Agriculture: Are Charcoal Coolers The Best Way To Keep Food Fresher For Longer?

A charcoal cooler is one of the most affordable and sustainable alternatives to refrigeration. It’s become a lifesaver for areas that don’t have access to electricity or where it would be too costly to refrigerate produce. Charcoal coolers increase the shelf-life of fruits and vegetables, which have a high spoilage rate when left at room temperature or outdoors. They work best in areas with atmospheric humidity lower than 30%.

How do charcoal coolers work?

These innovative solutions to a lack of refrigeration apply the principle of evaporative cooling. This is the removal of heat through the evaporation of the materials surrounding the storage device. The evaporation causes a decrease in temperature and increases humidity in the storage area. This results in an increase in the shelf life of products. Water is added periodically to the charcoal depending on the weather. Some cooling chambers use different materials like bricks, soil, or sawdust which require different amounts of water. Large coolers are used to store subtropical produce such as sweet potatoes. But the smaller units store fruits and vegetables.

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The higher humidity and low temps of the coolers increase the shelf life because they reduce the rate of respiration and water loss of vegetables. The external material of the cooler has to remain humid. Warm, dry air passes through the charcoal and draws heat energy resulting in refrigeration. Charcoal works well because it is a poor conductor of heat. It’s highly porous which makes water and moisture pass through efficiently.

Are there other types of energy-free coolers?

Zero-energy coolers were first invented in India in the 1980s to address food loss. They made them using double brick walls with brick floors and covered with a straw mat. The space between the brick walls is filled with clean river sand which retains water. Food is stored in unsealed plastic containers or crates which maintains sanitation and keeps the air circulated. In the hot season, they can maintain temperatures as low as 18°C lower than the ambient temperature.

In addition to the charcoal and brick coolers, there are evaporative cool rooms. They are a larger scale energy-free cooler that requires a pump to distribute the water and a ventilation fan in the ceiling. Their design is similar to the vents within greenhouses.

Areas of Nepal use semi-underground cellar storage to keep produce fresh. They’re mostly used in areas of high altitude. They use the earth for climate control to maintain low temperatures and high humidity. This protects the food from rot in the summer and frost in the winter. Fruits and potatoes can be stored for up to 6 months using this method. It’s made using a double-walled structure consisting of mud and mortar. The cavity is filled with sand which is supplied with water using a pipeline to keep the sand perpetually wet. Two-thirds of the storage structure is at an underground level and can reduce temperatures to 7°C.

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Why more farmers should invest in charcoal coolers

Horticultural farmers should invest in charcoal coolers due to the high spoilage rate of fruits and vegetables. Studies show that fruits and vegetables also account for the largest percentage of post-harvest loss. They are highly perishable and are subjected to poor post-harvest handling. Additionally, inadequate storage and processing infrastructure contribute to food waste.

It’s estimated that up to 50% of fruits and vegetables are lost due to a lack of proper storage infrastructure in sub-Saharan Africa. One method of reducing food waste is by integrating the cold chain within the production process. In addition, most agriculture is practised in rural areas where electricity is expensive and unavailable. Electronic refrigeration would take too long to implement for most farmers. However, charcoal coolers require less resources.

Storing produce in charcoal coolers not only preserves the quantity of the harvest but also maintains the quality. The fruits and vegetables remain hard, fresh, or juicy. This makes it easier to sell them. Buyers are less likely to buy wilted produce even if it’s still unexpired. This also contributes to more food security.

Energy-free coolers are cost-friendly and easy to maintain compared to refrigeration. Rural farms also have more space to set these up. Not only does it increase food security but it also helps boost environmental protection and safeguards agricultural income.