Fast pyrolysis of beetle-killed trees

• Beetle-killed lodgepole pine is proposed as a feedstock for fast pyrolysis.
• Beetle-killed lodgepole pine has low moisture and high energy content.
• The decay stage did not affect the quality of bio-oil from fast pyrolysis.
• Hydrocarbon yield of 40.0 wt.% was achieved during catalytic fast pyrolysis.
• Bio-oil from catalytic fast pyrolysis had a high HHV of 40.9 MJ/kg.

In this article, we propose beetle-killed lodgepole pine (BKLP) as a feedstock for fast pyrolysis due to its low moisture and high energy content. To the best of our knowledge, no previous studies on fast pyrolysis of beetle-killed trees have been reported. Samples of healthy lodgepole pine and three decay-stage BKLPs were used as feedstock to investigate the effects of the decay stage on the performance of both non-catalytic and catalytic fast pyrolysis using a Py–GC/MS. Compared to the healthy tree, BKLPs were found to have slightly more extractives and less lignin. The decay stage, however, did not affect the product yield and selectivity for both non-catalytic and catalytic fast pyrolysis. A variety of oxygenated compounds were produced in non-catalytic fast pyrolysis, but most of those were converted into aromatic hydrocarbons in the presence of HZSM-5. For non-catalytic fast pyrolysis, the yield of char decreased from 22 wt.% to 11 wt.% as the pyrolysis temperature increased from 450 °C to 650 °C. The average HHV of volatile compounds was found to be around 26 MJ/kg. For the catalytic fast pyrolysis, the yield of hydrocarbons was as high as 40 wt.%, and the yield of char was as low as 5 wt.%. The average HHV of volatiles was found to be about 41 MJ/kg, which is close to the HHV of commercial gasoline and diesel (∼46 MJ/kg). A high yield of toluene (11 wt.%) and xylenes (9 wt.%) was also observed in the catalytic fast pyrolysis process. Our work suggests that beetle-killed trees are a good feedstock for fast pyrolysis, because the bio-oil derived from the trees that have been dead for four years showed the same quality as that from the healthy trees.