by Julián A. Restrepo* Green Chemistry, Ecological, Sustainable or Sustainable Chemistry is a branch of chemistry that has emerged about 30 years ago as a response of some scholars for their concern about the impact that some chemical processes cause on the environment.
It is clear to understand everything that chemistry does for us: From the first alchemists who obtained the first synthetic pigments, to modern times where chemistry allows the obtaining of agrochemicals, polymers and plastics, raw materials for different sectors (including paints and coatings), products for the textile and food sector, it even allows space travel.
But along with all these advantages that chemistry provides, there is the problem of contaminants, toxic substances associated with chemicals, among which it is important to mention:
VOCs (Volatile Organic Compounds), generated by the emission of vapors and gases by using organic solvents, such as alcohols, ketones, aromatic and aliphatic hydrocarbons; for its adverse effect on occupational health and its role in the formation of tropospheric ozone and "smog".
Fossil fuels (or mineral fuels), such as coal, petroleum products and natural gas; for its important contribution to the "greenhouse effect" and "global warming".
Toxic and hazardous substances (and others reported in the so-called "dirty list"), such as NPEOs (ethoxylated nonyl-phenols) and other surfactants, for being "endocrine disruptors"; compounds with heavy metals, because they are carcinogenic and cause tumors, and in general, because they are contaminants of water sources.
POPs (Persistent Organic Pollutants), such as dioxins and furans, hexachlorobenzene, PCBs (polychlorinated biphenyls) and certain phthalates, such as dibutyl phthalate (DBP) and diethylhexylfthalate (DEHP); for its toxic effects on water and air pollution, and for having associated problems of bioaccumulation, toxicity and persistence.
CFCs (Carbon Chlorofluoro) and COHs (Halogenated Organic Compounds), such as methane tetrachloride, chloro-methane, methane trichloride, halons; for its known effect on the destruction of stratospheric ozone (ozone layer).
It must be said that, under current production schemes, any commercial product manufactured in a chemical process is associated with a certain number of by-products, waste materials or hazardous waste, whether during its manufacture, storage, use, transport, disposal and so on, which if they cannot be properly used become polluting materials and of course, Take environmental importance: Depending on the way in which they are disposed, they will have a greater or lesser impact on the environment, depending on their degree of toxicity and danger to it.
Pollutants are, in simple terms, toxic substances emitted into the environment, due to human activity and industrial processes, which alter the natural balance of the natural environment. In this sense, a factor E has been defined, defined as [1]: E = (kg. of waste) / (kg. of product), which relates the amount of unwanted waste produced per product of interest manufactured. Some E values for different industrial processes are reported in the following table:
Industrial sector
Annual production (ton)
Factor E = (ton residues) / (ton product)
Oil refining
106 - 108
<0.1
"Bulk chemicals"1
104 – 106
1 – 5
Fine chemistry
("specialty chemicals")2
102 – 104
5 – 50
Pharmaceuticals
10 – 103
25 - 100
The table above shows that the "Fine Chemistry" and "Pharmaceuticals" sectors produce the highest amount of waste per unit of commercial product manufactured: The pharmaceutical sector produces almost 1000 times more waste than the oil sector.
{mospagebreak}
In fact, it can be observed that the oil refining industry is a "cleaner industry" than others, because to be economically profitable it must minimize the amount of waste generated as much as possible (contrary to what might initially be thought). Naturally, this is without taking into account the concept of "Life Cycle Analysis" (LCA), since the problems inherent in the use of hydrocarbons and their derivatives are known; and in addition, we must consider the environmental impact associated with oil spills, when they occur.
Concept of sustainability
The concepts of sustainability and "Sustainable Chemistry" are directly related to that of "sustainable development" and have been defined as [2]: "Development that meets the needs of the present without compromising the ability of future generations to meet their own needs"..., that is: Enjoy the planet, but leave it more or less as you found it.
It is curious, but this last paragraph has been declared for 100 years in the philosophy of the "Law of the explorers" (boy-scouts), and it is seen that, from its inception, an innocent group of young people realized how important it is to take care of and maintain the planet.
The chemical industry, for its part, has needed a little more time to notice it, and so despite the enormous benefits that chemistry provides to modern societies, the social perception of it is increasingly negative for society as a whole.
At this point it is important to say that the term sustainable is derived from the English word "sustainable", which in some cases is indifferently translated as "sustainable" or "sustainable" [3]; and it must be said that the term "sustainable development" was initially ill-defined, in the sense that it was associated with that which allowed to maintain the current level of development, which is a geometric progression that will be unsustainable (some experts affirm that if the current production system continues, three earth planets will be required to sustain it). In fact, today there is a fairly widespread view that the production and use of chemicals cannot be maintained within the current parameters [4].
Today the term "sustainable development" has been redefined, and although it is aptly better defined, the term "sustainable development" is more commonly used in this sense.
Concept of "Green Chemistry"
"Green chemistry" underpins the concept of "sustainable development" and is defined in 12 principles [5], which are summarized below:
1.Prevent waste, consciously using the products.
2.Design safer chemicals and products.
3.Design the least dangerous chemical synthesis.
4.Use renewable raw materials.
5.Use safe catalysts and reagents.
6.Avoid chemical derivatives.
7.Maximize the atomic economy.
8.Use safer solvents and control reaction conditions.
9.Increase energy efficiency.
10.Design chemicals to be biodegradable.
11.Analyze processes in real time, to prevent contamination.
12.Minimize the potential for accidents.
It is therefore seen that most of these principles are aimed at making our products less bad, but it is necessary to be more ambitious, we must manage to develop, if not ecological products, environmentally friendly products.
Perhaps in some way, these principles are implicitly stated in other philosophies or methodologies associated with production processes, such as "Quality Management Systems (ISO 9000 and 14000)", "Integral Responsibility", among others; that some Latin American companies have already incorporated (even for several years) into their production schemes.
Although the new technologies of "Green Chemistry" are initially focused on chemical reactions and catalysis in industrial processes, their contribution to the paints and coatings sector has not been so direct, since this is a sector that has always proven to be very versatile and has managed to offer environmentally friendly alternatives for some years now, such as water-based paints, mineral paints, powder coatings, high solids paints, UV curing paints and the use of benign solvents.
That is, the paint industry had already thought about the concepts of "Green Chemistry" long before other sectors did. The concept of water-based paints (as an alternative to reduce the content of VOCs), is already "very old" and the use of reactive diluents (in epoxy paints); as well as the development of biocides free of mercurial compounds, and in more recent years, the development of anticorrosive pigments free of heavy metals (such as lead and chromium), metal dryers replacement of lead derivatives, such as zirconium dryers; less toxic pH regulators, among others.
Conclusion
"Green Chemistry" aims to respond to this need for change through a more rational use of our resources and knowledge, framing this new philosophy in the principles of "Sustainable Chemistry" [4]. The paint industry has not been oblivious to this problem and even before the "boom" of "Green Chemistry" had already developed environmentally friendly technologies, and although the problem par excellence associated with the painting sector is that of VOC emission, its contribution is lower than that caused by other sectors, such as transport and commercial industrial processes.
The paint industry shows that it is a very dynamic sector and prepared to adapt to the future changes that the development of environmentally friendly products can cause. But it must be borne in mind that before the market moves towards a sustainability approach, it is also necessary to fill the existing gap in safety: Stricter legislation to force the shift towards cleaner technologies, which will lead to a sustainable, environmentally friendly and cheap future.
References
[1] Sheldon, R. A.; Chem. & Ind., 1992, 903-906.
[2] Report of the World Commission on Environment and Development (Brundtland Commission): Our Common Future, UN, 1987.
[3] Restrepo, J. A.; "Ecology and VOCs: Development of environmentally friendlier products". Inpralatina, Vol. 11, No. 4, July/August 2006, pp. 34-36.
[4] Mayoral, J.A.; "Use of alternative solvents", publication on the Internet: www.unia.es/ nuevo_inf_academica/ bisualizar_file_adjunto.asp? ID = 1606.
[5] Anastas, P. T. and Warner, J.C.; Green Chemistry: Theory and practice; Oxford University Press; Oxford, 1998.
*INVESA S.A. / Universitat Jaume I.Castellón, Spain. [email protected]
Leave your comment