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Composting and Recycling of Municipal Solid Waste

Composting and Recycling of Municipal Solid Waste. By Dr. Seema Jilani (Associate P rofessor) I nstitute of Environmental S tudies U niversity of Karachi Karachi, Pakistan. Content. Description of Composting & Compost Benefits of Composting End use of Compost

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Composting and Recycling of Municipal Solid Waste

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  1. Composting and Recycling of Municipal Solid Waste By Dr. SeemaJilani (Associate Professor) Institute of Environmental Studies University of Karachi Karachi, Pakistan

  2. Content • Description of Composting & Compost • Benefits of Composting • End use of Compost • Pilot research study on Assessment of MSW composting & compost quality • Conclusions

  3. Compost What is composting? Controlled biological decomposition process Grass clippings Food scraps Leaves In composting naturally occurring microorganisms help to convert organic wastes into a humus material called compost

  4. What is compost? Compost is a dark brown with crumbly, porous, earthy smelling, soil like material which can be used as fertilizer / soil conditioner.

  5. Benefits of composting • Recycling Organic Waste ----It is an environmentally sound means of recycling organic materials • Waste Minimization ---It is one way to reduce the amount of waste we produce. • Cost Reduction---Garbage handling is the most largest expense for many cities. Composting can reduce those costs • Kill Pathogens

  6. End use of Compost • Improve soil structure, texture & aeration • Prevent erosion • Increases the soil's water-holding capacity. • Compost loosens clay soils and helps sandy soils to retain water. • Green-house gas reduction

  7. Assessment of MSW Composting & Compost Quality

  8. Facts & Figures • Generation rate of MSW = 12000 tons per day - 80% Solid Waste is recyclable in nature - 65-70 % is food waste - 25 -30% comprises of bones, paper, plastic, glass, metal, textile, leather etc.. • About 60% garbage transported to dumping grounds • 20-25% garbage picked up by scavengers • Uncollected waste end up in drain either burned or left at the mercy of nature

  9. Current Constraints • Existingsystem of SWM  inefficient, inadequate • No scientifically designed landfill site • Poor hygienic condition • Low level awareness regarding SWM. • Large amount of recyclable material and energy are thus discarded.

  10. Research Objectives • To assess the feasibility of MSW composting • To analyze the quality of finished compost samples • To propose an effective and sustainable SWM for Karachi city

  11. Research Methodology • Solid waste samples were collected from different localities of Karachi. • For compositional analysis, manual sorting and weighing of individual component was conducted • The sorted organic matter was then subjected to open windrow composting • Windrow composting is one of the cheapest and easiest methods used for organic wastes management.

  12. Windrow Composting • A pile of waste was formed • To speed up the natural decay process following factors were managed • Air (oxygen 5-15%) • Moisture ---- 50 – 60% • Food (C:N ratio---30:1), and • Temperature ---- 55 – 75C (thermophile range) By managing these factors you can speed up the process otherwise slow natural decay process

  13. Phases of Composting Composting goes through three distinct phases that can be characterized by temperatures. • Mesophilic Phase (moderate temperature, 40 oC) • Thermophilc Phase (high temerpature, 55oC–65oC) • Mesophilic Phase (moderate temperature again)

  14. The Main players • Bacteria:major decomposers, breakdown simpler forms of organic material • Actinomycetes:degrade complex organics such as cellulose, lignin, chitin, and proteins – earthy” smell, long “spider webs” filaments • Fungi:Break down tough debris, too dry, too acidic or too low in nitrogen for bacteria to eat

  15. When is composting finished? • When mature compost is obtained with following characteristics • The color turn dark brown • It is crumbly, loose, & • humus-like • It has an earthy smell • It contains no readily • recognizable feedstock • The pile size shrunk to • about 1/3 of its original volume

  16. Material flow for the conventionalComposting process

  17. Research Methodology • Composting duration = 12 weeks • Curing duration = 3 weeks • Finished compost samples screened out and analyzed in the laboratory using Standard method

  18. Simple test for finished Compost Bag test: sealing compost in a plastic bag for several days should not produce foul odor when open

  19. Research Methodology • Parameters selected: • pH • Soluble salts • Organic matter • Nutrients (Nitrogen, Phosphorus & Potassium) • C/N ratio • Analytical technique followed: • ASTM • USEPA method

  20. Components High Middle Low • ( % by weight) • Organicwastes 74.10 73.45 71.15 • Paper & Cardboard 9.30 6.92 4.33 • Plastic & polythene 6.00 9.50 13.72 • Textile 1.50 2.73 5.40 • Rubber & Leather 1.10 1.30 - • Metals & Tin 3.60 1.90 - • Glass 4.40 3.10 1.60 • Miscellaneous - 1.10 3.80 Results Table 1. Composition of MSW generated in Karachi

  21. Table 2. Physical and Chemical Characteristics of MSW Parameters Average Values Standards *Average of 8 samples

  22. Table 3. Comparative average values of pH, Soluble Salts & Organic Matter in MSW composts, cowdung and chemical fertilizer samples. Sample Type pHSoluble saltsOrganic matter (m.mhos/cm) (dry basis) MSW Compost 7.50 4.19 58 (High income) (6.8-7.8) (3.90-4.50) (56-60) MSW Compost 7.42 4.72 56 (Middle income) (7.1-8.0) (4.35-4.82) (54-58) MSW Compost 7.78 4.83 48 (Low income) (7.0-8.1) (4.72-5.10) (45-50) Cowdung 7.91 4.81 50 (organic fertilizer) (7.6-8.2) (4.75-4.88) (48-52) Chemical fertilizer 6.95 5.67 38 (6.8-7.1) (5.40-5.80) (37-39) Proposed Italian Standard 5.5-8.0 <5 >20

  23. Table 4. Comparative average nutritional values and C/N ratio in the • sample of composts, cowdung and chemical fertilizer Sample Type Org.Carbon Nitrogen Phosphorus Potassium C/N Ratio (%) (%)dry basis (%) dry basis (%) dry basis MSW Compost 33.64 1.18 0.57 1.61 28.51 (High income) (0.94-1.35) (0.42-0.70) (1.30-1.80) MSW Compost 32.48 1.11 0.58 1.58 29.26 (Middle income) (0.95-1.18) (0.45-0.72) (1.20-1.80) MSW Compost 27.80 1.09 0.64 1.32 25.50 (Low income) (0.91-1.20) (0.55-0.85) (1.00-1.50) Cowdung 29.00 1.19 0.55 3.81 24.37 (Organic Fertilizer) (0.95-1.50) (0.43-0.65) (3.10-4.40) Chemical fertilizer 22. 00 0.86 0.75 0.18 25.58 (0.73-0.98) (0.55-1.00) (0.16-0.20) MSW Compost Quality Standard >25 >1 > 0.5 > 0.7 <25

  24. Conclusions • Karachi MSW suitable for composting due to • high percentage of biodegradable organic waste (71- 74%) • suitable moisture content (35 - 40%) and • C/N ratio (35 - 40:1) • Compost Quality were found with in acceptable limits • pH ( 6.8 - 8.1) • Soluble Salts (3.90- 5.10m.mhos) • Organic Matter (45 - 60%) • Nitrogen (0.91- 1.35%) • Phosphorus (0.42 - 0.85%) • Potassium (1.0 - 1.80%)

  25. Conclusions • Application of MSW Compost would be good for Karachi sandy soil • High quality compost could be produced by mixing nitrogen containing compounds (cow manure, poultry manure, yard waste etc). • Further investigation is required to evaluate the economic and technical feasibility of composting

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