Turning organic waste into a resource: Can Sri Lanka make it work?

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By P. K. Balachandran

COLOMBO – The Sri Lankan government appears determined to switch over entirely to organic farming, rejecting the mixed or step by step approach. In this context, the question as to whether organic fertilizers can be manufactured in sufficient quantities and sold at an affordable price to meet the need of the farmer is being raised.

According to the World Bank, 64 % of the waste generated in poor countries is organic. And the proportion is set to increase exponentially in the coming years. The magazine Nature has predicted the global rate of solid waste generation will triple by 2100.

“There is thus great scope for the developing countries to turn organic waste into a resource.  Organic waste could be turned into compost to grow crops. And clean organic waste could be used to feed animals,” the World Bank has said.

Both in the developed and developing countries, attempts are being made to give up dumping waste in landfills, and recycle and use it to make compost or generate power. Massachusetts became the first US state to impose a ban on landfills.

Three scientists, Andante Hadi Pandyaswargo, Dickella Gamaralalage and Jagath Premakumara went into the question of financial sustainability of modern composting in the developing countries of Asia in their 2014 paper titled ‘Financial sustainability of modern composting: the economically optimal scale for municipal waste composting plant in developing Asia’ published in International Journal of Recycling of Organic Waste in Agriculture.

They noted that despite all the discussion about using municipal organic waste to make compost, composting is still not considered a significant and strategic alternative to landfilling. There is also very little evidence available of the economic feasibility of composting.

They, therefore, did a cost-benefit analysis with data from five composting plants in Asia: Surabaya (Bali), Bekasi (Indonesia), Beijing (China), and Matale (Sri Lanka) and found that the “medium-scale and lower large-scale composting plants had an optimal opportunity for being financially feasible as compared with the smaller and larger capacity plants.”

The study also found that the viability of composting plants depended on the selection of suitable processing methods, the technology used, the scale of the operation, the quality of the product, and marketing strategies.

According to the UN Environment Program (UNEP), in 2009, many cities in developing countries allocated 20 to 50 % of their annual budget for Municipal Solid Waste Management (MSWM), but only 50 % of the population was served.

In developing countries, MSW is mostly organic waste, but not properly segregated, making its scientific use a tedious process. So, landfilling is resorted to as it is an easy way out. However, the landfills in the under-developed countries are poorly designed and maintained, thus posing a serious threat to public health. The landfills also cause global warming as organic waste is the main source of methane gas emissions.

In these countries garbage is mainly organic waste with low caloric values, making them more suitable for biological treatment rather than thermal treatment. Developing countries in Asia generally practice two biological treatment methods in organic waste management, namely, Aerobic Composting and Anaerobic Digestion.

Aerobic composting is decomposition using microorganisms that require oxygen.  The microbes responsible for composting are naturally occurring and live in the moisture surrounding organic matter. The heat produced in aerobic composting is sufficient to kill harmful bacteria and pathogens, as these organisms have not adapted to the environmental conditions. It also helps support the growth of beneficial bacteria species which thrive at higher temperature levels.

Pandyaswargo, Gamaralalage and Premakumara point out the Anaerobic Digestion (AD) method allow both material and energy recovery, with the material recovery being compost fertilizer and the energy recovery being electricity and heat.  With 100 tonnes of food waste per day, Anaerobic Digestion can generate enough energy to power 800 to 1,400 homes each year. AD plants are more popular due to these two benefits, but on the downside, they are highly sensitive to input quality. Therefore, AD technology is mostly used in Asia to treat animal manure, kitchen, and agricultural waste because of the uniformity and purity of the organic content. The application of AD technology has not been very successful in Asian cities where segregation of ‘waste-at-source’ is poor.

The scientists also point out that the rate of AD technology implementation is hindered by the high up-front investment, maintenance costs and technical skill requirements. “These failures can be seen in Delhi, Bangalore, Lucknow and other cities in India,” they elaborate, adding that Aerobic composting, on the other hand, is more “forgiving” towards input quality and requires less investment and operational costs.

One of the main reasons for failures in composting is the lack of a market for the compost, with market acceptance dependent on the price, quality, and consistency of the product. It should also be free of contaminants such as heavy metals, glass, inert materials, and plant and animal pathogens. Larger scale composting plants receive a large volume of mixed waste with contaminants, the authors point out.

Then there are the technical issues. Technological failures in composting are primarily due to failure of the mechanical pre-processing systems, the scientists say, noting,  “Large-scale composting facilities with the complex mechanical pre-processing to remove non-compostable materials have largely failed because there is hardly any mechanical system which can adequately identify and separate all of the materials in the mixed waste to ensure production of good-quality compost.”

They also point out that there is a failure to understand the nature of the biological processes that underlie composting. “Compost bacteria, insects, and microorganisms require certain environmental conditions to thrive. If these conditions are absent or interrupted, it badly affects the composting process and its quality,” they say.

The scientists conclude that medium-scale (51 TPD) and lower large-scale (200 TPD) composting plants have a better opportunity to be financially sustainable as the waste input and product quality of these plants are more controllable than larger scale composting plants. They also highlight the necessity for government aid in terms of financial, technical, and market-oriented inputs.

-ENCL

 

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