7.3 Solid waste

Every time societies extract and use natural resources, they generate waste. That waste can be described in two ways: by its source (where it comes from) and by its type (what it is).

The three main sources are:

• Domestic waste, produced by households and communities, covering everything from food scraps and packaging to old electronics and clothing.
• Industrial waste, generated by factories, construction sites, and manufacturing processes. This category often includes chemical residues, heavy metals, and e-waste, and tends to be more hazardous than household waste.
• Agricultural waste, arising from crop production, livestock farming, and forestry. Crop residues, animal manure, and pesticide containers all fall here. When mismanaged, agricultural waste drives nutrient runoff into water bodies, for example the dead zone in the Gulf of Mexico, fed largely by nitrogen and phosphorus from Midwestern farming.

The three key types to know are:

• E-waste, discarded electronic devices such as phones, laptops, and batteries. These contain hazardous metals including lead, mercury, and cadmium alongside recoverable precious metals such as gold and palladium. Poor handling causes toxic pollution; Agbogbloshie in Ghana became one of the world's most polluted sites partly through informal e-waste processing.
• Food waste, uneaten or spoiled food from households, restaurants, and supply chains. Roughly one third of all food produced globally (around 1.3 billion tonnes per year) is wasted, even as hundreds of millions face food insecurity. In landfill, decomposing food produces methane, a potent greenhouse gas.
• Biohazardous waste, infectious or potentially infectious material from hospitals, laboratories, and research facilities, including used syringes, contaminated PPE, and biological specimens. Improper disposal risks spreading disease and harming wildlife; the COVID-19 pandemic generated a global surge in discarded masks and gloves.

A typical waste stream from a high-income household contains most of the following:

• Paper and cardboard: newspapers, magazines, packaging. Readily recyclable when clean and dry, but once contaminated with food it becomes difficult to process. The US generates roughly 67 million tonnes of paper waste annually; about two thirds is recovered.
• Glass: bottles, jars, window glass. Glass can be recycled indefinitely without loss of quality. Sweden recovers around 94% of its glass. Breakage complicates collection but does not prevent recycling.
• Metals: aluminium cans, steel tins, scrap metal. Energy-intensive to produce from ore, so recycling carries large energy savings. Recycling a single aluminium can saves enough energy to run a television for around three hours. Coated or composite metal items are harder to separate.
• Plastics: bottles, films, bags, containers. Persistent in the environment and difficult to degrade. Only around 9% of all plastic ever produced has been recycled; the rest sits in landfill, in the environment, or has been incinerated. Many plastics are non-recyclable in practice because of contamination or mixed polymer construction.
• Organic waste (kitchen and garden): food scraps, fruit peels, garden trimmings. Biodegradable and suitable for composting. In landfill, however, anaerobic decomposition produces methane.
• Packaging: wrappers, foam, multilayer films. Often single-use and composed of mixed materials that resist straightforward recycling. Amazon alone was estimated to have generated over 320 million kg of plastic packaging in 2021.
• Construction debris: bricks, timber, cement, tiles, and hazardous legacy materials such as asbestos or lead paint. China produces between 1.5 and 2 billion tonnes of construction waste annually, most of which goes to landfill despite much of it being technically recoverable.
• Clothing and textiles: discarded garments, shoes, and fabric off-cuts. The fast fashion model has accelerated turnover: the global fashion industry generates roughly 92 million tonnes of textile waste each year, and many synthetic garments are non-biodegradable.