Welcome to the worldwide waste web

Each year, the world’s population produces 7-10 billion tonnes of waste, including 300-500 million tonnes of hazardous waste. Now, researchers from Spain and Colombia have mapped a worldwide “waste web” that tracks the movement of hazardous waste around the world. Their findings are published in the journal Nature Communications.

What is hazardous waste and why does it move around the world?

Hazardous waste includes substances that are toxic, flammable, explosive, corrosive, or may carry disease risks. Approximately 10 per cent of hazardous waste is traded between countries through a network the researchers called the “worldwide waste web”, or W4 for short. Countries may export hazardous waste to avoid the costs of processing it, or import waste as a source of cheap raw materials.

The volume of hazardous waste traded internationally is estimated to have increased by 500 per cent in the past three decades.

The research team created a mathematical model of a network to represent the W4, based on data tracking 108 categories of waste moved between countries between 2001 and 2019 (except 2010, for which no data were available). Under the United Nations’ 1989 Basel Convention on the Control of Trans-boundary Movement of Hazardous Wastes and their Disposal, countries are required to self-report how much hazardous waste they import and export, as well as where the waste is coming from or going to.

Altogether, the researchers reported that more than 1.4 million metric tonnes of waste were reported under the Basel Convention during the study period – equivalent to more than 4000 times the weight of New York’s Empire State Building.

Hazardous waste is also transported and dumped illegally, but this couldn’t be captured in the dataset, which was based on countries’ self-reporting.

What did the new study find?

The new study focused mainly on the three most common types of waste reported, which together made up more than 95 per cent of the reported waste traded. Type I waste includes clinical, medical and pharmaceutical waste; type II is wastes containing specific chemicals including valuable metals; and type III includes waste produced by households.

The research team examined hazardous waste trading patterns in relation to countries’ incomes and environmental performance. The model developed for the study can identify when countries reach their “carrying capacity” for specific types of waste. Based on this information, the study highlights countries such as Mexico, India and Uzbekistan that are at a high risk of becoming congested with hazardous waste.

Waste congestion carries risks including improper handling and disposal, as well as the health and environmental effects of pollution from hazardous waste. For example, heavy metals from e-waste can enter waterways if waste containing these metals is not processed or recycled appropriately.

The study also examined changes in W4 over time. For example, countries including Germany, France, the US and Ukraine changed from balancing imports and exports to become net exporters of hazardous waste over the study period. By contrast, the Netherlands, Belgium, Spain and Canada became net importers of hazardous waste.

“The current results trigger some red alert about the critical situation of some countries and the necessity of substantial investment in waste management at a global level,” the authors write in the article.

They hope that their W4 model can be useful in understanding the impacts of waste import bans and how the global waste ecosystem will cope with the influx of waste arising from the COVID-19 pandemic.