Chapter 1 - The importance of chemical toxicants in Water, Sanitation, and Hygiene (WASH) provision

1.4 The origins of biochar water treatment

Aqueous Solutions’ world headquarters, circa 2007.

Once upon a time, in an adobe mud hut in Thailand…

The entire concept of biochar water treatment traces back to a question that I was asked by members of a farming community in northern Thailand in late 2006. Their farm is called Pun Pun, Thai for “Thousand Varieties,” a name signifying their mission to conserve traditional vegetable, fruit, and rice strains. Specifically, the folks of Pun Pun wanted to know if charcoal (the term biochar had not gained popularity yet) could be used to remove pesticides from drinking water. 

It was their idea, not mine. Charcoal has been used to treat drinking water for thousands of years in Thailand and elsewhere. This practice is still widely used today – particularly in rural areas of major charcoal-producing countries such as Brazil, India, China, and throughout South-East Asia[54]. Even the Sanskrit ‘Ousruta Sanghita’ written around 2,000 BCE states, ‘It is good to keep water in copper vessels, to expose it to sunlight, and filter through charcoal’[55]. 

However, when this project landed in my lap in December 2006, no research existed on whether this ancient water treatment method would work on modern synthetic chemical pollutants like pesticides. Over the next several months, during my days off from work on the farm I would bicycle into Chiang Mai and spend long hours in internet cafes (this was before widespread mobile internet access) doing research online. Using a “borrowed” login I was able to access Web of Science and the peer-reviewed literature through the University of California library system. I found that, while no research had yet taken place on the use of charcoal or biochar as a pesticide adsorbent, there was a wealth of literature on the use of activated carbon for this purpose. I reasoned that, since charcoal and activated carbon are both made by carbonizing biomass (or coal, in the case of many activated carbons) into a porous graphite-like material, they might have similar properties for adsorbing organic compounds such as pesticides. During each internet café session I downloaded dozens of activated carbon research papers. I bicycled back to the farm with the stacks of papers and read them hungrily in my thatch-roofed adobe mud hut.

I was determined to help Pun Pun meet their community’s need for safe drinking water in a self-reliant manner. (In addition to agrobiodiversity conservation, promoting local self-reliance is a mainstay of their mission.) Though Pun Pun is an organic farm, most farms throughout the region are not. Thai farmers generally have high awareness that pesticides can be dangerous to human health and the environment. However, many farmers have been lured into debt by global agribusiness companies, and so feel compelled to use chemical-intensive methods for growing export crops in order to service their debts. (For example, a 2011 survey of 295 farmers across 12 villages in the highlands of northern Thailand found that 97% of farms relied on synthetic pesticides for pest management[56].) My first questions were, What kinds of chemicals were being used? How harmful are those chemicals? Are they likely to impact drinking water sources? In other words, are Pun Pun’s concerns about harmful pesticides in their water justified? If this wasn’t really a problem then there was no sense in inventing an entirely new method for water treatment in low-resource settings.

I set out to find out how bad things actually were. 

Unfortunately, it’s a common practice in developing countries to casually discard empty pesticide containers around farm fields and ponds (Figure 1.2). (Or worse – use them in the home to contain household items and even food! Yep, that happens.) Thailand is no exception to this. I went all around the region within a few kilometers of Pun Pun collecting discarded containers. With Pun Pun colleagues I talked with local farmers about what agrichemical products they used. Friendly shop owners would let me survey their shelves, making lists of product names and formulas on pesticide packaging (Figure 1.3). I made lists and lists and lists of trade names and active ingredients. Then, on my trips to the internet café in town, I would look up all the chemicals using the Pesticide Action Network’s online database of health effects[57]. During this survey over about two months’ time, I found that 60 pesticides were widely available and in use in the area. Of these common chemicals, 33 were identified as moderately to acutely toxic to humans, 15 as cholinesterase inhibitors (neurotoxins), 19 as suspected endocrine disruptors, 8 as reproductive or developmental toxins, 14 as possible carcinogens and 9 as known carcinogens, and 20 as known threats to groundwater contamination. (These numbers add up to >60 because many compounds constitute a threat in multiple categories.)

So, yeah, Pun Pun’s concerns about harmful pesticides in their water were well justified.

Figure 1.2 Discarded pesticide containers collected from farm fields around Pun Pun, circa 2007.

Figure 1.3 Chemical warfare, over-the-counter. A typical assortment of pesticides sold in ag shops near Pun Pun, circa 2007. 

Pesticide use and occurrence in Thailand

My little survey was conducted in a cluster of villages and farm fields near Pun Pun, a region that is a sprightly 2.5-hour bike ride due north of Chiang Mai. What about the country as a whole? Was my survey representative, or was this little region unluckily extra-polluted? I needed to do some more research.

What I found out is that Thailand experienced a fourfold increase in pesticide use over the first decade of this century, with nearly 120,000 tonnes of active ingredients imported in 2010. 

For insecticides, organochlorine compounds such as DDT, hexachlorocyclohexane compounds, aldrin, and dieldrin are among the most commonly used in Thailand and other Asian countries because of their low cost and broad-spectrum versatility against pests[58]. (DDT and chlorinated cyclohexanes are banned in Thailand, but are still used illegally.) Herbicides made up the largest proportion of pesticide imports by mass at over 80,000 tonnes in 2010. Among the most commonly imported pesticides, which constitute ∼75% of the total imported herbicides, insecticides, and fungicides, 7 are moderately or acutely toxic, two are reproductive or developmental toxins, 3 are neurotoxins, 8 are suspected endocrine disruptors, 3 are possible and 3 are known carcinogens, and 7 are potential or known threats to groundwater contamination. Two are classified by the WHO as highly hazardous, and 6 are considered moderately hazardous.

At the time of my research, over 20,000 unique pesticide formulations were being sold in Thailand. There were over 26,000 retailers licensed to directly sell pesticides without restriction to any buyers or farmers as long as the products were legal to sell. However, many more unlicensed pesticide retailers exist in the country. Because of the large number of unlicensed retailers there are widespread sales of unregistered and prohibited pesticides. Around 100 pesticides are prohibited in Thailand; however, enforcement of restrictions is weak, and numerous reports have shown widespread use of banned chemicals. Banned substances are illegally stocked by insufficiently policed vendors and continue to be smuggled into the country.

Yeah but were these chemicals getting into Thai water sources? Like many lesser-developed countries, data on environmental chemicals in Thailand are scarce. Based on the literature available at the time, I identified 7 organochlorine and 4 organophosphorus pesticides that were commonly detected[59]. The organochlorine compounds were more widely detected, but the organophosphorus compounds were detected at higher concentrations. This makes sense, because there have been attempts to phase out organochlorine compounds due in-part to their environmental persistence. Organophosphorus insecticides have been developed as replacements in-part because they break down more rapidly in the environment. Their detection in the environment is generally a sign of heavy, continuous use. Of the 11 compounds my research at the time identified, 10 are acutely toxic, 3 are reproductive or developmental toxins, 4 are neurotoxins, 9 are suspected endocrine disruptors, 5 are known carcinogens, and three pose a likely threat to groundwater[59].

Ok, some pretty toxic chemicals are used in Thailand and detected in the environment. But are Thai people exposed to potential harm? Organophosphorus and pyrethroid insecticides and herbicides have been detected in Thai children’s urine samples[60, 61]. The most frequently detected metabolites included breakdown products of malathion, chlorpyrifos, permethrin, and other pyrethroids. The highest concentrations of pyrethroid metabolites were found in children of farmers, and the average urinary pesticide metabolites in Thai children are roughly double those measured in US children[60, 61]. A survey of Hmong tribe women living in the Thailand–Burma border region that reported detection of DDT and its major metabolites in 100% of mothers’ milk samples[62]. A number of other organochlorine biocides were also frequently detected. Infants’ exposure to DDT, heptachlor and heptachlor epoxide (the chemical formed when the human body metabolizes heptachlor) exceeded by up to 20 times the acceptable daily intakes as recommended by UN-FAO and WHO[62].

We can safely conclude that people in Thailand are exposed to a number of agrichemicals that can cause serious negative health effects.

A startling response from the WASH sector

I eventually published the results of my pesticide survey in the Journal of Water, Sanitation, and Hygiene for Development[59]. The pesticide survey provided context from some really exciting research results that colleagues and I had just obtained demonstrating that biochar made from a high temperature gasification process (described in Chapter 4) could adsorb herbicide from surface water nearly as well as commercial granular activated carbon. The interesting backstory of that paper was that I initially submitted it to a different WASH journal. That journal requests that authors pitch ideas for articles to the editor first, before submitting a full manuscript. So I emailed the article abstract to the editor, and was shocked by their reply. They wrote, “I wouldn’t expect that herbicide would be a big risk in most developing countries.”

I was stunned. Had this WASH journal editor ever been to a developing country?

Around the same time, I was presenting the results of our herbicide experiments at academic conferences. The work was well-received at chemistry and environmental engineering conferences. It was a totally different story at WASH conferences. My talks at WASH conferences were met with strange looks, incomprehension, dismissal, sometimes even hostility. And baffling statements like, “developing countries are too poor to have access to chemicals,” and “they don’t live long enough to get cancer.”*

What in the world was going on? I began to realize – the WASH sector really has no idea about this problem. I knew from my travels that poor farmers in Thailand and India get it. Hill Tribe people in Burma get it. In other words, poor people with little or no formal education are hip to this problem – affluent WASH professionals, not so much. The lesson for me was that at WASH conferences I couldn’t just launch into talking about adsorption, pyrolysis, biochar, herbicides, etc. First, I was going to have to bring people on board with the idea that chemical pollutants are an important component of WASH that was being overlooked. I couldn’t sell them on a solution (biochar) to a problem they didn’t know that they had. My advocacy for this topic eventually took the shape of the WASH-Toxics Working Group[63], a consortium of researchers and field practitioners who want to get chemicals on the WASH development agenda. Check it out, and join up if you like.

Returning to Pun Pun

During the spring of 2007 it started to dawn on me that, if we could solve the problem of agrichemicals in Pun Pun’s water supply, it could potentially be reproduced in low-resource settings all around the world. It could possibly have a massive global public health impact. I felt that I was on the edge of something huge, and if I decided to undertake this challenge, I was going to need help – a lot of help. So in June of 2007 I formed Aqueous Solutions ( in order to attract the needed resources and talent to the cause. Our world headquarters was my 49 square foot adobe hut pictured at the top of this post.

And now you know the story of Aqueous Solutions and biochar water treatment.

* That last one really gets me. Not only does it belie a profound ignorance of the environmental pollution poor people are exposed to, it displays a callousness I just can’t wrap my head around.

[Next up: 1.5 Chapter summary and 1.6 References]