Recipient Organization
UNIVERSITY OF ARIZONA
888 N EUCLID AVE
TUCSON,AZ 85719-4824
Performing Department
AGRI & BIOSYSTEMS ENGINEERING
Non Technical Summary
The rising cost of fuels necessitates the development of alternative fuels such as biofuels. The rationale for the development of clean-alterative fuels, specifically "biofuels" such as biodiesel, is threefold - economic development, energy security and environment-friendliness. This study aims to produce biodiesel fuel using algae cultures grown in bioreactors.
Animal Health Component
40%
Research Effort Categories
Basic
20%
Applied
40%
Developmental
40%
Goals / Objectives
The objectives of the study are as follows: Phase 1: Bench-Top Microalgal Culture Optimization 1. To determine the effects of critical environmental factors, such as light intensity, culture density, and CO2 supply rate on the growth rate and hydrocarbon productivity of the algal culture; 2. To determine the effects of tertiary-treated wastewater (100%, 50%, 0%) on the growth rate and hydrocarbon productivity of the algal culture using the optimal settings for the environmental factors determined in the previous objective; and, 3. To determine reduction rates in N and P in the tertiary-treated wastewater used for algal culture. Phase 2: Bench-Top Microalgal Photobioreactor System 4. To determine the effects of various reactor parameters, such as height to diameter (H/D) ratio, ratio of cross-sectional riser and downcomer areas (Ar/Ad), number of internal optical cables, etc., on the growth rate and hydrocarbon productivity of the algal culture using the optimal
settings for the environmental factors determined in Phase 1, and as a function of liquid flow rate; 5. To determine the performance of the photobioreactor in terms of growth rate, hydrocarbon productivity and reduction rates in N and P when the optimal level of tertiary-treated wastewater is used at the optimal settings for the reactor parameters and for the environmental factors previously determined; and, 6. To evaluate the economic feasibility of the photobioreactor.
Project Methods
Employing algal cultures grown in 125-mL flasks, a full-factorial experiment will be conducted with the following specifications: Factors (independent variables): Light intensity (100, 200, 250 micromol m-2 s-1) Culture density (0.05, 0.10 g/L), CO2 level (ambient, 5%) CO2 supply rate (0.002 l gas l-1 medium min-1, 0.0104 l gas l-1 medium min-1) Response Variables (Dependent Variables): growth rate, CO2 fixation rate, and hydrocarbon productivity Experimental Design: Thus, there will be a total of 3 x 2 x 2 x 2 = 24 experimental treatments. Each treatment will have three sample flasks. Also, a second time replication will be conducted. Experimental Set Up: The flasks containing the cultures will be in water baths (MW-1130A-1, Blue M, Blue island, IL, USA) to keep their temperature constant at 25 C. The treatments will be illuminated using 1.22-m (48-in) long, 40-W fluorescent lamps. The photoperiod will be set at 16 h per day. The average room ambient CO2 concentration
over 24 hours is within the range of 370-405 ppm (micromol/mol) and will be verified during the course of the study. For elevated CO2 conditions, pre-configured 5% CO2 in cylinders will be used. The pre-configured 5% CO2 will be supplied to the batch cultures contained in flasks via a 1/8-OD tubing system. The CO2 concentration within ppm level will be measured using an IRGA, LCA-4 (Analytical Development Company Limited, Hertfordshire, England). Also employing flask experiments -- using the optimal settings for the environmental factors determined in the previous objective -- two treatments that use tertiary-treated wastewater (50%, 100%) will be evaluated with reference to a control (0% tertiary-treated wastewater). With the tertiary-treated wastewater being rich in nitrogen (N) and phosphorus (P), the aim is for the algae to further treat the water by assimilating the N and P, which the algae need for growth, while the algae is producing hydrocarbons. With the treatments and the
control each having three sample flasks, there will be a total of 3 x 3 x 3 = 9 flasks. A second time replication will be conducted. The algal growth rates and hydrocarbon productivity will be measured in the same way as in the previous objective. Six 5-L bioreactors will be used for experimental treatments and three 5-L bioreactors will be used for the controls. The three treatments will have three combinations of H/D and Ar/Ad. The three controls will have the same three combinations of H/D and Ar/Ad, but will not be equipped with polymer cables for internal lighting. Each treatment will be tested with two levels (high and low) each of # fiberoptic cables and gas supply rate. Thus, there will be 2 x 2 = 4 runs for each of the three experimental treatments representing three combinations of H/D and Ar/Ad. Thus, there will be a total of 3 x 4 = 12 treatment runs and 3 x 4 = 12 control runs. A time replication will be performed.