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Antibiotic distribution and analysis within liquid and solid fractions of manure are highly variable due to each compound's respective physiochemical properties. This study developed and evaluated a uniform method extracting 10 antibiotics from 4 antibiotic classes (tetracycline, sulfonamides, macrolides, and β-lactam) from unprocessed manure, solid–liquid separated manure, and composted solids. Through systematic manipulation of previously published liquid chromatography tandem mass spectrometry methods; this study developed an extraction protocol with optimized recovery efficiencies for varied manure substrates. The method includes a two-step, liquid-solid extraction using 10 mL of 0.1 M EDTA-McIlviane buffer followed by 10 mL of methanol. Antibiotics recoveries from unprocessed manure, separated liquids, separated solids, and heat-treated solids using the two-step extraction method had relative standard deviations < 30% for all but ceftiofur. Total antibiotic recoveries were 67–131% for tetracyclines, 56% for sulfonamide, 49–53% for macrolides, and 1.3–66% for β-lactams. This is the first study to use one protocol to assess four classes of antibiotics in liquid and solid manure fractions. This study allowed for more precise risk assessment of antibiotic transport in manure waste stream applied to fields as a liquid or solid compost. [ABSTRACT FROM AUTHOR]

Lasalocid is an antibiotic from the group of carboxylic ionophores, and it is commonly used in cattle and poultry as a coccidiostat and for growth promotion. The widespread use and persistence of lasalocid have led to its detection in the environment. The objective of this study was to determine the fate and effect of veterinary ionophore lasalocid during the anaerobic digestion of dairy manure. Duplicate plug flow field-scale digesters were operated using either non-amended dairy manure or dairy manure amended with 1 or 5 mg/L lasalocid. Results showed that lasalocid was reduced approximately 75% during anaerobic digestion. Methane production from digesters treating manure amended with 1 and 5 mg/L lasalocid were comparable with CH4 production from the duplicate digesters operated without added lasalocid. These results suggest that anaerobic digestion can be used to reduce lasalocid levels in dairy manure, and lasalocid did not affect digester stability at concentrations expected in dairy manure. [ABSTRACT FROM AUTHOR]

Forage radish, a winter cover crop, was investigated as a co-substrate to increase biogas production from dairy manure-based anaerobic digestion. Batch digesters (300 cm 3 ) were operated under mesophilic conditions during two experiments (BMP1; BMP2). In BMP1, the effect of co-digesting radish and manure on CH 4 and H 2 S production was determined by increasing the mass fraction of fresh above-ground radish in the manure-based co-digestion mixture from 0 to 100%. Results showed that forage radish had 1.5-fold higher CH 4 potential than dairy manure on a volatile solids basis. While no synergistic effect on CH 4 production resulted from co-digestion, increasing the radish fraction in the co-digestion mixture significantly increased CH 4 production. Initial H 2 S production increased as the radish fraction increased, but the sulfur-containing compounds were rapidly utilized, resulting in all treatments having similar H 2 S concentrations (0.10–0.14%) and higher CH 4 content (48–70%) in the biogas over time. The 100% radish digester had the highest specific CH 4 yield (372 ± 12 L kg −1 VS). The co-digestion mixture containing 40% radish had a lower specific CH 4 yield (345 ± 2 L kg −1 VS) but also showed significantly less H 2 S production at start-up and high quality biogas (58% CH 4 ). Results from BMP2 showed that the radish harvest date (October versus December) did not significantly influence radish C:N mass ratios or CH 4 production during co-digestion with dairy manure. These results suggest that dairy farmers could utilize forage radish, a readily available substrate that does not compete with food supply, to increase CH 4 production of manure digesters in the fall/winter. [ABSTRACT FROM AUTHOR]

Pilot-scale digesters (850 L) were used to quantify CH 4 and H 2 S production when using forage radish cover crops as a co-digestion feedstock in dairy manure-based digesters. During two trials, triplicate mixed digesters were operated in batch mode with manure-only or radish + manure (27% and 13% radish by wet weight in Trial 1 and 2, respectively). Co-digestion increased CH 4 production by 11% and 39% in Trial 1 and 2, respectively. As H 2 S production rapidly declined in the radish + manure digesters, CH 4 production increased reaching high levels of CH 4 (⩾67%) in the biogas. Over time, radish co-digestion lowered the H 2 S concentration in the biogas (0.20%) beyond that of manure-only digestion (0.34–0.40%), although cumulative H 2 S production in the radish + manure digesters was higher than manure-only. Extrapolated to a farm-scale (200 cows) continuous mixed digester, co-digesting with radish could generate 3150 m 3 CH 4 /month, providing a farmer additional revenue up to $3125/month in electricity sales. [ABSTRACT FROM AUTHOR]

Highlights: [•] ATAs were conducted on four food processing wastes at 2%, 5%, 15% and 30% (by volume). [•] There were significant decreases in pH, with media addition, at each inclusion rate. [•] Above 5% inclusion, all four food processing wastes showed signs of toxicity. [•] Without co-digestion, CH4 production may be inhibited with food processing wastes. [Copyright &y& Elsevier]

Abstract: An emergy analysis was performed to assess the relative sustainability and environmental impact of small-scale energy production using Taiwanese model plug-flow anaerobic digesters to treat livestock manure in Costa Rica. Emergy analysis quantifies all inputs to a system by converting them to solar energy equivalents, thus allowing for direct comparison of the diverse inputs of renewable energies, human labor and economic goods needed to construct and maintain anaerobic digestion systems. The digesters were located on the campus of EARTH University, Costa Rica, and the biogas was utilized to power a 40kW generator that supplies electricity for farm operations. Separate emergy analyses were performed for the biogas production and the combination of biogas production and generation of electricity. Manure was the largest input in both analyses, accounting for 85.3% of the annual emergy input for biogas production and 66.9% for electricity generation from the biogas. The fraction of emergy inputs from renewable sources (ΦR) was 66% for biogas production and 52% for electricity generation from the biogas. The transformities of biogas and electricity generation from the biogas were 5.23E+04sej/J and 1.01E+06sej/J respectively. The emergy yield ratios (EYR) were 2.93 for biogas production and 2.07 for electricity generation indicating that these digesters efficiently match purchased resources and renewable energies to produce energy from livestock manure. The generation of electricity from the biogas resulted in a decrease in the emergy sustainability index (ESI) from 5.67 to 2.22 and an increase in the environmental loading ratio (ELR) from 0.52 to 0.93. Using a generator to convert the biogas to electricity does decrease the sustainability of the system, largely due to the high emergy value associated with the electrical generation equipment and machinery, but these results demonstrate that the production of biogas and the generation of electricity from Taiwanese model digesters in Costa Rica are environmentally sustainable processes that result in the production of energy that is largely dependent on renewable and recycled energies. [Copyright &y& Elsevier]

This study quantified the potential of farm-scale composting to degrade antibiotics in dairy manure. The compost windrow, consisting of sick cow bedding from a 1000-cow US dairy farm, was managed using the dairy farm's typical practices and monitored for tetracycline and nutrient composition. Samples were collected over 33 days, which was the time from compost pile formation to land application as fertilizer, and analyzed for solids, antibiotics, and nutrient content. Average tetracycline concentrations at the beginning of the study (452 ng/g DW) were lower than at the end of composting (689 ng/g DW), illustrating that antibiotic degradation was not greater than degradation of the compost solids. Total Kjeldahl nitrogen (TKN) increased from 15.3 to 18.4 g/kg during the composting period due to decreases in solids and likely inhibition of N-mineralization due to the presence of antibiotics. The results indicated that antibiotics were not completely degraded when using the farm's compost pile management techniques, with antibiotics possibly impacting nitrogen transformation in the compost, which should be considered in nutrient management when using sick cow bedding. Additionally, the results showed that antibiotic degradation during farm-scale composting can vary from reported laboratory-scale due to differences in management, composting duration, and temporal conditions, illustrating the need for more extensive on-farm research including common farm practices and real-world conditions. [ABSTRACT FROM AUTHOR]

• Unmodified biochar added to a digester resulted in 90.5% H 2 S removal efficiency. • The biochar particle size did not significantly affect the H 2 S removal efficiency. • Iron-impregnated biochar resulted in complete removal of H 2 S from the biogas. • Activated carbon was not effective when used as an in-situ desulfurization agent. • Biochar addition did not significantly affect the methane yield during digestion. Corn stover biochar (CSB) and maple biochar (MB) were added into anaerobic digesters and evaluated for hydrogen sulfide (H 2 S) reductions. This was the first study to show Fe-impregnated biochar can eliminate H 2 S production. The novel study evaluated biochar addition on H 2 S reduction and nutrient concentrations using three experiments to test the effect of: 1) biochar concentration, 2) biochar particle size, and 3) Fe-impregnated biochar using triplicate lab-scale reactors. At the highest biochar dose (1.82 g biochar/g manure TS), H 2 S production was 90.5% less than the control treatment (351 mL H 2 S/kg VS). Biochar particle size did not significantly affect H 2 S concentration. The Fe-impregnated biochar (0.5 g biochar/g manure TS) reactors had no H 2 S detected in the CSB-Fe system. Methane (CH 4) in the biochar and control treatments were not significantly different in all three experiments. The results show that biochar added to digesters can significantly reduce H 2 S production without affecting CH 4 production. [ABSTRACT FROM AUTHOR]