Dry Composting Toilets: A Sustainable Sanitation Solution

By Aundria McMillan Humphrey

Access to clean water and proper sanitation remains a pressing challenge for many rural communities. The Rotary Club of San Miguel de Allende – Midday, in partnership with CEDESA, has been at the forefront of implementing sustainable sanitation solutions through the construction of dry composting toilets. These systems offer a practical, water-conserving, and eco-friendly alternative to traditional sewage and septic systems, bringing dignity, hygiene, and environmental benefits to families in need.

Carla Cadena is the Project Team Leader for the Dry Composting Toilets. She has been involved with this project since 2018.

How Dry Composting Toilets Work

Unlike conventional flush toilets, dry composting toilets function through separate chambers that independently process solid and liquid waste. Solid waste is covered with a drying mixture—comprising dry soil, leaves, sawdust, ash, and lime—which aids in decomposition and prevents odors. Meanwhile, liquid waste is diluted and can be used as a nutrient-rich liquid fertilizer. This system eliminates the need for water in waste disposal, conserving an estimated 13 to 20 liters per flush—a crucial advantage for communities where water is scarce, contaminated, or nonexistent.

Water scarcity is an ongoing issue in San Miguel, with 82% of the groundwater being allocated to agriculture. By providing dry composting toilets, families gain access to safe, private, and dignified sanitation, while also addressing the larger issue of dwindling water sources.

Additional Benefits Over Traditional Systems

• Zero Water Consumption: Eliminates the need for water in waste disposal, reducing strain on limited resources.

• Prevents Water Contamination: Processing waste separately eliminates the risk of contaminating groundwater.

• Production of Organic Fertilizer: The system creates nutrient-rich compost that supports agricultural activities and combats food scarcity.

• Minimal Maintenance Costs: Upkeep is inexpensive and manageable for families.

• Odor-Free and Hygienic: The separation of liquid and solid waste prevents anaerobic decomposition, eliminating foul odors.

• Reduction of Disease-Carrying Pests: Properly maintained dry toilets deter flies, mosquitoes, and other disease carriers.

O

verall, the implementation of these toilets results in improved public health, enhanced agricultural productivity, and sustainable waste management.

Overcoming Cultural and Logistical Challenges

When first introduced, many individuals had doubts, primarily due to unfamiliarity with the system. However, once they understood the benefits and witnessed the success of others, acceptance increased. Rotary Club and CEDESA actively engaged in educational initiatives, demonstrating how the system works and showcasing families who have seamlessly integrated dry composting toilets into their daily lives.

Enhancing Soil Health and Agricultural Sustainability

One of the most significant advantages of composting human waste is its positive impact on soil health. To ensure proper composting, key conditions must be maintained:

Temperature: The compost chamber should remain above 68°F (20°C) for effective decomposition.

• Humidity: Optimal moisture levels (45%–70%) prevent odors and facilitate composting.

• pH Balance: Maintaining alkalinity (pH above 9) with carbon-rich materials ensures high-quality organic matter.

• Proper Ventilation: Adequate airflow is necessary to prevent excess moisture and accelerate decomposition.

• Sufficient Time: The composting process requires at least six months to produce safe, nutrient-rich compost.

• When these conditions are met, the final compost product is non-toxic and highly beneficial for farming, promoting sustainable agriculture while reducing reliance on synthetic fertilizers.

Maintenance and User Training

Ensuring proper maintenance is vital for the continued success of dry composting toilets. Families are trained by promoters and monitoring committees on:

• Using the drying mixture after each use.

• Keeping the toilet closed to prevent insect infestations.

• Rotating between composting chambers, allowing waste to decompose fully.

• To reinforce these practices, monitoring committees conduct six periodic visits to each household, providing guidance, inspections, and reminders.

Growing Adoption and Community Impact

Following the pilot project, demand for dry composting toilets surged, prompting the Rotary Club of San Miguel de Allende – Midday to apply for a global grant from The Rotary Foundation. As a result, more families have actively engaged with CEDESA to build their own sanitation systems with Rotary funding. Since 2018, over $300,000 USD has been invested through global grants, supporting the construction, education, training, and monitoring of approximately 200 dry composting toilets.

Future Expansion and Sustainability

Given the program’s success, the Rotary Club anticipates submitting additional grant applications to expand the initiative. The long-term goal is to ensure that more families in rural communities gain access to sustainable sanitation solutions, improving health, water conservation, and agricultural sustainability. Through education, community involvement, and continued investment, the Rotary Club is empowering rural families to embrace sustainable, dignified, and ecologically responsible sanitation practices.

Aundria McMillan Humphrey www.slowdowngranny.com