If you segregate waste at source, you probably categorise a range of items as dry waste – scraps of paper, glass bottles, metal pieces, old shampoo bottles, cardboard boxes, food containers. How much of this can actually be recycled and what happens to the rest?
On an average, Indian cities generate around 1.5 lakh tonnes of municipal solid waste every day. Over half of this is wet waste, which is biodegradable and can be used to make compost or biogas.
Of the 45% of non-biodegradable waste, around 15% is inert materials such as silt components, stones, wood pieces, broken glass. This has to be disposed of in landfills as per the Municipal Solid Waste Management Rules, 2016. The other 30% makes up what households usually categorise into dry waste. Of this, just around 5% can be recycled and recovered.
Of the total dry waste that includes paper, metal pieces, glass bottles, one-time usable plastic covers and hard plastics, the recyclable materials are mainly metals, tins, hard plastic, cardboard boxes and reusable glasses. These are usually collected by wastepickers and land up in the recycling industry through scrap shops and dealers.
There is still no solution for non-reusable and low quality plastics such as polythene bags, covers used in packaging products like biscuits and soaps, packing covers, plastic containers containing home delivered food
What happens to this material
The non-recyclable dry waste is currently dumped into open landfills, often mixed with inert materials and wet waste. Countries such as Germany, Australia, USA, Canada and Singapore generate power by using this material as refuse -derived fuel in their waste-to-energy plants.
Indian cities, however, have not yet been able to set up and run large, scalable, efficient and sustainable waste-to-energy plants.
The main reasons for this are the lower calorific value of the material due to high moisture content, lack of segregation at source and shredding options, and capacity in local governments to run cluster level waste-to-energy plants.
Landfills have been subject to fire accidents, especially in summer, because this waste can catch fire easily due to the increased calorific value and moisture evaporation rate in hot weather. Sometimes, these landfill fires last for months.
Managing burning landfills is tough and expensive. When any material with a higher calorific value is left unattended, it runs the risk of fire accidents. Mixing wet and dry waste makes it more difficult to make compost.
Some solutions
The first approach is to drastically reduce the usage of non-recyclable material. This is ideal for the environment and has been implemented in some countries by ensuring that only reusable bottles, bags, plastics are used. In India, this is difficult since this material is extensively used almost everywhere and finding a substitute is challenging.
With the outbreak of the Covid-19 pandemic, dry waste generation has also increased in some ways due to more online shopping and home delivery of food, which has increased packaging waste.
Governments have tried banning polythene bags by enforcing laws in states, including Karnataka and Kerala, while others like Sikkim have also worked towards reducing plastic pollution. But implementing such measures across the entire country, especially in bigger states, is a challenge.
Fuel from waste
The other approach is to use this material as refuse-derived fuel. If this material is not mixed with wet waste, it would have a decent calorific value of over 3,500 kcal/ kg. (A higher calorific value means more heat will be generated on burning, which means it can generate more energy if used as fuel).
At present, the low-quality plastic material is mostly mixed with organic waste, which adds moisture and silt and brings down the calorific value to about 2,000 kcal/kg-2,500 kcal/ kg.
An ongoing study by the Indian Institute for Human Settlements analysed the calorific value of mixed waste dumped in landfills across five Indian cities – Davanagere, Kalaburagi, Chitradurga, Haveri and Ranebennur – and the calorific value in these landfills was found to be in the range of 2,000 kcal/ kg-2,400 kcal/kg, with a moisture content of 18%-20% and silt content of 5%-8%.
By setting up efficient segregations systems and reducing the moisture content of this material, it is possible to use it as heating material.
Cement industries use coal in their kilns to generate heat. With some changes in the design and functioning of these kilns, it is possible to use this non-recyclable dry waste material as fuel.
This can also help combat the shortage of coal. Using non-recyclable dry waste in cement kilns was also recommended in the guidelines of the Swachh Bharat Mission released by the ministry of urban development in 2018
In June 2021, a cement factory in Ariyalur district of Tamil Nadu’s Trichy district achieved its milestone of meeting a quarter of its fuel requirement through waste material. There are environmental concerns over using dry waste as fuel since they emit toxic gases, but it is a realistic situation in light of overflowing landfills.
On any day, the first choice for handling dry waste would be to cut down on single-use plastic for which governments need to impose serious strict measures.
While a complete reduction will take time and effort, the option of using this material as refuse-derived fuel can be explored to reduce landfill fires and increase the efficiency of waste management.
For this to happen, municipalities should set up an efficient segregation system to reduce the moisture and silt component in dry waste and commit to supply good quality refuse-derived fuel material to the cement industries.
Pushkara SV is a practitioner at the Indian Institute for Human Settlements, Bengaluru, with experience of working at over 60 Urban Local Bodies across the country. His work has focused on improving the efficiency of waste collection and processing.
