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1Mayapan, Belize Swine Waste Treatment SystemSML Engineering Inc.Statement of the Problem Design a system to treat pig waste for use as fertilizer for organic cacao crops– Government funded– Limited technology– Treatment system smaller than others builtMayapan, BelizeSoil and Pig Waste Characteristics 10 to 25 Pigs Expected Waste is 10% Solids C:N:P:K = 7:1:0.38:0.53 Produce 4 to 13 pounds of Waste per Day Rainforest Soil is Devoid of Virtually All Nutrients Cacao grown is OrganicCacao Two Harvest Peaks: Jan-Feb; Mar-June Ripe Pod Contains about 40 Seeds Seeds are Dried and Fermented to Cocoa BeansFuture Conditions Current design for 1 organic cacao farmer– 10 total farmers in Mayapan– 3 are successful at organic cacao farming Total crop area not expected to increase2N P KIdeal Nutrients for Cacao Trees39% 4% 57%Raw Solid Pig Waste Nutrients6.6% 2.5% 3.5%Standard Store Bought Fertilizer30% 10% 10%Product GoalsProduct Goals Pathogen Destruction– Main route of destruction through elevated temperature– Other physical and chemical disinfectants not feasible because of energy, money or other reasonsUsing Bacteria to Make Fertilizer “Good” bacteria that treat waste are not the same as “bad” pathogenic bacteria Types of Bacteria–Aerobic – Anaerobic• MethanogensConstraints and Criteria Non-cost Criteria (50%)1. Quality of resulting fertilizing agent (10%)2. Long-term effectiveness/ reliability (9%)3. Protection of human health and environment (7%)4. Community acceptability (7%)5. Maintenance effort (7%)6. Expandability of the treatment unit (5%)7. Positive byproducts such as biogas (3%)8. Odor (2%) Cost Criteria (50%)1. Capital Cost (30%)2. Operation and maintenance over lifetime (20%)Alternatives Anaerobic Digestion Anaerobic/Aerobic Digestion Composting Anaerobic Batch ReactorAnaerobic DigestionReactor 1 HomogenizationReactor 3 Anaerobic DigesterReactor 2 Anaerobic DigesterPigpenMethane Recovery Fertilizer3Anaerobic Digestion Decision Matrix Score = 3.29 Total Capital Cost = $2,310Anaerobic/Aerobic DigestionAnaerobic DigesterReactor 3 Mixed Aerobic DigesterAnaerobic DigesterPigpenReceiving BasinFertilizerAnaerobic/Aerobic Digestion Decision Matrix Score = 3.35 Total Capital Cost = $2,780Composting Periodically turned to provide oxygen Composting pit maintained at 50-60% water content. Covered during rainy season Composting Decision Matrix Score = 4.03 Total Capital Cost = $80Anaerobic Batch Reactors Multiple Reactors  After one reactor is full close and begin filling the next reactor in the series Easily expanded upon4Anaerobic Batch Reactors Decision Matrix Score = 4.26 Total Capital Cost = $1,512Final DesignMixingAmmonia Concentration Concerns Ammonia at high concentrations (3000-3500 mg/l) is toxic to methanogons Water Dilution will keep ammonia concentrations acceptableAmmonia Level in “raw” Swine Waste4,200 mg/lAmmonia Created by Biomass 1,602 – 2,106 mg/lTotal Ammonia Load in Reactor 5,802 – 6306 mg/lWater Dilution Factor 1Final Product Mostly Liquid (1.6% solids which is a solid reduction of 69%) System not pH sensitive C:N:P:K = 6.9 : 1.0 : 0.38 : 0.53Biogas Recovery Methane and carbon dioxide, the main compounds in biogas, are greenhouse gases so biogas collection is important Use of gas bag is the simplest solution5Uses of Biogas Cooking on Biogas Stove Run a Biogas fueled generator to create electricityOperational and Startup Information The system startup should be seeded with cow manure 20% of the biomass should be left behind after each cycle The system should be mixed at least twice a day for ten minutes The waste will need to be diluted by an equal amount of waterFinal Capital CostMaterials Total Cost2" PVC Pipe $7.884" PVC Pipe $1.22Pipe fittings (caps, etc)* $126.001250 L (330 Gallon) Tank $2,520.00Shovel/Scoop $20.00Heavy-duty Wheelbarrow $50.00Methane Recovery System $500.00Total $3,225Schedule 2-5 Days for Construction 2 months to fine tune residence times, percentage of recycle, and dilution factorVampire Bat Problems Vampire bats in Mayapan often bite the pigs The pigpen needs to have a physical barrier from the bats Total Cost $270Additional Considerations The system would be experimental as the smallest system we found in research had a 10,000 liter reactor. In a co-op system the benefits would be much greater as electricity production could be considered.  For a co-op system much larger reactors built of concrete would need to be designed, however design principals previously discussed would still be valid6Questions ? SML Engineering


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CU-Boulder CVEN 4434 - Swine Waste Treatment System

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