The effect of chipper cut length on wood fuel processing performance

The authors tested the same chipper under two alternative cut length settings (7 mm and 20 mm), with and without a piece breaker. The study included 10 repetitions per treatment, over 2 different feedstock types: chestnut logs and locust logs. The total number of repetitions was 80, each consisting of about 30 kg of logs. Cut length setting and piece breaker option are the main drivers of chip size, and they are manipulated with the main purpose of managing particle size distribution. Our study showed that the proportion of small chips increased dramatically with the shortest cut length setting (7 mm). Installing a piece breaker allowed maximizing the incidence of small chips, which reached 70% of the total mass when the piece breaker was used in combination with the shortest cut length setting. All else being equal, reducing cut length determined a substantial decrease of productivity (ca. 30%), and an even higher increase of specific fuel consumption (ca. 50%). All strategies to reduce chip size also resulted in increasing the incidence of fines. These results were obtained with new sharp blades. Blade wear may enhance or weaken the effect of cut length and piece breaker option.