A model for simulating the effect of air recycling on the performance and energy consumption of a concurrent rotary dryer for vegetable wholesale by-products is proposed. Simulating results indicate that air recycling means energy savings of 21-38.5% and increases thermal efficiency in a 28-63% for the studied airflow rates. It was found that for great recirculation ratios, greater retention times are required to obtain the same final product moisture content, resulting in a decrease of dryer work capacity. Optimum recirculation ratios were determined for different performance conditions. A table to estimate break-even for the investment necessary to provide the dryer with appropriate air recycling installations is presented. (C) 2002 Elsevier Science Ltd. All rights reserved.