(716e) Green Approach to Produce Bio-Jet Fuel From Microalgae

Green
Approach to Produce Bio-jet Fuel from Microalgae

Marian Elmoraghy, Ihab H. Farag*

Chemical Engineering Department, University of New
Hampshire, Durham, NH

* Correspondence, ihab.farag@unh.edu

Introduction

Renewable
jet fuel for the aviation industry, also termed bio-jet fuels could reduce
flight-related greenhouse-gas emissions by 60 to 80 percent compared to fossil
fuel based jet fuel. The green bio-jet fuel is made by blending microalgae bio-fuels with conventional petroleum-derived jet
fuel to provide the necessary specification properties. The major advantage of
using microalgae oil for biodiesel is the high oil production capacity by
microalgae, as they could produce up to 58,700 L oil per hectare.

Sustainable production of bio-jet fuel requires minimizing
the energy requirements and reducing fresh water usage while simultaneously
lowering the production cost of bio-jet fuel. These are challenges to the
biodiesel production from microalgae. Considerable
efforts have been made to develop efficient and cost-effective photobioreactors
for microalgae growth. Yet, the high cost of installing and operating
artificial light sources in conventional photobioreactors with artificial
illumination systems remains a major problem.

Objectives

The goal of this research is to develop an
economical process to produce bio-jet fuel while minimizing the energy requirements,
reducing water usage and meeting the jet fuel specifications. To accomplish
this goal the following objectives were defined. 1- Investigate minimizing the
energy requirements by replacing fluorescent lights with light emitting diodes
(LEDs); 2- Investigate the use of municipal waste water in growing microalgae to
reduce fresh water usage; 3- Study the one-step production of biodiesel using
in situ algal biomass transesterification process to reduce production time and
cost, and 4-investigate biodiesel blending with jet-fuel in order to obtain
bio-jet fuel that has specific properties. 

 Microalgae Growth Using LEDs:

LEDs are lighter than the fluorescent
lights and small enough to fit into virtually any photobioreactor (PBR). Other
advantages of LEDs include a longer life-expectancy, lower heat generation, and
a greater tolerance for switching on and off. LEDs use less electric energy
than fluorescent light to produce the same light intensity hence their use
lowers the energy requirement for algae growth, and make the process greener by
eliminating the CO2 emitted in generating the excess electric power needed for
the fluorescent light.

Production of bio-jet fuel:

There are three routes to produce bio-jet fuel from
microalgae. Figure 1 shows these three routes. The first route involves using microalgae
oil to produce Bio-SPK (Bio derived synthetic paraffinic Kerosene) by cracking
and hydro-Processing. This can be used for kerosene-type fuels include jet A,
jet A-1, JP-5 and JP-8. FT-SPK (Fischer?Tropsch
Synthetic Paraffinic Kerosene) is the second route which involves pyrolysis of
solid biomass
to produce pyrolysis
oil
or gasification to produce a syngas which is then possessed
into FT SPK. The third route involves algae growth, harvesting, oil extraction
and transesterification or (in situ process) to produce biodiesel. The
biodiesel will be blended with Jet fuel to produce bio-jet fuel.

Approach:

One of the purposes of this research is to improve
energy efficiency of the microalgae cultivation in photobioreactor by comparing
LEDSs with fluorescent light sources, and the use of wastewater versus reverse
osmosis (RO) water. Chlorella Vulgaris microalgae were grown in wastewater and in
RO water. Two LED color panels were used for this comparison: a red panel and a
red-blue Panel. The measured light intensities were maintained at a value of
2000 Lux. The absorptivity and the cell counts measurements were recorded while
the algae were growing using the spectrophotometer and the microscope. Then,
the algae were harvested after the maximum growth was reached. The biomass
freeze dried algae were determined after centrifugation and freeze drying
processes. Research is still progressing towards production of biodiesel
through the in situ process and production of bio-jet fuel.

Discussion:

The highest algae growth (3.2 g freeze dried algae/L
over a growth period of 18 days = 178 mg. freeze dried algae/L-day) was obtained
using red-blue LEDs and RO water. The lowest algae growth (1.21 g of freeze
dried algae/L over a growth period of 18 days = 67 mg freeze dried algae/L-day)
was obtained using fluorescent light and waste water. Algae growth (3.2 and
1.63 gm. freeze dried algae/L over a growth period of 18 days = 178 and 91 mg.
freeze dried algae/L-day) were obtained using RO water and waste water
respectively with red-blue LEDs. Also, Algae growth (1.95 and 1.25 gm. freeze
dried algae/L over a growth period of 18 days = 108 and 69 mg. freeze dried
algae/L-day) were obtained using RO water and waste water respectively with red
LEDs. The results indicate that red-blue LEDs are more effective than red LEDs
using either RO water or waste water. Since the power requirements of the fluorescent
light and the LEDs are 68 and 45 Watts respectively, the total saving energy by
LEDs is about 34%. Light capture efficiencies of LEDs and fluorescent light,
based on the heating value of the algae produced compared to the incident light
energy over the growth period, are 0.72% and 0.48% respectively.

Figure 1 Production of Bio-jet fuel through
three different routes.