Clay pot coolers are simple and inexpensive technologies that can be made with locally available materials.
By providing a cool humid environment, clay pot coolers can improve the shelf life of many common fruits and vegetables in dry regions. D-Lab is working to identify and disseminate the most effective and practical clay pot cooler designs.
MIT D-Lab is currently working with the World Vegetable Center and Institut d'Economie Rurale (IER) to evaluate the performance of clay pot coolers and other similarly-sized storage devices in a laboratory setting. The current effort are building on design and user research work conducted in 2017 and the development of a heat and mass transfer model for clay pot coolers that the team developed.
The temperature and humidity inside the storage devices are evaluated with data-logging sensors designed in partnership with Sensen, and the shelf-life of vegetables in each device is measured and compared with storage in ambient conditions. The vegetables included in this study are spinach, cowpea leaves, amaranth, tomatoes, eggplant, and the shelf-life is measured through a combination of quantitative and qualitative techniques including weight loss, colorimetry, firmness, vitamin C content, acidity, wilting index, and visual evaluation. This research has shown that clay pot coolers can extend the shelf life of leafy greens from 1-2 days to over 4 days the stored in a clay pot cooler.
Dissemination of clay pot coolers in Mopti, Mali
To raise awareness and build local capacity to construct and sell clay pot coolers, MIT D-Lab, the World Vegetable Center, and Institut d'Economie Rurale (IER) developed a training curriculum covering:
- Importance of proper vegetable storage
- Principles of evaporative cooling
- Best practices for constructing and using clay pot coolers
- User identification and marketing
This curriculum includes “A Guide to Assembling, Using, and Maintaining Clay Pot Coolers”, which is available in French and English.
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 trained hundreds of people and distributed this guide throughout the Mopti region.
Evaporative Cooling Technologies for Improved Vegetable Storage in Mali
In 2018, MIT D-Lab and the World Vegetable Center published a research report evaluating clay pot coolers and brick evaporative cooling chambers. The methodologies used included interviews with users of the cooling and storage technologies, interviews with stakeholders along the vegetable supply chain, and sensors to monitor product performance parameters.
A Guide to Assembling, Using, and Maintaining Clay Pot Coolers
Provides an overview of how evaporative cooling works, the importance of proper fruit and vegetable storage, types of clay pot coolers and how to assemble them, and best practices for using clay pot coolers. The guide is available in French and English.
Eric Verploegen, MIT D-Lab Research Engineer