Enhancing the Shelf Life of Kale and Tomato Using a Zero-energy Cooling Chamber in Ethiopia

The post-harvest fruit and vegetable loss in Ethiopia is estimated to reach 40 %. In this research, the authors assessed the effectiveness of a zero-energy cooling chamber (ZECC) in prolonging the shelf life of kale and tomatoes in two locations: Addis Ababa and Woliso. The ZECCs were constructed using bricks and sand with dimensions of 1.5 m wide and 2.15 m long. The experiment involved five treatments: two storage devices with two precooling treatments in ZECC and room storage as a control. Following a completely randomized design (CRD) with three replications, 500 g of kale and 1 kg of tomatoes were stored in each device. Key parameters, including physiological loss of weight (PLW), wilting index, visual quality, and total soluble solids (TSS), were monitored, alongside environmental factors such as temperature and relative humidity (RH). The ZECC significantly reduced maximum temperature (up to 6.82°C) and increased RH (up to 40%) compared to room storage, resulting in a shelf-life extension of kale by 2 days and tomatoes by 10 days. These effects were more pronounced in Woliso, a warmer location. Irrespective of storage devices and precooling treatments, in Addis Ababa, ZECC extended the shelf life of tomatoes from 16 to 24 days (50%) and kale from 1.5 to 3.5 days (133.3%). In Woliso, tomatoes’ shelf life increased by 83.3% (from 12 to 22 days), while kale’s shelf life rose from 1 day to 2.5 days (150%). In addition, the breakeven analysis showed that ZECC generated additional income of USD 158 and USD 226 from tomato storage in Addis Ababa and Woliso, respectively, and USD 241 and USD 204 from kale storage. The cost recovery period for ZECC (USD 439) was shorter in Woliso (1.9 years) than in Addis Ababa (2.8 years) for tomatoes, and 1.8 years in Addis Ababa versus 2.2 years in Woliso for kale. The result from our study demonstrates that ZECC is a practical and affordable method to reduce postharvest losses, extend shelf life, and enhance income for vegetable growers, offering potential benefits for food security in Ethiopia and similar settings. Key words: Zero energy cooling chamber, shelf life, Ethiopia, kale, tomato