Prior extraction of essential oil and pectin does not alter the (catalytic) pyrolysis of pomelo (Citrus maxima) peels

This study explores the potential of pomelo (Citrus maxima) peel, a significant food waste product (2.8-4.7 million metric tons per year), as raw material for cascaded biorefining, involving extraction and catalytic pyrolysis. First, the essential oil (1.85 +/- 0.21 wt%) and pectin (13.60 +/- 0.57 wt%) were extracted from the pomelo peel using hydrodistillation and acid hydrolysis/ethanol precipitation, respectively. The results of GC-MS/FID showed that the main components of the essential oil (in relative peak area) were linalool and its oxides, Dlimonene, and trans-carveol. Upon pectin extraction, a water/ethanol liquid was obtained, which was rich in 5hydroxymethylfurfural (4.19 wt%), 5-methylfurfural (1.60 wt%) and furfural (11.80 wt%), all being (hemi)cellulose-derivatives. Consequently, micro-pyrolysis of plain pomelo peel and extracted pomelo peel showed that the pyrolysis products of both pomelo peels were nearly identical, with a total identified FID area of 58.14 area% and 58.98 area%, respectively. Main compounds were furfural (13-14 wt%), methanol and acetic acid. Using HZSM-5, yields nearly identical pyrograms for plain and extracted pomelo peel, with toluene (20.68 area% and 19.52 area%), p-xylene (13.81 area% and 14.72 area%), and benzene (7.97 area% and 7.36 area%) as major compounds. Building on the micro-pyrolysis, a meso-scale pyrolysis plant (250 g & sdot;h-1) was used, allowing mass balance closure and analysis of three pyrolysis fractions: average bio-oil yield was 52.5 wt% and average biochar yield was 37 wt%. In conclusion, prior extraction of essential oil and pectin does not alter the (catalytic) pyrolysis of pomelo (Citrus maxima) peels, opening a route towards a more comprehensive valorization of this voluminous waste stream.