Page 136 - CW E-Magazine (13-8-2024)

Point of View

Implementation of Green Chemistry
The 12 Principles of Green Chemistry and the related Principles of Green Engineering have the potential to lower emissions by a substantial 30%,
though many changes will need regulatory approvals to ensure continued safety and efficacy of the drug products.

Measures include solvent recovery and recycling; process redesign to focus on high yield chemistry (such as biocatalysis); and adoption of
continuous processes, instead of the dominant batch process, to name just a few.
Flow chemistry, a process intensification technique, for instance, involves atom- and energy-efficient, highly-controlled reactions with very low
residence times, resulting in high reaction selectivity, high product purity, and excellent productivity. Importantly, it can be conducted safely and
precisely in miniaturised highly-flexible continuous plug-flow reactors, with very low downstream clean-up operations, dramatic reduction in use
of solvents, excess reagents and energy.

Biocatalysis has emerged as a powerful tool for synthetic chemistry, and is employed for the production of several APIs and intermediates
(e.g., antibiotics, statins, and enantiomerically pure building blocks), fine chemicals (e.g., amino acids and vitamins), and food ingredients
(e.g., sweeteners, lipids, and nutraceuticals). Novel enzymes, discovered just a decade ago have been engineered and applied at scale. Its scope
will expand in the years to come, as part of a portfolio including homogeneous, heterogeneous, and electro-catalysis. While the choice of catalytic
technique employed for a transformation will depend on the target molecule, the availability of different catalysts at industrial scale, the ability to
develop appropriate analytical methods and, of course, cost, there is no denying biocatalysts are set for greater deployment.

A 2023 Cornell University report indicates that increasing solvent recovery rate from 30% to 70% could reduce the API industry’s cradle-to-gate
emissions by 26%, with an additional 17% reduction possible by increasing the solvent recycling rate to 97%. A 2024 literature review conduction
by the Technical University of Denmark evaluated the sustainability of 34 APIs produced via chemical and fermentation routes and found that the
latter had a 35 times lower carbon footprint compared to the former. Continuous operations have been explored for both small- and large-molecule
APIs and demonstrated 10-40% operational cost savings that stem from smaller physical footprint of continuous systems, more efficient use of
materials, and greater utilisation of capacity.

Sustainable feedstock and solvents procurement
While shifting procurement to producers offering sustainable feedstock (bio-based) and solvents (green solvents) has the potential to reduce
emissions by as much as 50%, they currently come at high costs. But progressive companies are looking to engage with such suppliers and grow
as the technologies and markets evolve. This seems missing in an Indian context, wherein the emphasis is still on procuring cheap.
One of the challenges here is the lack of visibility on input emissions, so as to accurately determine Scope 3 emissions, which are the result
of activities from assets not owned or controlled by the reporting organization. To cite one example, the carbon emissions associated with 1-kg of
acetonitrile (a widely used solvent) can range of 1.5-kg to nearly ten times as much, depending on the region in which it is produced, the technology
used for making it, and the energy & raw material choices made at the plant.

Process efficiency improvements
Efficiency improvements in materials and energy usage are in some sense low-handing fruits that have quick and significant paybacks. They are
typically low-cost and regulatory friendly (meaning there are no cumbersome approvals) and can offer a 5-10% reduction potential in carbon emissions.

A few such measures include improved heat integration, including usage of waste and low-grade heats; improvement in energy efficiency of
existing equipment, such as chillers, pumps, etc.; replacement of older equipment with contemporary ones; and close performance monitoring of
equipment such as heat exchangers, pumps, etc. using sensors, to ensure design-level performance.
Transition to renewable energy
A shift to green electricity and renewable fuels from biomass (for steam generation) offer a potential 5-10% decline in carbon intensity. The
increasing adoption of electrified boilers and heat pumps, for example, can tie-in nicely with greater adoption of green power.

Indian initiatives
The leading Indian API producers are cognisant of the challenges and are focussed on improving manufacturing efficiencies, lowering
energy consumption, cutting wastes, recycling solvents, etc. Lupin, for example, has streamlined manufacturing of 14 APIs, cutting solvent and reagent
consumption by 61% and reducing synthesis steps by a third. Dr. Reddy’s is targeting 100% renewable power use by 2030, driving energy management,
conservation and efficiency projects to achieve energy goals, and in FY23 worked on 16 products incorporating Green Chemistry principles to make
processes more sustainable.
While the need for a vibrant manufacturing ecosystem for APIs and their raw materials has never been greater, due the industry’s strategic
importance to health, many more participants need to better their environmental compliance.
Ravi Raghavan

136 Chemical Weekly August 13, 2024

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