Original article on Engineering for Change website
Introducing the Guide to Assembling, Using, and Maintaining Clay Pot Coolers, the result of a collaboration by MIT D-Lab, the World Vegetable Center (WVC), and Institut d’Economie Rurale (IER). This is how clay pot coolers can keep produce fresh without electricity, why it matters, and tips on how to make one.
Fruits and vegetables can spoil quickly in arid climates, leading to the loss of food, time, and money. Roughly 50% of fruits and vegetables harvested in Sub-Saharan Africa are lost between harvest and reaching the consumer, in part due to the lack of suitable storage in regions where electricity is scarce or too expensive. However, one solution is inexpensive and relatively simple: a clay pot cooler. Using clay pot coolers can increase the shelf lives of many common fruits and vegetables, including tomatoes, leafy greens, eggplant, and okra, among others.
Clay pot coolers take advantage of the "evaporative cooling" effect in the same way that the evaporation of perspiration cools the human body. The evaporation of water from the outer surface of the clay pot removes heat and creates a cooling effect for the fruits and vegetables inside. By providing a cool—as much as 10°C below the ambient temperature—and humid environment, people living in areas without access to other kinds of refrigeration can improve their overall food security and gain other monetary and labor efficiencies. For example, the shelf lives of many leafy greens can be extended from approximately one day, when stored in ambient conditions, to over four days when stored in a clay pot cooler, reducing the risk of food loss and allowing families to travel to a market twice a week instead of every day.
Simple to build
Clay pot coolers can be made in multiple forms, including a smaller pot nested inside a larger cylindrical pot or a pot placed in a plastic basin, and the sizes of the pots can be selected based on what is most practical for a given user. Sand is placed between the inner pot and outer vessel, and a cloth or sack is placed over the cooler as a cover. Clay pot coolers can cost between $5 and $40, depending on their size and local material prices. Regardless of the size and design, the best practices for using clay pot coolers include storing them in a shady and well-ventilated area, keeping the sand between the inner and outer pots wet, covering the cooler with a wet cloth or sack, and regularly cleaning the inside of the cooler.
The research underway
Since 2016, MIT D-Lab, the World Vegetable Center (WVC), and Institut d'Economie Rurale (IER) have been collaborating to evaluate the suitability of clay pot coolers for household use in Mali, how the devices perform, how people use the devices, and the most effective approaches for disseminating the technology. While most people in Mali are familiar with the concept of using clay pots to keep water cool, research found that very few people were aware that two pots, some sand, and a covering could be assembled into a storage device that improves the shelf lives of fruits and vegetables.
As part of an initial research study to evaluate the performance of clay pot coolers and understand user behavior, the team distributed assembled clay pot coolers to households with basic instructions for using the coolers to store their fruits and vegetables. Based on survey results, participants who used clay pot coolers reported reduced food loss due to spoilage, which resulted in financial savings and increased availability of fruits and vegetables for their households. However, there was a lack of awareness about where the devices could be purchased or how to make the coolers themselves.
Guidebook: How to Build, Use and Maintain a Clay Pot Cooler
In an effort to bridge this gap, the team has developed “A Guide to Assembling, Using, and Maintaining Clay Pot Coolers” to disseminate information about this simple, low-cost technology with great potential to improve nutrition, and, in some cases, livelihoods. The guide, now available in French and English, and covers the following aspects:
- How evaporative cooling works
- Importance of proper fruit and vegetable storage
- Types of clay pot coolers and how to assemble them
- Fruit and vegetable compatibility
- Best practices for using clay pot coolers
Training program in Mali
The team is using this guide as the centerpiece of an ongoing training program funded by the Innovation, Technology, & Research Hub at USAID and the Islamic Development Bank in the Mopti region of Mali. The approach we are taking in Mali is to start by sharing this information with agricultural extension agents and clay pot producers through in-depth training-of-trainers (ToT) sessions. The ToT participants will go on to conduct more focused trainings with larger groups of fruit and vegetable sellers, pot makers, farmers, and other community members.
During the pilot round of trainings in 2020, 39 people were trained from the Mopti area in northern Mali. The program was improved after this pilot round, and at the end of February 2021, WVC and IER conducted a ToT with 11 agricultural extension officers and clay pot makers, who will be training hundreds of people and distributing this guide throughout the Mopti region over the coming months.
Call to action
We are looking to further scale up the training program throughout Mali and other countries where these inexpensive devices are most needed. If you are interested in connecting with the project team, contact Eric Verploegen.
About the Authors
Eric Verploegen joined MIT D-Lab in 2014 to expand D-Lab’s research efforts in the areas of food water and energy. His two main areas of work are related to evaporative cooling for vegetable preservation and D-Lab’s Energy Needs Assessment Toolkit, supporting organizations to identify the most pressing energy needs in the communities where they work.
Melissa Mangino is Senior Program Associate at MIT D-Lab where she provides administrative support for D-Lab academics and the Scale Ups program. In her previous life, Melissa was a high school social studies teacher and has many years of experience in K-12 education advocacy, community outreach, and engagement.
A Guide to Assembling, Using, and Maintaining Clay Pot Coolers
Clay Pot Coolers: Preserving Fruits and Vegetables in Mali: Report 2016-2021
MIT D-Lab Evaporative Cooling for Vegetable Preservation
Eric Verploegen, MIT D-Lab Research Engineer, Evaporative Cooling Lead