetable waste, cattle manure and saw dust, in a household (250 l) batch scale Rotary Drum composter and Windrow Pile. Physico-chemical parameters were analyzed to study the organic matter transformations. Total organic matter reduced from 63.8% to 36.2% in rotary drum and 39.6% in windrow pile composting. The C/N ratio decreased from 26.52 to 8.89 and 14.33 in rotary drum and windrow pile composting. The indigenous population of total heterotrophic bacteria decreased in rotary drum and windrow pile composting after 20 days. However, total fungal load initially increased within initial 4 days, then subsequently reduced in final composts. The average number of fecal coliforms and fecal Streptococci showed decrement with time, in both composting systems. Escherichia coli and Salmonella species number deduced during the study. Composting cycle started with Gram positive rods but ended up with the dominance of Gram negative bacilli shaped bacteria. Transformation of organic compounds during the biodegradation of organic waste, difference in the utilization of nutrients (organic matter) by the different group of microbes and high temperature could be cited as a possible reason of the above changes. Scanning electron microscopy has been used to obtain the surface structures of the cultured mycoflora. Results of the study revealed that higher diversity of microbes prevailed in rotary drum as compared to windrow pile, yielding more stable and pathogenic free compost in lesser period of composting. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Researchers tested using pulsed electric field (PEF) technology to enhance conversion of organic solids material in waste activated sludge (WAS) and pig manure to soluble and colloidal forms, which are more bioavailable for methane production during subsequent anaerobic digestion. Operating parameters were varied from 1.1 to 19.8 kWhr/m 3 to show the influence amount of treatment has on soluble chemical oxygen demand (SCOD), small colloidal solids, and methane production via the biochemical methane potential test. When PEF treatment exceeded a threshold, which was approximately 10 kWhr/m 3 , focused pulsed treatment solubilized approximately 10% of the total COD, increasing SCOD from as low as 20 mg/L to more than 1000 mg/L. The process also disrupted a larger portion of the volatile suspended solids (VSS) to form small colloids not measured by the VSS assay (between 0.2 and 1.2 μm). The effects increased the biological methane potential of the samples significantly: by 80% for pig manure and 100% for WAS after 25 to 30 days. These results support the conclusion that PEF pretreatment before anaerobic digestion has the potential to significantly improve digester performance, resulting in added methane production and decreased residual biosolids.

Appropriate treatment of agricultural waste is necessary for the protection of public health in rural areas because land-applied animal manure may transmit zoonotic disease. In this study, we evaluated the potential of using a pilot anaerobic membrane bioreactor (AnMBR) to treat agricultural waste. The AnMBR system, following a conventional complete mix anaerobic digester (CMAD), achieved high removals of biological and chemical agents. The mean log 10 removals of Escberichia coli, enterococci, Clostridium perfringens, and coliphage by the AnMBR were 5.2, 6.1, 6.4, and 3.7, respectively, and for the CMAD were 1.5, 1.2, 0.1, and 0.5, respectively. Compared with other indicators, coliphage was observed most frequently and had the highest concentration in effluent samples. Bovine adenoviruses and bovine polymaviruses (BPyV) were monitored in this study using nested PCR methods. All of the CMAD influent and CMAD effluent samples were positive for both viruses, and three AnMBR effluent samples were BPyV positive. The mean removals of total Kjeldahl nitrogen, total phosphate, chemical oxygen demand, total solids, and volatile solids by the entire system were 31, 96, 92, 82, and 91%, respectively, but there was no rernoval of ammonium. When the AnMBR was operated independent of the CMAD, AnMBR achieved similar E. coli and enterococci removals as the combined CMAD/AnMBR system. The high quality of effluent produced by the pilot AnMBR system in this study demonstrated that such systems can be considered as aiternatives for managing animal manure.

Acidogenic digestion with lime pretreatment was proposed as a means of reducing soluble reactive phosphorous concentrations in dairy cow manure while producing calcium carboxylate salts as a chemical platform for production of fuels and chemicals via the MixAlco Process. When concentrated in small geographic areas, large dairy operations can have environmentally harmful impacts on their watersheds, due to excess nutrients causing eutrophication of local water bodies. In Central Texas, as in many other areas, phosphorous contamination from confined animal feeding operations is a leading cause of human induced eutrophication. It was found that lime pretreatment followed by acidogenic or methanogenic anaerobic digestion led to substantial reductions in soluble reactive phosphate (SRP) levels while also producing potentially valuable products. Dairy manure filtrate was analyzed for SRP before and after the process steps of lime pretreatment and anaerobic digestion. An average reduction of SRP by 89% was observed through the two step process for lime pretreatment coupled with acidogenic digestion. Acidogenic digestion was demonstrated to produce mixed organic acids at mesophillic temperatures and primarily acetic acid at thermophillic temperatures. Using the MixAlco Process, the carboxylate salts of these organic acids could potentially be converted into marketable fuels and chemicals. © 2008 American Institute of Chemical Engineers Environ Prog, 2009

BACKGROUND: The production of biodegradable wastes and their disposal cause a major financial problem in many industrial activities. Co-composting was thought to be a feasible alternative for disposing of a strongly alkaline waste from the pharmaceutical industry (AW), mainly consisting of animal fats and partially hydrolysed proteins in a stable emulsion. The AW was added gradually, during the early phase of the composting process, to a substrate made up of ‘alperujo’ (AL), the wet, lignocellulosic, solid by-product of the olive oil industry, and fresh horse manure, which was added to improve the physical structure of the composting substrate. RESULTS: The addition of AW reduced organic matter degradation during composting, enriched the amount of organic compounds in the water- and alkali-soluble fractions and increased mineral salt contents. Thus, significantly higher electrical conductivity, humification indices and contents of organic matter, P, K and Na were recorded in the end-composts resulting from AW treatments. However, the application of one AW-based compost led to soil N immobilisation, as revealed by an incubation experiment, which must be considered in order to avoid potential N starvation in the short term. CONCLUSION: According to these results, composting can be used as a disposal alternative for AW, leading to end-products with potential uses as organic amendments or fertilisers for agricultural systems. In addition, these composts could be used to produce alternative liquid organic fertilisers, based on the extraction of their humic-like fraction. Copyright © 2009 Society of Chemical Industry

To control ammonia (NH(3)) volatilization from the dairy cattle (Bos taurus) manure composting process, a compost pile was covered with mature compost and the gas emissions evaluated using the dynamic chamber system. The peak of NH(3) volatilization observed immediately after piling up of the compost was reduced from 196 to 62 mg/m(3) by covering the compost pile with mature compost. The accumulation of NH(4)-N to the covered mature compost was also observed. Covering and mixing the compost with mature compost had no effect on the microbial community structure. However, over time the microbial community structure changed because of a decrease in easily degradable organic compounds in the compost piles. The availability of volatile fatty acids (VFA) was considered to be important for microbial community structure in the compost. After the VFA had disappeared, the NO(3)-N concentration increased and the cellulose degrading bacteria such as Cytophaga increased in number.

BACKGROUND: The concentration of ATP in selected samples from the composting process of several organic wastes (municipal solid wastes, wastewater sludge, animal by-products and cow manure) has been determined in order to characterize the aerobic biological activity of such wastes. RESULTS: The values obtained ranged from 0 (in old stable compost from cow manure) to 0.07 µmol ATP g−1 dry matter in thermophilic samples of municipal solid wastes composting. In general, it was found that ATP levels were in agreement with the stage of the composting process (initial stage, thermophilic period and maturation). On the other hand, ATP concentration correlated well (P < 0.05) with the overall respiration activity during a complete composting process of municipal solid waste at full scale. CONCLUSION: ATP concentration can be used to determine the biological activity of organic solid wastes in different stages of their biological treatment and to predict compost stability prior to soil application. Copyright © 2008 Society of Chemical Industry

BACKGROUND: Nitrogen removal by organic biofilters treating pig manure is incomplete and has to be optimized. This could be achieved by promoting the activity of denitrifiers, this being the limiting factor for nitrogen removal in this kind of process. However, changing the operating conditions could impair nitrification; no data are currently available about the activity and distribution of nitrifiers in organic biofilters. A better knowledge of the process of colonization by nitrifiers is needed to determine their potential to oxidize ammonia and whether they share the same physical space as denitrifiers or not. RESULTS: Data showed that nitrifiers were principally localized near the surface and that a microbiological gradient, in terms of nitrifying activity, was present from top to bottom. Moreover, in each section studied, the potential nitrifying activity measured was always higher than the observed nitrifying activity. These results suggest that the biomass had the capacity to oxidize more ammonia and that these transformations occurred near the surface of the biofilter. However, nitrifying activities were not limited by environmental factors but rather by the concentration of ammonia supplied to the process. CONCLUSIONS: Because denitrifiers and nitrifiers share the same physical space in this kind of process, particular precautions will have to be taken to maintain nitrification, while modifying conditions to promote denitrifier activity. Copyright © 2007 Society of Chemical Industry

Composting can provide a viable alternative for poultry manure management in the Fraser Valley of British Columbia, Canada. However, it has a high potential for ammonia emission because of the high nitrogen content of poultry litter. The objective of this study was to reduce ammonia emission by precipitating ammonia into struvite before it can volatilize from the composting matrix. Nitrogen transformation occurs during composting, but struvite formation can help to conserve nitrogen, and does not allow a large amount of nitrogen to be released into the environment as ammonia or nitrate, because ammonium-nitrogen becomes bound in struvite. It would also be possible to remove phosphorus from the manure. A laboratory-scale experiment was conducted to examine the feasibility of struvite formation during poultry manure composting. Magnesium and phosphate salts were supplemented to create favorable conditions to form struvite. Results indicated that ammonia emission was reduced by 40% to 84%, while the nitrogen retention in compost was enhanced. The struvite formed in compost was confirmed by means of X-ray diffraction; and scanning electron microscopy with energy dispersive X-ray spectroscopy. Copyright © 2007 Society of Chemical Industry

This paper describes the enhancement of biogas production in laboratory-scale anaerobic digesters (with batch and semi-continuous operation) using iron-enriched duckweed as a supplement to the digestion of feedstock. The relationship between the level of enhancement achieved and the retention period of the digesters was also investigated. The trials demonstrated that, in batch digesters, iron-enriched duckweed significantly improved the rate of microbial succession. Batch digesters receiving no duckweed took 40 days to reach peak methane production compared to 15 days when duckweed was added. In the semi-continuous digesters, an increase in gas production of about 44% was observed.

Over the last three decades there has been a great increase in the production of waste from urban, industrial and agricultural activity that could be recycled as a source of plant nutrients, and used to enhance soil quality. The use of these materials could partially offset the need for mineral fertilizers, giving both economic and environmental benefits. An incubation experiment was carried out using different organic waste materials applied to a Cambic Arenosol. Air-dried soil was mixed with increasing amounts of composted solid municipal waste, secondary pulp-mill sludge, hornmeal, poultry manure, solid phase from pig slurry, and composted pig manure, resulting in applications equivalent to 0, 40, 80, 120, 160 and 200 kg ha -1 of Kjeldahl nitrogen. The samples were incubated for 244 days under a controlled environment of 24°C and 60% water holding capacity of the soil. The increasing amounts of waste applied always led to a greater amount of potentially available nitrogen present in the soil/waste mixture. Based on the proportion of their active N fraction, wastes were ranked: poultry manure > hornmeal > solid phase from pig slurry > composted pig manure > secondary pulp-mill sludge > composted municipal solid waste. The results were well described by a one-pool exponential mineralization model, and mineral N formation was proportional to the quantity of waste applied. Of the wastes tested, those from animal sources showed greater nitrogen mineralisation. Nitrification was rapid, and concentrations of ammonium nitrogen remained relatively small.

Vast 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

Batch anaerobic codigestion of municipal household solid waste (MHSW) and digested manure in mesophilic conditions was carried out. The different waste-to-biomass ratios and intensity of mixing were studied theoretically and experimentally. The experiments showed that when organic loading was high, intensive mixing resulted in acidification and failure of the process, while low mixing intensity was crucial for successful digestion. However, when loading was low, mixing intensity had no significant effect on the process. We hypothesized that mixing was preventing establishment of methanogenic zones in the reactor space. The methanogenic zones are important to withstand inhibition due to development of acids formed during acidogenesis. The 2D distributed models of symmetrical cylinder reactor are presented based on the hypothesis of the necessity of a minimum size of methanogenic zones that can propagate and establish a good methanogenic environment. The model showed that at high organic loading rate spatial separation of the initial methanogenic centers from active acidogenic areas is the key factor for efficient conversion of solids to methane. The initial level of methanogenic biomass in the initiation centers is a critical factor for the survival of these centers. At low mixing, most of the initiation methanogenic centers survive and expand over the reactor volume. However, at vigorous mixing the initial methanogenic centers are reduced in size, averaged over the reactor volume, and finally dissipate. Using fluorescence in situ hybridization, large irregular cocci of microorganisms were observed in the case with minimal mixing, while in the case with high stirring mainly dead cells were found.

An important but little understood aspect of bioenergy production is its overall impact on soil carbon (C) and nitrogen (N) cycling. Increased energy production from biomass will inevitably lead to higher input of its by-products to the soil as amendments or fertilizers. However, it is still unclear how these by-products will influence microbial transformation processes in soil, and thereby its greenhouse gas (GHG) balance and organic C stocks. In this study, we assess C and N dynamics and GHG emissions following application of different bioenergy by-products to soil. Ten by-products were selected from different bioenergy chains: anaerobic digestion (manure digestates), first generation biofuel by-products (rapeseed meal, distilled dried grains with solubles), second-generation biofuel by-products (nonfermentables from hydrolysis of different lignocellulosic materials) and pyrolysis (biochars). These by-products were added at a constant N rate (150 kg N ha-1) to a sandy soil and incubated at 20 °C. After 60 days, >80% of applied C had been emitted as CO2 in the first-generation biofuel residue treatments. For second-generation biofuel residues this was approximately 60%, and for digestates 40%. Biochars were the most stable residues with the lowest CO2 loss (between 0.5% and 5.8% of total added C). Regarding N2O emissions, addition of first-generation biofuel residues led to the highest total N2O emissions (between 2.5% and 6.0% of applied N). Second-generation biofuel residues emitted between 1.0% and 2.0% of applied N, with the original feedstock material resulting in similar N2O emissions and higher C mineralization rates. Anaerobic digestates resulted in emissions