To build greater understanding and awareness of traditional knowledge and inform action by indigenous peoples, local communities and policymakers, the United Nations University Institute for the Advanced Study of Sustainability (UNU-IAS) launched the Traditional Knowledge Initiative in 2007. This initiative’s study of current native practices and use of long-established knowledge is crucial in a world where predominant approaches to development have brought so many problems. Indeed, contemporary societies can and should look to even past indigenous societies for valuable insights and lessons on how to more efficiently use resources and improve their waste management systems.

Between 2000 and 2050, the world’s population is projected to grow by 50 percent, global economic activity by 500 percent and global energy and materials use by 300 percent. This will put additional pressure on the Earth’s resources and environment, already under significant stress. During the 1992 Earth Summit, world leaders declared that “a principal cause of the continued deterioration of the global environment is the steady increase in materials production, consumption and disposal”. Rio+20, the Earth Summit’s 20-year follow-up, affirmed that green economy policies in the context of sustainable development and poverty eradication should promote sustained and inclusive economic growth, as well as sustainable consumption and production patterns.

Resource use and waste management tend to differ markedly in the developed and the developing world. The wealthier the person or society, the more resources consumed and the more wastes (solid and liquid) generated. Thus, developed countries consume more energy, water, metals, plastics, and so on, than developing countries. The average resident of the United States generates 3.5 kg of wastes per day, while the residents of some African cities generate less than 200 grams/person/day according to 2012 World Bank data.

The waste generation rates in the developed world show a trend towards stabilization or slow growth. This reflects the maturity in their economic systems as well as their slow or declining population growth. Developed countries are implementing efforts to improve resource efficiency, prevent waste and maximize reuse and recycling so that economic growth does not translate into a commensurate rise in waste generated.

Meanwhile, waste generation rates are increasing rapidly in the developing world due to economic growth and urbanization. Growth in waste generation will be fastest in Africa and Asia in the near future says the World Bank. Over the next two decades, for example, the waste produced by sub-Saharan Africa will triple. China now generates the world’s largest amount of solid waste, having surpassed the United States in 2004.

Many cities in the developing world are still struggling to provide proper waste collection and disposal systems for their populations, resulting in air, water, and land pollution, and negative impacts on public health. Appropriate waste management, however, can create job opportunities and reduce a society’s ecological footprint. Solid waste policy should thus aim to minimize waste generation and maximize reuse and recycling of waste materials.

While technological innovation is often seen as the answer to modern waste problems, what can we learn from the historical methods used by great ancient societies such as the Aztecs of Mexico? How can past systems like Aztec waste management and resource use possibly be relevant to the contemporary world?

Origin and rise of the Aztecs

Originally nomads from the arid regions of Northern Mexico or the Southwestern United States who survived by hunting and gathering, the Aztecs migrated south and found a temperate climate and abundance of water in Central Mexico (in the 14th century, five interconnected lakes existed in the area). According to legend, the Aztecs were guided by a priest’s dreams of a god who instructed them to settle where they found an eagle perched on a prickly pear cactus eating a snake. They reportedly found this on a small island in one of the lakes, and this is where they founded Mexico-Tenochtitlán, today’s Mexico City, in 1325.

The Aztecs had modest beginnings, serving as mercenaries for other nations. In time, their reputation as fierce warriors grew and they built a city-state. Since other indigenous nations had already settled around the lakes on more desirable land, the only way for the Aztecs to accommodate a growing population was to develop around the small island. The Aztecs expanded Mexico-Tenochtitlán by building chinampas, or artificial islands.

Though the Aztecs did not invent chinampas (they were already being used by other native nations when the Aztecs founded their city) they made the most of them. To build the chinampas, the Aztecs first formed rectangles of varying sizes — usually 91 metres long and from 4 to 9 metres wide — by staking out the area and fencing it with reeds. The fenced-off area was then filled with mud, lake sediment and various organic materials, until it rose above the water level of the lake. Then trees were planted to “anchor” each chinampa. Most residents of Mexico-Tenochtitlán lived on chinampas, where they also grew their crops. Lake channels surrounded all four sides of each chinampa and were wide enough for a canoe to navigate. These channels provided crop irrigation and an easy way to transport products to market.

Aztec waste management

The city expanded and the number of chinampas grew with it. By the year 1519, when the Spaniards arrived, Mexico-Tenochtitlán had a population of over 200,000. It was the largest city in the Americas, and one of the largest in the world — bigger than any European city at the time. Its size, orderliness and cleanliness impressed the Spaniards. The city, laid out on a grid plan (which can be seen in the background of the fresco image at top of the page) that covered over 12 square km, was the centre of the most powerful empire in Mesoamerica at the time. Due to the abundance of water and sunlight, as well as a temperate climate, the chinampas were highly productive, producing up to four crops a year, and about two-thirds of the food consumed in the city.

Another important factor in maintaining that high productivity was the intensive recycling of nutrients. The Aztecs disposed of all kinds of organic wastes in the chinampas, such as food leftovers and agricultural residues, which fertilized the crops. Further, the most valuable fertilizer used on the chinampas was human excrement. With other uses, such as for tanning leather, the excrement was so valued that the city had a network of public latrines from which it was collected and eventually sold at the city’s main market.

Human urine was used as a mordant (fixative) in the dyeing of fabrics, and, thus also considered a resource. Nearly every household had ceramic containers used to store urine in order to sell it. In Aztec times, Mexico did not have cattle, sheep, goats or chickens (they were introduced by the Europeans), but the Aztecs consumed animal protein from turkeys, ducks, deer, fish, and other wild animals. They also raised a breed of dog they called itzcuintli for human consumption, feeding them food leftovers.

If released into the environment, organic waste, excrement and urine can cause air, water, and land pollution, and pose risks to human health. By recovering and recycling this waste, the Aztecs prevented pollution in the lakes that surrounded Mexico-Tenochtitlán. Any burnable materials, such as textiles, were recovered and burned at night in order to illuminate public spaces.

How did the Aztecs manage to go from being hunter-gatherers to creating one of the largest cities in the world and a powerful empire in a relatively short time? First, their adherence to law and order created an organized city and society. Second, they created a meritocratic system, where hard work was rewarded. The Aztecs considered education as a high priority. All children had to attend school: boys and girls, commoners and nobles. Education prepared children to become productive members of society. They also developed a resource-efficient culture that made the best use of any available resources in order to survive. These factors shaped their waste management practices.

Scavengers have been recycling wastes for at least 700 years, first in Mexico-Tenochtitlán and today all over Mexico.

During the rule of Moctezuma II (1502 to 1520) dumping of waste and even littering in public spaces was prohibited and penalized. In some cases the penalties for violating the law would be considered disproportionate by today’s standards: a person could be sentenced to death for cutting down a living tree without proper authorization. Aztec society expected its rulers and nobility to be role models and stipulated stiffer penalties for them than for the general population if they violated the law. Wastefulness was not tolerated, particularly among the elite: children of nobility were sentenced to death if they were wasteful. This contrasts markedly with most contemporary societies, where high government officials and policymakers enjoy legal immunity from prosecution, and their children sometimes flaunt their wealth and privileges.

Mexico-Tenochtitlán had officials in charge of maintaining cleanliness and street sweeping. Scavengers — called pepenilia — were in charge of recovering recyclable materials. Interestingly, Mexican scavengers today are still called pepenadores (singular pepenador), which stems from the verb pepenar, for “to scrounge/select” that is itself derived from a Náhuatl (the Aztecs’ language) word for to choose/select. Thus, scavengers have been recycling wastes for at least 700 years, first in Mexico-Tenochtitlán and today all over Mexico. (See the bottom of this page for previous Our World articles on contemporary scavenging in Mexico.)

No descriptions or records have been found of Aztec garbage dumps. Instead they developed a system that is similar to a sustainable materials management system, considered today as the most desirable way to manage solid wastes, conserve resources and protect the environment. The Aztecs maximized recycling, burned some materials and disposed of the remainder in their chinampas. From what we know about Aztec society, they found productive uses for all wastes. Unfortunately, after the Spaniards defeated the Aztecs militarily they dismantled the waste management system, drained the lakes, and built Mexico City over the lake bed. Waste management became a problem that still poses challenges to Mexico City officials today.

What the Aztecs can teach the modern world

I would argue that the contemporary world can learn valuable lessons from the Aztecs, such as the following:

Societies can be highly adaptable — The Aztecs adapted quickly and successfully from a nomadic, hunter-gatherer lifestyle to a sedentary, agricultural one, which has been called “agrarian urbanism”. And, in the process, they developed a resource-efficient culture with a highly-productive agricultural system that recycled nutrients from their wastes. Their intensive recycling practices created a competitive economy that minimized wastes and used them productively to satisfy their needs. The Aztecs had to survive in a region where other nations already lived and were not always friendly. A strong economy allowed them to eventually build an empire. Contemporary societies face significant challenges such as the need to feed a growing population, environmental pollution, habitat destruction, biodiversity loss and the possible negative impacts of climate change. Societies today need to transition to a development model that is more inclusive, less unequal, more resource-efficient, and low-carbon. The transition will not be painless, but the Aztecs demonstrate that a society can successfully adapt to dramatic changes in environmental conditions and build a strong economy by making an efficient use of resources and not wasting anything.

Wastes are actually resources — The Aztecs learned that “wastes” are resources that can be recovered, reused, recycled and used productively in manufacturing and agriculture. Necessity made the Aztecs pursue self-sufficiency. In time, they discovered that some waste materials were actually very valuable — so valuable, that they were bought and sold, such as human excrement and urine. For recycling to be economically sustainable in the long term, it needs to respond to demand. If a waste material has a price, people will recover it in order to make extra money. In the modern world, prices of materials — metals, paper, plastics, and so forth — need to reflect the environmental impact of their extraction and processing as well as their disposal. Under these conditions, the market would favour recycling and resource efficiency. When government policies, particularly subsidies, make energy, water, and natural resources artificially cheap, they encourage wastefulness.

Carrots and sticks — The Aztecs developed a system that encouraged productive use of wastes and cleanliness through a mix of economic incentives and penalties for non-compliance with city ordinances. People were penalized for dumping wastes in public spaces; but if they recovered the recyclables in their wastes, they would avoid the penalties and benefit from a clean and productive city. Too many cities in the contemporary world rely on penalties to try to encourage its population to keep their cities clean and to recycle their wastes. Cities need to institute incentives to maximize recycling. Community involvement in waste management and recycling is crucial. Furthermore, about 15 million scavengers or waste pickers, make a living recovering recyclable materials from waste worldwide (for more information on this topic, read The informal recycling sector in developing countries).

Most cities in the developing world view the informal recycling sector as a problem that needs to be eliminated. If cities in the developing world want to maximize recycling, create jobs, reduce poverty and protect the environment, they need to work together with the informal recycling sector, not against it.