Performance Summary Report
Evaluation of GreenFuel’s 3D Matrix Algae Growth
Engineering Scale Unit
APS Red Hawk Power Plant, AZ
June – July, 2007
Prepared By:
Dr. Otto Pulz
IGV Institut für Getreideverarbeitung GmbH
September, 2007
Table of Contents
Tables and Figures……………………………………………………………………………………. .2
Summary………………………………………………………………………………………………..3
Definitions……………………………………………………………………………………………...4
1. Introduction……...………………………………………………………………………………….5
1.1
Emissions-to-Biofuels™ Process Description……………………………………….5
1.2
Algal Culturing Systems – Existing Technologies and Past Work………………….5
2. 3D Matrix System (3DMS).…...……….…………………..…………………………………....6-10
2.1
Concept……………………………………………………………………………….6
2.2
3DMS Lab Scale Unit…………………...…………………………………………....6
2.3
3DMS Engineering Scale Unit (ESU)……… ………………................................7-10
3. Productivity Results…………...……………………….…………………………………………..11
4. Discussion of Productivity Results…………...…….……………..……………………………….12
5. Conclusions……………………...……………………..………………………………………….13
About the Author……………………………..……………………………………………………….14
Tables and Figures
Table 1: Comparative Values of SVR and LAI in Algal Cultivation Systems…...................................6
Table 2: Areal Productivity of Algal Cultivation Systems……………………………....……………..6
Table 3: Set Points for Physical and Chemical Parameters of the ESU………………………...….....10
Table 4: Comparative 3DMS Scale results……………………………………………….………..…12
Figure 1: Algal Cultivation Systems……………………………………………...……………………5
Figure 2: ESU Hosted at the APS Redhawk Power Station…….……………....……………...………7
Figure 3: Downstream Unit…………………………..……..……...…………………………….…….8
Figure 4: Bird’s Eye View: The ESU Greenhouse Structure….................….……………....................8
Figure 5: Side View: The ESU Greenhouse………...……………..…...……..................……………..9
Figure 6: Traditional Bag System for Developing Seed Culture………………………....………..…..9
Figure 7: ESU Areal Productivity and PAR Results……………………………………….…………11
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Summary
GreenFuel Technologies Corporation (GreenFuel) is developing algal-based Emissions-to- BiofuelsTM
systems, which recycle CO2 into biodiesel, ethanol, and other products. In June and July of 2007,
GreenFuel conducted an Engineering Scale Unit (ESU) field performance, testing one of its portfolio
technologies – the 3D Matrix System (3DMS). The ESU assessment was performed at the Redhawk
Power Station, a 1060MW combined cycle natural gas power generation plant owned and operated by
Arizona Public Service. The ESU was exposed to local weather conditions and operated using the
power plants’ flue gas emissions, as well as local industrial water.
The goal of this program was to assess the performance (areal productivity) of the 3DMS technology
for at least two continuous weeks of growth. Based on the previous performance of a lab-scale
system, target average areal productivity of 80 g/m2/d was set. Achieving this goal would allow a
commercial algal system to significantly decrease its footprint, minimizing one of the main limiting
factors of large-scale algal farming – land cost and availability.
The scope of work involved construction, commissioning and subsequent operation of the ESU at the
host site. Engineers and scientists monitored the performance of specific unit operations, algae health
and overall system productivity. While GreenFuel personnel were conducting the experimental work,
the author served as an observer for external verification. All sampling methods and data analyses
were based on standard practices used in commercial algae cultivation.
The performance of the 3DMS system exceeded the target goal. Average areal productivity of
98g/m2/d (ash free, dry weight basis), with highs of over 170 g/m2/d, was achieved during a run time
of 19 days. Thus, this is one of the most productive algal cultivation systems ever built.
Due to local weather conditions during the run time, the daily average light input dropped by about
25%. In addition, low (2%) CO2 concentrations and suboptimal harvest procedures compromised the
result. It is expected that operating with higher CO2 concentrations and optimizing the harvest
procedure would yield higher areal productivity. Longer term test periods could deliver sustainable
results both in terms of productivity and stability of the biological system.
The 3DMS technology demonstrated record-high field productivity. It can offer a viable solution in
areas with limited or expensive land. Nevertheless, this technology should be assessed in the overall
context of GreenFuel’s development program and portfolio of technology solutions. In addition to
areal productivity, capital cost, operational cost, net CO2 reduction, and lead time to commercial
rollout are all critical factors.
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Definitions
Biomass Density is defined as biomass per unit volume. Typically this is reported as grams of
biomass (dry weight, ash free) per liter (g/l).
Volumetric Productivity is defined as the rate-of-change of biomass density. Typically this is
reported as grams of biomass (dry weight, ash free) per volume per day (g/l/d).
Productivity is calculated based on biomass density measurements by:
Productivity = (D2-D1) / (T2-T1)
Where D2 is biomass density at time T2, and D1 is biomass density at time T1.
Areal Productivity is described as biomass produced per unit area per unit time (e.g. g/m²/d). Where
B2 is biomass at time T2, and B1 is biomass density at time T1, and A is the system’s footprint area.
In the case of the 3DMS, A is the areal footprint of the matrix.
Areal productivity = (B2-B1) / A / (T2-T1).
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1. Introduction
1.1 Emissions-to-BiofuelsTM Process Description
GreenFuel’s Emissions-to-Biofuels™ process is a flexible platform using algae to convert CO2
emissions into a range of renewable fuels. The process is designed to be retrofitted to flue stacks with
minimal or no impact to ongoing operations. The CO2-rich gas streams are introduced to the algal
farm system, in which algae are dispersed in an aqueous medium with nutrients and other
environmental parameters controlled to optimize their growth. A portion of the liquid culture is
withdrawn (harvested) periodically from the farm system and sent to dewatering. The dewatering
operation uses conventional processing technology, designed to increase the concentration of algal
solids in order to yield a cake suitable for downstream processing. Water removed from the
dewatering operation is then returned to the system. Make-up water is added to maintain the culture
volume. Using an induced draft fan, flue gas is pulled through the farm system. This process
provides several operating advantages, including ensuring minimal disruption to power plant
operations, simplifying retrofits to existing power plants and minimizing parasitic power of the
facility. The unit operations for algal oil extraction and conversion of the dewatered algae into final
fuel products is the downstream portion of the process.
1.2 Algal Cultivation Systems – Existing Technologies and Past Work
Globally, there are a number of technologies employed for the purpose of mass cultivation of
microalgae. These include shallow lakes, constructed ponds and designed tubular cultivation
facilities. The images below highlight a few alternative technologies.
FIGURE 1: Algal cultivation systems
In comparing these technologies, it becomes apparent that open systems (such as ponds and
raceways) are the least productive due to inefficient light utilization.
Closed tubular systems, such as fence-tube reactors, consistently show higher areal productivities
compared to open systems. However, they too become limited by their ability to optimize photon
utilization.
When scaled algal cultivation for biofuels is considered, land cost and availability stands out as one of
the key limiting factors. Recognizing this problem, GreenFuel undertook to develop a new system
that would increase areal productivity.
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2. 3D Matrix System (3DMS)
2.1 Concept
Due to the proprietary nature of the technology, this report will only disclose general design
principles, without disclosing technical details. The scientific concept behind 3DMS technology
follows the idea of increasing the photosynthetic active area per areal footprint. This way, algae are
exposed to diluted light levels in which the photon flux density supports maximal light utilization.
The areal (footprint) productivity is an integral part of the productivity for the corresponding
photosynthetic active surface area.
Contrary to known culturing systems like ponds or tubular systems, the 3DMS system uses a
proprietary productivity enhancement technology, referred to as the matrix. The design of the matrix
enables increased growth per unit of areal footprint. Enhancement of Surface to Volume Ratio (SVR)
by the matrix significantly boosts areal productivity. SVR evaluations in algal cultivation system
design have become recently common, and combined with footprint areal productivity, provide
sensible data for design development.
Open system
Closed system
3D Matrix System
Surface to volume
3-4
70-100
1500-2000
ratio (SVR) m²/ m³
TABLE 1: Comparative values of SVR in Algal Cultivation Systems
2.2 3DMS Lab Scale Unit
Externally-validated lab scale experiments for performance verification of the 3DMS demonstrated
enhanced areal productivity when compared with traditional algal cultivation systems.
Productivity data was collected on a small (matrix footprint area of 10m2), laboratory based,
artificially illuminated 3DMS. All sampling methods and data analyses were based on standard
practices used in commercial algae cultivation.
The objective of the lab testing was to establish a baseline areal productivity. The full details of this
test program are not in the scope of this report, however, using environmental conditions that aimed
to simulate the field conditions in Arizona, areal productivity of the reactor generally ranged between
80-130 g/m²/d (ash free, dry weight basis).
The table below compares the areal productivity of the 3DMS lab scale unit with published data for
areal productivity of alternative technologies.
Productivity
g/m²/d
Average
Peak values
Open systems
Closed Systems
3D Matrix System
10 - 20
35 – 40
80 -100
30
70
130
TABLE 2: Areal Productivity of Algal Cultivation Systems
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2.3 3DMS Engineering Scale Unit (ESU)
The 3DMS ESU is a field-based algal cultivation system including the matrix enhancement. It was
hosted throughout this performance test at the Redhawk Power Station in Arizona.
Redhawk is a 1060 MW combined cycle gas turbine power plant, located about 65 miles west of
Phoenix. It is owned and operated by Arizona Public Services (APS).
The images on the next few pages show the ESU located at the host site.
Redhawk, Phoenix, AZ, 2007
FIGURE 2: ESU Hosted at the APS
Redhawk Power Station near Phoenix, AZ
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FIGURE 3: APS Future Fuel Program Manager, Raymond Hobbs (left) and GreenFuel’s
Manager of Field Operations, Marcus Gay (right) in front of the downstream unit
FIGURE 4: Bird’s eye view: The ESU greenhouse structure (circled)
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FIGURE 5: Side view: The ESU greenhouse structure
The ESU was inoculated with an algae species and operated throughout the performance test as a
semi-continuous batch culture.
FIGURE 6: Traditional bag system for developing seed culture
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The physical and chemical parameters of the culture were maintained between set points that are
identified in Table 3.
Flue Gas CO2 Concentration
2 – 4%
Culture Temperature (Daily Average)
24 – 35ºC
Culture pH
6.5 – 7.8
Nitrogen Concentration
700 – 1400 ppm NO3
Phosphorus
300 – 600 ppm PO4
TABLE 3: Set Points for Physical and Chemical Parameters of the ESU
The goal of this program was to assess the performance (areal productivity) of the 3DMS technology
for at least two continuous weeks of growth. Based on the performance of the lab scale system, target
average areal productivity of 80 g/m2/d was set.
The seed culture was introduced into the system on June 27th and inoculated the growth matrix
rapidly. The system ran for over 2 weeks. The system was harvested every 2-3 days, and
measurements of algal biomass density were taken (ash-free, dry weight basis) before and after
harvesting. Run times between harvests are referred to as growth periods. Again, all sampling
methods and data analyses were based on standard practices used in commercial algae cultivation.
While GreenFuel personnel were conducting the experimental work, the author served as an observer
for external verification.
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3. Productivity Results
200
1000
180
950
160
900
140
850
120
800
100
750
80
700
60
650
40
600
20
550
0
500
G1
G2
G3
G4
G5
Average Daily PAR ( μ E/m2/s)
Productivity (g/m2/d)
During the 6 consecutive growth periods (designated G1-G6), areal productivity ranging from 62 to
174 g/m2/day with an average of 98 g/m2/day, was accomplished. Due to weather conditions, light
supply varied during the systems’ run time, with highs (daily average) of 868 μmol/m2/s and lows of
646 μmol/m2/s.
G6
FIGURE 7: ESU Areal Productivity and PAR Results
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4. Discussion of Productivity Results
In general, the productivity results of the 3DMS ESU averaged 98 g/m²/d, with a high of 174 g/m²/d.
These are record-high results. With this type of productivity and test trial run time, the ESU exceeded
the test target numbers (80 g/m²/d, two weeks run time).
The data showed a high degree of variability (62-174 g/m²/d). This variability could be explained by
changes in the operational conditions, mainly light input, CO2 supply, and harvesting. During the
ESU’s run time, the light supply dropped about 25% (due to sand storms and dust). There was
variability in the CO2 concentration inputs (data not shown), with lows of 2% and highs of 4%.
In addition, the harvesting procedure was not optimized. Some of the harvests brought the culture
partially out of the exponential growth phase/optimum density in the matrix. This is an operational
procedure, which can be adjusted in the future in order to meet the necessary level of harvesting
concentrations. As a result, productivity in growth periods G3-G6 ranges between 62 and 94 g/m²/d - clearly much lower than productivity in the first two growth periods (100-173 g/m²/d).
In spite of variability, the ESU productivity and lab scale productivity had very similar results, with
the ESU productivity highs exceeding the performance of the lab scale unit.
Productivity
Field ESU
Lab Scale
g/m²/d
Average
98
80 -100
Peak values
174
130
TABLE 4: Comparative 3DMS Scale Results
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5. Conclusions
The 3DMS ESU test run resulted in average productivity of 98 g/m²/d footprint, ranging between 62
and 174 g/m²/d. Productivity target for the test was exceeded.
The 3DMS design demonstrated an extraordinarily high microalgae biomass productivity of up to 174
g/m²/d. Even though such productivity for the ESU-test represents peak values, it underlines the high
potential of the design principle.
The harvesting system should further be developed to support harvesting within a window of optimal
matrix concentrations. It is expected that operating with higher CO2 concentrations and optimizing
the harvest procedure would yield higher areal productivity.
For future development of this technology, one of the critical challenges is a further advancement of
the technical basis allowing a long-term test run period delivering sustainable results both on
productivity and on the biological system.
By increasing areal productivity, this portfolio algal farm system design could potentially address one
of the limiting factors, land cost and availability, thus allowing mass algal cultivation for the
production of biofuels. Other key factors such as capital cost, operational cost, net CO2 reduction,
and lead time to commercial rollout should be assessed in the overall context of GreenFuel’s portfolio
development program.
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About the Author
Dr. Otto Pulz is currently the President of the European Society of Microalgal Biotechnology and the
Head of the Biotechnology Department at IGV Institut für Getreideverarbeitung GmbH, where he has
been leading the department for 26 years. In addition to this, Dr. Pulz is the Professor of Phototrophic
Biotechnology at the University of Applied Sciences Lausitz in Senftenberg, Germany. He has also
been involved with the International Society of Applied Phycology at the ILU Institute for Food and
Environment Research (advisory board/executive committee), and has published over 40 journal
papers and reviews dealing with biotechnology of microalgae, food and feed microbiology, and
rheology and functions of phycocolloids in food.
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