Techno-economic analysis of ash removal in algal biomass
Date
2018
Journal Title
Journal ISSN
Volume Title
Abstract
Large-scale microalgae cultivation for biodiesel production is expected to be performed utilizing open air growth infrastructure which will inherently introduce ash into the system. High ash content biomass represents a significant challenge for the production of biofuel as it increases processing capital and operational costs. This study directly assesses the economic viability of pretreatment processes focused on the removal of ash from biomass grown with an algal turf scrubber (ATS) unit. An engineering process model of biofuel production was developed based on an ATS growth architecture followed by an ash removal process and conversion of the biomass to fuels through hydrothermal liquefaction. The model was validated with literature for the growth and conversion processes and validated with experimental data for the de-ashing process. A total of 14 different scenarios were investigated based on two different ash removal techniques, water wash and alkaline extraction treatment operated at various temperatures and alkaline levels. The engineering process model was integrated with techno-economic modeling to investigate the impact of ash on the required biomass and fuel selling price for economic viability. Capital costs associated with the conversion of biomass to biofuel were found to double as ash content increased from 0% to 70%, correlating to a 21% increase in fuel selling price. Integrating an ash removal step resulted in reduced conversion capital costs. However, only the water wash at 25°C scenario was found to reduce the overall fuel selling price. Operational expenses associated with required waste water treatment, chemical cost associated with the alkaline extraction de-ashing technology, and heating of the microalgae slurry during the de-ashing process were found to significantly increase the overall fuel selling price of the microalgae biofuel.
Description
Rights Access
Subject
ash removal
hydrothermal liquefaction
techno-economic analysis
biofuel
algal turf scrubber
microalgae