[0] Pine chips (example of forest residues from timber and fiber harvests) [1] 8,000-9,120 [2] 10-20 dry tons/acre of on-site residues following logging; harvested every 20-40 years [3] Relatively inexpensive if chips produced at the roadside as a byproduct of wood processing Infrastructure to handle forest residues exists [5] An expanded ethanol industry using wood can also be an additional source of biopower as a co-product [4] 
High retrieval cost when tops and branches collected in forest due to labor-intensive collection and transportation Tops and branches may not be accessible or environmentally sustainable to remove for chipping, depending on location and soil type