July 2024 - Sally Brown Research Library & Commentary

Provided for consideration to MABA members by
Sally Brown, PhD., University of Washington

Time for the biosolids time machine. Back to the days when ‘night soil’ was the name. Long before the days of centralized wastewater treatment, human waste was an integral part of cropping systems. That all changed when the connection was made between pathogens in the poop and disease. Centralized wastewater with public health as a focus put resource recovery on the back burner. Nowadays with regenerative agriculture increasingly understood as a key tool for sustainability, organic amendments are valuable again. Will that also hold for biosolids? To see the future, you must first study the past. So, here we go. 

The first article in the library, Agricultural use of organic amendments: A historical perspective was written by scientists from the USDA Agricultural Research Service. My lab at USDA when I was a graduate student was right next door to Cheryl, the technician for one of the authors. I can tell you first-hand that these guys knew their sh**t back when they wrote this article in 1992. They talk about the origins of agriculture and how early farmers in 2000 BC understood best management practices including use of organic amendments. They talk about F.H. King, Chief of the Division of Soil Management in the USDA in the early 1900s. He took a trip to the Far East to see how farmers there maintained rich and productive soils over centuries. Here is what he discovered on his trip: 

Anyone remember the theme of Biofest last year?

Farmers in the near east used legumes and manures to maintain soil fertility. In the Roman empire there was extensive research on agriculture with many important advances in growing systems. Here too, the value of organic matter additions including composting, animal manures and ‘applying sewage wastes’ was recognized. Soil quality was first mentioned by Xenophon, a Greek philosopher in 400 BC. In 1973 Allison wrote that ‘soil organic matter has been considered by many as the elixir of life’. In 1938 - prompted by the dust bowl, WC Lowdermilk, Assistant Chief of the Soil Conservation Service, toured Africa and the Near East to see why once fertile lands had collapsed. He did this to find answers to the soil erosion problems in the US. He recognized the critical importance of controlling soil erosion. What happened instead was that US agriculture veered in the other direction. A shift from mixed crop-livestock operations to monocultures has made matters worse. 

Here is a table that sums it up:

The authors talk about municipal biosolids and the organic components of MSW in the context of their value for agriculture. They were at the USDA when much of the research on the 503s was ongoing and when the Beltsville static pile compost system was developed. They quote from farm bills that recognize the value of organic wastes. Perhaps now would be a good time to revisit that conversation? 

Article #2 Sewage: Waste or resource? A historical perspective was written in 1980 by Christopher Hamlin when he was a doctoral candidate in history. A Google Scholar search shows that he went on to publish extensively on water and health. Here he starts with a quote from Victor Hugo, best known as the author of Les Misérables.

He notes that land treatment of waste was a grand experiment in France in the 19th century but that over-application resulted in fields becoming sewage lagoons. Modern day wastewater treatment solved this problem, creating the potential for an easily recycled resource. By not using these materials he says: ‘We are, it seems, spurning the pennies from Heaven’. Almost as good as Hugo. The paper provides a great history of how widespread recycling of sewage almost happened and why it didn’t. When it was something in everyone’s face every day, people saw the value. With centralized treatment and the growth of cities, the value faded and the yuck factor prevailed. As he puts it: 'The rise of the water closet doomed the night soil business’. Here dilution was not the solution. Instead, use of storm sewers for sewage killed the rivers in Europe. No one likely remembers the summer of 1858 in London - dry and hot and known as the ‘Great Stink of 1858’. This started the public perception of sewage as nasty, foul smelling and dangerous. 

From here came efforts to capture the nutrients in the water for subsequent sale to farmers leaving the water clean enough to be discharged into lakes. Sound familiar? Of the range of processes, the most successful was the ABC method - adding alum, blood and clay. To my knowledge, that one, at least in its original form, hasn't lasted. Those that didn’t buy into their ABCs relied on sewage farms. Using untreated waste for irrigation resulted in impressive yields for the farms that were well run. The others with over irrigation did not get such rave reviews. The next development, with us even now, was an understanding of the role of microbes in stabilizing wastewater. Another great quote, 'Ironically, just as we finally learned how to treat sewage, we forgot about it being a resource’. This is a terrific paper and a great read. 

To drive that last quote home we go to paper #3 Anthropogenic Dark Earth in Northern Germany — The Nordic Analogue to terra preta de Índio in Amazonia. Here the authors are focused on localized soils in Germany that show that same dark richness of the terra preta soils in Brazil. And while the biochar frenzy started from those soils in Brazil, it wasn’t just char. Rather a combination of residuals, including human wastes, were responsible for the dark soils in Brazil and the dark soils described in this paper. These soils have retained their fertility since the 1100s. You can see it with your own eyes:

So, how has Germany responded to this knowledge? By banning land application of biosolids.

To answer that question we turn to papers #4 Nightsoil and the ‘Great Divergence’: human waste, the urban economy, and economic productivity, 1500–1900 and #5 Markets for waste and waste-derived fertilizers. An empirical survey. Paper # 4 provides a history of nightsoil workers and use in Asia in comparison to Europe. The author notes that the fertile soils in Asia, a result of the night soil, were responsible for higher wages and an economic advantage over Europe. Instead of seeing this as a behavior to adopt, Europeans viewed this practice as evidence of their superiority over their Asian counterparts. He describes the ‘waste business’ in Europe and that in Asia. In Europe it was more collect and dump. In Asia - the collected materials were taken to night soil merchant processing centers where the collectors were paid by the pound for what they brought in. To put this in perspective - poop from about 10 households would get you enough cash to buy a 6 month supply of grain. He talks about how the robust nightsoil market kept waterways clean in Japan. Population growth in Japanese cities resulted in a peri urban farming system to supply fresh vegetables, and more demand for night soil. Each acre received between 6-10 wet tons of animal and/or human waste each year. Europe and the US finally started catching on to the beauty of night soil. At least until the 1870s. The switch to synthetic fertilizers happened first in Europe, reducing labor costs and increasing productivity. Letting sewage once again be considered a waste. 

The final article takes us to the present. The focus here is on understanding why and where markets exist for waste derived fertilizers. The author notes their efficacy (she likely read up on night soil, too) and their critical role in a circular economy. She starts with a discussion of the oxymoron ‘markets for waste’ noting that by definition, ‘waste’ is not something that one markets. Redefine, repurpose, rename, modify. And stop using that ‘dispose’ word. She then talks about relative costs as a factor. As fertilizer prices go up, there is a tendency for more demand for organics. As landfill disposal and combustion prices go up, composting seems like a very rational alternative. She goes into a range of factors that can influence decisions for or against residuals use. Then she compares and contrasts Switzerland where biosolids is banned and France, where it is often used. She describes concerns about biosolids safety stemming from Mad Cow disease. Ha - a contaminant from long ago and far away. Many companies had started to refuse to purchase foods grown in biosolids. The French government stepped in and held meetings between a range of stakeholders to reassure everyone involved. The fact that most of the wastewater industry in France is run by Suez and Veolia, two large multinational companies that have government support also helped. As of 2012, 73% of the biosolids are used with about 29% of that total composted prior to use. Then we travel to Switzerland. Home of Alps, chocolate and combustion. Here organic standards coupled with the announcement by organic producers that they wouldn’t accept foodstuffs grown in biosolids lit the fires of those fluidized bed facilities. Beneficial use of biosolids fell from 55% in 1994 to 29% in 2002. It disappeared completely by 2010. Concerns about safety and socio-political factors were the death hammer here. In Switzerland, small municipalities that did not work together to change regulatory and public opinion were no match for ‘scientific uncertainty’. In France, large private companies with political power were. 

So, where are we in the US? For an interesting perspective on that and some excellent advice, I encourage you to listen to this month’s Master Class where Dan Thompson, formerly the head of Tagro talks about his experience. 

Sally Brown is a Research Associate Professor at the University of Washington, and she is also a columnist and editorial board member for BioCycle magazine. 

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