Green chemistry metrics tell us how green a chemical process is. It could belong to any industry, but for this post we take the pharmaceutical industry as an example. It could be a continuous or a batch process. There are four ways to decide the greenness of any process:
- Atom economy
- Effective mass yield
- Life cycle analysis
To understand how to calculate this, refer to the lecture by Imperial College London, also available for download here.
Pharmaceutical processes comprise of many number of stages and with it comes waste generation. Therefore its E-factor is huge. Processes that are continuous and catalytic in nature are very easy to control, hazards associated with them are less as compared to batch processes. Hence, petroleum refinery has less by-products (kg/kg of product). In this context, a continuous and a catalytic process means minimum waste.
Waste hierarchy is a an upgraded version of the 3R concept. Going back to pharmaceutical industries, they do not do the recycling part of the pyramid because they are worried about purity, fairly so.
One may ask, why do people still look out for greener methods for batch processing? It is because, certain products are only needed in batch quantities and hence need to be produced in a batch process. Also, some companies can only afford batch equipment.
I presented a seminar on ‘Greener methods for Batch Sulfonation’ during my post-graduation. You can take a look at it here: Seminar on Greener methods for Batch Sulfonation
Last edited: December 19th 2017