An analysis of the global waste network reveals where the most dangerous accumulate

Each year they take place between 7,000 and 10,000 million tons from waste worldwide, of which between 300 and 500 million are hazardous waste, i.e. toxic, flammable, explosive, corrosive or biohazardous. Countries trade with them and in the last 30 years the volume of hazardous products has grown by 500%.

A part of all that is left over does not stay in its country of origin and travels through a global waste network, the global waste network, to be processed elsewhere. There are economic incentives to market them, however, importing countries often face management and environmental health issues. In some, congestion problems already appear, when the amount of this garbage exceeds the amount of processing.

Now researchers from Institute of Interdisciplinary Physics and Complex Systems (IFISC)a mixed center of CSIC and the University of the Balearic Islands), used data from 2001 to 2019 (except 2010) to track the trade in 108 categories of hazardous waste between countries and developed a mathematical framework to model the global waste network.

The results of the study, published in the journal Nature Communicationsallowed the identification of net exporters and importers of waste and the countries with the greatest risk of congestion, identifying the moment when they reach their carrying capacity and become saturated with a certain type of waste.

Thus, the authors identified 28 countries that are at high risk of waste congestion, which can cause inappropriate material handling and possible contamination that affects both the environment and human health. That includes Mexico, India and Uzbekistanthat import large volumes of hazardous waste.

The data also shows that countries such as Germany, France and the United States have moved from having more balanced waste streams to becoming predominant net exporters, with China becoming the top net exporter of hazardous materials.

Countries with the highest chemical pollution from waste include China, Mozambique, Senegal and Afghanistan, and four European countries are at medium risk: Ukraine, Bosnia, Belgium and Bulgaria.

The global trade in waste, “on the one hand, is to dispose of waste more cheaply in the case of waste-exporting countries, and on the other hand, to have easy access to materials collected by recycling these wastes, in the case of importing countries. global waste network it is a directional and weighted network, that is, waste travels from country A to country B, but not the other way around or in the same amount from A to C, for example”, he explains. Ernest Estradathe IFISC researcher leading the work.

This characteristic is evident in the great asymmetry that exists in the import and export of hazardous waste between developed countries (typically exporters) and developing countries (typically importers).

study methodology

To carry out the research, the authors defined a different network for each of the analyzed waste types using the database. Basel Convention on the Control of the Transboundary Movement of Hazardous Waste and its Disposal (Bac) and compared with the individual capacity of each country to manage them during the years analyzed.

The capacity to process waste is not the same for all countries, and many of them are at risk of becoming congested, that is, importing more waste than they are able to manage without compromising the environment. To quantify this, the researchers used the Environmental Performance Index (PPE), a ranking that indicates which countries are best tackling the environmental challenges faced by each nation and that provides information on the ability to manage different types of waste.

This index, together with the structure of the global waste network, allows identifying countries with a high risk of rapid congestion if their PPE does not match the amount of hazardous waste they import. Of the 57 countries that are in this high-risk situation, 29 of them are in Africa, 16 in Asia, 5 in America, 4 in Europe and 3 in Oceania.

Spain is in the safe zone, like most European countries, as its infrastructure capabilities and environmental trajectory mean that the incoming and outgoing waste stream does not pose a high risk of environmental impact.

Ernesto Estrada (IFISC, CSIC-UIB)

The impact of these countries with a high risk of congestion can be verified through the analysis of chemical fingerprints or chemical fingerprintschemical elements generated by waste that leave quantifiable residues in the environment in the form of heavy metals, volatile organic compounds or persistent organic pollutants.

“Spain is in the safe zone, like most European countries, as its infrastructure capabilities and environmental trajectory mean that the inflow and outflow of waste does not pose a high risk of environmental impact”, points out Estrada, “although The fact that it is in this area does not mean that a country cannot be at high risk if its waste imports increase beyond its processing capabilities.”

Among the 28 countries most at risk there is none in Europe. However, four European countries are in a situation of average risk: Ukraine (the period studied does not include the impact of the war), Bosnia and, although to a lesser extent, Belgium and Bulgaria.

As for the structure of global waste networkthe study states that the density of connections decreased between 2001 and 2019, in addition to noting that many countries are becoming exclusive importers of waste (such as Mexico), or exclusively exporters (such as China).

The authors indicate that their study will help to assess global waste scenarios and the impacts that some policy changes may have, for example, due to the pandemic or import bans. They also emphasize that their work opens the door to a more efficient management of hazardous waste, which allows for the implementation of measures that guarantee better control.