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United States Department of Agriculture

Agricultural Research Service

2006 Annual Report

1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter?
Maryland's dairy farms, like those across the nation, face the increasingly difficult task of containing manure nutrients on-farm. Even using best manure management practices, a large fraction of manure nitrogen is lost to the atmosphere as ammonia from barns, manure lagoons and during land application. Of course, this nitrogen isn't lost at all, but typically returns to the local watershed during the next precipitation event. However, even if dairies were given unlimited financial resources to cut these nitrogen losses, there are few appropriate technologies and fewer still that have been tested with manure liquids. There is a urgent need to provide farmers with economically and technologically appropriate effluent treatment systems that efficiently recycle manure nutrients. By immediately treating manure effluent, the environmental risks, odors, and atmospheric emissions associated with manure lagoons will also be greatly reduced or eliminated. In this project we will continue to develop and evaluate algal systems for the treatment of dairy and swine manure effluents with respect to capturing N and P from raw and anaerobically digested dairy manure effluents, utilization of the algal biomass, and overall system nutrient uptake efficiency and costs of integrated farm-scale systems.

Modern livestock production also involves the use of antibiotics as growth promoters and for therapeutic purposes. When untreated manures are applied on the field, any remaining content of antibiotics or metabolites present in the manure may reach surface water by either run-off or leaching. Due to their biological activity, antibiotics are potential micro-pollutants. In this project, we will determine levels and biological effects of the antibiotics oxytetracycline and chlorotetracycline in manure from treated animals on composting, anaerobic digestion, and land application. We will also determine levels of antibiotic resistant organisms in manures from animals treated with oxytetracycline and chlorotetracycline.

2.List by year the currently approved milestones (indicators of research progress)
FY06: Completed improvement of N and P mass balance from dairy manure effluent using algal treatment; completed energy and cost projections for dairy manure effluent treatment using algal technology; determine manure treatment method that degrades oxytetracycline (OTC) most effectively; determine effect of OTC on efficiency of composting and anaerobic digestion treatment processes.

FY07: Development of alternative (non-fertilizer) uses for algal biomass from manure effluent treatment; optimization of algal treatment processes for swine effluent; determine treatment method that degrades chlorotetracycline (CTC) most effectively; determine effect of CTC on efficiency of composting and anaerobic digestion.

FY08: Optimization of algal biomass harvesting and processing for nutrient conservation and pathogen control; completed guidelines for algal treatment technologies for dairy manure effluent; determine effect of manure treatment processes on OTC and CTC resistant organism populations in treated manures.

FY09: Completed guidelines for algal treatment technologies for swine manure effluent; completed guidelines for treating manure for degradation of antibiotic residues.

4a.List the single most significant research accomplishment during FY 2006.
Completed economic assessment of algae-based manure treatment technology at the farm-scale for a hypothetical 1000-cow dairy. The vulnerability of ecosystems and groundwater to pollution has forced increasingly stringent environmental regulations to be imposed on dairy farms. However, harnessing solar energy to grow algal biomass on wastewater nutrient could provide a holistic solution to nutrient management problems at livestock operations. Since anaerobic digestion increases the availability of manure nutrients, the combination of anaerobic digestion followed by algal production could be synergistic. In addition, energy recovered from manure by digestion can be used for drying the biomass and carbon dioxide from burned biogas can be directly recycled back into the algal ponds. In this study, we assessed the economics of the Algal Turf Scrubber (ATS) treatment technology at the farm-scale for a hypothetical 1000-cow dairy. The majority of capital costs were due to land preparation, installation of liner material, and engineering fees. The majority of operational costs were due to energy requirements for water pumps, biomass drying, and to labor costs. On farms using anaerobic pretreatment, waste heat from burning of biogas could be used to offset approximately 90% of the energy requirements of biomass drying. Under the best case (algal treatment system coupled with anaerobic digestion pretreatment), the yearly operational costs per cow, per kg of nitrogen, per kg of P, and per kg of dried biomass were $404, $5.50, 27.60, and $0.68, respectively. Although the annual costs per animal are very high compared to the average net profit per animal in Maryland ($500-$1000), the costs are very low compared to other strategies under consideration for meeting N and P targets within the Chesapeake Bay watershed.

4b.List other significant research accomplishment(s), if any.
Determined the fate and effect of the antibiotic oxytetracycline (OTC) during composting of manure from treated beef calves. OTC is the most widely used tetracycline compound and is administered to animals to control intestinal and respiratory infections. Repeated application of manure containing tetracyclines to agricultural soils may increase , because of their high persistence and adsorption capability. Composting is a treatment process that is increasingly integrated into manure management operations. Although there is no information on the effect of composting on tetracyclines and their residues, a variety of studies have shown significant reductions of other relatively persistent organic compounds. The objectives of this study were two-fold: to determine whether OTC residues in manure from treated beef calves inhibit composting microbial processes and to determine the effect of composting on levels of extractable OTC in manure. Approximately 23 % of the OTC fed to the calves was recovered in the manure. The presence of OTC did not appear to affect composting processes. Within the first six days of composting, levels of extractable OTC in the compost mixture decreased from 115 ug/g dry weight to less than 6 ug/g dry weight (a 95% reduction). In contrast, levels of extractable OTC in room temperature incubated and sterilized mixtures decreased only 12 and 25 % after 37 and 35 days, respectively. Levels of total bacteria and OTC resistant bacteria in the finished compost mixture were roughly 30 fold higher and 10 fold lower, respectively, than levels in the mixture prior to composting. Although the basis of the OTC disappearance during composting is not known, the preponderance of OTC sensitive bacteria and the decrease of OTC resistant bacteria in the finished compost suggests that OTC residues have been rendered biologically inactive or unavailable. Farmers should be advised of the persistence of OTC in untreated manure and could compost manure (especially within the first week of treatment) to reduce OTC residues. Other research in our lab has shown that OTC residues in manure is not effectively reduced during anaerobic digestion and reduces biogas production.

Showed that extractable residues of chlorotetracycline (CTC) in manure from treated calves rapidly decrease during composting. Preliminary results from incubation studies using sterilized manure samples showed that removal is not due to biological processes, but instead is due to enhanced binding of antibiotic residues at composting temperatures (> 55 C). Farmers should be advised of the persistence of CTC in untreated manure and could compost manure (especially within the first week of treatment) to reduce CTC residues.

In collaboration with a scientist from Virginia Tech, initiated experiments on the effect of manure loading rate on algal total lipid and fatty acid content. Microalgae are a potential source for renewable oil production. Although this research area has been the focus of numerous studies over nearly 50 years, microalgal bioenergy production has been limited largely because of the difficulty of harvesting and drying biomass from suspended microalgal culture systems. However, as the quest for renewable energy sources intensifies, there is renewed interest in microalgal production for bioenergy, especially in regard to oil production from microalgal systems designed to treat agricultural wastewater or animal manure. Our research has focused on the use of filamentous freshwater algae for manure treatment because the resulting biomass is relatively easy to harvest and dewater. The objective of this study was to determine the effect of manure loading rates on the lipid content of freshwater filamentous algae grown in algal turf scrubbers (ATS) with and without carbon dioxide supplementation. Algal biomass was harvested weekly from laboratory scale ATS units using three loading rates of anaerobically digested dairy manure effluent corresponding to daily loading rates of 0.37 to 1.8 g total N per sq. meter. The harvested algal biomass was air dried, ground, and stored at 20 C prior to lipid analysis. The total lipid content of the dried biomass from ATS grown with CO2 supplementation was roughly 7% of dry weight and did not change with increased loading rate. In contrast, the total lipid content of dried biomass from ATS grown without CO2 supplementation increased with loading rate from 7 to 11% of dry weight. Further experiments will focus on manipulation of algal growth conditions and algal inocula to enrich for species with increased lipid content.

The Choptank watershed on Maryland's eastern shore was monitored for a year to establish baseline data on antibiotic, heavy metal, and hormone levels in water and sediment samples. Samples were obtained from 14 subwatersheds of the Choptank system and from the Choptank itself, at 4 equally-spaced time intervals over a year. Concentrations of two antibiotic class groups, the sulfonamides and the tetracyclines, were measured as well as steroidal compounds including natural hormones and the birth control agent 17 alpha- ethinylestradiol. Three of the 14 subwatersheds had repeated detections of the tetracycline class of antibiotics. In addition, sediment samples from the Choptank contained measurable concentrations of chlorotetracycline and sulfamethaxazole. It appears that sediment samples provide better long-term monitoring for these compounds than water sampling. Higher levels of copper and arsenic were positively correlated with the sampling sites where higher antibiotics were detected. Hormone levels were mostly below the detection limit of the atmospheric ionization mass spectrometric method that was being used. Improvements in the method appear to be needed to detect hormones at typical field levels in samples at these locations. Animal feeding operations are likely sources for the higher levels of antibiotics and arsenic that were detected. This baseline information will be useful for evaluating the effects of future changes in land use and agricultural practices.

4c.List significant activities that support special target populations.

5.Describe the major accomplishments to date and their predicted or actual impact.
This was the first full year of this project. The major accomplishments are listed above in 4a and 4b.

6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
The major constraint on adoption of the algal based manure treatement technology is its cost to producers. Implementation of nutrient trading credit programs within the Chesapeake Bay region will provide the needed financial incentive to producers and/or associated support industries to adopt this technology.

7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).

Review Publications
Pizarro, C.X., Mulbry III, W.W., Blersch, D., Kangas, P. 2006. An economic assessment of algal turf scrubber technology for treatment of dairy wastewater. Ecological Engineering. 26:321-327.

Arikan, O.A., Sikora, L.J., Mulbry III, W.W., Khan, S.U., Rice, C. 2006. The fate and effect of oxytetracycline during the anaerobic digestion of manure from therapeutically treated calves. Process Biochemistry. 41:1637-1643.

Last Modified: 7/30/2014
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