Algae Conversion

BEI’s thermochemical program conducts research into conversion of algae into fuels and products.

Here is a listing of some of our more significant published papers in this area. Click on title to view article in a new window from the publication Website.

Fast pyrolysis of microalgae remnants in a fluidized bed reactor for bio-oil and biochar production

Kaige Wang, Robert C. Brown, Sally Homsy, Liliana Martinez, and Sukh S. Sidhu (2013), Bioresource Technology
[CHART]Yields vs. Pyrolysis Products

Comparison of fast pyrolysis product yields for C. vulgaris remnants (this study) and pine wood (Kasparbauer, 2009)

In this study, pyrolysis of microalgal remnants was investigated for recovery of energy and nutrients.Chlorella vulgaris biomass was first solvent-extracted for lipid recovery then the remnants were used as the feedstock for fast pyrolysis experiments using a fluidized bed reactor at 500 °C. Yields of bio-oil, biochar, and gas were 53, 31, and 10 wt.%, respectively. Bio-oil from C. vulgaris remnants was a complex mixture of aromatics and straight-chain hydrocarbons, amides, amines, carboxylic acids, phenols, and other compounds with molecular weights ranging from 70 to 1200 Da. Structure and surface topography of the biochar were analyzed. The high inorganic content (potassium, phosphorous, and nitrogen) of the biochar suggests it may be suitable to provide nutrients for crop production. The bio-oil and biochar represented 57% and 36% of the energy content of the microalgae remnant feedstock, respectively.

Catalytic pyrolysis of microalgae for production of aromatics and ammonia

Kaige Wang and Robert C. Brown (2013), Green Chemistry

[DIAGRAM]Algae pyrolysisWe report an economically- and environmentally-promising microalgae biorefinery pathway, which uses catalytic pyrolysis with HZSM-5 catalyst to convert whole microalgae into aromatichydrocarbons. This process produces valuable petrochemicals and ammonia, the latter of which can be recycled as a fertilizer for microalgae cultivation. We tested samples of lipid-lean green microalgae, Chlorella vulgaris, at various reaction temperatures and catalyst loads. We also tested samples of lignocellulosic biomass, red oak, for comparison. Our results demonstrated that catalytic pyrolysis of microalgae produces better aromatic yields and better aromatic distributions than catalytic pyrolysis of red oak. The maximum carbon yield of aromatics from microalgae was 24%, while that from red oak was 16.7%. Moreover, catalytic pyrolysis of microalgae produced more monocyclic aromatics than were produced by catalytic pyrolysis of lignocellulosic biomass. Microalgae present many advantages as a feedstock for biofuel. With the promise catalytic pyrolysis offers for solving some of microalgae’s disadvantages, microalgae biorefineries move one step closer to economic and environmental feasibility.

A techno-economic analysis of microalgae remnant catalytic pyrolysis and upgrading to fuels

Rajeeva Thilakaratne, Mark M. Wright, and Robert C. Brown (2014),  Fuel

Microalgae have been proposed as potentially promising feedstock for the production of renewable transportation fuels. The plants are intriguing for their capacity to serve both as a source of renewable carbon fuels and as a powerful tool for carbon sequestration. Microalgae remnant, a low-cost by-product of microalgae lipid extraction, is a particularly appealing candidate for these processes. Through catalytic pyrolysis, microalgae remnant is capable of producing aromatic hydrocarbons that could be used for the production of drop-in biofuels. One of the most challenging barriers to this promising pathway is the high moisture content of harvested microalgae.

[DIAGRAM]Algae processingProcess block flow diagram for microalgae remnant catalytic pyrolysis and upgrading to drop-in transportation fuels.

The goal of this study is to compare the economics of two catalytic pyrolysis pathways for the production of drop-in biofuels, each pathway employing its own distinct method of feedstock dewatering: thermal drying or partial mechanical dewatering. The study presents chemical process models, capital expense and operating cost estimates, and sensitivity analyses of both scenarios.

Results indicate that thermal drying prior to catalytic pyrolysis (TDCP) incurs capital costs similar to those incurred in partial mechanical dewatering prior to catalytic pyrolysis (MDCP) ($346 million vs. $409 million). TDCP and MDCP yield minimum fuel-selling prices (MFSPs) of $1.80/l and $1.49/l, respectively. Energy analysis shows that TDCP achieves 16.8% energy efficiency and MDCP achieves 26.7% efficiency

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