Circular vs Linear Economy: Green Chemistry Overview

Circular Economy vs Linear Economy

• Industries use raw materials to produce products, utilize them, and eventually dispose of them.

History of Green Chemistry

• The Love Canal incident in Niagara Falls involved the dumping of 22,000 tons of chemical waste, including polychlorinated biphenyls, dioxin, and pesticides.
• Rachel Carson wrote the book Silent Spring, which brought environmental issues into the mainstream.
• President Richard Nixon established the U.S. Environmental Protection Agency (EPA) in 1970.
• The Pollution Prevention Act of 1990 shifted regulatory policy from pollution control to pollution prevention.
• The Office of Pollution Prevention and Toxics was established within the EPA in the late 1970s to facilitate environmental goals.
• The European Community's Chemistry Council published papers in the early 1990s, including “Chemistry for a Clean World.”
• Paul Anastas and John C. Warner co-authored the book Green Chemistry: Theory and Practice in 1998.
• The 12 Principles of Green Chemistry were developed in 1998.
• Staff of the EPA Office of Pollution Prevention and Toxins coined the phrase "Green Chemistry" in 1994.

Green Chemistry

• Green chemistry emphasizes chemical knowledge within the context of human well-being and environmental impact.
• It involves the practice of chemistry in a way that maximizes benefits and greatly reduces adverse impacts.
• It promotes innovative chemical technologies that minimize the use or generation of hazardous substances throughout the chemical product lifecycle.

Principles of Green Chemistry

• Prevention of pollution: Focus on preventing waste generation instead of cleaning it up afterward.
• Atom Economy: Design synthetic methods that maximize the use of materials, minimizing waste.
• Safer Chemistry for Accident Prevention: Choose substances and forms that minimize the risk of accidents like releases, explosions, and fires.

Atom Economy

• Atom economy measures the percentage of reactant atoms that end up in the final product.
• Higher atom economy means less waste and more efficient use of materials.
• It disregards the contribution of solvents or chemicals used in the reaction work-up, which are not included in the stoichiometric equation.

Atom Economy: Atom Economic Reactions

• Rearrangement reactions tend to be atom-economic, since all atoms of the reactant are incorporated into the product.
• Catalyzed reactions may have drawbacks if the catalyst is used in stoichiometric amounts, leading to significant waste.

Reducing Toxicity: Measuring Toxicity

• LD50 (Lethal Dose): The dose of a chemical that kills 50% of a test group of animals. Measured in mg/Kg.
• LC50 (Lethal Concentration): The concentration of a chemical in air or water that kills 50% of the test animals. Measured in ppm or mg/m3.

Reducing Toxicity: Measuring Toxicity

• Ames Test: Used to screen for potential carcinogens. It observes mutations in the bacterium Salmonella tryphimurium, which carries a defective gene preventing histidine synthesis. Mutagenic chemicals induce mutations, allowing the bacteria to synthesize histidine and grow.

Explore the key principles of circular and linear economies, highlighting their impact on industries. This quiz also traces the history of green chemistry, covering significant events and legislation such as the Love Canal incident, Silent Spring, and the establishment of the EPA.