1 The optimum slash pile size for grinding operations : 2 Grapple excavator and horizontal grinder operations 3 model based on a Sierra Nevada , California survey 4

The processing of woody biomass waste piles for use as fuel instead of burning them was 11 investigated. At each landing slash pile location, a 132 kW grapple excavator was used to transfer 12 the waste piles into a 522 kW horizontal grinder. Economies of scale could be expected when 13 grinding a larger pile, although the efficiency of the loading operation might be diminished. Here, 14 three piles were ground and the operations were time-studied: Small (20 m long × 15 m wide × 4 m 15 high), Medium (30 × 24 × 4 m), and Large (35 × 30 × 4 m) piles. Grinding the Medium pile was found 16 to be the most productive at 30.65 bone dry tons per productive machine hour without delay 17 (BDT/PMH0), thereby suggesting that there might be an optimum size of slash pile for a grinding 18 operation. We also examined modeling of the excavator and grinder operations, and we observed 19 that the constructed simulation model well-replicated the actual operations. Based on the 20 modeling, we estimated that the productivity of grinding at a landing area of 710 m2 of slash pile 21 location was 31.24 BDT/PMH0, which was the most productive rate. 22