An innovative shear-based solution for bucking logs for energy production

The economic sustainability of energy-oriented forest supply chains depends on the ability to process low-value biomass using robust and cost-efficient technologies. In such contexts, reducing maintenance requirements, minimizing downtime, and maximizing operational productivity are essential to maintain profitability. Conventional grapple-saw systems, although widely adopted, are primarily designed for higher-value assortments and may not represent the most efficient solution when bucking material destined for energy production. This study evaluates a radio-controlled shear prototype powered by an autonomous 89 kW engine, designed to provide a simple and robust bucking system for low-value biomass assortments. Field trials were conducted in aged chestnut coppice stands, where whole logs were bucketed at a landing into two target lengths (2.4 m and 6 m), comparing the shear prototype with a conventional grapple-saw. When bucking to 6 m lengths, the shear prototype achieved a productivity of 10.21 m3 h-1, approximately 49% higher than the grapple-saw (6.85 m3 h-1). Bucking to shorter 2.4 m lengths reduced productivity by 29% for the shear prototype and by 53% for the grapple-saw, highlighting a greater sensitivity of the conventional system to shorter assortments. Fuel consumption per unit volume was reduced by approximately 58% at 6 m and 76% at 2.4 m with the shear prototype compared to the grapple-saw. The results demonstrate that shear-based bucking provides a technically reliable and advantageous alternative for low-value biomass, combining higher productivity with substantially lower fuel use, thereby reducing operational costs and improving the overall efficiency of energy-oriented harvesting operations.