Chemistry is the most ancient of mankind’s sciences. Centuries of discoveries, experimentation and research yielded slow results, but as the world entered the 20th century, the growing need to prevent pandemics, the world wars and a fast growing population accelerated the growth in the chemical industry. And as the years have progressed, the need has grown exponentially. But with this accelerated growth, what got left behind, is the legacy of knowledge, which led to an exponential growth creating thousands of new products being manufactured by a multitude of chemistries, but what never got questioned is the environmental impact of these products, both before and after its manufacturing and to a larger extent, during the manufacturing process itself. The adverse impacts of such chemicals and processes were affecting the environment and life. However, the need of the hour, then was more on developing, introducing, innovating new products and molecules the concern of sustainability then, was not even in the hindsight.
In the late 80s and early 90s, we realized the devastating impact of chemicals used in manufacturing processes It was this realization that lead Prof. Paul Anastas & Dr. John Warner during the late 90s to formulate certain rules and principles of green chemistry, as structure to the science. But the world of chemistry is ever evolving, and rapid growth has led to many changes and revisions to the chemical industry. As the regulations changed, as consumer references changed, so did green chemistry practices. But costs and sustainability were still a question.
Scientists needed to break the vicious cycle of chemical production. For instance, the processes that are used for the manufacturing of generic APIs or Active Pharmaceutical Ingredients and its intermediates already generate substantial pollution in the form of aqueous effluents.
The toxicity of the aqueous effluents which gets generated from a pharmaceuticals’ manufacturing unit is just one edge of the problem, the other and perhaps more looming is the sheer quantity of its effluent load, which is best comprehended by Prof. Roger Sheldon of Delft University in his study of calculating the Environmental Factor (E-factor) for various industry sectors.
The E-factor calculation is defined by the ratio of the mass of waste per unit of product:
E-factor = total waste (kg) / product (kg)
The metric is very simple to understand and to use. It highlights the waste produced in the process as opposed to the reaction, thus helping those who try to fulfil one of the twelve principles of green chemistry to avoid waste production. E-factors ignore recyclable factors such as recycled solvents and re-used catalysts, which obviously increases the accuracy but ignores the energy involved in the recovery (these are often included theoretically by assuming 90 % solvent recovery).
|
Industry sector |
Annual production (t) |
E-factor |
Waste |
|
Oil refining |
106-108 |
Ca. 0.1 |
105-107 |
|
Bulk chemicals |
104-106 |
<1–5 |
104-5×106 |
|
Fine chemicals |
102−104 |
5–50 |
5 × 102−5 × 105 |
|
Pharmaceuticals |
10–103 |
25–100 |
2.5 × 102−105 |
As seen here the Pharma industry produces the most amount of waste. You can find out more about E-Factor here:http://www.sheldon.nl/http://en.wikipedia.org/wiki/Green_chemistry_metrics
It is this pollution that leads to an unhealthy environment, further impacting the inhabitants –leading to more complex and large quantities of API molecules that consequently result in more pollution! The vicious cycle needs to be reconsidered and if need be, even reversed!
Green chemistry aims to eliminate hazards right at the design stage. The practice of eliminating hazards from the beginning of the chemical design process has health and environmental benefits throughout the design, production, use/reuse and disposal processes.
One of the principles of green chemistry is to prioritize the use of alternative and renewable materials including the use of agricultural waste or biomass and non-food-related bioproducts. Many Universities and Research organisations are studying the chemical properties of various renewable feedstocks such as Soy, corn, orange peels, etc.
Green Chemistry principles also call for revisiting the Periodic table and evaluate the characteristics of all elements from the green perspective. One of such attempts has been made by the experts’ team at National Science Foundation (NSF).
Other principles focus on prevention of waste, less hazardous chemical syntheses, and designing safer chemicals including safer solvents. Others focus on the design of chemicals products to safely degrade in the environment and efficiency and simplicity in chemical processes. A transformation to green chemistry techniques would result in safer workplaces for industry workers, greatly reduced risks to fenceline communities and safer products for consumers. Because green chemistry processes are more efficient companies would consume less raw materials and energy as well as save money on waste disposal.
Here are the Twelve Principles of Green Chemistry which have the potential to revolutionize everyday living:
- Atom Economy
Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product. - Prevention
It is better to prevent waste than to treat or clean up waste after it has been created.
- Less Hazardous Chemical Syntheses
Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
- Designing Safer Chemicals
Chemical products should be designed to effect their desired function while minimizing their toxicity.
- Safer Solvents and Auxiliaries
The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.
- Design for Energy Efficiency
Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.
- Use of Renewable Feedstocks
A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.
- Reduce Derivatives
Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.
- Catalysis
Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
- Design for Degradation
Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.
- Real-time analysis for Pollution Prevention
Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
- Inherently Safer Chemistry for Accident Prevention
Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fires.
This is where the scope of green chemistry gets intervened . The term is defined as the invention, design and application of chemical products and processes to reduce or to eliminate the use and generation of hazardous substances. It’s evident from the definition that the science is not merely a preventive one, but actively seeks to stop or at least minimize any chemical pollution. There are a set of rules that define the science and make it a holistic science that can be applied to all levels of production to achieve the final goal of controlling toxicity in the environment.
Incidents such as the Bhopal Gas Tragedy have slowly and surely begun to address the need for green chemistry. Chemical industry sectors are understandably reluctant to change or modify their tried and tested existing hardware and methods in exchange for adopting “greener” ways; neither perceives the regulatory requirements as an innovation driver for meeting triple bottom line profits. But stringent environmental laws, environmental awareness and the realization that it can even lead to cost reduction has popularized green chemistry. The market demands sustainability and that’s what the manufacturers have to provide. The governments across the world are now encouraging green chemistry technologies and we hope that as quickly as chemistry evolved in the past few years, green chemistry evolves even quicker!
Industrial Green Chemistry World 