LOW←TECH MAGAZINE English

Urban Fish Ponds: Low-tech Sewage Treatment for Towns and Cities

Sun, 28 Mar 2021 00:00:00 +0000

Image: Fish ponds in the East Kolkata Wetlands – the largest sewage-fed aquaculture system in the world today. Source: Edwards, 2008. [^8]

After we eat and drink, we excrete into toilets, which use water to flush our effluent into municipal sewage systems. By and large, the resulting sewage is either untreated, or treated in different kinds of wastewater treatment plants, the most advanced of which are expensive to run and have high energy demands. ¹

But even if sewage is treated, effluent is still high in levels of nitrogen, phosphorous, dissolved oxygen, and biological matter—essential nutrients for life on Earth. This causes eutrophication. The high levels of these nutrients lead to algal blooms, which in turn may produce toxins leading to mass fish deaths and biodiversity loss in rivers, lakes, and oceans. ²

Essentially, the core of the issue is that rather than nutrients being recycled, as occurs in most ecosystems, it’s a one-way flow. Fixing these problems by, for example, making water use more efficient, or using more energy-intensive sewage treatment plans, doesn’t solve the root of the problem: the nutrient cycle is leaky. And you can’t fix a leaking sink by changing the amount or kind of water you use.

Too much of a good thing

If we want to fix the leaking sink, we need to move away from the idea that human waste is inherently toxic, or that human activity is always bad for the environment. This way of thinking is grounded in the assumption that humans are somehow separated from nature. The logical conclusion of this assumption, then, is to separate us from natural cycles even more: building more refined, chemically and energy-intensive sewage treatment, building hard boundaries between food production and watersheds, and, failing that, using large-scale geoengineering experiments to clean our rivers.

But the main issue here is not that we are somehow toxic and so a burden to our environment. It’s that the nutrients we are releasing into the environment are too highly concentrated. This is especially the case when it comes to the “problem” of eutrophication. Caused by high-nutrient wastewater and agricultural run-off, it is generally thought as a bad thing. But consider the Greek root of the word: “becoming well fed.”

The main issue is not that we are somehow toxic and so a burden to our environment. It’s that the nutrients we are releasing into the environment are too highly concentrated.

Eutrophication is only bad because good nutrients like nitrogen, carbon, and phosphorous, necessary for the majority of biotic life, are too concentrated—causing rapid algal growth, leading to too little oxygen in the water, as well as too many toxins produced by algae, both of which are deadly to fish. However, fish eat algae, so if algae growth were to be slowed down a bit, fish populations would multiply instead. The problem is not that wastewater is polluted, but that there is too much of a good thing, too highly concentrated for the ecosystem to absorb.

How to fix a leaking sink

I first learned about the system of treating sewage through aquaculture when I lived in Hanoi. There, I found out that it’s actually very common, especially in poor agricultural communities, to reuse human waste for production.

Image: An overhung latrine on a fish pond in Vietnam. Source: UNEP International Environmental Technology Centre. (2002). Environmentally Sound Technologies for Wastewater and Stormwater Management: an International Source Book (Vol. 15). International Water Assn.

In countries like Vietnam and Indonesia, toilets are often placed above fish ponds. Human and livestock waste may also be collected manually and put in fish ponds. Why? Stimulated by the added nitrogen, phosphorous, and carbon, algae and phytoplankton grow rapidly and start breaking down the nutrients and bacteria and produce oxygen. As oxygen levels go up, fish are able to swim in the water and eat the algae and phytoplankton. Then the fish are caught and sold on the market. Finally, when the pond is drained, fish droppings and any remaining sediments can also be used to fertilize surrounding crops, like rice or fruit trees.

In China, the use of excreta in agriculture and aquaculture has a tradition of centuries. During the communist period, many fish farmers had limited access to fish feed and local state cooperatives started organizing human waste collection systems. Eventually, in many Chinese cities, up to the 1990s, trucks and boats collected human manure in cities—some run by the state and some clandestine, illegal operations—and transported them to aquaculture operations in peri-urban land. From 1952 to 1966, about a third of fertilizers (which includes fish feed) used in China came from nightsoils, and by 1966, 90% of excreta were recycled. ³ Incidentally, today, massive seaweed production off the coast of China has likely greatly reduced the likelihood of eutrophication—an accidental form of bio-remediation and nutrient recycling. ⁴

Image: Sewage water being pumped into a fish pond in the outskirts of Hanoi, Vietnam. Source: Edwards, 2005. [^15]

Image: Wastewater after treatment in fishponds, Hanoi. Source: Edwards, 1996. [^5]

One interesting large-scale example is the system that emerged in the outskirts of Hanoi in the 1960s. Hanoi, the capital of the newly independent communist nation, fighting a drawn-out war against Western occupying forces, had no municipal wastewater treatment. Sewage led out into two rivers, which flowed south and eventually merged with the Red River.

During the communist period of collectivization of farmland, Vietnamese farmer cooperatives were excluded from the international market and so often used whatever resources available to them to feed fish, such as slaughterhouse wastes or spoiled grains. Seeing the untreated wastewater in the canals—a resource out of place—farmers started pumping it into large ponds.

Seeing the untreated wastewater in the canals—a resource out of place—farmers started pumping it into large ponds.

After trial and error, and investing the little they had in infrastructural improvements, they determined the right sewage-and-freshwater ratio needed that would dilute the wastewater enough so the fish wouldn’t die.

Image: A local retail fish market in Yen So commune. Anders Dalsgaard. Source: Thi Phong Lan, Nguyen, et al. \"Microbiological quality of fish grown in wastewater-fed and non-wastewater-fed fishponds in Hanoi, Vietnam: influence of hygiene practices in local retail markets.\" Journal of Water and Health 5.2 (2007): 209-218.

Farmers also grew plants such as water hyacinth to reduce the erosion of the banks, and which could then be fed to livestock. These also had the benefit of drawing out heavy metals from the water. They also practiced fish polyculture, where species like catfish, carps, and tilapia were farmed together, and thus were more effective in cleaning the water and protecting small fry from predators. Every year, the ponds were drained, and the sludge at the bottom was then applied to nearby fields, further reusing available nutrients.

Eventually, these farmers developed a system that, by 1995, provided 40-50% of Hanoi’s total fish supply every year. Scientific measurements showed that the water from the fish ponds, when pumped back into the river, was well below the World Health Organisation’s recommended level for biological oxygen demand—an indicator to determine the efficiency of water treatment systems. ⁵ Essentially, they had created a water treatment plant for a city of 1.5 million people, at almost no cost to the state.

A “low-cost folk technology” serving an entire city

You might be thinking: sure, this is one example of an interesting, but ultimately doomed, alternative to wastewater treatment. It is an aberration, and couldn’t possibly be maintained for long. Unfortunately for your internal cynic, it actually can be. The city of Kolkata (formerly Calcutta), India—population 14.8 million—has the largest sewage-fed aquaculture system in the world. Though farmers had been using sewage to feed fish in different ways since the 19th century, the system became more developed starting in the 1940s.

Image: Fish ponds in the East Kolkata Wetlands, the largest sewage-fed aquaculture system in the world today. Source: iStock.

During the British colonial period, administrators built a series of canals through the city that functioned as its sewers. These let out into the Bidyadhari River. However, this river quickly silted up and became unusable. As a result, an adjacent wetland area transformed from tidal salt marshes to primarily freshwater marshes. Two sewage canals were then built in 1940 to further extend the city’s effluent to the ocean. It was at this point that local farmers started rerouting the sewage water into fish ponds in the former salt marshes, growing vegetables on the banks of the sewage canals, and forming cooperatives to manage the wastewater.

Though the Kolkata system was developed over time, it is quite systematic. Every year, ponds are first drained and sludge is applied to fields. Sewage water is fed into the pond slowly at low depth and allowed to sit for two weeks. This basically mimics conventional sewage treatment systems, where sewage is first treated through stimulating algal and bacterial growth, harmful sediments are left to settle, and most parasites are killed because their eggs and worms die if they don’t find a host within two weeks. Then, fish are stocked in another pond, and slowly sewage water is introduced into the pond at a sewage-to-water ratio of 1:4. All of this requires skill and knowledge developed over generations, allowing farmers to know when oxygen levels are too low, which could kill the fish. ³ ⁶ The resulting effluent can reach the water quality of conventional treatment. ⁷

Image: A sluice gate made of bamboo at the Eastern Kolkata Wetlands. Water hyacinth is grown to help purify the water and to feed livestock. Source: Mukherjee, 2020. [^6]

Image: Every year, the ponds are drained, and the sludge at the bottom is applied to nearby fields, further reusing available nutrients. Source: [Take pride in the East Kolkata Wetlands](https://www.facebook.com/takeprideineastkolkatawetlands/) (Facebook-page).

Through trial and error and good judgement, local farmers have developed a wastewater treatment system that is extremely efficient and adaptive to local conditions. They can distinguish the kind of effluent—industrial or domestic—through the hues it gives off, and will control or dilute it when necessary. For example, sewage from tanneries can be toxic to fish, so they will not use it. They vary water levels according to season, weather, and available quantities of effluent. They know the hue of greenish-black the water needs to be to have an optimal oxygen and ammonia level for fish. They can tell whether there is too little oxygen by paying attention to the degree by which fish come up to the surface to gulp air. Farmers harvest snails in the water to protect fish growth, which are then crushed and fed to ducks, whose droppings in turn fertilize fish ponds and nearby soils. They plant water hyacinths and duckweed to absorb heavy metals from the sewage water. ⁷ ⁸

The Kolkata fish farms provide 40% of the region’s fish production and process 80% of the city’s sewage.

The Kolkata fish farms provide 8000 tons of fish per year to the city, or 40% of the region’s fish production. It processes 80% of the city’s sewage, and reduces the nutrient and organic loads of the city’s sewage water by 50-90%, while keeping bacterial loads to an acceptable level under WHO guidelines. It is calculated to save the city an equivalent of $64,400,000 per year in sewage treatment costs—making Kolkata an “ecologically subsidized city”. ⁹ The system provides farmers a return over investment of 28% and provides 200,000 people with a livelihood. ¹⁰

While profit shouldn’t itself be the goal of this system—it’s a public service, after all—it certainly helps to defray costs of wastewater treatment. In a small municipality in Karnal, northern India, one study showed that municipal sewage-fed fish ponds, installed in the 2010s, provided over $25,000 of net profit per year to the municipality, as well as indirect benefits such as improving nearby soils through the sale of treated wastewater to farmers. ¹¹

Image: Waste-fed fish ponds provide steady sources of protein for small-holder farmers. Source: [Fish Farming in the East Kolkata Wetlands, Ramble On, Priya Mallic](https://takeabookalong.wordpress.com/2013/08/12/fish-farming-in-the-east-kolkata-wetlands/).

Image: Fish harvested from the East Kolkata Wetlands. Source: [Fish Farming in the East Kolkata Wetlands, Ramble On, Priya Mallic](https://takeabookalong.wordpress.com/2013/08/12/fish-farming-in-the-east-kolkata-wetlands/).

Still, when introduced into small rural communities, the benefits extend far beyond monetary profit, to the social, cultural, and ecological services provided by the fish ponds. This includes improving soil quality, adaptability of local communities to climate change, leisure (e.g. fishing with friends), and steady sources of protein for small-holder farmers. For example, even if they don’t sell the fish, a small sewage-fed fish pond can provide a family of six with 8kg of fish, per person, per year—a significant raise in protein intake for many rural communities. ¹² In the case of the Eastern Kolkata Wetlands, the fish ponds also help to recharge the ground water—a serious issue in India where many aquifers are nearing depletion. ¹³

Kolkata’s wetlands are a “low-cost folk technology” ¹⁴ treating the majority of the sewage of a city with a population the size of New York. This is made possible through the development of a vast human-fish-plant ecosystem, a city-scale wastewater treatment plant that emerged through the creativity, ecological knowledge, and direction of local farming communities.

Over 90 systems in Germany in the early 20th century

By this point, your internal cynic might have come up with another counter-argument: sure, so it works at scale. But you would have to be pretty desperate, and poor, to stoop down to farming fish in sewage water. While it might work in India, and worked for a while in Vietnam and China, it would never work in developed countries, where there are higher sanitation standards, and where no one would want to eat the fish farmed in sewage anyway.

Image: A view of the former sewage-fed aquaculture system in Munich, Germany, today a bird sanctuary. Photo: Peter Schleypen, 2012. Source: [Historisches Lexikon Bayerns](https://www.historisches-lexikon-bayerns.de/Lexikon/Abwasserbehandlung_(nach_1945))

You may be surprised to learn that, in fact, over 90 such systems existed in Germany in the early 20th century. ¹⁵ Up until the 1990s, the city of Munich still processed most of its wastewater through fish farming. Indeed, Germany has pioneered some of the more detailed and rigorous scientific investigation into the large-scale viability of sewage-fed fish ponds, as early as the 1890s.

Up until the 1990s, the city of Munich in Germany still processed most of its wastewater through fish farming.

Like in China, wastewater-fed fish ponds have a long but unappreciated history in Europe. Castle moats, monasteries, and villages often had wastewater-fed fish ponds. As cities grew rapidly in the 19th century, untreated wastewater was simply flushed into rivers, leading to the collapse of fisheries across Europe as well as generally unsanitary conditions and the spread of disease. There was a growing recognition that sewage should be treated; one common indicator of adequate treatment methods was that trout are able to live in the treated water. As a result, civil engineers and scientists constructed small fish ponds to test the quality of municipal sewage treatment plants.

Gustav Oesten, a civil engineer charged with wastewater treatment in Berlin, began to experiment in the late 1880s with using fish to treat wastewater, and to harvest fish as a secondary product of sewage treatment. He was able to spend the good part of a decade conducting experiments with different fish species, designs for ponds, and various local and weather conditions. ¹⁵

Image: Feed channel for the fish ponds of the Munich sewage-fed aquaculture system. Image by Bjs (CC BY-SA 3.0), Wikimedia Commons.

Through these experiments, he showed conclusively that fish growth accelerates in sewage water, and that fish in turn help purify sewage water. Trout were not very good fish for this purpose, because they cannot tolerate water with high oxygen levels—common in wastewater systems, a byproduct of rapid algae growth. Carp, who can come up for air when oxygen levels are intolerable, grew very well—those fed with sewage far exceeding production of those in normal fish ponds. But, using trout, he proved that the water was of high enough quality to enter back into the water shed. His experiments suggested that fish ponds could be designed to help address Europe’s water crisis and, at the same time, provide an economic return through the sale of fish.

By the beginning of the 20th century scientists throughout Germany started conducting more small-scale experiments. Bruno Hofer, a fish scientist better known for pioneering the study of fish pathologies, started scaling up these experiments, showing in the early 1900s that wastewater of larger institutions like hospitals, breweries, and factories, as well as smaller municipalities could theoretically be treated with fish ponds. He even went further, and “dared” to propose such a system for a city as large as Munich—a notion that was perhaps considered outlandish at the time.

Image: A sprinkler introducing secondary treated wastewater diluted with river water into a wastewater-fed fishpond in Munich, Germany. Source: Edwards, 2005. [^15]

By 1929, however, after several successful implementations of Hofer’s design around Germany, the city of Munich built its own fish pond wastewater treatment system, which served the whole city until the 1990s. This was the largest such system implemented at the time in the world, initially designed to process the wastewater of 500,000 people. The system was so efficient that the water leaving the ponds, fully treated, was comparable to natural water in quality and nutrient level. ¹⁶

Many applications

As these examples illustrate, sewage-fed aquaculture is a solution to many interlinked problems. It processes waste—from agriculture, livestock, and cities—and cycles those nutrients back into the system through food and agricultural production. It reduces nitrogen and phosphorous levels in the water, preventing eutrophication further downstream. It reuses available water, slowing down the water cycle and replenishing groundwater. It further reduces unnecessary inputs like chemical fertilizers, phosphates, and energy-intensive fish feed. Finally, it creates jobs and a source of income, especially necessary in poor countries.

If we were to calculate the fertilizer potential of sewage water alone, this would be reason enough to develop systems to reuse it. For example, one study estimated that, in the year 2000, all of India’s sewage was worth an equivalent of $2,000,000 per day in fertilizer costs. ¹⁷ In other words, on any given day, all of India is flushing several million dollars down the toilet. Waste-fed fish ponds would be of great help in capturing this wealth. Perhaps counter-intuitively, scientists have found that waste-fed fish ponds may actually be especially useful for arid countries, where water is scarce, by re-using wastewater for protein production. ¹⁸ Fish ponds don’t have to be for productive use alone. They can be integrated into wetlands and conservation areas, leisure fishing, tourism areas, or educational sites. They provide opportunities for improving biodiversity and making urban life more permeable for nature.

Fish ponds don’t have to be for productive use alone. They can be integrated into wetlands and conservation areas, leisure fishing, tourism areas, or educational sites.

Another reason waste-fed fish ponds continue to be relevant is that it is low-cost and low-tech, and therefore has little barriers for implementation. While high-tech, high-input systems like hydroponics, vertical gardening, and automated agriculture are getting a lot of press these days, the fact is that the majority of the world’s farmers have little to no access to capital and relies on small, but mostly sustainable, interventions to feed a stunning 70% of the global population. ¹⁹ Waste-fed fish ponds offer a source of subsistence at little financial risk to these small farmers. ⁸ Equally, when developed at the municipal level, they offer small towns, villages, and resource-poor communities opportunities to defray the costs of wastewater treatment, as well as generating local employment and improving sanitation. ¹¹ ¹²

Why don’t we do this more often?

Despite many advantages, most sewage-fed aquaculture systems have either been totally stopped or are in decline. So what happened? The first possible reason, and the one that most people might raise, is the “yuck factor”. Perhaps it’s just too gross for most people to eat fish grown from poop. By and large, this wasn’t the problem: consumers’ surprising acceptance of waste-fed fish is a constant in the research on urban fish ponds. ²⁰ Furthermore, about 10% of the world’s population probably already consumes food irrigated with wastewater ²¹, and, even in the European Union, where agricultural regulations are famously strict, many farmers already apply sewage sludge to their fields—but European consumers don’t seem to care too much.

Image: Tilapia.

Image: Vietnamese catfish.

Image: Common carp.

The second possible reason for their decline is that it’s not safe. And, it’s true, here is where the most care needs to be taken in designing effective wastewater treatment. There is good evidence showing that sewage treatment in fish ponds can be as safe as conventional methods. Some of the strongest evidence to support this comes from a city-sized experiment conducted in the 1980s in Lima, Peru, sponsored by the World Bank and the United Nations Development Project. Aid agencies worked closely together with the city government to design a large-scale aquaponic sewage treatment site. ²²

The site was basically a city-sized proof-of-concept. Endless measurements were taken over its two decades of operation, adjusting different variables throughout the project’s lifespan, and controlling for changes in volume of sewage and weather. It was found quite conclusively that fish-based sewage treatment was not only a viable and economical alternative for low-income countries, it also met stringent World Health Organization guidelines for water sanitation. The fish were also tested for human consumption. In all three trials, 100% of fish tested were rated at “very good” in safety levels. ²³ This study wasn’t alone: numerous studies have investigated the safety of fish grown in sewage ponds. ²⁴

More than just a leaking sink

If it’s not the “yuck factor” or safety, then what was it? In Hanoi, the waste-fed fishponds were not fully recognized for their potential, and peri-urban development in the 1990s began to encroach on the fish ponds. As the communist era came to an end, land near the city became increasingly valuable, and ponds were filled up for housing construction. Sewage became mixed with untreated industrial effluent, leading to large amounts of sewage being poisonous to fish, in turn leading farmers to switch to pelleted feed, by then increasingly available as Vietnam’s domestic market was opened to foreign trade.²⁵ ²⁶ Today, Hanoi only treats 22% of its sewage, the rest flows directly into its river systems, and 180,000 cubic meters of waste water are discharged every day into the To Lich river, the same river that serviced the fish ponds. ²⁷ ²⁸

The disappearance of fish ponds in Germany can also be largely attributed to urban growth. As cities grew, peri-urban areas—where fish ponds necessarily needed to be placed due to them having to be close to sewage lines and sources of fresh water—became more valuable. Pressured by booming real estate prices, less availability of land, high costs of labour, as well as diminishing returns on investment as domestic fish breeding had to compete with international markets, governments inevitably chose to close the fish ponds, or convert them into more conventional sewage treatment plants. Even in Munich, the largest system built in Germany, management was costly and became less and less appealing to the municipality. Munich’s fish ponds were eventually converted into a nature reserve, where migrating birds come to rest. Fish production is no longer its primary goal, and the estuary only absorbs a small percentage of Munich’s wastewater. ¹⁵

Image: The East Kolkata Wetlands in 2005. Source: Google Earth.

Image: The East Kolkata Wetlands in 2019. Source: Google Earth.

The system at Kolkata is still operational, but suffering from similar symptoms. At their peak, fish ponds in the East Kolkata Wetlands were as large as 12,000 hectares. This has shrunk to 4,000 hectares due to encroaching urban development. In Kolkata, too, workers struggle to deal with industrial effluent such as that from the sizeable leather tanning industry, which is poisonous to the fish and indiscriminately dumped into the municipal wastewater system. ⁶ ¹⁰ ²⁹ ³⁰ Thankfully, unlike Hanoi’s government, the city of Kolkata and the Indian government recognized the importance of this system, and put in a series of regulations to protect it from further development. Still, informal and illegal development—where developers fill up ponds with debris overnight and then build on it as farmers are forced to abandon it—is slowly chipping away at the wetlands.

So the main driver of their disappearance is urban expansion into the peripheries. This is largely due to the global speculation on real estate—which constitutes 60% of all capital investments today. ³¹ When given a choice between selling peri-urban land to the highest bidder, and pairing sewage treatment with some fish production, most officials won’t think twice—the fish ponds have got to go! A second reason is the high prevalence of toxic chemicals in our water systems—which are too concentrated for ecosystems, and aquaculture systems, to absorb. We should ask ourselves if it’s really worth it to permit these products if they make it harder for us to mend the ecological rift between our settlements and their surroundings.

More messy, organic systems are often derided as backwards and primitive, when in fact they may be far more appropriate and sustainable than the energy-intensive, easily replicable “solutions” valued by planners and engineers.

A third reason is the relatively cheap cost of fossil fuels. In most industrialized countries, it is much more rational to choose for sewage treatment plans with a small land footprint but a large carbon footprint. In a world where energy is cheap, environmental costs can be pushed further and further downstream. But they will eventually circle back to us, and already are. Finally, a significant factor, and one which we shouldn’t ignore, is the bias of our leaders and of professional engineers against more messy, organic systems like that of wastewater-fed aquaculture. Such low-tech solutions are often derided in popular culture as backwards and primitive, when in fact they may be far more appropriate and sustainable than the energy-intensive, easily replicable “solutions” valued by planners and engineers. ³²

Each reason points to a deeper problem: our economy’s inability to value the right things. Like so many sustainable solutions today, and many of those discussed on this website, sewage-fed fish ponds suffer from the “you can’t change this one thing without changing the whole system” problem. These systems are beset by global real estate speculation, toxic chemicals in our food and household products, contamination by industry, the cheap price of fuel, and the deep-seated idea that humans are separate from the ecosystems they are embedded in. At the root of it all is a system of value that is not in line with our ecological needs as a species, and as a member of Earth’s living community.

Fish ponds are a low-tech, low-cost, safe, and sustainable way to fix our society’s leaking sink. But when we get down there on our hands and knees, we might find a lot of other things that need fixing.

Aaron Vansintjan

Thank you to Henning Fehr for doing research on the fish pond system in Germany, Michael DiGregorio for telling me about the Vietnamese system, Phuong Anh Nguyen for the extra research into it, and Geert Vansintjan for always keeping me inspired.

For example, in many developed countries, sewage treatment often involves constant automated stirring of large ponds of water—a system which is hard to maintain and takes a lot of energy. While sewage treatment only accounts for 4% of national energy use in the US, they account for up to 50% of municipal energy use—a significant portion of the domestic energy footprint. That means that towns and cities could actually decrease their energy impacts significantly if they switched to different treatment plants. See https://betterbuildingssolutioncenter.energy.gov/sites/default/files/Primer%20on%20energy%20efficiency%20in%20water%20and%20wastewater%20plants_0.pdf ↩︎
It also contributes to a little-understood phenomenon called coastal darkening, where our ocean floors become muddier and darker, leading to a lower albedo, or reflectivity, of the Earth’s surface, in turn triggering global heating as well as reduced ability for marine life to receive daylight. https://www.hakaimagazine.com/news/the-environmental-threat-youve-never-heard-of/ ↩︎
Edwards, P. (2003) Philosophy, principles and concepts of integrated agri-aquaculture systems. In: Gooley, G. J., & Gavine, F. M. (Eds.), Integrated agri-aquaculture systems: a resource handbook for Australian industry development. Rural Industries Research and Development Corporation. ↩︎ ↩︎ ↩︎ ↩︎
Edwards, P. (2015). Aquaculture environment interactions: past, present and likely future trends. Aquaculture, 447, 2-14. ↩︎
Edwards, P. (1996). Wastewater reuse in aquaculture: Socially and environmentally appropriate wastewater treatment for Vietnam. The ICLARM Quarterly, January. ↩︎
Mukherjee, J. (2020). Blue Infrastructures. Springer Singapore. ↩︎ ↩︎
Ho, L., & Goethals, P. L. (2020). Municipal wastewater treatment with pond technology: Historical review and future outlook. Ecological Engineering, 148, 105791. ↩︎ ↩︎
Edwards, P. (2009). Traditional asian aquaculture. In New Technologies in Aquaculture (pp. 1029-1063). Woodhead Publishing. ↩︎ ↩︎ ↩︎
A term attributed to Dhrubajyoti Ghosh, a high-profile activist for the Eastern Kolkata Wetlands. ↩︎
Banerjee, S., & Dey, D. (2017). Eco-system complementarities and urban encroachment: A SWOT analysis of the East Kolkata Wetlands, India. Cities and the Environment (CATE), 10(1), 2. ↩︎ ↩︎
Kumar, D., Chaturvedi, M.K., Sharma, S.K. and Asolekar, S.R., 2015. Sewage-fed aquaculture: a sustainable approach for wastewater treatment and reuse. Environmental monitoring and assessment, 187(10), pp.1-10. ↩︎ ↩︎ ↩︎
Lightfoot, C., Bimbao, M.A.P., Dalsgaard, J.P.T. and Pullin, R.S., 1993. Aquaculture and sustainability through integrated resources management. Outlook on Agriculture, 22(3), pp.143-150. ↩︎ ↩︎
Datta, S. (2006). Waste Water Management Through Aquaculture. Journal of Environmental Management. 1. 339-350. ↩︎
Mukherjee, J. (2020) citing Dhrubajyoti Ghosh. ↩︎
Prein, M. (1988, December). Wastewater-fed fish culture in Germany. In Edwards, P. and Pullin, RSV Wastewater-Fed Aquaculture. Proceedings of the Internation al Seminar on Wastewater reclamation and Reuse for Aquaculture, Calcut ta, India (pp. 6-9). ↩︎ ↩︎ ↩︎ ↩︎
One issue with the fish ponds in the German case was the high variability of the weather. Less sun in the Fall and Spring meant that algal production was much lower, in turn impacting fish growth and the ability of the system to treat wastewater at constant rates. In the winter months, ponds will often freeze, leading to oxygen deficiencies and fish deaths. As solar radiation can fluctuate throughout the day, the fish ponds require daily management to balance fish growth, algal growth, nutrient removal, and too much sewage that would lead to fish deaths. ↩︎
Calculated using the Indian Rupee to US Dollar exchange rate in 2000, adjusted by the author for inflation of USD in 2021 from data provided by Jana, B. B., Heeb, J., & Das, S. (2018). Ecosystem Resilient Driven Remediation for Safe and Sustainable Reuse of Municipal Wastewater. In Wastewater management through aquaculture (pp. 163-183). Springer, Singapore. ↩︎
In Israel, for example, mid-century kibbutzim colonies, which were often limited in the groundwater available to them, experimented in the 1960s with reusing sewage for fish production.In Egypt, the government has put its hope in wastewater-fed aquaculture, in an attempt to increase domestic protein production and maximize use of water. ³ ¹⁹ See also Kolkovsky, S., Hulata, G., Simon, Y., Segev, R., & Koren, A. (2003). Integration of agri-aquaculture systems the Israeli experience. In: Gooley, G. J., & Gavine, F. M. (Eds.), Integrated agri-aquaculture systems: a resource handbook for Australian industry development. Rural Industries Research and Development Corporation. ↩︎
El-Zohri, M., Hifney, A. F., Ramadan, T., & Abdel-Basset, R. (2014). Use of Sewage in Agriculture and Related Activities. In: Pessarakli, M. (Ed.), Handbook of plant and crop physiology. CRC Press. ↩︎ ↩︎ ↩︎
In Germany in the 20th century, consumers at first rejected these fish, but municipalities engaged in public communication campaigns to convince people otherwise. ¹⁵ In Lima, Peru, researchers conducted a study of whether the fish were accepted by consumers at the market, and were surprised to find out that people weren’t so bothered when they found out where the fish came from. ²¹ In Kolkata, too, sewage-fed fish still constitute 40% of the local fish market, even when consumers have alternatives available. ↩︎
WHO (2015) Sanitation. Fact sheet no. 392. World Health Organization, Geneva ↩︎ ↩︎
Cointreau, S. J. (1990). Aquaculture with treated wastewater: A status Report on studies conducted in Lima, Peru. Applied Research and Technology (WUDAT), Technical Note No. 3. The World Bank Water Supply and Urban Development Department: p. 1-56. ↩︎
In a fourth trial, only 6% were rated as “unacceptable”, but this was because they deliberately increased the ratio of sewage-to-water above the acceptable level, to mimic an “accident”. Still, these same fish were then rated as “very good” when the sewage level was decreased for a subsequent 30 days. This shows that even in the case of an accident, fish can easily recover to being safe for consumption. See UNEP International Environmental Technology Centre. (2002). Environmentally Sound Technologies for Wastewater and Stormwater Management: an International Source Book (Vol. 15). International Water Assn. ↩︎
Where there are insufficient resources to build sanitary requirements into the system, researchers recommend that cleaning, butchering, and packaging be done in sanitary conditions, so that fish muscle does not risk being contaminated with pathogens on the skin or in intestines. Cooking fish thoroughly is also recommended—and in Kolkata, local cuisine fortunately does not include raw fish. Another proposal is to transfer fish to clean water ponds two weeks before harvest; this both reduces the risk of pathogens being present in fish muscle and intestines, and helps to eliminate possible unpleasant odours. Edwards P. (1990) Reuse of human excreta in aquaculture: A state-of-the-art review. Draft Report. World Bank, Washington DC. And when it comes to the presence of toxic chemicals, there is also good evidence to show that this is not a significant problem. However, this does depend on local conditions. For example, people in industrialized countries use many more detergents and pharmaceuticals that may impact the fish. This includes a broad category of toxins called “emerging contaminants” which are found in new products like beauty products and certain pharmaceuticals. There have been little recent studies in industrialized countries on the effects of these products on sewage-fed fish—in large part because these systems had largely been phased out by the time these household commodities became more prevalent in the last fifty years. ³ ⁸ ¹¹ ¹⁹ ²⁹ ³⁰ ³² ↩︎
Edwards, P. (2004). Decline of wastewater-fed aquaculture in Hanoi. Aquaculture Asia, Volume IX (4, October-December): 13-14. ↩︎
Hoan, V. Q., & Edwards, P. (2005). Wastewater reuse through urban aquaculture in Hanoi, Vietnam: status and prospects. Urban aquaculture. CABI International, Wallingford, 103-117. ↩︎
Saigoneer (2019). Only 13% of Vietnam’s Urban Sewage Is Treated Before Discharge. The Saigoneer. https://www.saigoneer.com/saigon-environment/17571-only-13-of-vietnam-s-urban-sewage-is-treated-before-discharge ↩︎
Kiet, Anh. (2019). No technology can radically clean Hanoi’s polluted river if sewage not treated: Mayor. Hanoi News. http://hanoitimes.vn/no-technology-can-clean-hanois-heavily-polluted-river-if-people-keep-pouring-sewage-into-it-mayor-300420.html ↩︎
Bunting, S. W. (2007). Confronting the realities of wastewater aquaculture in peri-urban Kolkata with bioeconomic modelling. Water Research, 41(2), 499-505. ↩︎ ↩︎
Jana, B. B. (1998). Sewage-fed aquaculture: the Calcutta model. Ecological Engineering, 11(1-4), 73-85. ↩︎ ↩︎
Stein, S. (2019). Capital city: Gentrification and the real estate state. Verso Books. ↩︎
Mara, D. (2013). Domestic wastewater treatment in developing countries. Routledge. ↩︎ ↩︎

The Messy World of Fermentation

Wed, 25 Jul 2018 00:00:00 +0000

Picture by nyam nyam.

There is a moment in the life of fruits and vegetables that has always puzzled and fascinated me. Put out a dish of strawberries, and in days some darker spots will appear. Maybe a thin tendril of mold sprouts out from the strawberry’s body. At this point, you can still eat it, simply by cutting off the moldy bit. But all of a sudden, the strawberry has clearly died. It’s inedible, sour. It has passed over in to the world of bacteria, mold, and minerals—it is no longer a self-regulating organism. It has stopped being an individual, but has become multitudes.

How does this happen? When is an organism living, and when is it dead? Where does death come from, and why does this change of state happen so quickly? Amazingly, we’ve developed some techniques to play with this boundary between life and death, stretch it, and blur it. I’m not talking about cryogenic freezing, blood transfusion, lab-grown meat, or any other modern technology. I’m talking about fermentation, the process of controlled decay of living organisms.

From coffee to ketchup, bread to sausage, wine to cheese, fermented foods are all around us. These types of fermentation tend to happen in far-off factories. Coffee berries are fermented before they’re roasted. To make ketchup, tomatoes are puréed en masse, left to rot, then heated to kill the bacteria. We usually don’t get the chance to see for ourselves the transformation of life—into other forms of life.

But you can. In this essay, I talk about fermentation: what makes it so magical, why people are so afraid of it. I talk about some strategies people use to make fermentation part of their daily life, and why modern life makes it so hard to do so. And finally, I speak to the ethics of fermentation—what we can learn from it and how it can help us think differently.

Taking time

Consider nukadoko, a fermented rice bran from Japan. Stir together salt, water, and bran—with optional ginger, dried fruit, and spices. Then ‘plant’ some vegetables like radish, beets, or carrots, burying them deep in the ‘soil’. Stir up to three times a day, preferably with your hands: get those skin microorganisms in there. After a week, you’ll have an active fermentation. Pretty soon it’ll be so strong that you can plant any vegetable in it and it’ll be pickled within one hour—these are then called nukazuke.

What happened? The salt inhibited the growth of the ‘bad’ bacteria and fungi. Without it, mold would’ve been sprouting all over the place, and the vegetables would’ve become inedible. Stirring it regularly ensures that the rice bran that was exposed to air gets buried again, so that any mold quickly dies in the anaerobic environment. Yeast starts eating the sugars in the vegetables, and then our friend Lactobacillus turns it into vinegar.

Make nuka, and you get to watch the transition from living organism to a crowd of multitudes. The only catch: to care for your nuka properly, you need to stir it daily, sometimes twice a day. The privilege of tending to life and death takes time.

To care for your nuka properly, you need to stir it daily, sometimes twice a day

Rosemary Liss, an artist who works with fermentation in her practice, learned about nuka at Hex Ferments, a group of food alchemists in Maryland, USA. ‘We had a pot and it was like a pet we had to tend to daily. I loved this ritual—the gestures and movements—it felt like a dance. Each day we lifted the heavy crock off the shelf, removed its colorful fabric covering and then unearthed the pickles before aerating the bran and adding fresh veg to the bed for a short lactic sleep.’

In Japan, the nuka gets passed down from generation to generation; each develops its own special flavors. They become unique microbiomes, only able to survive because of the daily work of grandmothers, mothers, and daughters. We have them to thank for this strange gift.

But that daily magic can quickly disappear when you get too precise. When Liss had the chance to start a residency at the Nordic Food Lab, she decided to work on nuka. She spent months trying to perfect it for a Nordic context. As she noted, ‘When this process was removed from the vibrancy of Hex and into a laboratory with only food grade plastic vessels available for controlled research I felt the magic had been lost.’

There’s something about fermentation that transcends exact science: it wants to be integrated into the rhythm of life. This rhythm is erratic; it’s embedded in culture, tradition, and habits.

Low-tech solutions for modern problems

When I talk to people new to fermentation, they often ask if it’s different from canning. According to Alex Lewin, author of Real Food Fermentation and Kombucha, Kefir, and Beyond, fermenting is the opposite: ‘It’s unlike canning—with canning you kill all of the microbes and seal it hermetically. With fermentation you invite the microbes you want and don’t let in the ones you don’t. Fermentation is diplomacy and canning is a massacre. Canning is a high-tech food technology.’

Picture by nyam nyam.

Canning requires glass and the ability to shape metal in very precise ways. That makes canning uniquely modern. Part of the conceit of modernity is that, to solve our problems, we need more high-tech solutions. But many of our problems are caused by technology in the first place—consider nuclear weapons, air pollution, climate change, and industrial food waste. On the other hand, fermentation is low-tech. You don’t need to be an expert to preserve food, or any fancy technology. Just a bucket, some salt, and trust in the world of bacteria and fungi.

One of the charms of fermentation is that it can help us deal with food waste. Our modern food system is extremely wasteful, with 30-40% of food going into the landfill in the United States, with 21% occurring at a household level. What’s more, it’s incredibly energy-intensive: 33% of global warming-related emissions come from agriculture. If consumers were to learn how to ferment at home, they could preserve their food without having to cook or freeze it—both requiring more energy. That makes it a low-tech solution to a high-tech problem.

Fear of having to care

If fermentation is so easy, why isn’t everyone doing it? To write this article, I reached out to friends and friends-of-friends who regularly ferment, asking them why they do it and why they think many don’t.

Ariadna Rodriguez and Iñaki Alvarez run nyam nyam, an art collective based in Barcelona, Spain. Like many people I interviewed, they’ve been greatly inspired by Sandor Katz, writer of books like Wild Fermentation and The Art of Fermentation. So when I asked them why they think some people have negative reactions to it, they cited him: ‘People do project their fears and anxieties of bacteria on fermentation. The ironic thing is it has always been a strategy for food safety.’

They also think it has to do with something else: people’s fear of messing up. As they put it: ‘They’re scared of having to take care of other microorganisms, they say they will have to travel, they will forget. I think it’s about responsibility, a big word nowadays, because the food industry makes everything for you that just needs to go from fridge to pan.’

We grew up hearing the horror stories about botulism and canning going wrong and don’t realize the fermentation process is much different.

Lina and Adam Esbold, a couple from Sweden, shared similar perspectives. ‘Most people’, they said, ‘are skeptical, they don’t like the taste and are put off by the idea of healthy bacteria… Even more people simply don’t care.’ Rosemary Liss, the artist, also thinks it has something to do with people’s fears of food safety. ‘I think the fear of contamination and making one’s self sick is the biggest barrier. We grew up hearing the horror stories about botulism and canning going wrong and don’t realize the fermentation process is much different.’

For Mark Reynolds, who runs Naughty Nettle Medicinals, ‘Lack of experience or first hand knowledge is a key part of this. There are those who try it once and have something go moldy so they won’t try it again.’ And yet, people can also get pretty excited when they first learn about fermentation—and how little responsibility it actually requires. Lewin describes the moment when he learned about fermentation from Sandor Katz’s book. ‘My head exploded—you can do that with food? You can chop up cabbage and leave it on the counter for a month? How is that possible? Part of what appealed to me is how rebellious that is, to cut something up and not put it in the refrigerator.’

Making death part of life

I’ve often met people who tried to ferment something once, and then they either forgot about it or got scared they did something wrong. There are cupboards full of abandoned kombuchas, fridges littered with old kefir and unfed sourdough.

It’s easy to start fermenting, but it can quickly get dispiriting, and then embarrassing. Rodriguez and Alvarez note that many people might worry that they don’t have the time to ‘collaborate’ with these microorganisms. But, they say, ‘the good thing is that you can always start again, you can always put new tea in the kombucha and everything will be OK. So as we say in Spanish: “no hay mal que por bien no venga”‘ (there is nothing bad that can’t be turned into good).

Lina Esbold and Adam Karlsson say it all takes balance and going with the flow. ‘Some weeks the fermentation gets to take more time and energy, but the opposite is also true, and we just let the cultivations whither.’ And that’s OK, too. Lewin learned to keep his projects out in the open: ‘One thing I do is I leave all of my fermentation projects in plain sight. I see them every time I go in the kitchen. It’s like gardening, you go out and you look at it and poke at it every once in a while.’

Picture by nyam nyam.

There’s also a couple of tricks you can practice to keep your fermentations alive. If white mold appears, simply scrape it off and shake it around a bit. Lewin notes that even if it does go bad, ‘it will be very obvious and very visible: fluffy green spores and you throw it away. If you’ve never had kombucha or kimchi, if you don’t know what it tastes like and you don’t know if it’s bad or not, you either take the leap or you find someone who has tried it before.’

At some point, you might get tired of it all. Simply pause your fermentation by putting it in the fridge, or better yet, in the freezer. Fermentation starters can also survive several years when you dry them. Once you’re ready to start them up again, just add whatever it needs (sugar and tea for kombucha, milk for kefir, or flour for sourdough). And yet, even if you try your best, fermentation isn’t always easy to keep doing. Our jobs and school uproot us; we work 9-5 and come home exhausted. For those who work irregular hours, it’s hard to build up the routine and habits needed to maintain that sourdough or make yoghurt or kefir daily.

And then there’s the food system. The supermarket is anathema to fermentation: live fermentation generates carbon dioxide and methane, stinking up the aisles and bursting through the packaging. In other words, it’s messy and weird. Partly because our access to food is limited to what the supermarket has to offer, it’s not easy to get hold of kefir grains or a kombucha mother. And when we do, it’s hard to get guidance. It can be intimidating if you don’t know anyone with experience fermenting.

Our society is also marked by what food researchers call ‘de-skilling’. We’ve largely lost the food practices handed down to us over generations. What remains is a semblance of our past food cultures: fermented pickles become canned; sauces rich in character and variety become, simply, ketchup.

The supermarket is anathema to fermentation: live fermentation generates carbon dioxide and methane, stinking up the aisles and bursting through the packaging.

Part of this is the industrialized food system, but another part is also the way the economy shapes our lives. A few generations ago, most Westerners lived in multi-generational households, children together with grandparents, several families sharing tenements, and a vibrant street culture that came from dense living arrangements and reliance on walking as the primary means of transportation. With modernity, every tradition, every routine, every relationship is constantly shifting and torn apart.

And even though science has given us unprecedented ways to understand the food that we eat, it also has its limitations. It seems like every week a study comes out that overturns the guidelines on what we’re supposed to eat. We’ve grown up with the idea of an official expiration date—leaving our trust in food safety to some largely invisible process, determined by experts. We have the science to understand the invisible stuff going on in our kitchens and in our guts, but a cultural attitude of fear that stops us from playing with our food—an attitude that inhibits microbiomes from flourishing in our kitchens.

When I talked to Jyotsana Singh, a friend, about this, she pointed out that we lack a common sense of how food spoils and what’s safe or unsafe to eat. As she put it, ‘people don’t trust their senses’. Ironic, with so much information available ‘at our fingertips’. She grew up in a family where, when concerned if the milk was OK, they wouldn’t look at the expiry date but instead sniff it. Perhaps due to this common sense she grew up with, combined with a knowledge of basic chemistry and biology, she rarely has a feeling of risk or fear when making food.

Through our conversation, we decided that there’s an important distinction between habits—the kind that allow us to ferment on a daily basis; common sense—an intuition of what’s going on under the surface, informed by today’s science and cultural knowledge; and tradition, where our upbringing guides us with confidence in the food we eat and make. Maybe it’s a balance of these that helps foster fermentation practices.

If you think about it this way, there’s something very political about fermentation. Our job makes it difficult to form daily habits. The modern food system has atrophied our cultural knowledge and traditions of food preservation practices. It makes sense that so many people find it hard to integrate into everyday life. To create a world where fermentation is the norm, we’d need to change the world.

Thinking with fermentation

The living body is always on the point of passing over into the chemical process: oxygen, hydrogen, salt, are always about to appear, but are always again sublated; and only at death or in disease is the chemical process able to prevail. The living creature is always exposed to danger, always bears within itself an other… -G. W. Hegel, Philosophy of nature

Thus politics… originated in the daily ferment of ordinary life in the agora. -Murray Bookchin, Urbanization without cities: The rise and decline of citizenship

As Hegel realized two centuries ago, we carry others within ourselves. What makes the body keep its integrity, surrounded by constant danger? The practice of fermentation raises these kinds of questions, and helps us think through a different ethics of being.

For Rodriguez and Alvarez, getting into fermentation opened them up to seeing multiple connections in life. ‘It all feels as part of the same thing,’ they say when I ask them how fermentation is part of their daily life: ‘Eating it. Having something fermented every meal. Then taking care of all the microorganisms that coexist with us, maybe taking out the tea from the kombucha, or changing the water and adding the sugar to the water kefir, tasting how the chilis are doing fermenting in the sun, opening the miso every now and then, and so on and on.’

Picture by nyam nyam.

All of this, they say, helps them visualize ‘all this activity in different scales interconnected between all the agents, our bodies, the microorganisms.’ Fermentation also informed Lewin’s approach to life. ‘Fermenting establishes a dynamic equilibrium of microbes—getting people comfortable with that is hard. In our overly determined world where everyone wants to understand everything completely, a lot of people are uncomfortable making a leap of faith. It’s a good practice to help people let go a bit. Maybe we don’t have to measure everything exactly, maybe we don’t have to control everything completely.’

Maybe we don’t have to measure everything exactly, maybe we don’t have to control everything completely.

To practice fermentation, we need to multiply experiences, not just with bacteria and fungi, but also with each other. It takes human relationships to learn how to ferment, and it takes knowledge given to us through science and culture. It also takes common sense. This common sense emerges through interaction with others. In ancient Athens, strangers met at the agora, the market place. It was here that politics happened, where people could learn to discuss with each other. The agora was messy, it was ordinary, but it was also the foundation of Athens’ democratic system. What kinds of fermented goods, I wonder, were sold in the Athenian agora, and what kinds of political conversations did they provoke?

When modernity meets its end-point and creates a world where everything is sterile, controlled, and known, there will be little space for fermentation. But there will also be little space for free thought: thinking that bubbles up out of the corners, appreciates complexity, multiplies relationships, navigates the subtle contours of life and death. Modern life makes fermentation unintuitive and difficult. But it’s precisely this practice that can help us come to a different way of thinking and approaching the world. A world where fermentation is integrated into our daily life might be a bit messier, but it would also be more caring to the many life forms with whom we co-exist. Perhaps it would be a world that lends itself to contemplation, letting us ponder the transition of life to death, rather than fearing it, hiding it away.

This article was written by Aaron Vansintjan as part of a collaboration between Low-tech Magazine and nyam nyam, an art collective based in Barcelona (Spain). The article forms part of the project “It is the microorganisms that will have the last word“, selected as an off-site project for Barcelona Producció 2017. The pictures were made by nyam nyam.

Aaron Vansintjan wrote several articles for No Tech Magazine & Low-tech Magazine. He keeps his own blog at Uneaven Earth.

This article originally appeared on No Tech Magazine.

Vietnam's Low-tech Food System Takes Advantage of Decay

Mon, 20 Feb 2017 00:00:00 +0000

Street food in Hanoi, Vietnam. Picture by [Maxime Guilbot](https://www.flickr.com/photos/maximeguilbot/8484619644/in/photolist-dVKTPA-cfWCeA-cfTe3L-6nZ3X8-p5vXc-cfTRUG-kBZu8H-8sNnce-9h6GiR-kC18EV-o4k4wP-cfV3gY-eLNpbx-cfTWo1-cfWFYU-6mCkEk-cfVMsq-6oK2Yk-j58xco-qdkP7Z-g7h4ou-nXrdQ2-cfT1LY-5RDStb-nHtZjf-cfWTV9-fqHDs8-g8obdJ-qfmiyi-cfWH7j-dSm888-5RDTs3-dVkwL4-cfWVWE-cfT2eo-nr2wPA-4z5Bhr-eLNder-cfVe6u-bNz7wz-iH98pX-qbMjDS-qgeWTq-nr2H9v-ixGovd-cfWKeQ-4z9Nv5-c5gCQm-vQfqd-cfUAgy).

The food system in the industrialised world is based on mass-production, global distribution, and constant refrigeration. It requires many resources and produces a lot of food waste. Aaron Vansintjan takes to the streets of Hanoi, where the Vietnamese practice a food culture based largely on fermentation.

Although food spoils much faster in a tropical climate, the Vietnamese will often store it without refrigeration, and instead take advantage of controlled decay. Vietnam’s decentralised food system has low energy inputs and reduced food waste, giving us a glimpse of what an alternative food system might look like.

Tropical Climate

In a tropical climate, everything decays faster. Bread gets soft and mushy, milk spoils, the walls get moldy just months after a layer of fresh paint. Food poisoning is a constant concern. The heat and moisture make for an ideal breeding ground for bacteria and fungi. In this environment, you’d think people would be wary of any food product that smells funny. But in tropical Vietnam, food can get pretty pungent.

Take mắm tôm, a purplish paste made of fermented pureed shrimp. Cracking open a jar will result in a distinct smell of ‘there’s something wrong here’ with hints of marmite to whelm through the whole room. You have chao, a stinky fermented tofu, which was so rank that the smallest bite shot up my nose and incinerated my taste buds for an hour (‘Clears the palate!’ said the waiter encouragingly).

Consider rượu nếp, which is sticky rice mixed with yeast and left to ferment for several days ‘in a warm place’—i.e. the counter. The result is a funky-smelling desert—literally rice left to rot until it turns in to a sweet wine pudding. On the 5th of May of the lunar calendar, Vietnamese people will eat rượu nếp in the morning to celebrate ‘inner parasite killing day’. Bonus: day-drunk by the time you arrive at work.

We shouldn’t forget Vietnam’s world-famous fish sauce — nước mắm — made from diluted fermented fish, a flavour that many people around the world continue to find totally intolerable.

A stall selling homemade dưa chua in a Hanoi market. Picture: Aaron Vansintjan.

In Vietnam, putrefaction is accepted as a part of life, even encouraged. But fermentation in Vietnam isn’t just an odd quirk in a tropical diet. To understand why fermentation is so integral to Vietnamese culture, you have to consider how it is embedded within people’s livelihoods, local agricultural systems, food safety practices, and a culture obsessed with gastronomy; where food is seen as a social glue. And when you bring together all these different puzzle pieces, an enchanting picture emerges: one in which fermentation can be a fundamental component of a sustainable food system.

Unlike many high-tech proposals like ‘smart’ food recycling apps, highly efficient logistics systems, and food packaging innovations, fermentation is both low-tech and democratic—anyone can do it. What’s more, it has low energy inputs, brings people together, is hygienic and healthy, and can reduce food waste.

Rotting Food can be Safe and Healthy

At the entrance of a market in Hanoi, a woman with a dưa chua stand tells us that making ‘sour vegetables’ is easy: you just add salt to some cabbage and let it sit for a couple of days. As we talk, several customers come by, eager to scoop some brine and cabbage into a plastic bag. Worried that we’re discouraging her customers, she shoos us away. She isn’t lacking business.

Is fermentation really so effortless? The short answer is yes. Many recipes will call for two things: water and salt. At just a 1:50 ratio (2%) of salt to food, you can create an environment undesireable for all the bad bacteria and encourage all the good ones. Sauerkraut, kimchi, fish sauce, sriracha, and kosher dill pickles—are all made according to this principle.

Yet other types of fermentation are a bit more complicated. They call for sugar (e.g. wild fermented alcohol like ethiopian honey wine), yeast starters (rượu nếp, most wines and beers), special fungi (tempeh, miso), or some kind of combination of fungi, bacteria, salt, or sugar (kombucha). Yet others are simpler: to make cooking vinegar, just let that bottle of bad wine sit for a couple of days, and to make sourdough, just mix water and flour and leave it on your counter.

Fermentation is both low-tech and democratic. It can be a fundamental component of a sustainable food system

All in all, fermentation is just controlled decay: your most important ingredient is time. This can sound like a bit too much, too fast. Take the woman I met at the entrance of the market. Her dưa chua, while in great demand, looks like wilted cabbage, soppy, floating in murky brine. Some bubbles are forming on the edges of the plastic container—for the trained eye a sign of an active fermentation process, but for the uninitiated, an alarm bell.

There’s no use beating about the bush. That dưa chua is in fact rotting in a very similar way that a peat swamp is constantly rotting, belching large doses of methane into the world. What’s happening is an anaerobic fermentation—that is, without significant amounts of oxygen. This absence of oxygen and the high levels of salt creates an environment supportive to several bacteria that also find their home in our own digestive systems.

Those bubbles forming in the container are by-products of these bacteria: CO2 and methane. The bacteria also lower the pH and start breaking down raw food—essentially pre-digesting it for you. And, once the pH goes down even lower, you’ve created a monster so voracious that no other fungus, bacteria, or parasite with bad intentions will dare to enter its domain. So yes, it’s rotting just like a stinky swamp, and that’s a good thing.

Woman sells nem chua—raw fermented pork—outside her house. Picture: Aaron Vansintjan

It’s a good thing especially in a climate like that of Vietnam. Every fermentation is a small victory against the constant war against heat and humidity, which destroys all edibles in its path. Instead of eating raw cabbage and risking death by a thousand E. Coli, you can eat fermented cabbage and know, for a fact, that it won’t have you hunkering by the toilet bowl any time soon.

Not only that, but eating fermented food has significant health benefits. You might’ve noticed the new fad of ‘pro-biotic’—well all that really means is that the product contains some kind of active bacterial culture that looks like the flora in your own stomach. That would include, not just Go-gurt, Yoplait, Chobani, and Danone, but also several kinds of cheese, pickles, beer, and just about any other fermented product.

Eat about a tablespoon of any of these at the end of every meal, and you inoculate your stomach with a fresh batch of microbes that help you digest—all the more necessary when we eat antibiotics in our meat and bland diets of white bread and peanut butter, and drink chlorine in most municipal water systems.

Further, products like fish sauce and shrimp paste provide many impoverished Vietnamese with micro-nutrients, B-12 vitamin, proteins, and omega 3 fatty acids—comprising a significant part of people’s nutritional requirements. For a country that still remembers hunger and starvation, this is no small fry.

A Diverse Food System

In the same market we talk to a vegetable vendor. Real estate in the neighborhood is getting more expensive, rents are going up. She’s having a hard time making ends meet. On her street many elderly have sold their farmland—which they used to grow vegetables and decorative flowers—and now, unemployed, they spend their time selling home-made fermented vegetables out of their front door.

In the same neighborhood, we meet Tuan, an elderly woman growing vegetables in the banks of a drained pond. She rarely goes to the market—she can grow much of her own food in this little patch. We ask her if she ever ferments her vegetables. Of course, but she doesn’t sell them—they’re just for herself and her family.

If you want a localised food system, you need to be able to store your food for long periods. Fermentation makes that possible.

After several months of studying Hanoi’s food system and the people who make their living off of it, Vân (my Vietnamese collaborator) and I are starting to see some patterns. In Western countries, the food system is shaped a bit like an hourglass: industrial farmers send their food to a supplier, who then engages with a handful of supermarket companies, who then sell to consumers.

In Vietnam, on the other hand, it looks more like an intricate web: wholesale night markets, mobile street vendors, covered markets, food baskets organized by office workers with family connections to farmers, guerilla gardening on vacant land. Food is grown, sold, and bought all over the place, and supermarkets are just a small (albeit growing) node in the complex latticework. Most people still get food at the market, but many also source their food from family connections.

A restaurant offers homebrewed rượu men, Vietnamese rice wine. Picture: Aaron Vansintjan

In Vietnam, many people might have one ‘profession’, but when you ask a bit more questions it’ll turn out that they have half a dozen other jobs for ‘extra income’. There’s a generalised ‘hustle’: everyone is a bit of an entrepreneur. After talking with Tuan for several hours, we learned that she has, throughout her long life, fished, grown vegetables, corn, and fruit trees, sold rice noodles, bread, ice cream, roses, and silk worms. Now, aged 68, she grows decorative peach trees and grows vegetables when she can.

With an economy just decades shy of a highly regulated communist regime where the only food you could get was through rations, and the memory of famine still fresh in people’s mind, this is entirely understandable: with a finger in every pot, you can just about manage to survive. These two factors, a highly distributed food system and diversified livelihoods, make for a fertile environment for fermentation practices. With easy access to wholesale produce, many can turn to small-scale fermentation to compliment their income—or, in the case of Tuan, to spend less on food at the market.

Preserving the Harvest, Bringing People Together

Vietnam hosts both the Red River delta and the Mekong delta—two of the most productive agricultural regions in the world. The heat and the vast water supply allow some areas of Vietnam to have three full growing seasons. That means three harvests, and that means lots of food at peak times, and sometimes so much that you can’t eat it all. That’s another bonus of fermentation: if your food system is local, you’re bound to stick to seasonal consumption. But by fermenting your harvest you can eat it slowly, over a long time period. It’s this principle that underlies much of fermentation culture in East Asia.

Take kim chi, a spicy fermented cabbage from Korea. Traditionally, the whole village would come together to chop, soak, salt, and spice the cabbage harvest every year. Then, these mass quantities of salted spicy cabbage were stored in large earthenware pots underground—where cooler temperatures lead to a more stable fermentation process. As a result, you can have your cabbage all year. If you want a localised food system, you need to be able to store your food for long periods. Fermentation makes that possible.

Food fermentation is a strange thing: it inverts what many regard as waste and turns it into a social, living, edible object.

Fermentation is also social. Fermenting large batches of summer’s bounty typically requires hours of chopping—the more the merrier. And chopping is the perfect time for sharing cooking tips, family news, and the latest gossip. In South Korea, now that kim chi production has been largely industrialized, people try to relive the social aspect of making it through massive kim chi parties in public spaces.

Cutting open nem chua a week later. I’m not dead yet. Picture: Aaron Vansintjan

In a country like Vietnam, where a traditional food system still exists for a large part, fermentation remains embedded in social relations. Relatives and neighbors constantly gift each other fermented vegetables, and many dinners end with a batch of someone’s homebrewed rice wine—rượu men. Fermentation lends itself well to a gift economy: there is pride in your own creation, but there is also no shame in re-gifting. And because of its low costs, anyone can take part in it.

Gastronomy, Tested with Time

It is a bit disingenuous to caricature Vietnam’s food culture as obsessed with rotting, and suggest that this is largely the result of a tropical climate. Rather, what we’re dealing here is difference in taste: what may seem strange and pungent to one culture is highly appreciated in another. In fact, one of the greatest impressions I have of Vietnamese culture is its deep appreciation for gastronomy: subtle, complex flavours, considered textures, modest spicing and well-balanced contrasts define Vietnamese cuisine.

Fermentation is a crucial part of this culture: the art of fermentation requires paying attention to how flavours change as food transforms, understanding these chemical shifts and using them to achieve a desired affect. It’s also clear that Vietnamese gastronomy is popular: it takes place in street food stalls, run by enterprising matriarchs, constantly experimenting with modern products and traditional flavors. It is cheap and, to ensure customer loyalty, it is surprisingly hygienic.

Street vendors rarely have fridges, nor do they have large cooking surfaces, dishwashing machines, or ovens. By and large, they make do with some knives, two bowls to wash fresh vegetables in, a large pot, a frying pan, coals or gas burners and—for products that may go bad during the day—fermentation. Having limited access to capital and consumer electronics, these vendors—most often women—ply their trade in a way that has stood the test of time.

They know the rules of hygiene and food safety, and, because they have to be careful with their money, they know exactly what kinds of food will go bad, and what kinds of food can be preserved. In doing so, they practice a food culture that has been passed down through generations—to a time before fridges, a global food system powered by container shipping, factory trawlers, and produce delivered to far-off markets by airplane.

Fresh dưa chua at a street stall, sold next to fermented garlic and figs. Picture: Aaron Vansintjan

While modern technology has provided many benefits for our diets, there are many innovations from the past that have been abandoned as the global food system was transformed by the availability of cheap fuel. One such innovation was the fish sauce industry that flourished during Ancient Roman times. For Romans, fermenting fish was a crucial aspect of a low-tech and seasonally-bound food system. In fact, it so happens that research now suggests Vietnamese fish sauce may actually have its origins in the Roman variant produced over 2,000 years ago.

Today, however, fermentation doesn’t fit so easily within the global food system. Harold McGee at Lucky Peach tells the story of how canned products were notoriously difficult to transport in the newly industrialized food system of the 19th century. Apparently, until the 20th century, metal cans would regularly explode, sending shrapnel and preserved tuna flying through the decks of transport ships. This was due to heat-resistant bacteria, which continued fermenting the product long after it was heat-treated.

Fermented food has to be produced locally: transporting it will risk explosions on the high seas

The solution was to subject the canned product to high temperatures over a long period of time, killing all remaining cultures, in turn changing their flavor. But in the case of fermented food, the problem has not gone away: if you want it to be actively fermenting, transporting it will risk explosions on the high seas. But heating stops the fermentation process, and kills its unique flavor.

It’s for this reason that products like kim chi, kombucha, and sauerkraut often have to be produced locally, despite increasing global demand. In some way, fermentation belies the industrial food system: the fact that it is alive means that it doesn’t quite fit in. You either have to kill it, thereby change it, or it will keep bubbling through the cracks.

A Low-tech Food System is Possible

Fermentation cultures in Vietnam give us a glimpse of what an alternative food system might look like, one that is both decentralized and doesn’t depend on high inputs of fossil fuel energy to preserve food, high waste, and high-tech. Why does this matter? Well, in a world facing climate change, we need a low-impact food system, and fast.

But there are other reasons: with increasing concern over the health side effects of common chemicals such as BPA, found in almost all cans and pasta sauce jars, people are looking to safer kinds of preservation, which aren’t killing them and their families slowly. And with the rise of the local food and food sovereignty movements, many are realising that we need food systems that support everyone: from small farmers to low-income families.

Because of its low investment costs, fermentation lends itself well to supporting small businesses, allowing them to take advantage of seasonality while practicing a time-tested low-tech method of food preparation. Today, in response to increasing food insecurity, we are hearing increasing calls for a smarter, more efficient food system. Proposals such as intensive hydroponic and vertical farming, big data-powered logistics systems, smart agriculture technologies, and food waste recycling apps clog the news.

But we already have a low-tech innovation that works very well. Fermentation, because it is accessible to everyone, because of its low energy requirements, and because it fits right in to a more sustainable food system, should not be abandoned in the search for global food security.

A fish sauce factory in Vietnam. Source: Mui Ne info & events.

It’s easy to get the impression that we live in a world of scarcity, where there just isn’t enough food to go around, and food production all around the world is limited by technological backwardness. On the other hand, many of us are more and more concerned with the increasing problem of food waste in Western food systems. We seem to live in a world of both scarcity and abundance at the same time.

Food fermentation is a strange thing: it inverts what many regard as waste and turns it into a social, living, edible object. As a friend of mine once said, if you have too many grapes, you make wine. If you have too much wine, you throw a party. If you still have too much wine, you make vinegar. Fermentation turns scarcity and abundance on its head, belying easy categories of what is waste and what is too much.

Sustainability advocates worry a lot about making the ‘supply chain’ more ‘efficient’—that is, increasing profits margins while making sure all food reaching consumers in a perfectly fresh state. Instead, we could consider taking advantage of decay. This isn’t hard: you just have to add some salt and water. We’ve done it for thousands of years, and, if we follow the example of food cultures like those in Vietnam, we can do it again.

Aaron Vansintjan