Predicting the higher heating value of microalgae biomass based on proximate and ultimate analysis

Abstract

Microalgae biomass is a unique feedstock capable of effluent bioremediation and thermochemical conversion. Energetic valorization routes require higher heating values (HHV) as an important parameter for system design. Equations to predict the HHV of various biomass are proposed in the literature, but none is found for microalgae biomass. This study aimed to propose equations to predict the HHV of microalgae biomass based on results from proximate (ash, volatile matter — Vm, fixed carbon — fC, and moisture — M) and ultimate analysis (carbon — C, hydrogen — H, oxygen — O, nitrogen — N, and sulfur — S). The equation based on proximate and ultimate analysis combined (HHV (MJ kg−1) = 20.6 − 0.352 C + 2114 N − 0.379 Vm + 0.1131 fC − 0.0394C N + 0.01166 C Vm) presented the highest statistical fit in terms of determination coefficient (R2 = 0.83), standard error of the estimate (SEy = 1.31 MJ kg−1), predicted residual error sum of squares (PRESS = 77.7), mean absolute error (MAE = 5.55%) and mean bias error (MBE = 0.46%).