Sixty-two tonnes a day and no landfill: choosing a waste system
A municipal ward generates 62 tonnes per day of mixed municipal solid waste. Composition by wet weight is 54% biodegradable, 12% recyclable, 8% inert and 26% other. Moisture content is 58%. About 90 informal waste pickers currently recover 6 tonnes per day at an open dump of 1.8 ha. The dump has no liner; leachate in a nearby pond shows chloride 1,240 mg/L and BOD 640 mg/L. The ward has no sanitary landfill and 0.6 ha of vacant land near a residential colony. Options costed by the consultant are windrow composting at ₹800 per tonne, refuse-derived fuel at ₹1,200 per tonne, and sanitary landfilling at ₹500 per tonne. The elected council wants a decision within a month and is under pressure from residents to remove the dump.
1. Carry out a mass balance for the ward and assess whether refuse-derived fuel is technically suitable.
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Mass balance: biodegradable 54% of 62 = 33.5 t/day; recyclables 12% = 7.4 t/day; inert 8% = 5.0 t/day; other 26% = 16.1 t/day. The informal sector already recovers 6 t/day, so source-separated recyclables could be about 7.4 t/day.
Composting: 33.5 t/day of feedstock, with about 25–30% compost yield after moisture and carbon loss, gives roughly 8–10 t/day of compost. That requires about 0.4–0.6 ha for windrows and a leachate collection area, so the 0.6 ha vacant land is tight but possible only with decentralised sites.
RDF: a moisture content of 58% is high. RDF needs dry, high-calorific material; much of the biodegradable fraction is wet, and the “other” fraction is undefined. Drying would consume energy and space, and the RDF offtake is not guaranteed. RDF is therefore technically weak unless the waste is first segregated and dried, and it can compete with recycling for paper and plastic.
Landfilling: only about 5 t/day of inert material plus rejects should go to a sanitary landfill. Landfilling 62 t/day would be a failure of the system.
2. Recommend a technology and collection system within the ward's constraints. Justify the choice and address the informal sector and the 0.6 ha site.
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Recommendation: source-separated collection, decentralised windrow composting, a materials recovery facility, and a small sanitary landfill for inerts and rejects. Do not make RDF the primary route.
Collection: door-to-door collection with two bins (wet and dry) and a separate hazardous-waste bag; three compaction vehicles on fixed routes; bulk generators such as markets and hotels segregated at source. A transfer point should not be located near the colony.
Treatment: two composting sites of about 0.25 ha each, with concrete pads, leachate collection and a roofed curing area; a 0.1 ha MRF for sorting dry waste. The 0.6 ha site can hold the MRF and a small sanitary landfill cell, not an unlined dump. Compost should be tested for heavy metals and sold to farmers.
Informal sector: integrate the 90 waste pickers into collection, sorting and composting with identity cards, safety gear, training and a share of compost or recyclable revenue. Excluding them would increase dumping and lose their recovery work.
Costs: composting at ₹800/t on 33.5 t is about ₹26,800/day; MRF and landfill costs are additional. Compare this with the health and water costs of the current dump.
3. Design a closure and monitoring plan for the existing 1.8 ha dump, including leachate and community safeguards.
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Closure: stop new tipping; regrade the waste to a stable slope; install a low-permeability cap with drainage; divert clean surface water around the dump; collect leachate from a toe drain and treat it in a constructed wetland or send it to a sewage treatment plant. Landfill gas should be vented; if methane generation is significant, flaring or small-scale capture should be considered. Fence the site and post warning signs. No housing should be built on the closed dump without gas and settlement testing.
Monitoring: sample the pond and downgradient wells quarterly for chloride, BOD, nitrate, iron, arsenic and conductivity. Chloride of 1,240 mg/L and BOD of 640 mg/L already indicate contamination; compare with an upgradient well. Measure leachate volume and treatment performance monthly, cap integrity and settlement annually, and gas periodically.
Community safeguards: inform residents of the closure schedule, provide an alternative water point if the pond is used for washing, and train former pickers for new jobs. Publish monitoring results. A closure plan without leachate control merely hides the dump.