Productivity and costs of sieving logging residue chips

Sieving of chipped forest fuels has recently been suggested as a way to reduce dry matter losses during storage. Sieving provides a more homogeneous acceptable material with better storage properties, which reduces the risk of energy and dry matter losses and spontaneous ignition. Screened chips can be priced higher due to better quality, and both acceptable and reject fractions are more homogeneous, which improves combustion control. Sieving is costly and the reject fraction is not suitable for storage. Five sieving operations were studied, three involving vibrating screens and two involving starscreens. On average, starscreens were more productive than vibrating screens. In all operations, the sieving machine limited productivity, and the loader feeding the machine was not fully utilized. Sieving costs were under two euro per MWh of chips, which may be recovered through higher values and lower storage losses in the acceptable fraction. If sieving operations were used to increase storage of chips, it could increase the annual utilization of chippers and chip trucks in the supply chain, thereby reducing supply costs. Profitable sieving operations require demand for the fine fraction at a price close to that of residue chips.

Automated summary

Sieving of chipped forest fuels is suggested to reduce dry matter losses during storage, providing homogeneous material with better properties. Starscreens were found to be more productive than vibrating screens, but sieving costs were high and machine productivity limited. Profitable sieving operations require demand for the fine fraction.