Impact/Purpose:

The world is facing a potential energy crisis due to fossil fuel energy demand and population increase. Pollution from fossil fuels affects public health, and causes global climate change because of carbon dioxide (CO₂) release. One of the ideas to solve this problem is to use microorganisms that can provide both renewable energy and CO₂ removal from the atmosphere. The objective of this project is to convert solar energy and waste CO₂ (carbon dioxide that is released in power plants by burning fossil fuels) into an array of biofuels by sequential use of microorganisms in bioreactors.

Description:

A 100 L photobioreactor for biodiesel generation from microalga Chlorella vulgaris was constructed from two parallel clear PVC 10 feet tubes (6’ diameter) with a small slope (10%). The gas mixture (5% CO2 and air) flowed up the top of the PVC tubes from the bottom as large gas bubbles. Photobioreactor was run in a batch mode for two weeks at room temperature. Continuous light was provided by cool white fluorescent lamps (136 - 186 μmol • m-2 • s-1 on the surface of the culture). Algal biomass was harvested at OD665 ~ 0.35 corresponding to a chlorophyll concentration of ~ 3 μg per ml, and concentrated by sedimentation with subsequent drying under 70◦C. Algal oil was extracted with hexane. The amount of oily material was expressed as a percentage of algal dry weight. Oil content in the algal cells in the bioreactor was found to be 10%. Algal oil was converted into biodiesel by transesterification with glycerol as a by-product. Next, glycerol was used as a substrate for making H2 and ethanol by bacterium Enterobacter aerogenes in batch culture (test tubes), and in hollow-fiber bioreactor. Highest H2 and ethanol production rates were observed under 2% glycerol, volume per volume (v/v), on a synthetic medium in test tubes. The yield of H2 from glycerol (0.9 mol/mol) was relatively high in batch culture (in test tubes). A lab-scale hollow-fiber bioreactor for conversion of glycerol into H2 and ethanol was constructed. The bioreactor was designed in a way that the glycerol diluted in growth medium was pumped from the outside of the fibers into the lumen (inside). Bacterial cells were readily adsorbed to the outer surface of the hollow fibers, and the cells consumed glycerol. Used growth medium was returned to the bioreactor medium reservoir, to create a close system in which it was possible to measure glycerol uptake and ethanol production by bacterial cells. The bioreactor was run under 30º C. Glycerol uptake efficiency by bacteria in the bioreactor was found to be 90% for 7 days. The assessment of H2 and ethanol-producing activity by bacteria in the hollow-fiber bioreactor in the presence of 2% glycerol (v/v) was made. Hydrogen production in the hollow-fiber bioreactor by E. aerogenes from glycerol was observed for 3 days at a maximum rate of 30 mL per hour (mL · h-1). Hydrogen from the hollow-fiber bioreactor was directly injected into a small fuel cell, and shown to be capable of generating enough electricity to power a small motor.

URLs/Downloads:

Final Progress Report

Record Details:

Record Type:PROJECT( ABSTRACT )

Start Date:08/15/2008

Completion Date:08/14/2009

Record ID: 200633

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Related Organizations:

Role :OWNER

Organization Name :AUSTIN PEAY STATE UNIVERSITY

Mailing Address :601 College St

Citation :Clarksville

State :TN

Zip Code :37044

Project Information:

Approach :

An interdisciplinary student team will first use microalgae in a photobioreactor to efficiently produce oil using CO₂ and solar light as an energy source. Then, produced oil will be converted into biodiesel by transesterification. Next, glycerol (also known as glycerin), a by-product of biodiesel production, will be used as a substrate for making H2 (biohydrogen) and ethanol by immobilized bacteria in a bioreactor. Finally, students will test the produced biofuels: biodiesel, H2 and ethanol in model engines. While these proof of concept studies will use purchased CO₂, an abundant supply of waste CO₂ from local power plants is available for commercial scale up.

Specific aims of this project are: (1) to design and build a novel photobioreactor for photoconversion of CO₂ into oil (biodiesel) by microalgae using solar light as the energy source; (2) to develop and test a hollow-fiber bioreactor for efficient fermentation of glycerol, the by-product of microalgal biodiesel production, into H2 and ethanol by bacteria; (3) to investigate the feasibility of using CO₂ emissions from local power plants and wineries for its utilization by microalgae in a photobioreactor.

Cost :$10,000.00

Research Component :Pollution Prevention/Sustainable Development

Approach :

An interdisciplinary student team will first use microalgae in a photobioreactor to efficiently produce oil using CO₂ and solar light as an energy source. Then, produced oil will be converted into biodiesel by transesterification. Next, glycerol (also known as glycerin), a by-product of biodiesel production, will be used as a substrate for making H2 (biohydrogen) and ethanol by immobilized bacteria in a bioreactor. Finally, students will test the produced biofuels: biodiesel, H2 and ethanol in model engines. While these proof of concept studies will use purchased CO₂, an abundant supply of waste CO₂ from local power plants is available for commercial scale up.

Specific aims of this project are: (1) to design and build a novel photobioreactor for photoconversion of CO₂ into oil (biodiesel) by microalgae using solar light as the energy source; (2) to develop and test a hollow-fiber bioreactor for efficient fermentation of glycerol, the by-product of microalgal biodiesel production, into H2 and ethanol by bacteria; (3) to investigate the feasibility of using CO₂ emissions from local power plants and wineries for its utilization by microalgae in a photobioreactor.

Cost :$10,000.00

Research Component :P3 Challenge Area - Energy

Project IDs:

ID Code :SU833915

Project type :EPA Grant