Some Mexican farmers and farming operations use night soil or composted human waste as fertilizer on crops. There are farms in Mexico that use untreated sewage to water crops and add nitrogen to the soil, but these crops are not usually imported to the US, but consumed in Mexico.
Traditionally human waste has been used in farming, treated and untreated for hundreds of years. As Mexico continues to modernize farming practices this practice is becoming less common in large agricultural operations.
One of the most famous regions using untreated waste water or agua negro has had the wastewater diverted to a wastewater treatment plant making the practice impractical.
Smaller farms that are sustainably minded may still compost human waste to use as a rich completely safe soil builder.
The concern about food borne illness from imported crops has resulted in many new laws and regulations on what is allowed to be imported for human consumption. For example, avocados were prohibited as an import until 1997 when the product was deemed safe and now is the primary producer of avocados eaten in the US.
The agricultural practices in Mexico are overseen by 6 different agencies and there are also USDA recommendations for imported produce. So, there is no lack of safety standards.
What Does Mexico Use as Fertilizer?
Commercial farming in Mexico is diverse and the use of chemical and organic fertilizer varies from site to site. Fertilizer products are regulated by the Processed Food and Nonalcoholic Beverages Commercial and Sanitary Information which requires all products be labeled in Spanish and include a list of ingredients.
Mexico Imports 57% of the world’s nitrogen fertilizer, mostly Urea from China and Russia, 25% of the phosphorus fertilizer and 18% of the potassium fertilizer.
These are the chemical fertilizers that are imported. They generally do not build soil healthy and may have a negative impact on soil biodiversity.
The current government of Mexico has passed legislation to help support smaller agricultural businesses to feed the Mexican people. It has cut some tax breaks for larger farming corporations to help promote more sustainable practices in Mexican farming.
Some small farms are using composted human waste, or night soil, to build soil health, soil biodiversity and soil quality over time.
This practice is more sustainable than the constant import of chemical fertilizer.
This along with the use of animal manure are a way forward for sustainable farming to maintain a steady food supply for Mexico and for exporting which is about 3.5% of the GDP.
Is It Safe To Eat Vegetables Grown in Human Waste?
Human waste can safely be used to fertilize vegetables and other crops for human consumption if it has been properly composted or treated to remove any pathogens. Human waste can pass harmful pathogens to humans that can lead to sickness and death if it is not properly treated.
Wastewater treatment plants use a combination of chemicals and heat to kill harmful bacteria, viruses and parasites. This works very well, but it is hard on the environment on a large scale.
Composting human waste can be composted safely when the temperature is monitored closely and it reaches 105 to 250 degrees fahrenheit and is composted in a water tight container so it cannot leech into public water.
The composting process can eliminate harmful pathogens completely when done responsibly.
The FDA considered biosolids (the name for properly treated human waste that is free from harmful pathogens) as a viable soil amendment.
They have created a guiding document for farmers who are considering using Biological Soil Amendments of Animal Origin and Human Waste or BASSOs. They allow for three treatment processes; chemical, physical and biological.
These treatments allow the BASSOs to safely be applied to crops.
Is Human Waste Safe As Fertilizer?
Human waste can be used safely as fertilizer when it has been treated by one of three ways; chemically, physically or biologically.
Chemical waste treatment is generally done in a wastewater plant and requires the application of heat to the wastewater. Chemical treatment is subject to the most scrutiny and microbial testing.
Physical treatment of human waste consists of mixing the waste with high alkaline substances like lime that creates a hostile environment for harmful pathogens that could be passed to humans. Human waste that is mixed with lime is generally considered safe for application on agricultural products.
Biological treatment refers to composting. To effectively compost human waste it must reach a high temperature and maintain the temperature over a period of time. There are two acceptable methods: 131 degrees fahrenheit for three consecutive days in a sealed watertight container or 131 degrees for fifteen days in an open pit.
These three methods all produce clean fertilizers that can be used on many agricultural products.
What Countries Use Human Waste as Fertilizer?
Biosolids, Night Soil or Human waste is used in some farms in almost every country. The percentage of waste water that is converted to biosolids and their farming application varies widely from country to country.
There is documented use of human waste in farming in:
It is used elsewhere and has been documented hundreds of years ago where the collection of human waste was a booming industry.
Human waste is used in most countries in large and small farming operations. This free or low cost fertilizer builds soil and supports soil biodiversity when the waste has been appropriately treated.
Use of Human Waste in Mexican Farming
Human waste is treated and used as fertilizer in farms in Mexico and around the world. This practice can be completely safe and is regulated by national and state agencies to ensure that food is safe for human and animal consumption.
The use of human waste in farming has been documented for hundreds of years in ancient civilizations in Japan, China and Mexico.
The practice of treating and using human waste to improve soil health and fertilize crops for humans and animal feed is a sustainable model for modern farming.
The use of human waste can be harmful to human health when pathogens are passed from human waste to vegetables that are intended to be consumed raw.
If you are concerned about foodborne illness be sure to get to know the source of your lettuces, fruits and berries and wash them well when preparing them at home.
Food that will be cooked like potatoes, squash, and corn can be safer when they are prepared at recommended temperatures.