By Eben van Tonder, 23 April 25

Abstract The potential role of aged human and animal urine in meat curing traditions has been underestimated in modern literature. This paper synthesises archaeological evidence, biochemical pathways, and recent agronomic studies to examine how ammonia-driven nitrogen transformations contribute to the formation of curing agents. It further investigates how volatile ammonia may have served as both a microbial inhibitor and insect repellent, and addresses long-standing culinary practices—such as roasting or boiling dried meat—as possible post-processing solutions to mitigate strong urine-derived odours.

1. Introduction

In pre-industrial cultures, meat curing relied heavily on ambient conditions, local microbial ecology, and accessible resources. Urine, rich in nitrogen compounds, represented a plausible and functionally versatile curing agent. Its biochemical transformation through microbial activity into ammonia (NH₃), nitrite (NO₂⁻), and nitric oxide (NO) mirrors modern synthetic curing pathways.

This paper builds on the research of Eben van Tonder (2023–2025), who has proposed that both human and animal urine were deliberately used in ancient curing systems to initiate these chemical conversions. Emerging agronomic research supports this hypothesis by confirming urine’s nitrification potential and its ability to repel insects—a discovery with important implications for open-air drying and preservation.

2. Historical Evidence for Urine Use in Curing

Van Tonder has developed a compelling theoretical framework supported by ethnographic and archaeological data. His work on fermentation pits, the role of lime and clay soils in stabilising ammoniacal environments, and the slow nitrification via urea hydrolysis forms the basis of a renewed appreciation for ancient curing systems.

Key sources include:

• Van Tonder, E. (2023). Ammonia from Urine and Horse Sweat.
• Van Tonder, E. (2024). Hallstatt and the Sacred Clay Pit.
• Van Tonder, E. (2025). The Pomo Hypothesis: Ammoniacal Fermentation in African Meat Culture.

3. Biochemical Transformation: From Urea to Nitrite

Urea Hydrolysis and Ammonia Generation: Urea is hydrolysed by urease-producing bacteria to form ammonia and carbon dioxide: CO(NH₂)₂ + H₂O → 2NH₃ + CO₂

This ammonia is then oxidised by nitrifying bacteria: NH₃ → NO₂⁻ → NO₃⁻

Under low-oxygen conditions, denitrifying bacteria reduce nitrate and nitrite to nitric oxide, which binds with myoglobin in meat to form nitrosomyoglobin, producing the characteristic cured meat colour.

Volatile Ammonia: Advantages and Challenges

Volatile ammonia presents both benefits and challenges in the context of meat curing:

Advantages:

• It exhibits antimicrobial properties, disrupting microbial cell membranes due to its alkalinity.
• It serves as a precursor in natural curing chemistry, undergoing microbial transformation into nitrite and nitric oxide.
• It appears to repel insects, reducing spoilage risks in open-air drying.

Challenges:

• Ammonia’s volatility limits its persistence on exposed surfaces, especially under heat and airflow.
• The intense odour may be unpalatable in the final product unless adequately mitigated post-curing.

4. Pest Control and Drying: Implications for Open-Air Preservation

Research by Amadou and Baoua (2025), as reported by Kazmer, found that plots treated with sun-aged human urine experienced 20.5 times less insect infestation and produced yields 1.8 times higher than untreated controls. The strong ammonia odour is hypothesised to disorient or repel insects.

These findings have significant implications for meat preservation in historical contexts. Open-air drying of meat, common in many regions, would have been highly susceptible to fly infestation. The application of urine, whether directly or through soil interaction, could have created a chemical deterrent against egg-laying insects. This suggests that urine’s role extended beyond curing chemistry to include preservation through pest management.

This view aligns with van Tonder’s proposal that in African and Hallstatt traditions, meat buried in pits or layered in clay underwent fermentation that not only converted nitrogenous waste to curing agents but also created inhospitable environments for insects.

5. Roasting and Boiling: Culinary Solutions to Ammonia Retention

The common practice of roasting or boiling cured meat prior to consumption may have evolved to address residual ammonia. Roasting initiates Maillard reactions, which introduce flavour and aromatic complexity while volatilising low-boiling-point compounds such as ammonia (boiling point: −33°C).

Boiling offers a gentler alternative, drawing ammonia and other volatiles into the cooking water while softening texture. In many cases, dried meats were pulverised into soups or stews, suggesting both flavour enhancement and odour mitigation.

Van Tonder (2024) notes that such culinary adaptations are documented in multiple Iron Age traditions. Rather than viewing these practices as purely gustatory, they should be interpreted as rational responses to the biochemical consequences of pre-modern curing systems.

6. Health and Safety Considerations

Sunlight-aged urine, as described by Amadou and Kazmer, reduces pathogens effectively. However, modern applications must consider contaminants such as PFAS or pharmaceuticals, which were absent in ancient waste streams. Filtration, controlled fermentation, or synthetic analogues of the microbial activity may be necessary.

In addition, the potential for nitrosamine formation—known carcinogens formed when nitrites react with secondary amines under high heat—necessitates controlled pH conditions and the inclusion of inhibitors such as ascorbate.

7. Conclusion

The integration of biochemical research, ethnographic analysis, and modern agricultural science supports the proposition that urine was historically significant in meat curing. Its dual role as a microbial substrate and an insect repellent may explain its value in societies dependent on natural preservation methods. The associated culinary practices of boiling and roasting reinforce the hypothesis that ancient communities developed practical strategies for managing both the chemical and sensory impacts of these methods.

Revisiting these practices through scientific and historical lenses presents an opportunity to reclaim and modernise sustainable curing techniques rooted in deep human ingenuity.

References

Van Tonder, E. (2023). Ammonia from Urine and Horse Sweat. Earthworm Express. https://earthwormexpress.com/bacon-the-art-of-living/chapter-12-06-2-ammonia-from-urine-and-horse-sweat/

Van Tonder, E. (2024). Hallstatt and the Sacred Clay Pit. Earthworm Express.

Van Tonder, E. (2025). The Pomo Hypothesis: Ammoniacal Fermentation in African Meat Culture. Earthworm Express.

Kazmer, R. (2025). Scientists make incredible breakthrough after studying human urine. The Cool Down. https://www.thecooldown.com/green-tech/human-urine-fertilizer-grass-and-pest-control/

Boukari Baoua, I., & Amadou, L. (2025). Urine as a dual-purpose agricultural input. New Scientist.

Scientific Research Publishing. (2025). Urine for Sustainable Agriculture in West Africa.

North Dakota State University Extension. (2024). Environmental Implications of Excess Fertiliser.

Earth.org. (2025). Health Hazards of Synthetic Agricultural Inputs.

United States Environmental Protection Agency (2025). PFAS in Agricultural Biosolids.