Chemistry lecture 24

GREEN CHEMISTRY

Chemistry has improved our quality of life, and made thousands of products possible. Unfortunately, this achievement has come at a price: our collective human health and the global environment are threatened. Our bodies are contaminated with a large number of synthetic industrial chemicals, many of which are known to be toxic and carcinogenic while others remain untested for their health effects. They come to us from unlabeled products, chemically contaminated food, air, water and dust while the developing fetus is exposed directly to chemicals in the womb. Many chemicals work their way up the food chain and circulate round the globe: pesticides used in the tropics are commonly found in the Arctic; flame retardants used in furniture and electronics are now commonly found in marine mammals.

Yet  as  cancer  rates  rise  and  evidence increases about the link between certain chemicals and  birth defects and learning disabilities¹ our regulatory system has been unable to make chemical producers provide full testing information  or  promote  inherently  safer chemicals. While some efforts are underway to overhaul chemicals policy, most notably by the recent passing of the European Union’s new chemicals policy, REACH, the focus must also be on overhauling the way chemicals are designed from the outset. This is what Green Chemistry sets out to do.

What is Green Chemistry?

Green chemistry is an approach to the design, manufacture and use of chemical products to intentionally reduce or eliminate chemical hazards. The goal of green chemistry is to create better, safer chemicals while choosing the safest, most efficient ways to synthesize them and to reduce wastes.

How is Green Chemistry Different?

Chemicals  are  typically  created  with the expectation that any chemical hazards  can  somehow  be  controlled  or managed by establishing  “safe” concentrations and exposure limits. 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 benefits for our health and the environment, throughout the design, production, use/reuse and disposal processes.³ In 1998, two US chemists, Dr Paul Anastas and Dr John Warner outlined Twelve Principles of Green Chemistry to demonstrate how chemical production could respect human health and the environment while also being efficient and profitable.

One example of the difference between traditional chemistry and green chemistry is the use of petroleum. Today’s chemical industry relies almost entirely on non-renewable petroleum as the primary building block to create chemicals. This type of chemical production typically is very energy intensive, inefficient, and toxic—resulting in significant energy use, and generation of hazardous waste. 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. In general, chemical reactions with these materials are significantly less hazardous than when conducted with petroleum products. 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.

The Benefits of Green Chemistry

• Economical

• Energy efficient

• Lowers cost of production and regulation

• Less wastes

• Fewer accidents

• Safer products

• Healthier workplaces and communities

• Protects human health and the environment

• Competitive Advantage

A transformation to green chemistry techniques would result in safer work places for industry workers, greatly reduced risks to fenceline communities and safer products for consumers. And because green chemistry processes are more efficient companies would consume less raw materials and energy as well as save money on waste disposal.

Green chemistry, also called sustainable chemistry, is a philosophy of chemical research and engineering that encourages the design of products and processes that minimize the use and generation of hazardous substances. Whereas environmental chemistry is the chemistry of the natural environment, and of pollutant chemicals in nature, green chemistry seeks to reduce and prevent pollution at its source. In 1990 the Pollution Prevention Act was passed in the United States. This act helped create a modus operandi for dealing with pollution in an original and innovative way. It aims to avoid problems before they happen.

As a chemical philosophy, green chemistry applies to organic chemistry, inorganic chemistry, biochemistry, analytical chemistry, and even physical chemistry. While green chemistry seems to focus on industrial applications, it does apply to any chemistry choice.

In 2005 Ryōji Noyori identified three key developments in green chemistry: use of supercritical carbon dioxide as green solvent, aqueous hydrogen peroxide for clean oxidations and the use of hydrogen in asymmetric synthesis. Examples of applied green chemistry are supercritical water oxidation, on water reactions, and dry media reactions.

Bioengineering is also seen as a promising technique for achieving green chemistry goals. A number of important process chemicals can be synthesized in engineered organisms, such as shikimate, a Tamiflu precursor which is fermented by Roche in bacteria.

There is some debate as to whether green chemistry includes a consideration of economics, but by definition, if green chemistry is not applied, it cannot accomplish the reduction in the "use or generation of hazardous substances."

Environmental chemistry

Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It should not be confused with green chemistry, which seeks to reduce potential pollution at its source. It can be defined as the study of the sources, reactions, transport, effects, and fates of chemical species in the air, soil, and water environments; and the effect of human activity on these. Environmental chemistry is an interdisciplinary science that includes atmospheric, aquatic and soil chemistry, as well as heavily relying on analytical chemistry and being related to environmental and other areas of science.

Environmental chemistry involves first understanding how the uncontaminated environment works, which chemicals in what concentrations are present naturally, and with what effects.

Without this it would be impossible to accurately study the effects humans have on the environment through the release of chemicals.

Environmental chemists draw on a range of concepts from chemistry and various environmental sciences to assist in their study of what is happening to a chemical species in the environment. Important general concepts from chemistry include understanding chemical reactions and equations, solutions, units, sampling, and analytical techniques.

Environmental chemistry is used by the Environment Agency (in England and Wales), the Environmental Protection Agency (in the United States) the Association of Public Analysts, and other environmental agencies and research bodies around the world to detect and identify the nature and source of pollutants. These can include:

·       Heavy metal contamination of land by industry. These can then be transported into water bodies and be taken up by living organisms.

·       Nutrients leaching from agricultural land into water courses, which can lead to algal blooms and eutrophication.

·       Urban runoff of pollutants washing off impervious surfaces (roads, parking lots, and rooftops) during rain storms. Typical pollutants include gasoline, motor oil and other hydrocarbon compounds, metals, nutrients and sediment (soil).

·       Organometallic compounds.

Green Paints in All Colors

Many now recognize that volatile organic compounds (VOCs), the source of “new paint smell,” are harmful to health and the environment. Old-fashioned, water-soluble “milk paints” in powder form have been around for decades, but are still not widely available. Great strides have been made to bring home paints to the market that contain low or no VOCs, and are just as attractive. One company, Archer RC paint, won a 2005 Presidential Green Chemistry Award with a bio-based paint which in addition to lower odor, has better scrub resistance and better opacity.

Green Carpets in All Sorts of Places

In 2003, Shaw Carpet won a Presidential Green Chemistry Challenge Award with its carpet tile backing, EcoWorx. EcoWorx replaces conventional carpet tile backings that contain bitumen, polyvinyl chloride (PVC), or polyurethane with polyolefin resins which have low toxicity. This product also provides better adhesion, does not shrink, and can be recycled. Carpets with EcoWorx backing are now available for our homes, schools, hospitals and offices.