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It is accepted globally that a “leaner” yet ‘bigger’ dairy industry is much more productive than small farm holdings. Contrary to this belief we suggest mechanization is not an alternative but can be a complement to smallholding farms. Mechanization is understood as loss of jobs for farmers. This may be true for the crop sector; however, in dairy farming this is not always the case. Given Pakistan’s spread of smallholdings and very low level of existing mechanization; job losses are unlikely to happen. Empirically, any job loss phase comes only after a degree of mechanization has been reached | Dairy Waste Anaerobic Digestion Handbook Options for Recovering Beneficial Products From Dairy Manure Dennis A. Burke P.E. June 2001 Environmental Energy Company 6007 Hill Street Olympia WA 98516 1 Environmental Energy Company www.makingenergy.com 360-923-2000 Table Of Contents Anaerobic Digestion Dairy Waste Handbook.1 Introduction.1 Dairy Operations.3 Housing System.3 Free Stall Barns.3 Corrals.4 Milk Barn.4 Open Lot.5 Transport System.5 Flush Systems.6 Scrape Systems.6 Front end Loader.6 Vacuum Systems.7 Bedding.7 Manure Processing.8 Holding Tanks and Chopper Pumps.8 Primary Screens.9 Gravity Separators.10 Primary Holding Ponds.13 Secondary Holding Ponds.14 Summary.14 Anaerobic Digestion.16 Bacterial Consortia.16 Factors Controlling the Conversion of Waste to Gas.17 Waste Characteristics.17 Dilution of Waste.18 Foreign Materials.19 Toxic Materials.20 Nutrients.20 Temperature.20 i Environmental Energy Company www.makingenergy.com 360-923-2000 pH.21 Hydraulic Retention Time HRT .21 Solids Retention Time SRT .21 Digester Loading kg m3 d .23 Food to Microorganism Ratio.23 End Product Removal.24 Digester Types.24 Processes that are not Appropriate for Digesting Dairy Manure.25 Processes that can be used for Digesting Dairy Manure.27 Anaerobic Lagoons Very Low Rate .27 Completely Mixed Digesters Low Rate .28 Plug Flow Digesters Low Rate .30 Contact Digesters High Rate .31 Sequencing Batch Reactors High Rate .32 Contact Stabilization Reactors High Rate .32 Phased Digesters.33 Hybrid Processes.35 Qualitative Analysis of Anaerobic Processes.35 Solids Concentration Limitations.35 Digestion of the Entire Waste Stream.35 Foreign Material Processing.36 Odor Control.36 Stability Flexibility and Reliability.36 Nutrient Concentration and Retention.37 Additional Substrate Processing.37 Energy Production.38 Conventional Digesters.38 Lagoons.40 High Rate Anaerobic Reactors.40 Cost of Anaerobic Processes for Dairy Waste.42 Alternative Waste Management Systems.44 Existing Manure .
