Quantification of gas emissions from stored softwood chips as solid biofuels

Western Red Cedar (WRC) is one of the abundant softwood species, which is considered as a good source of biofuel. This paper aims at quantifying gas emissions from stored WRC woodchips and studying the potential health impact during storage and transportation. Experiments were conducted using lab-scale reactors for a range of temperatures under both non-aerobic and aerobic conditions depending on oxygen level. Results from tests using non-aerobic reactors showed that the highest carbon dioxide emission factor of 2.8 g/kg dry matter (DM) was observed at 20 °C for a storage period of 2 months. Although the carbon monoxide emission factor was much lower at 0.03 g/kg DM, it increased with increasing temperatures due to chemical oxidation. Carbon dioxide and carbon monoxide emissions from the aerobic reactors exhibited similar trends as the non-aerobic reactors with respect to the effect of temperature. Total gas emissions were higher from the aerobic reactors compared with those from non-aerobic reactors. Results from the qualitative gas chromatography–mass spectrometry analysis indicated a range of volatile organic compounds was emitted from the stored WRC woodchips. Some of these volatile organic compounds might be associated with the characteristic pungent smell of WRC which could cause odor nuisance to the neighboring community. The total volatile organic compounds concentration was found to be positively correlated with temperature. At the end of the storage period, percent DM loss was below 1 % for both the non-aerobic and aerobic reactors, reaffirming the decay-resistance characteristics of WRC.

Keywords
Gas chromatography analysis; Volatile organic compounds; Storage; Aerobic; Non-aerobic; Dry matter loss