E-Waste Management, Climate Change Chemistry and Sustainable Development

E-waste

Electronic waste — discarded electrical and electronic equipment: computers, phones, televisions, appliances, batteries, cables.

It is the fastest growing waste stream in the world, driven by shortening product lifetimes and rising ownership. India is among the largest generators, and a large fraction is handled by the informal sector.

What is in it

Valuable: gold, silver, copper, palladium, platinum, rare earths, aluminium, plastics. A tonne of circuit boards contains more gold than a tonne of gold ore — commonly by a factor of tens. This is urban mining, and it is the economic reason recycling happens at all.

Hazardous: lead in solder and older CRT glass; mercury in lamps and switches; cadmium in some batteries; hexavalent chromium; brominated flame retardants — the halogenated compounds of Module 2; and beryllium.

The danger is the combination. The valuable metals give an incentive to dismantle e-waste; the hazardous ones make unregulated dismantling harmful. Informal recovery by open burning of cables to reclaim copper, or acid leaching of boards in open vessels, releases dioxins and heavy metals directly to workers, soil and groundwater — and the workers are frequently children.

The management hierarchy

In order of preference:

1. Reduce — design for longevity, repairability and modularity. The most effective and the least practised.
2. Reuse — refurbish and resell. Retains the whole embodied energy of the device, which is far larger than the material value.
3. Recycle — recover materials for new manufacture.
4. Recover — extract energy or individual materials where recycling as such is not possible.
5. Dispose — secure landfill or incineration, the last resort.

Recycling methods:

• Mechanical — dismantling, shredding, magnetic and eddy-current separation, density separation.
• Pyrometallurgical — smelting to recover metals. Effective but energy-intensive, and it destroys the plastics and can emit dioxins unless gas cleaning is thorough.
• Hydrometallurgical — leaching with acids or cyanide, then solvent extraction or electrowinning. Selective and lower energy, but it generates hazardous liquid effluent.
• Biometallurgical — bacteria and fungi leach metals. Cheap and gentle, but slow, and still largely at research scale.

Legislation. India's E-Waste (Management) Rules place the obligation on producers through Extended Producer Responsibility, requiring them to collect and channel a rising proportion of what they sell to authorised recyclers.

The chemistry of climate change

The greenhouse effect

The mechanism, in four steps:

1. The Sun radiates chiefly in the visible and near infrared, because it is hot — around 5800 K.
2. The atmosphere is largely transparent to this, so it reaches and warms the surface.
3. Earth, at about 288 K, re-radiates in the far infrared around 10 μm.
4. Greenhouse gases absorb that outgoing infrared and re-emit it in all directions, including downward. The surface is warmed by more than sunlight alone would achieve.

The natural greenhouse effect is essential. Without it Earth's mean temperature would be about −18 °C rather than +15 °C, and the planet would be frozen. The concern is the enhanced effect from added gases, not the effect itself.

Why only some gases do it — and this is where Module 3 pays off. A gas absorbs infrared only if a vibration changes its dipole moment. N₂ and O₂ are homonuclear, their single stretching vibration creates no dipole, and they are transparent to infrared however abundant. CO₂, H₂O, CH₄ and N₂O all have vibrations that do change the dipole, so they absorb at trace concentrations.

The greenhouse gases:

Global warming potential compares a mass of gas with the same mass of CO₂ over a period. Methane is far more potent per molecule but shorter-lived, roughly twelve years against centuries for CO₂ — so cutting methane acts fast, and cutting CO₂ acts for a long time.

Water vapour is treated separately for a reason. It is the largest contributor by quantity, but its concentration is set by temperature rather than by emissions. It amplifies whatever warming other gases cause — a feedback — and cannot be controlled directly.

Consequences: rising mean temperature, sea level rise from thermal expansion and ice melt, more frequent extremes, shifting monsoon patterns, and ocean acidification, which is separate from warming: dissolved CO₂ forms carbonic acid, lowering pH and impairing the formation of calcium carbonate shells and coral.

Ozone depletion

A different problem from climate change, frequently confused with it, and worth separating clearly.

Stratospheric ozone, 15–35 km up, absorbs ultraviolet-B, which damages DNA. The natural Chapman cycle creates and destroys it in balance:

CFCs destroy it catalytically. Chlorofluorocarbons are inert in the troposphere — which is exactly why they were adopted as safe refrigerants — so they drift intact to the stratosphere, where UV finally breaks them:

Note the chlorine atom is regenerated. It is a catalyst, not a reactant, so a single chlorine atom destroys on the order of a hundred thousand ozone molecules before it is finally removed. That multiplication is why trace quantities of CFCs mattered so much.

The Antarctic ozone hole forms because polar stratospheric clouds in the extreme winter cold provide surfaces that convert reservoir compounds into active chlorine, which then destroys ozone rapidly when sunlight returns in spring.

The Montreal Protocol (1987) phased out CFCs and is the most successful environmental treaty yet made: the ozone layer is measurably recovering and is projected to return to 1980 levels around the middle of this century. It is worth knowing as the counter-example to the claim that global environmental agreements cannot work.

The distinction to hold: ozone depletion is caused by CFCs in the stratosphere and admits more UV. Climate change is caused by greenhouse gases in the troposphere and traps outgoing infrared. Two different problems, different gases, different altitudes, different mechanisms — related only in that some CFCs happen to be potent greenhouse gases as well.

Sustainable development

Development that meets the needs of the present without compromising the ability of future generations to meet their own — the Brundtland definition, 1987.

Three pillars: environmental, social and economic. Sustainability requires all three; a solution that is environmentally sound but unaffordable, or profitable but socially destructive, does not hold.

The Sustainable Development Goals — 17 goals adopted by the UN in 2015 for 2030. Those most relevant to chemistry and engineering:

• 6 Clean water and sanitation — the water treatment of this module.
• 7 Affordable and clean energy — solar cells, fuel cells, batteries from Modules 1 and 2.
• 9 Industry, innovation and infrastructure.
• 11 Sustainable cities and communities — waste management.
• 12 Responsible consumption and production — e-waste, recycling.
• 13 Climate action.
• 14 and 15 Life below water and on land.

Green chemistry applies the same idea to chemical practice: prevent waste rather than treat it, maximise atom economy, use safer solvents, design for energy efficiency, prefer renewable feedstocks, and design products to degrade after use.