Optimizing Agricultural Drying Technologies: A Systematic Review of Charcoal, Gas, and Hybrid Kilns for Sustainable Food Preservation

Abstract

In global agriculture, post-harvest losses continue to be a major problem, especially in developing nations where insufficient drying technologies lead to significant food waste. This study systematically evaluates the performance of charcoal and gas drying kilns, focusing on efficiency, cost, and operational flexibility. Boolean search techniques were used to examine drying technologies in a thorough evaluation of peer-reviewed research using databases such as IEEE Xplore, ScienceDirect, and Scopus. The results show that, although they are inexpensive and widely available, charcoal kilns have inconsistent heat output, high emissions (1671g CO₂/kg charcoal), and deforestation risks. In contrast, gas-fired kilns exhibit superior temperature control, energy efficiency (up to 70.9% exergy efficiency), and lower emissions, but they also require a higher initial investment. A balanced solution for environments with limited resources was provided by hybrid systems that combined gas and charcoal technologies to save drying times by 50% without sacrificing product quality. The study emphasizes trade-offs: gas kilns are cleaner but more difficult to reach, whereas charcoal kilns are more expensive but environmentally unsustainable. A promising substitute that can be adjusted to the fuel supply is a hybrid system. Scaling hybrid technology, implementing regulatory incentives to encourage the use of cleaner energy, and conducting additional research on the integration of renewable energy sources are among the recommendations. This evaluation helps engineers and farmers choose the best drying options to improve sustainability and food security.