The influence of harvest and storage on the properties of and fast pyrolysis products from Miscanthus x giganteus

The research investigates the fuel property variations associated with the time of harvest and the duration of storage of Miscanthus x giganteus over a one year period. The crop has been harvested at three different times: early (September 2009), conventional (April 2010) and late (June 2010). Once harvested the crop was baled and stored. Biomass properties of samples taken from different storage zones were compared. The thermochemical properties have been investigated using a range of analytical equipment including thermogravimetric analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). In addition, bio-oil has been produced from the early, conventional and late harvest using a laboratory scale (300 g h−1) fast pyrolysis unit. The potential organic liquid yield (on dry basis, also excluding the reaction water generated) based on the laboratory fast pyrolysis processing undertaken in this study, was found to vary between 2.82 and 3.18 dry t ha−1 for the early and the late harvest respectively. The bio-oil organic yield was reduced by approximately 11% (0.36 t ha−1) between the early and the late harvest. Char yield was also reduced by approximately 18% (0.61 t ha−1). The highest gas yield (18.03%-1.60 t ha−1) was observed for the conventional harvest. Gas chromatography-mass spectrometry (GC-MS) analysis of the bio-oil shows that levoglucosan, methylbenzaldehyde and 1,2-benzenediol all increase as a consequence of delayed harvest. It was also observed that by delaying the harvest time the O:C atomic ratio is reduced and a more carbonaceous feedstock is produced.