Page 127 - CW E-Magazine (2-1-2024)

Point of View

Waste to chemicals – an option to clean our cities

and enable the chemical industry meet carbon goals

The management of wastes, in particular municipal solid waste (MSW), is a growing problem especially in urban pockets. And the
scale of the problem is only getting bigger thanks to rapid urbanisation as people flock to cities for better economic prospects. But urban
infrastructure in much of India still remains poorly developed, leading to congestion and pollution, and tackling both has to have high priority.

Last week this column had commented on the challenges associated with wastewater treatment in urban India, and the limited
role large industries – especially in the chemicals sector – can play a role in mitigating the crises, while finding a partial solution for the
freshwater challenges industry itself faces.

The problem and partial solution with regard to MSW is somewhat similar.

The scale of the problem
Globally, about 2-bn tonnes of MSW is generated globally every year, and economic & population growth will ensure this will only
rise. According to analysis by the World Bank, by 2050 the quantity of MSW generated will soar nearly 50%, and about 20% of the total
wastes will be generated in South Asia, with India bearing about three-quarters of this burden.

Currently, a vast majority of the MSW generated in Indian cities – after some segregation to remove items of some residual value (glass,
metals, plastics and to a limited extent paper) largely through an efficient but unorganised system – lands up in landfills at best. At the
worst, they are burnt uncontrolled, significantly contributing to air pollution, or dumped indiscriminately all around, which breeds ill-health
besides being an eyesore. In most cities in India landfills are running out of space, and more sustainable solutions are clearly needed.

The manufacture of chemicals from MSW is but one option and several technological approaches have been taken. Not all are ready
for commercial deployment, but some are.

Neat fit with chemical industry goals
Using wastes to make chemicals also fits in with the ambition of the chemical industry to lower its dependence on fossil-derived
carbon (be it from coal, crude oil or natural gas), and transition to a more sustainable path of growth. Several approaches are being taken
in this direction, including the use of bio-based resources such as vegetable oils, fats, starches, sugars, and biomass. MSW can be seen
as an extension of this approach. The dry fraction of waste – comprising unsegregated plastics, woody biomasses, food wastes, and
many other types – can become valuable sources of carbon to be used as a substitute for traditional fossil raw materials.

Many challenges
The challenges associated with using MSW as feedstock for chemicals manufacture stems largely from its variability in type & quality,
and the logistics of getting it to a processing site. The former poses stiff challenges to the reliability of plant operations and astute
engineering is required to ensure plants do not suffer frequent interruptions that can play havoc with economic returns. Logistical chal-
lenges dictate both the location and the size of the conversion plants, and the eventual aim is to go as large as technically feasible without
having to cart low-value waste long distances (which not only adds to costs, but also increases the carbon footprint).

Gasification as an option
One of the fundamental technologies used to manage MSW is gasification. This generic technology has been practiced for long –
first with coal and then natural gas. Gasification is done at high temperatures in a limited supply of oxygen, air or steam. When steam is
used, the process is known as reforming and is well known to the chemical industry. Indeed, steam reforming of natural gas, followed by
downstream processing, is currently the primary pathway for the production of ammonia, hydrogen and methanol.

Just like with fossil fuels, gasification can turn MSW into synthesis gas (syngas, for short) – a mixture of carbon monoxide (CO) and
hydrogen (H ), which can go down several paths of chemical conversion. Gasification also produces some quantities of carbon dioxide
2
(CO ), methane (CH ) and has some trace impurities – all of which can be removed using various cleaning and conditioning methods before
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Chemical Weekly January 2, 2024 127

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