Integrated solid waste management for local authorities in Sri Lanka: a viable model for better management
By Eng. (Prof.) Mahesh Jayaweera
Solid waste management has become one of the burning issues worldwide. Urbanization and rapid population growth have geared to increase the quantity and complexity of waste generated. The inefficient management and improper disposal of solid waste have created negative impacts on people’s health and wellbeing and the environment. Some of the impacts are (i) soil, water, and air pollutions, (ii) public health issues, (iii) public nuisance, among others. Therefore, finding an integrated and holistic approach to managing solid waste in an environmentally, socially, financially, and economically feasible manner is a timely decision.
Integrated Solid Waste Management (ISWM) is an integrated and holistic approach to solid waste management that has been widely used in many countries. ISWM for a small local authority (LA) with daily collection of municipal solid waste (MSW) being less than 20 MT can be surmised as an approach to a systematic way to the sustainable management of MSW by waste reduction, segregation, collection, composting/anaerobic digestion, recycling, and final disposal by controlled landfilling/waste to energy. The ISWM addresses the collective management of all types of waste in an environmentally feasible manner with maximizing resource use efficiency.
The current regime of Sri Lanka has planned to implement an ISWM system to manage the MSW generated in many LAs. To this end, two major policy decisions concerning solid waste management have been taken by the government; the Ministry of Public Services, Provincial Councils and Local Government is responsible for collecting and transporting the MSW generated within the local authority limits to the collection sites, and the Ministry of Urban Development, Coast Conservation, Waste Disposal and Public Sanitation is responsible for managing the collected waste until the final disposal.
The proposed ISWM concept follows the government’s new policy, “Vistas of Prosperity and Splendor,” as the policy dictates to go for the integrated approach for solid waste management. Further, the proposed concept is in line with the National Physical Plan, prepared by the Department of Physical Planning, as it directs for integrated management when dealing with solid waste management projects.
Proposed ISWM concept:
The entire ISWM concept is schematically presented in Figure 1. This diagram illustrates each component of the MSW collected separately.
Figure 1: ISWM plan for different components of the MSW collected
Sorting MSW at source (under the Tier 1):
The entire MSW to be collected will be subject to sorting at the source into categories such as biodegradables, recyclables, construction and demolition waste, street sweeping waste, and non-biodegradables. It is a prerequisite to improve the sorting or separation at the source. The Ministry of Public Services, Provincial Councils and Local Government will instruct all the local authorities to promote MSW sorting at the source. Further, the local authorities must carry out the collection only if the households will practice the separation or sorting of MSW to biodegradables, recyclables, and non-biodegradables. In the case where mixed garbage is kept for collection, such waste should not be collected.
LAs in the form of leaflets or visiting door-to-door should make people aware of the separation efforts. In these efforts, the assistance of NGOs, societies, and popular personalities could be looked for. Capacity building programs for all involved in ISWM in LAs (both desk-type and hands-on experience) will be conducted so that they could impart the knowledge to others. Also, LAs could practice the correct protocols in managing the MSW. Propaganda work for reduction, reuse, and recycling (3R concept) of waste among people through media, newspapers, NGO involvement for door-to-door campaigns, etc., will be conducted. Separate days and times will be allocated to collect the sorted waste in the entire UC. Once MSW is sorted, different categories of MSW will be collected by the respective local authorities and transported to the designated collection center/transfer station. The details of the collection and transport of sorted MSW are explained below.
Collection and transport of sorted MSW (under the Tier 1):
The respective LAs will only collect the sorted waste on a regular basis. People are informed about the waste collection schedules and types of waste being collected as per the schedules. Some methods deployed for MSW collection are door-to-door collection, bell collection, communal collection (curbside collection, bin collection). A sufficient workforce will be involved in the collection of waste.
A sufficient vehicular fleet will be maintained by each LA to collect the sorted waste and transported to the collection center/transfer station. Compactor trucks, skip hoists, tippers, tractors with trailers, and dump trucks can be used to collect the waste from main roads, while the two-wheel tractors with trailers and hand carts can be used to collect the waste from by roads and cart roads. An optimized plan for the collection route needs to be worked out by each LA depending on the vehicular fleet, and accordingly, prioritization on collection efforts will be done. The GPS-assisted system will be made available for every vehicle for an effective and efficient collection plan to be mobilized.
Collection of street-sweeping and drain cleaning (under the Tier 1):
It is of utmost importance to keep the road network clean for which street sweeping early in the morning and drain cleaning from debris, sediments, and garbage trapped are practiced. The garbage collected from the street sweeping and drain cleaning usually comprises heavy soil particles and grit particles with non-degradable. Such materials will be collected separately on pre-determined days and times and sent to the collection center/transfer station.
Final disposal system (under the Tier 2):
• For biodegradable waste
Biodegradables received by the compost yard will be subject to composting so that the final product of compost will be made. Composting is an aerobic biological process involving decomposition by aerobic microorganisms under high temperature (above 65 0C) to a product, which is biologically stable with no phytotoxic effects on plants when applied. Windrow composting has relatively low operating costs when compared to other composting methods. Passively aerated windrow composting is the most common composting method used in many parts of Sri Lanka because of its suitability for a wide range of feedstocks and easy facility management. This method involves the feedstocks being formed into long, low piles known as windrows. The windrows are regularly moved or turned to re-establish porosity, break up, and blend material. The turning process also reintroduces oxygen into the windrow. Forced aeration is another approach to supplying oxygen to the composting process other than turning. A key element in a forced aeration system is the aeration floor. It serves as the primary working surface and distributes air through the compost pile. The forced aeration windrow composting is high in terms of operational cost factors compared with the passively aerated windrow composting. The benefits of composting instead of open landfilling are (i) protection of human and environmental health, (ii) reduction of risks of landfill-associated calamities, (iii) contribution to land preservation, (iv) production of compost as a beneficial material for many applications, (v) decrease of public nuisance, (vi) provision of job opportunities, (vii) Provision of longer life for landfills, (viii) reduction of pollution potential of groundwater, surface water, land, and air.
Further, organic biodegradable waste can be subjected to anaerobic digestion (AD), whereby organic matter is decomposed in the absence of oxygen by microorganisms. The AD can be applied to process biodegradable organic matter in airproof reactor tanks, commonly named digesters, to produce biogas. Various groups of microorganisms are involved in the anaerobic degradation process, which generates two main products: energy-rich biogas and a nutritious digestate. The energy-rich biogas can be used as a source of energy, while the nutritious digestate can be used as a liquid fertilizer.
The entire operation of the composting/AD system will be carried out under the leadership of the Ministry of Urban Development, Coast Conservation, Waste Disposal and Public Sanitation. The operation and maintenance of the plants are to be done by appointing qualified personnel through the said ministry.
• For non-biodegradable waste:
The street sweeping and drain cleaning waste, non-biodegradable and non-recyclable waste, together with residues from the compost plant, if any, will be disposed of in a landfill or used to generate energy (waste to energy). Landfills should be properly engineered facilities that are located, designed, operated, monitored, closed, and cared for after closure to ensure minimal impacts on the environment and human health. The technical guidelines to be applicable in constructing a landfill are given in Technical Guidelines on Solid Waste Management in Sri Lanka prepared by the Central Environmental Authority (CEA).
Aruwakkalu Sanitary Landfill, which is currently under construction, is a major sanitary landfill that exists in Sri Lanka. Therefore, transporting waste from other regions that are far away from Aruwakkalu is financially not feasible. A regional sanitary landfill must be worked out by government mediation for every province. Leachate management, stormwater management, gas control, maintaining a buffer zone, application of a liner system, and operation and maintenance aspects are some of the major aspects to be looked into while designing a landfill.
The entire operation of the landfills to be constructed will be carried out under the Ministry of Urban Development, Coast Conservation, Waste Disposal and Public Sanitation. The operation and maintenance of the landfill are to be done by appointing qualified personnel through the said ministry. Energy recovery from waste, often called waste-to-energy, converts waste, which has high calorific value, to energy (heat, fuel, or electricity) through incineration (combustion, pyrolyzation, gasification, etc. One waste-to-energy plant is at work in Kerawalapitiya, taking care of the MSW of Colombo Municipal Council. The plant belongs to a private company and the electricity generated through the plant will be sold to the Ceylon Electricity Board. However, the government of Sri Lanka has made a decision to stop approving further waste-to-energy plants because of their high tariff structure for electricity generation that cannot be afforded in the long run.
• For recyclable waste:
The recyclable waste collected is to be handed over to the resource center located within the LA area. People can hand over such materials directly to the resource center at a price. Recyclable materials are also collected by the LA workers during MSW collection and handed over to the center. For the LAs not having resource centers, they need to be provided. In the meantime, private recyclable waste collectors are encouraged to collect recyclable waste directly from the people.
The entire operation of the resource centers shall be carried out under the leadership of the Ministry of Urban Development, Coast Conservation, Waste Disposal and Public Sanitation. Competitive prices will be offered to the public for handing over the recyclable waste to the center or to the garbage collecting vehicles. Once bulk quantities are collected in the center, the collected materials will be sold to a third-party at nominal prices.
• For construction and demolition waste:
Construction and demolition waste will be collected and transported to the debris collection yard located in the LA areas. The Ministry of Public Services, Provincial Councils and Local Government will carry out the collection and transport of waste. The Ministry of Urban Development, Coast Conservation, Waste Disposal and Public Sanitation will carry out the operation of the debris collection yard. Construction and demolition waste (reusable portions) will be sold to those who need filling material or used as a daily cover for the active cell of the landfilling if available.
Making a viable business:
In the proposed concept, except for landfilling, all other streams will yield financial benefits to the LA. Financial analysis of the proposed concept shows that the O&M costs of the management of MSW could be recovered fully with the collection of nominal tariffs from the commercial entities. No collection of separate tariffs is required from households. However, if a LA is to finance the capital costs under the government’s current lending terms, the LA will have difficulty servicing the years’ obligation. The analysis shows that the income excess over O&M costs can finance a small portion of the capital costs. The rest of the capital investment should come from the treasury from time to time. It is evident that the proposed concept is sufficient to maintain the O&M budget without any burden to the government. The economic analysis of the proposed concept guarantees that the economic internal rate of return (EIRR) is greater than 12%, and the concept is, therefore, feasible. Further economic net present value (ENPV) is positive except in case of a 1-year delay in accruing benefits. Based on the anticipated economic benefits of the proposed development, it is economically viable; hence, economically sustainable.
Various other intangible benefits are not easy to be included in the computation, and these include a multitude of social benefits.
It is high time for us to embrace such well-managed concepts for a better tomorrow, and it is our duty to keep Sri Lanka in a state of cleaned paradise for future generations. We being the engineering fraternity, should work unprecedentedly to achieve such a reality near future.
Eng. (Professor) Mahesh Jayaweera
B.Sc. (Civil Eng), Ph.D. (Env Eng)
Professor, Department of Civil Engineering, University of Moratuwa
Chartered Engineer, Member of IESL, IWA, SLAAS-Section C, and SLAAS-Chair of Committee for popularization of Science