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

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

Controlled biological decomposition process What is composting? Controlled biological decomposition process Grass clippings Compost Food scraps It is an aerobic, biological process which uses naturally occurring microorganisms to convert biodegradable Leaves In composting naturally occurring microorganisms help to convert organic wastes into a humus material called compost

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

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

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 may be used to condition heavy clay or mineral soils

Assessment of MSW Composting & Compost Quality

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

Current Constraints Existing system 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.

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

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.

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) heap is made up to 1.5-2.0 feet above the ground level By managing these factors you can speed up the process otherwise slow natural decay process

Phases of Composting Phases of Composting  Initial decomposition is carried out by mesophilic microorganisms, which rapidly break down the soluble, readily degradable compounds. As the temperature rises above about 40°C, the mesophilic are replaced by thermophilic, At temperatures of 55°C and above, many microorganisms that are human or plant pathogens are destroyed. During the thermophilic phase, high temperatures accelerate the breakdown of proteins, fats, and complex carboydrates like cellulose and hemicellulose, the major structural molecules in plants. temperature gradually decreases and mesophilic microorganisms once again take over for the final phase of "curing" or maturation of the remaining organic matter. 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)

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

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

Material flow for the conventional Composting process

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

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

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

Results Table 1. Composition of MSW generated in Karachi Components High Middle Low ( % by weight)   Organic wastes 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

Table 2. Physical and Chemical Characteristics of MSW 6.4 5.5-8.0 Moisture (% dry basis) 36  <50 Organic matter (% wet basis) 57 >20 Nitrogen 0.81 0.6 Carbon 33 No specs C/N ratio (total dry weight) 40:1 25-50:1 Parameters Average Values Standards *Average of 8 samples

Table 3. Comparative average values of pH, Soluble Salts & Organic Matter in MSW composts, cowdung and chemical fertilizer samples. Sample Type pH Soluble salts Organic 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

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

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%)

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 in the context of other waste management options.