• Monday, Oct 26, 2020
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OP-ED: Waste is a resource, not a liability

  • Published at 09:18 pm October 16th, 2020
Waste
Manage it right / BIGSTOCK

A roadmap for sustainable resource management in Bangladesh

The world is moving towards a more urbanized future, and the amount of municipal solid waste (MSW) is growing even faster than the rate of urbanization. The projected increase in waste generation is highest (more than triple by 2050) in low income countries, including Bangladesh, as these countries are expected to have higher economic and population growth. 

Even though source reduction, recycling, composting, and WTE are preferred choices of waste management, over 70% of solid waste is open dumped or landfilled globally. Typical landfills/dumpsites occupy large areas from several to hundreds of acres. 

A lack of available space, both in developed countries and major metropolitan cities in developing countries, for new dumpsite/landfills/waste management facilities every 20/30 years is causing a major challenge for future waste management. 

Therefore, sustainable waste or resource management is a major issue for developing countries.

stainable resource management 

Landfilling or open dumps had been the primary methods of waste management around the globe for many years. In the last 40-50 years, developed countries had moved from open dumps to sanitary or engineered landfills and, recently, developing countries have been following the same trend. However, due to urbanization and inflow of people from rural to urban areas:

1) Populations in urban mega cities are increasing at an alarming rate. With increasing population and people’s purchasing power, the amount of waste generated is also increasing. 

2) Land/space for residential houses are shrinking and getting available land for building sanitary landfills every 20-25 years in cities is becoming impossible and unsustainable. 

3) Moving from open dumps to sanitary landfill systems may be moving towards a better environmental solution, but it is still not a long-term sustainable solution. 

Figure 1:  Sustainable resource management system

To eliminate problems associated with traditional landfills, including loss of materials, climate change impacts, and post-closure monitoring costs, sustainable resource management is a major issue for both developed and developing countries. 

The proposed method (as presented in Figure 1) exhibits greater material recovery and reuse, accelerated waste degradation rates, renewable energy generation, perpetual operation in the same location (without need for additional space). The proposed sustainable resource/waste management system has three main components: 

1) Increasing waste collection in developing countries 

2) Processing collected waste through Material Recovery Facility (MRF) and increasing the rate of recycling and/or reusing recycling materials or creating a sustainable market for recycled materials

3) Designing a sustainable resource management facility (SRMF) which will include material diversion through recycling, composting before processing of leftover waste for final disposal, and processing for energy recovery through anaerobic digester (AD), perpetual landfilling, and biocell, and/or waste to energy (WTE). AD and biocell produces energy from biogas, and for WTE produces energy through incineration. 

The major benefits of the proposed method are to transform landfills into sustainable resource management facilities (SRMF), which leads to better reuse of materials, production of renewable energy, decreased demand for landfill space, and improved public perception and acceptance by the greater urban community. 

To remove the non-biodegradable plastics, glass, metals, inorganics, and even organic waste, a material recovery facility (MRF) can be built as part of SRMF facility (one of the sample flow charts is presented in Figure 2). 

An MRF processes a mixed solid waste stream and then proceeds to separate out designated recyclable materials through a combination of manual and mechanical sorting. Once the sorted recyclable materials are recovered from the waste stream, then possibly organic waste can be separated from the mixed waste. 

The separated organic waste can be diverted from final disposal through composting, and if there is any left after composting, they can be processed through the anaerobic digester. 

Only, the remaining waste can also be processed through a biocell or WTE facility, if technically feasible. Operating landfills as biocells have been studied extensively and implemented in Texas, and are under consideration for implementation in African, East European, and Latin American countries. 

Figure 2: Sustainable resource management facility -- material flow 

The complete decomposition of MSW will be completed in less than 15 years, and gas production will be accelerated if they are operated as biocells. The collected gas from biocells can be converted to electricity. The cells can continue to be re-used in perpetuity, eliminating the need to find additional landfill space. 

For example, a small city in a developing country generating less than 100 tons of waste per day with 80% food waste and 20% recyclables or other waste can design their SRMF Facility as follows: 

1) Sorting the waste in MRF within the sustainable resource management facility 

2) 80 tons of organic waste (can be diverted from final disposal)

l Two composting facilities (20 ton capacity each): 40 ton waste

l Two small-scale AD at site (20 ton capacity each): 40 ton waste -- biogas from AD can be used for electricity generation or cooking gas

3) 20 ton mixed waste with recyclables -- assumption: 10 tons recycled 

4) Leftover 10 tons for final disposal in biocell or WTE (whatever is technically feasible based on the waste characteristics and calorific value)

5) Material diversion is 90% (land requirement for final disposal reduced by 90%)  

If properly collected and managed, waste is not a liability, but a resource. The sustainable resource management facility (SRMF) addresses the issue of space availability for construction of new landfills every 20-30 years. 

Moreover, collection of generated gas through AD and biocell and conversion to electricity can provide access to electricity in remote areas where electric grids are not available. The SRMF will create green jobs and provide healthy living conditions for all. This is the perfect example of a circular economy in a developing country. 

Md Sahadat Hossain is PE Director, Solid Waste Institute for Sustainability (SWIS), and Professor, Department of Civil Engineering, the University of Texas at Arlington. Email: [email protected] 

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