1906a656_uide_to_Small_Batch_Composting__POSSIBLE_CAUSE
[POSSIBLE SOLUTION] Large bulky pieces of wood or stocks compost very slowly. For best results, keep particles in small batches less than one inch and wood products in sawdust size. Screen out large material. [POSSIBLE CAUSE] 
Particle size is too large
How to Compost: Guide to Small Batch Composting
POSSIBLE CAUSE