Progress 09/01/08 to 02/28/11
Outputs
OUTPUTS: Manure amendments have been touted as a practical manure management alternative for reducing odor emission. Moreover, some amendments are claimed to reduce ammonia, hydrogen sulfide, and/or greenhouse gas (carbon dioxide, methane and nitrous oxide) losses. However, few studies have investigated amendment use in cattle manure. This research investigated 22 dairy manure amendments in a screening trial to select a limited number for replicated study. Replication trials focused on seven amendments which were evaluated by addition to two-kg samples of dairy slurry (urine:feces 1:1.7; 12% solids) in 3.8 L glass jars, following manufacturer's use recommendations. Samples were incubated for 3 d, 30 d and 94 d at 20 degrees C or 10 degrees C. An essential oil feed additive treatment was also included in the study. For this treatment, two kg of manure from cattle on the diet was placed in 3.8 L jars and incubated at the same temperatures and holding times indicated above. Due to logistical constraints, incubation of the 32 treatment samples (7 manure amendments + 1 feed additive x 2 temperatures x 2 replicates) were spread over eight trial events. Untreated control samples were prepared and incubated at times and temperatures identical to treated manure samples. An incubation unit equipment failure with the 10 degree C samples produced freezing conditions, ultimately resulting in an unavoidable decision to repeat this portion of the experiment. Repeat trial treatments were prepared and incubated following the same protocol. Selected duplicate manure sets incubated at 20 degrees C served as a cross check (bridge) to address potentially confounding effects due to differing manure collection dates in the overall study. For all trials, odor emissions from samples were assessed by six qualified odor assessors using internationally recognized standard protocols for Triangular Forced-Choice dynamic olfactometry. Odor quality characterizations were performed to supplement odor emission data. Cotton fabric odor quality characterizations were also performed for selected trials, using 10-cm x 10-cm odorless cotton swatches exposed to slurry jar headspaces for 30 min. Gas emissions were measured using a multi-chamber steady-state detection system under temperature-controlled conditions. The system employed a photoacoustic multi-gas field-monitor and pulsed fluorescence analyzer to measure gas concentrations from each of eight flux chambers every 72 min over a 24-h period. Individual flux chamber vessels consisted of the 3.8-L glass jar containers that were used for incubation. Each flux chamber jar was provided with a continuous supply of filtered, sweep air. Six of the eight flux chamber jars contained 2 kg of manure slurry (treatments and control). Two jars contained distilled water as control vessels, providing a check for cross-contamination of sampling lines and determination of background gas concentration levels. PARTICIPANTS: Arlene Adviento-Borbe: Post-Doc, Agricultural and Biological Engineering [ABE]; statistical analysis, research design, and instrumentation quality-assurance quality-control (QAQC), and written products. Robin Brandt: Lecturer, ABE; Director of the Penn State Odor Assessment Lab; oversee lab and field odor emission collections and human odor-panel QAQC, and written products. Mary Ann Bruns: Associate Professor, Crop and Soil Sciences [CSS]; technical adviser for microbiological and biochemical interaction of manure amendment selection and analysis, and review of written products. Hershel Elliott: Professor, ABE; technical adviser chemical and biochemical analysis of manure amendment trials, and review of written products. Robert Graves: Professor, ABE; technical implementation and analysis of manure storage and barn trials, and review of written products. Alex Hristov: Associate Professor, Dairy and Animal Science [DAS]; implementation and analysis of essential oil nutritional trials, and review of written products. Jessica Tekippe: M.S. Student, DAS; facilitate, conduct, and analyze dairy nutritional trials. Deborah Topper: Technologist, ABE; operator and QAQC of dynamic olfactometer during panel assessment, and written products. Patrick Topper: Senior Research Technologist, ABE; design, fabrication, and operation of odor and gas emission collections, and written products. Gabriella Varga: Professor, DAS; technical implementation and analysis of lactating cow nutritional trials, and review of written products. Eileen Wheeler: Professor, ABE; primary administrative manager and technical director to oversee implementation, QAQC, and analysis of all trials; supervise technologists and post-doc, and written products. Odor Assessors: a group of twenty-two individuals qualified and compensated for odor evaluations. TARGET AUDIENCES: Dairy producers and their advisers (servicemen, veterinarians, Extension educators, etc.) are targeted for odor- and gas emissions-related information. These audiences benefit from odor and gas baseline data and understanding of principles behind the recommendations for mitigation via manure amendments or diet strategy. Manufacturers of some of the products studied have expressed interest in continuing evaluations at field scale. Air quality researchers in other PSU departments and at other universities can access the Penn State Odor Assessment Lab's capabilities. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Twenty-two manure amendments and one feed additive were investigated for efficacy in reducing odor, ammonia, hydrogen sulfide, and greenhouse gas (GHG) emissions from dairy manure. Manure samples were incubated at 20 degrees C and 10 degrees C for 3 d, 30 d and 94 d to assess temporal effectiveness. Amendments representing seven different modes of action were evaluated, including: two microbial digest/enzymes; two oxidizing agent/chemical; one disinfectant; and two essential oils. Odor emission thresholds from treated and untreated manure slurries were determined by six qualified odor assessors following the Triangular Forced-Choice method. Odor quality characterizations were performed, including: hedonic tone (pleasantness), Labeled Magnitude Scale and ASTM odor intensity reference scale method for supra-threshold odor intensity and environmental odor classification descriptors to depict how they were perceived by assessors. Gas emissions were quantified using a multi-chamber steady-state gas emission detection system equipped with a photoacoustic multi-gas analyzer (ammonia and GHG) and pulsed fluorescence analyzer (hydrogen sulfide). No consistent, significant reductions were found for odor and gas emissions for the amendments and feed additive treatments when considering all three storage periods at two storage temperatures. Average daily odor emission rates ranged from 5 to 94 OU(E) cm(-2) d(-1). A significant reduction (31%; P=0.032) in odor emission was found with abandoned mine drainage (AMD) sediment treatment after 3 d at 20 degrees C, suggesting some promise for short-term odor reduction prior to land application of manure. Essential oils, Hyssopus and peppermint, reduced odor emission by 27 to 48% after 94 d at 20 degrees C. But for 30 d at 10 degrees C these essential oil treatments increased odor emission by 29 to 65%. Mean gas emission rates were 1.4 to 2 times higher at 20 degrees C than at 10 degrees C (P=0.04, <0.0001). Only the AMD sediment reduced ammonia and carbon dioxide emissions after both 30 d and 94 d (P=0.02, <0.0001). One microbial digestive treatment (powder enzymes and bacteria) reduced ammonia emission after 94 d (P=0.006, <0.0001) at 10 degrees C and 20 degrees C, and methane emission (12%) after 30 d at 10 degrees C (P=0.005). Storing treated dairy manure for 94 d either at 10 degrees C or 20 degrees C reduced odor and greenhouse gas emissions by 88-100% compared to emissions at 3d. All treated and untreated manure slurries had unpleasant to extremely unpleasant quality and 76 to 100% of odor assessors described the manure samples as offensive, earthy, medicinal and/or fishy. Hedonic tone was related to odor intensity while odor emission was correlated with hydrogen sulfide, methane and carbon dioxide emissions. Odor emission was inversely related to ammonia emission. For the conditions and products investigated in this study, findings show highly variable results.
Publications
- Wheeler, E. F., M. A. A. Adviento-Borbe, R. C. Brandt, P. A. Topper, D. A. Topper, H. A. Elliott, R. E. Graves, A. N. Hristov, V. A. Ishler, and M. A. Bruns. 2010. Amendments for mitigation of dairy manure ammonia and greenhouse gas emissions: Preliminary screening. Submitted CIGR EJournal June 2010; conditional acceptance Oct 2010.
- Wheeler, E. F., P. A. Topper, N. Brown, M. A. A. Adviento-Borbe, R. S. Thomas, and G. A. Varga. 2010. Multiple-chamber steady-state instrumentation for monitoring gas flux from manure. Submitted J. Appl. Engr. Ag summer 2010; peer review completed Jan 2011; revisions underway.
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Progress 09/01/09 to 08/31/10
Outputs
OUTPUTS: Manure amendments may provide practical and cost-effective dairy manure management alternatives for reducing emissions of odor, ammonia, hydrogen sulfide, and greenhouse gases (carbon dioxide, methane and nitrous oxide). Few studies have investigated amendment use in cattle manure. In this reporting period, previous screening trial results that investigated 22 amendments were used to select a limited number of promising amendments for replicated study. Seven odor reducing manure amendments were evaluated by addition to individual two-kg samples of dairy slurry (urine:feces 1:1.7; 12% solids) in 3.8 L glass jars, following manufacturer's use recommendations. Samples were incubated for 3 d, 30 d and 94 d at 20 degrees C or 10 degrees C. An essential oil feed additive treatment was also included in the study. For this treatment, two kg of manure from cattle on the diet was placed in 3.8 L jars and incubated at the same temperatures and holding times indicated above. Due to logistics constraints, incubation of the 32 treatment samples (7 manure amendments + 1 feed additive x 2 temperatures x 2 replicates) were spread over eight trial events. Untreated control samples were prepared and incubated at times and temperatures identical to treated manure samples. An incubation unit equipment failure with the 10 degree C samples produced freezing conditions, ultimately resulting in an unavoidable decision to repeat this portion of the experiment. Repeat trial treatments were prepared and incubated following the same incubation protocol. Selected duplicate manure sets incubated at 20 degrees C served as a cross check (bridge) to address potentially confounding effects due to differing manure collection dates in the overall study. For all trials, odor emissions from samples were assessed by six qualified odor assessors using internationally recognized standard protocols for Triangular Forced-Choice dynamic olfactometry. Odor quality characterizations were performed to supplement odor emission data. Cotton fabric odor quality characterizations were also performed for selected trials, using 10-cm x 10-cm odorless cotton swatches exposed to slurry jar headspaces for 30 min. Gas emissions were measured using a multi-chamber steady-state detection system under temperature-controlled conditions. The system employed a photoacoustic multi-gas field-monitor and pulsed fluorescence analyzer to measure gas concentrations from each of eight flux chambers every 72 min over a 24-h period. Individual flux chamber vessels consisted of the 3.8-L glass jar containers that were used for incubation. Each flux chamber jar was provided with a continuous supply of filtered, sweep air. Six of the eight flux chamber jars contained 2 kg of manure slurry (treatments and control). Two jars contained distilled water as control vessels, providing a check for cross-contamination of sampling lines and determination of background gas concentration levels. PARTICIPANTS: Arlene Adviento-Borbe: Post-Doc, Agricultural and Biological Engineering [ABE]; statistical analysis, research design, and instrumentation quality-assurance quality-control (QAQC), and written products. Robin Brandt: Lecturer, ABE; Director of the Penn State Odor Assessment Lab; oversee lab and field odor emission collections and human odor-panel QAQC, and written products. Mary Ann Bruns: Associate Professor, Crop and Soil Sciences [CSS]; technical advisor for microbiological and biochemical interaction of manure amendment selection and analysis, and review of written products. Hershel Elliott: Professor, ABE; technical advisor chemical and biochemical analysis of manure amendment trials, and review of written products. Robert Graves: Professor, ABE; technical implementation and analysis of manure storage and barn trials, and review of written products. Alex Hristov: Associate Professor, Dairy and Animal Science [DAS]; implementation and analysis of essential oil nutritional trials, and review of written products. Jessica Tekippe: M.S. Student, DAS; facilitate, conduct, and analyze dairy nutritional trials. Deborah Topper: Technologist, ABE; operator and QAQC of dynamic olfactometer during panel assessment, and written products. Patrick Topper: Senior Research Technologist, ABE; design, fabrication, and operation of odor and gas emission collections, and written products. Gabriella Varga: Professor, DAS; technical implementation and analysis of lactating cow nutritional trials, and review of written products. Eileen Wheeler: Professor, ABE; primary administrative manager and technical director to oversee implementation, QAQC, and analysis of all trials; supervise technologists and post-doc, and written products. Odor Assessors: a group of twenty-two individuals qualified and compensated for odor evaluations. TARGET AUDIENCES: Dairy producers and their advisors (servicemen, veterinarians, Extension educators, etc.) are targeted for odor- and gas emissions-related information. These audiences benefit from odor and gas baseline data and understanding of principles behind the recommendations for mitigation via manure amendments or diet strategy. Manufacturers of some of the products studied have expressed interest in continuing evaluations at field scale. Air quality researchers in other PSU departments and at other universities can access the Penn State Odor Assessment Lab's capabilities. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Manure amendments and a feed additive were studied for efficacy in reducing odor, ammonia, hydrogen sulfide, and greenhouse gas (GHG) emissions from dairy manure incubated at 20 degrees C and 10 degrees C for 3 d, 30 d and 94 d. Seven amendments representing different modes of action were evaluated, including: two microbial digest/enzymes; two oxidizing agent/chemical; one disinfectant; and two essential oils. Odor emission thresholds from treated and untreated manure slurries were determined by six qualified odor assessors following the Triangular Forced-Choice method and odor quality characterizations were performed, including: hedonic tone (pleasantness), Labeled Magnitude Scale and ASTM odor intensity reference scale method for supra-threshold odor intensity and environmental odor label descriptors to depict how odors were perceived by assessors. Gas emissions were quantified using a multi-chamber steady-state gas emission detection system equipped with a photoacoustic multi-gas analyzer (ammonia and GHG) and pulsed fluorescence analyzer (hydrogen sulfide). No consistent, significant reductions were found for odor and gas emissions for the amendments and feed additive treatments when considering all three storage periods at two storage temperatures. Average daily odor emission rates ranged from 5 to 94 OU(E) cm(-2) d(-1). A significant reduction (31%; P=0.032) in odor emission was measured in the abandoned mine drainage (AMD) sediment treatment after 3 d at 20 degrees C showing some promise for short-term odor reduction prior to land application of manure. Essential oils, Hyssopus and peppermint, reduced odor emission by 27 to 48% after 94 d at 20 degrees C. But for 30 d at 10 degrees C these essential oil treatments increased odor emission by 29 to 65%. Mean gas emission rates were 1.4 to 2 times higher at 20 degrees C than at 10 degrees C (P=0.04, <0.0001). Only the AMD sediment reduced ammonia and carbon dioxide emissions after both 30 d and 94 d (P=0.02, <0.0001). One microbial digestive treatment (powder enzymes and bacteria) reduced ammonia emission after 94 d (P=0.006, <0.0001) at 10 degrees C and 20 degrees C, and methane emission (12%) after 30 d at 10 degrees C (P=0.005). Storing treated dairy manure for 94 d either at 10 degrees C or 20 degrees C reduced odor and greenhouse gas emissions by 88-100% compared to emissions at 3d. All treated and untreated manure slurries had unpleasant to extremely unpleasant smell and 76 to 100% of qualified odor assessors described the manure samples as offensive, earthy, medicinal and/or fishy. Hedonic tone was related to odor intensity while odor emission was correlated with hydrogen sulfide, methane and carbon dioxide emissions. Odor emission was inversely related to ammonia emission. For the conditions and products investigated in this study, findings show highly variable results.
Publications
- Adviento-Borbe, M. A. A., E. F. Wheeler, N. E. Brown, P. A. Topper, R. E. Graves, V. A. Ishler, and G. A. Varga. 2010. Ammonia and greenhouse gas flux from manure in freestall barn with dairy cows on precision fed rations. Transactions of the ASABE 53(4):1251-1266.
- Brandt, R. C., H. A. Elliott, M. A. A. Adviento-Borbe, E. F. Wheeler, T. E. Johnston, W. E. Toffey, and J. Golembeski. 2010. Statistical Confidence of Field Olfactometry and Biosolids Odor Assessment. In Proceedings: Water Environment Federation Residuals and Biosolids Conference, 2010. Savannah, GA. May 23-26, 2010. 23 pgs.
- Brandt, R. C., H. A. Elliott, M. A. A. Adviento-Borbe, E. Wheeler, P. J. A. Kleinman, and D. B. Beegle. 2009. Influence of manure application method on odors emissions. Presented at: Amer. Soc. Agronomy International Meeting. Pittsburgh, PA. Nov 1-5, ASA-CSSA-SSSA, Madison, WI. (Abstracts). Paper #53418.
- Brandt, R. C., T. E. Johnston, W. E. Toffey, and J. E. Golembeski. 2009. Use of field olfactometry for quantification of WWTP dewatering facility odor emissions. In proceedings: WEFTEC-2009, 82nd annual Water Environment Federation Technical Exhibition and Conference. Orlando, FL. October 10-14, 2009. Paper 071_330, 18 pages, 4644-4661.
- Wheeler, E. F., M. A. A. Adviento-Borbe, R. C. Brandt, M. A. Bruns, P. A. Topper, H. A. Elliott, A. N. Hristov, V. A. Ishler, D. A. Topper, R. E. Graves, R. S. Thomas, and G. A. Varga. 2010. Dairy manure amendment effects on odor and gas emissions. XVIIth World Congress of the International Commission of Agricultural Engineering (CIGR). Paper No. CSBE10644.
- Wheeler, E. F., A. Adviento-Borbe, P. A. Topper, D. A. Topper, H. A. Elliott, R. E. Graves, A. N. Hristov, V. A. Ishler, and M. V. Bruns. 2010. Amendments for mitigation of dairy manure ammonia and greenhouse gas emissions: Preliminary screening. ASABE. St. Joseph, MI. ASABE Paper No. 1008662.
- Stowell, R., J. Heemstra, R. Sheffield, K. Janni, and E. Wheeler. 2010. Using webcasts to highlight air quality research. In Proceedings: International Symposium on Air Quality and Manure Management for Agriculture. ASABE. St. Joseph, MI. Publication Number 711P0510cd. 5 pgs.
- Hristov, A. N., C. Lee, T. Cassidy, M. Long, K. Heyler, E. Wheeler, and P. Topper. 2010. Effect of Dietary Inclusion of Medium-Chain Saturated Fatty Acids on Ammonia and Methane Emitting Potential of Dairy Manure. In Proceedings: International Symposium on Air Quality and Manure Management for Agriculture. ASABE. St. Joseph, MI. Number 711P0510cd. 8 pgs.
- Johnston, T. E., M. A. Higgins, R. C. Brandt, and W. E. Toffey. 2009. Effect of amendment addition on biosolids odors based on gas chromatography analysis and odor panel observations. In proceedings: WEFTEC-2009, 82nd annual Water Environment Federation Technical Exhibition and Conference. Orlando, FL. October 10-14, 2009. Paper 071_Alt1. 20 pages, 4694-4713.
- Johnston, T. E., M. A. Higgins, R. C. Brandt, W. E. Toffey, and R. C. Eschborn. 2009. Effect of amendment addition on biosolids odors based on gas chromatography analysis and odor panel observations. In proceedings: Water Environment Federation Residuals and Biosolids Conference, 2009. Portland, OR. May 3-6, 2009. Paper 9A, 20 pages, 607-626.
- Wheeler, E. F., M. A. A. Adviento-Borbe, R. C. Brandt, P. A. Topper, D. A. Topper, H. A. Elliott, R. E. Graves, A. N. Hristov, V. A. Ishler, and M. A. Bruns. 2010. Amendments for mitigation of odor emissions from dairy manure: Preliminary screening. ASABE. St. Joseph, MI. ASABE Paper No. 1008658.
- Wheeler, E. F., M. A. A. Adviento-Borbe, R. C. Brandt, P. A. Topper, D. A. Topper, H. A. Elliot, R. E. Graves, A. N. Hristov, V. A. Ishler, and M. A. Bruns. 2010. Amendments for Short- and Medium-Term Mitigation of Odor Emissions from Dairy Manure. In Proceedings: International Symposium on Air Quality and Manure Management for Agriculture. ASABE. St. Joseph, MI. Publication Number 711P0510cd. 8 pgs.
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Progress 09/01/08 to 08/31/09
Outputs
OUTPUTS: The use of amendments may have potential to assist practical and cost-effective manure management for reductions of odor, ammonia [NH(3)] and greenhouse gas (carbon dioxide [CO(2)], methane [CH(4)] and nitrous oxide [N(2)O]) emissions in dairy manure. The use of manure amendments has variable results in reducing odor and gases; much evidence is anecdotal. Few studies have documented amendment use in cattle manure. Twenty-two amendments were evaluated in dairy manure incubated at room temperature for short- and medium-term duration. The 22 amendments represent different modes of action that include microbial digest/enzymes, oxidizing agent/chemical, disinfectant, masking agent and adsorbent. Each amendment was added to 2kg dairy manure slurry (1:1.7 feces:urine; 10% total solid) following the manufacturer recommended rates. In this preliminary screening of products only one sample of each amendment was evaluated. Untreated manure slurry was also evaluated. Odor emissions from manure slurries incubated at 3d and 30d were estimated by six certified odor assessors following international standard EN13725:2003 for Triangular Forced-Choice dynamic olfactometry. Odor characterizations were estimated using a hedonic tone scale (-11 for extremely unpleasant to +11 for extremely pleasant), a Labeled Magnitude Scale and ASTM odor intensity reference scale method [E544:99 (2004)] for suprathreshold odor intensity and an odor character wheel for odor description. Gas emissions were measured with a photoacoustic multi-gas analyzer. PARTICIPANTS: Arlene Adviento-Borbe: Post-Doc, Agricultural and Biological Engineering [ABE]; statistical analysis, research design, and instrumentation quality-assurance quality-control (QAQC). Robin Brandt: Lecturer, ABE; Director of the Penn State Odor Assessment Lab; oversee lab and field odor emission collections and human odor-panel QAQC. Mary Ann Bruns: Associate Professor, Crop and Soil Sciences [CSS]; technical advisor for microbiological and biochemical interaction of manure amendment selection and analysis. Hershel Elliott: Professor, ABE; technical advisor chemical and biochemical analysis of manure amendment trials. Robert Graves: Professor, ABE; technical implementation and analysis of manure storage and barn trials. Alex Hristov: Associate Professor, Dairy and Animal Science [DAS]; implementation and analysis of essential oil nutritional trials. Jessica Tekippe: M.S. Student, DAS; facilitate, conduct, and analyze dairy nutritional trials. Deborah Topper: Technologist, ABE; operator and QAQC of dynamic olfactometer during panel assessment. Patrick Topper: Senior Research Technologist, ABE; design, fabrication, and operation of odor and gas emission collections. Gabriella Varga: Professor, DAS; technical implementation and analysis of lactating cow nutritional trials. Eileen Wheeler: Professor, ABE; primary administrative manager and technical director to oversee implementation, QAQC, and analysis of all trials; supervise technologists and post-doc. Odor Assessors: a group of twenty-two individuals compensated for and qualified for odor evaluations. TARGET AUDIENCES: Dairy producers and their advisors (servicemen, veterinarians, Extension educators, etc.) are targeted for odor- and gas emissions-related information. These audiences benefit from odor and gas baseline data and understanding of principles behind the recommendations for mitigation via manure amendments or diet strategy. Manufacturers of some of the products studied have expressed interest in continuing evaluations at field scale. Air quality researchers in other PSU departments and at other universities can access the Penn State Odor Assessment Lab's capabilities for a per-sample evaluation fee. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Odor emissions were significantly different between 3d and 30d incubation at 20C (P =<0.0001). None of the 22 manure amendments significantly reduced odor emissions from dairy manure for both 3d and 30d incubation periods. Products that acted as microbial digest/enzymes, disinfectant, and masking agent provided statistically significant short-term control of odor (P =<0.0001). However, after 30d, only one microbial digest/enzyme, with frequent re-application, retained its efficacy. For all products tested, it appears that aging the manure slurry for 30d at 20C reduced malodor gas production and odor strength by 10 to 105% (P = <0.0001). Hedonic tone ranged from -2 to -6 indicating a slight to moderate unpleasant smell. For all amendments, 27 to 67% of odor assessors reported that the manure gas had earthy and offensive character. Odor emissions were significantly correlated with odor intensity of dairy manure while no relationship was found between odor emission and hedonic tone. All amendment products affected the production of NH(3), CO(2) and CH(4) after 3d and 30d yet none significantly reduced effluxes. Nitrous oxide flux rates were very low (<1 microgm/cm2/hr). Six amendment products significantly reduced ammonia by >10% (P =0.04 - <0.0001) after both 3d and 30d incubation. Microbial digest/enzymes with nitrogen substrate appear effective in reducing CH(4) fluxes after short- and medium-term incubation. Most of the masking agents and disinfectants significantly produced CH(4) in both incubation periods (P =0.04 - <0.0001). The majority of tested products reduced CO(2) production by 12 to 52% after the medium incubation period. For both CH(4) and CO(2) fluxes, aging the manure slurry for 30d significantly reduced gas production by 11 to 100% (P = <0.0001). While some products provided short-term reduction of gas and others after medium-term period, our results show that the 22 amendments efficacy to mitigate gas emissions from dairy manure is finite and require re-application even for a static amount of manure. Results of this screening were used to select six amendments for replicated study at two temperatures (10 and 20C) and three storage periods (3d, 30d and 94d). This data collection was completed in mid-October 2009 with data analysis ongoing.
Publications
- No publications reported this period
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