If it stinks, goes an old science joke, it’s chemistry; if it’s green and slimy, it’s biology, and if it doesn’t work, it’s physics. But chemistry is now going green as scientists cheerlead a revolution to cut industry’s use of hazardous raw materials and the release of poisonous byproducts. ‘Green chemistry’, or ‘sustainable chemistry’, has been growing quickly since it formally emerged in the early 1990s. More of a concept than a science, it encourages designing and creating chemical agents that are not hazardous to people or the environment.
Chemistry, and chemicals, surrounds us — from paints, dyes, fertilisers, pesticides and plastics, to medicines, electronics and water purification. The basics of life, such as photosynthesis and cell replication, depend on this. Properties of chemicals are determined by molecular structure. By changing the bonds between atoms and molecules, we can modify these properties. Green chemistry recognises ‘hazard’ as another property of a chemical substance, which can be altered. Nature, the greatest chemist, churns out thousands of incredibly complex molecules, using cells as sophisticated chemical factories. Science can still only wonder at this biochemical prowess, which helps our bodies translate DNA into proteins, respond to viral attacks, and transform sugar into cellular fuel. Green chemistry helps scientists mimic this to develop manufacturing processes without using any hazardous materials and cutting waste-disposal costs.
Harvard University researchers recently used a ‘biomimicry’ technique to run multiple chemical reactions simultaneously in the same vessel. They tethered molecules — that would never react when dissolved in the same solution — to DNA strands that naturally zip together. When molecules on either side of this ‘zipper’ end up close enough, they undergo chemical reaction.
For Cornell University chemists, green is orange. They make bioplastics from, well, oranges. Limonene is a carbon-based compound that makes up the oil in orange peel (which gives household cleaners their ‘citrus’ scent). When oxidised, it becomes limonene oxide, which reacts with carbon dioxide to produce biopolymers. This is exciting stuff since almost every plastic we use petroleum as a building block.