TECHNOLOGICAL INNOVATION IN LYCHEE DRYING USING BIOMASS FUEL IN NORTHERN VIETNAM

The application of drying technology plays a crucial role in extending storage time and increasing the added value of lychee products. Currently, most processing facilities still employ direct-firing dryers in which the drying agent is combustion flue gas, resulting in unstable product quality, low energy efficiency, and high emissions. This study evaluates the current drying technologies used in northern lychee-producing regions and presents the experimental results of a forced-convection drying model using indirect heat from biomass, with a processing capacity of over 5 tons of fresh material per batch. The results indicate that, for a final moisture content of ≤ 15%, fuel consumption reaches 1,345 kg of biomass per batch, reducing energy costs by over 25% and shortening the drying duration by 17% (down to 1 51 hours) compared to existing technologies. The dried product exhibits high sensory quality, no smoke contamination, and improved uniformity due to controlled airflow distribution and 10-50% staged exhaust recirculation. The investment cost of the model is 40-45% of an equivalent indirect steam drying system, with simple operation and modular scalability, making it suitable for household and cooperative-level processing. The results confirm that biomass-based indirect drying is an energy-efficient, environmentally friendly, and seasonally appropriate solution for lychee producing regions, with potential applicability to other agricultural products such as longan, plum, bamboo shoots, turmeric, and ginger.