Integrated waste management can reduce pollution caused by open dumping, says IIT Bombay study

Managing the tons of municipal waste we generate is a challenge that municipal bodies are trying to crack. A study by scientists from the Indian Institute of Technology Bombay (IIT Bombay) has attempted to solve this. The researchers compared various waste management methods that are available today and suggest that combining these options, instead of dumping the waste in the open, can reduce the impact on our environment.

“Not many studies are done in India regarding waste management. This study analyses the life cycle environmental impacts under an integrated waste management approach”, says Prof. Munish Chandel from the Centre for Environment Science and Engineering at IIT Bombay, who is also a co-author of the study, talking about why this study is topical and important. 

Statistics say that over 9000 tonnes of municipal solid waste (MSW) is generated in Mumbai every day. Most of this ends up at two open dump sites and a bioreactor landfill in the city. Often, the waste is burnt in the open, and toxic pollutants from the fires have known to can cause respiratory problems, cardiovascular diseases and adverse birth defects. In addition transporting, handling, and disposing such a huge amount of waste results in the emission of greenhouse gases, fumes of sulphur dioxide and oxides of nitrogen (also called acid gases), particulate matter, and other toxic substances.

However, there are many alternative scientific options available that prove to be better than open dumping. Paper, plastic, clothes, and leather can be recycled. Kitchen waste can be turned into compost. Incineration--a method where organic waste is burnt and the inorganic residue turns into ash--can be used too. Here, the heat generated during the burning process can be used in thermal power plants, resulting in low carbon emissions and higher benefits to the environment and the society. 

Now, how about a waste management scheme that integrates all these beneficial methods? That is what the researchers from IIT Bombay have evaluated using a method called life cycle assessment (LCA). LCA is a systematic way to estimate the environmental impact of any product, process or activity throughout its life cycle.

The researchers compared six different combinations of integrated waste management scenarios, with the currently method of open dumping in a landfill. They considered scenarios where different proportions of waste were directed to recycling, composting and anaerobic digestion (degradation in the absence of oxygen), based on the composition, recyclable portion and type of waste. They also analysed the global and local environmental impact using 27 parameters including particulate matter, carbon dioxide, methane, dioxins, arsenic, nickel, and nitrogen oxides. These parameters were clubbed under the impact categories of global warming, acidification, eutrophication (excess growth of algae in water bodies due to phosphate and nitrate-rich pollutants), and human toxicity. 

Since recyclable materials constitute about 16% of the total waste generated in Mumbai, the researchers studied the how recycling varying portion of the recyclable waste impacted the environment. They varied the portion to be recycled starting from 10%, up until 90%. 

The results of the study show that there is no single MSW management scenario that performs best in all the impact categories. Although the current practice of open dumping emitted the least amount of acid gases, it still contributed to maximum eutrophication. Incineration, on the other hand, was low on greenhouse gas emissions, but emitted toxic and acid gases. Composting was found to have the lowest impact on eutrophication and human toxicity, but could not be applied for all kinds of waste. In addition, the researchers found that even if the waste was dumped in a landfill, recycling some of it could significantly decrease the impact on the environment. Hence, the researchers recommend an integrated approach that combines composting, anaerobic digestion and landfill dumping, which might help in an overall reduction in pollution.  

Studies such as this can help provide some direction to policymakers battling the odds of waste management. “Indian policymakers should be able to decide which technology is better by considering the life cycle environmental impacts of different waste management options”, advocates Prof. Chandel. 

While various methods of waste management may vary among different cities because of the differences in the composition of waste, each city needs a specific approach to understand the risks involved in open dumping, and move towards approaches that benefits the people and the environment at large.