SERI/TP-231-3325

UC Category: 244

DE88001146

An Outdoor Test Facility

for the Large-Scale

Production of Microalgae

Donna A. Johnson

Joseph Weissman

Raymond. Goebel

March 1988

Presented at the Institute of Gas

Technology Energy from Biomass

and Wastes XII

February 15-19, 1988

Prepared under Task No. BF811010

Solar Energy Research Institute

A Division of Midwest Research Inst itute

1617 Cole Boulevard

Golden, Colorado 80401-3393

Prepared for the

U.S. Department of Energy

Contract No. DE-AC02-83CH10093
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TP-3325

AN OUTDOOR TEST FACILITY FOR THE LARGE-SCALE

PRODUCTION OF MICROALGAE

Donna A. Johnson

Solar Fuels Research Division

Solar Energy Research Institute

Golden, Colorado 80401

and

Joseph Weissman and Raymond Goebel

Microbial Products, Inc.

Fairfield, California 94533

ABSTRACT

The goal of the U.S. Department of Energy/Solar Energy Research Institute's

Aquatic Species Program is to develop the technology base to produce liquid fuels from

microalgae. This technology is being initially developed for the desert Southwest. As

part of this program an outdoor test facility has been designed and constructed in

Roswell, N. Mex. The site has a large existing infrastructure, a suitable climate, and

abundant saline groundwater. This facility will be used to evaluate productivity of

microalgae strains and conduct large-scale experiments to increase biomass productivity

while decreasing production costs.

Six 3-m2 fiberglass raceways 'were constructed. Several microalgae strains were

screened for pro~th, one of which had a short-term productivity rate of greater than 50

g dry wt m- d-. Two large-scale, O.l-ha raceways have also been built. These are

being used to evaluate the performance trade-offs between low-eost earthen liners and

higher cost plastic liners. A series of hydraulic measurements is also being carried out to

evaluate future improved pond designs. Future plans include a O.5-ha pond, which will be

built in approximately 2 years to test a scaled-up system. This unique facility will be

available to other researchers and industry for studies on microalgae productivity.

I
TP-3325

AN OUTDOOR TEST FACILITY FOR THE LARGE-SCALE

PRODUCTION OF MICROALGAE

INTRODUCTION

The worldwide energy shortage and Arab oil embargo of the early 1970s encouraged

many nations to look for new sources of oil, electricity, and gas. Resources such as

biomass were often viewed as attractive solutions to the energy problem because of their

nondepletable, renewable nature. The first biomass sources considered, such as wood or

corn, were readily available, but it was apparent that new biomass sources should also be

developed, including aquatic species.

Oil imports are expected to increase 13896 by 2010 while domestic production is

expected to decrease by 4096. The United States currently imports $50 billion of oil each

year. By 2010 the cost of imports will have increased to $195 billion. Technological

advances in biofuels could make biofuels competitive with petroleum-based fuels.· The

current U.S. Department of Energy (DOE) emphasis is placed on developing technology

for our future energy supplies rather than finding more commodities (2).

One technology option being explored is the DOE/Solar Energy Research Institute

(SERI) Aquatic Species Program to develop the technology base for large-scale production of oil-yielding microalgae and for conversion of the oil into gasoline and diesel

fuels. These fuels should be cost-eompetitive with petroleum-derived fuels by the year

2010.

Microalgae are small, unicellular plants that range in size from 1 to 200 urn, Their

productivity rates are higher than those of most other plants. Table 1 shows the productivity rates of many other plants and indicates the order of magnitude greater productivity that we expect can be obtained in microalgae outdoor culture ponds. Microalgae

are also unique organisms in that. they can accumulate storage lipid in large quantities

within their bodies (up to 6596 of their total biomass). Historically, microalgae have been

grown in mass culture for food production and waste treatment (1).

Table 1. Comparative Productivity Rates in

Different Plant Communities (adapted

from Ref. 6)

Plant Community

Continental:

Tropical rain forest

Temperate deciduous forest

Woodland and scrubland

Desert and semidesert scrub

Cultivated land

Marine:

Open ocean

Continental shelf

Algal beds and reefs

Microalgae ponds

2

2200

1200

700

90

650

125

360

2500

12,500
TP-3325

Following the energy crises of the 1970s, the possibility of using algae as a source

of energy received widespread attention. Microalgae can be grown in large outdoor

ponds, using the resources of sunlight, saline water, nitrogen, phosphorus, and carbon

dioxide to produce proteins, carbohydrates, and lipids. In the process, they can double

their biomass one to two times a day in large outdoor ponds. After a rapid growth phase,

the algae can be transferred to induction ponds where, under nutrient limitation, many

algae stop growth and division and use all their energy to make Iipids as storage products

for survival. Once the cells have accumulated lipids, they are harvested, and the water is

recycled back into the growth ponds. The harvested cells are subjected to an extraction

process to remove the lipids, primarily triglycerides with fractions of isoprenoids, glycolipids, and hydrocarbons. Lipids contain more oxygen and are more viscous than crude

petroleum. The two most promising fuel conversion options are transesterification to

produce diesel fuels and catalytic conversion to produce gasoline. Although microalgal

lipids represent the premium energy product, the energy trapped in the other biomass

constituents can also be used; e.g., the cell residue after lipid extraction can be digested

anaerobically to produce methane and carbon dioxide. The carbon dioxide can be recycled

for use in the algae production system.

The emphasis of the program at this time is on developing a mass culture technology for cultivating oil-yielding microlagae using saline groundwater in desert regions.

The largest constraint to this technology is the economical production of an oil-rich

microalgal feedstock. In addressing this constraint, the Aquatic Species Program has

concentrated research on (1) selecting fast-growing, high-oil-yielding microalgae species;

(2) improving the most promising species; and (3) developing the best culture and management methodologies.

In the past 7 years, the Aquatic Species Program has operated several different

outdoor facilities in California, Hawaii, and Israel. Each facility was to tes-t algae, which

had already been screened in the laboratory, under outdoor conditions for high growth

rates and lipid (oil) yield. In 1986 it .became apparent that the program needed to consolidate into one outdoor test facility in the geographical area for which this technology

was being developed. In addition, it was apparent that the size of the previous test facili- .

ties (approximately 25 - 50 m) was no longer adequate to meet program goals. The very

high productivity rates seen in the small outdoor ponds needed to be confirmed in larger

ponds; engineering scale questions needed to be resolved, and large amounts of biomass

would be needed for the program to begin conversion research of algal lipids to liquid

fuels.

SITE SELECTION AND DESIGN

Growth conditions in algae mass cultures can be divided into two categories: those

dictated by the location of the culture and those based on culture management strategy.

Location-related variables include insolation, evaporation, rainfall, temperature, and

wind velocity. Variables that can be managed include salinity, nutrient concentration,

carbon dioxide concentration, culture mixing, culture aeration, and residence time of the

population.

Growth conditions dictated by location are among the prime considerations in siting

the production facility. The DOE/SERI program has been based on the assumption that it

will be necessary to locate a production facility in an area that receives large amounts of

sunlight and has relatively warm temperatures. To ~v~ the best success, the facility

must be l~ated in an area that receives 5000 kcal rn" d" and has more than 180 frostfree d yr-. This limits large-scale production to the southern United States (Figure O.

3
TP-3325

kcallm2/day x 103

A - 4.75-5.00 F - 3.50-3.75

B - 4.50-4.75 G - 3.25-3.50

C - 4.25-4.50 H - 3.00-3.25

o - 4.00-4.25 I - 2.75-3.00

E - 3.75-4.00 J - < 180 frost-free days

Figure 1. Solar Radiation in thf United States Where There are More than

180 Frost-Free d yrHowever, it is also necessary to .consider the trade-offs involved in locating in an area

of high insolation. If the costs of land, raw materials, or operation are significantly

increased at a location with high insolation, siting solely by the solar input may be

disadvantageous.

Roswell, N. Mex. was chosen as the location for the Outdoor Test Facility (OTF).

Roswell is 170 miles southeast of Albuquerque. The site meets the insolation and temperature requirements plus there is an abundant saline water supply and a large amount

of existing infrastructure. Roswell is the site of a former Department of Interior desalinization plant that has been given to the town for water research purposes. There are

'offices, laboratories, large indoor working bays, and three 3D-acre evaporation ponds.

This infrastructure greatly decreased the additional government funds needed to start up

the OTF.

Many other production conditions in outdoor systems are dictated by the engineering design and the management strategy. Three designs were examined in FY 1984 for

the large-scale production of microalgae--open ponds, raceways, and enclosed tubes.

The proposed costs for construction and operation of these three systems are shown in

Table 2. All costs need to be kept to a minimum if the feedstock is to be produced

inexpensively, thereby producing an economic liquid fuel, so open-pond systems were

chosen as the facility plan for outdoor production (Figure 2).
TP-3325

Table 2. Capital Construction Costs

for Three Different Algal

Production Systems

Engineering Design Cost ($/ha)

Open ponds 76,000

Raceways 161,000

Enclosed tubes 348,000

-

.-

Sump Section

Figure 2. Open-Pond Design for Large-Scale Microalgae Production (from Ref. 4)

/?.e OTF design plans include a small-scale system composed of six 3-m2 ponds, a

50-m inoculum pond, two O.l-ha growth ponds, and one 0.5-ha pond. The sizes of the

ponds were determined by optimizing research benefits with construction and operating

costs. Programmatic objectives and economic constraints were also major factors in the

size determination.' The larger the pond, the higher the operating costs; thus, it was

important to determine what sizes were needed and suitable to answer the biological and

engineering questions.

SMALL-SCALE SYSTEM

The small-scale system was designed for the purpose of evaluating the growth

performance of microalgae. It is necessary to determine optimum conditions (pl-I, carbon

supply, culture density, mixing speed, temperature, etc.) in order to maximize each

successful laboratory strain for yield, lipid production, and culture stability under outdoor conditions. To meet these objectives, it was necessary to have replicate ponds.

Economic constraints dictate that this be done at the smallest practical jcale. Both

construction and operation costs are minimized at a scale of 1.5 20 10 m • However,

sidewall sh~ing becomes very important at sizes smaller than 3 m • Therefore, a pond

size of 3 m was chosen to minimize cost while not adding additional variables to the

research. Six ponds were installed to provide for multiple experimental capability and

also to provide replicability (see Figure 3). .

5
TP-3325

~- ~Concrete pad 3 m2 growth ponds

with paddle wheel mixers

8 C02 and chemical

o storage shed

• •

Automatic

sampler

and sample

refrigerator

Media mixing """"'--;"-.0<" tanks

Utility trench:

fresh water

salt water

media

CO2

Drain

Electrical

Transfor~

Figure 3. Design of the Small-Scale Microalgae System

Each pond can be operated at depths of 15 to 20 em. Each pond is stirred by paddle

wheels, which "are made from clear Plexiglas to reduce shading. Mixing speed, pH, temperature, and salinity are maintained constant. Samples are taken automatically and

refrigerated. The ponds are monitored with an automated data acquisition system.

There are media mixing and holding tanks and effluent holding tanks so the systems can

be operated as batch, semicontinuous, or continuous cultures. The small-scale system is

located in the southeast corner of the Roswell Test Facility.

Construction of the small-scale systems was completed in July 1987. At this time

screening began to test under outdoor conditions microalgae that had grown well in the

laboratory. Figures 4- and 5 show the prime climatological factors affecting microlagae

productivity: light and temperature from August through November. These initial data

provide an indication of the range of the dominant variables as the2se~ons change from

summer to 2winter. Insolation decreased from 6000 kcal m- d" in August to

3500 kcal m" d- 1 in November. Minimum and maximum pond temperatures from August

through November are shown in Figure 5. As expected, temperature decreased with the

onset of winter from 32° to 20°C maximum and 20° to O°C minimum. In November the

ponds froze solid for one week. The ponds were operated in pairs, and one of the ponds

was heated during the day beginning in late September. Most algae strains grow better

under warmer temperatures.

During July and August a fast-growing, warm-water strain of diatom, CycZotella

cryptica, was grown in two of the ponds under identical conditions. Dilution was semicontinuous until August 5 and continuous thereafter. Approximately 4-5% of the pond

volume was harvested each day. Productivity rates for CycZotella are shown in Figure 6

6
TP-3325

. 1000

2000

5000

7000r------------------------.

6000

4000

E

:::::

3000

August . September October

Date

November

November

c Unheated max

o Unheated min

+ Heated max

x Heated min

Daily Total Insolation at the Outdoor Test Facility

August

Figure 4.

50

40

6' 30

Q)

'-:::l

- 20 to

'-Q)

Q.

E

Q) 10 ....

0

-10

September October

Date

Figure 5. Maximum and Minimum Pond Temperatures in Heated and Unheated

Ponds in the Small-Scale System

for these 2 months. Productivity averaged 24.7 g m-2 d- 1 in Pond 1 and 29.0 g m- 2 d- 1 in

Pond 2. In mid-August Pond 1 was invaded by another diatom species Amphora and the

experiment in this pond was discontinued. As one can see from the figure, there was very

good reproducibility between the two ponds unti~ thif time. During late August Pond 2

exhibited very high productivity rates of 56 g m- d"". It is unknown what caused 2hesy

high uields, but we are encouraged that the current target program goal of 50 g m- dean be reached.

7
TP-3325 .

+

+

+

+

+

+ +

+

c Pond 1

+ Pond 2

+

cC

c

60"T'""----------------------~

8

30-

50-

't:lE

40- c

o +0 + u. +

«

S

>-

;;

'sg 20

't:l

e

a.

10

Jul28 Aug 17 Aug 27

0+....~..........."'T'"'"'T.........,r_T""".,.....,......................r""""T"".,......,._r_r_._..........."'T'"'"'T.........,~...............................r""""T"".,......,.................,.......4

Jul 18 Aug 7

Date

Figure 6. Productivity of Cyclotella cryptica in the Small-Scale System

During the colder months, a green microal2ae, Monoraphidiwn, was tested for

growth in the ponds. Productivity rates of 7 g m- d- 1 were e~pe!ited during this time

(5). However, productivity rates averaged 15.7 and 16.8 g m" d" in Ponds 1 and 2,

respectively (Figure 7). Pond 2 was heated during the day, but there was very little

difference in production in the two systems. During December, the unheated pond froze

solid and when it thawed a week later, the algae continued to grow. This has a major

impact on the economics of large-scale production, since if a freeze does occur in the

large ponds, they do not require relnoculation, which is an expensive process.

40-r----------------------, ;;;

30-

35-

-'t:l

......

E

c 25 u,

«

S 20

>-

.s;

-;;

c

:J

't:le 10

a.

+

c Pond 1

+ Pond 2

o

+

5

Oct 11 Nov 10

o-+-,.""T""T'".......-......-,........,...................."'T""T"".,....,...-l""T""1r--r-r-.--r""T""T'".......-.,....,.....,........,...................."'T""T"".,....,...-,....,....,...-r-r-l

Oct 1 Oct 21 Oct 31

Date

Figure 7. Productivity of Monoraphidium minutum in the Small-Scale System

8
TP-3325

These small-scale systems will be the workhorse of the microalgae OTF. They will

be used to screen outdoors for productivity (Le., minus any potential scale-up limitations), lipid production, and optimal culture managements strategies. In addition, the

types of invaders, predators, and potential disease organisms will be monitored. If organisms that grow well in the laboratory do not grow well under outdoor 1onditions at

Roswell, they will be sent to SERI for testing and optimization in 1.5-m greenhouse

ponds where conditions can be better controlled. After optimal growth conditions are

identified, the strain will be sent back to the OTF for further testing.

The first phase of the large-scale system was completed in December. Two O.l-ha

ponds have been built approximately 1 mile from the Roswell Test Facility (Figure 8) in

Moat

~Existing

-e: 30 acre

1!;;;:;;::;;::::;j1evaporation

pond (#1)

Aerial view showing

Roswell Test Facility

new salt and fresh water lines

and 0.1 ~:oc:~::est Po,s

Existing

evaporation

pond (#2)

1.

Hondo 4'.fl' ". Fresh water. . /

line /

<; -,

Pump . )-'--Salt.water

station .I'" line

1"__4' uS ':JroO

i' r

Roswell

Test

Facility

Figure 8. Aerial View of the Outdoor Test Facility

LARGE-SCALE SYSTEM

the southern 30-acre evaporation pond. These ponds are the open-pond design shown in

Figure 2. In addition, fresh- and salt-water lines were run from the Roswell Test Facility

to the ponds. One-tenth hectare ponds were chosen for the first scale-up size because (1)

significant economy is realized in the construction of 0.1 - 0.2-ha ponds compared to the

smaller ponds, and (2) operating costs are decreased by $6,000 - $10,000 by having a

O.l-ha pond rather than a 0.2-ha pond. These two ponds are not identical. One pond is

lined with inexpensive earthen materials, and the second is lined with higher cost plastic.

9
TP-3325

FUTURE ACTIVITIES

A 50 m2 inoculum pond will be built this spring to provide inoculum for the largescale system. In addition, a series of hydraulic measurements will be made and studies

done on injecting the carbon dioxide in the two O.l-ha ponds. Velocity, pond roughness,

paddle wheel efficiency, and outgassing will all be measured. After these are calculated

and optimized in the two ponds, the best organisms from the small-scale system results

will be inoculated into the large-scale system, and a year of productivity and economic

data will be collected. Neenan et ale (3) estimated the relative costs of building and

operating a microalgae outdoor test facility (Figure 9). Measurements made at the OTF

for the cost of constructing and operating the large-scale system will be used to compare

and update the model developed by Neenan et ale Results from this study will determine

the future research priorities for the aquatic species program to further lower the cost

of large-scale microalgae production.

Future plans call for the construction of a 0.5-ha pond in 1989 or 1990, based on

available funding. This pond will be used to extrapolate the performance from the

smaller systems and test the credibility of the hydraulic results. This size should also

give data that can be extrapolated with confidence to a final operation size of approximately 5 ha, .

This unique facility will be available for other researchers and industry for studies

on microalgal productivity, harvesting, engineering design, or conversion. As long as the

research project does not affect the ongoing research but can supplement or occur simultaneously, the facility will be available for use. Office and laboratory space is also

available.

REFERENCES CITED

1. Benemann, J. R., D. M. Till~_tt, and J. C. Weissman, 1987, "Microalgae Biotechnology," Trends in Biotechnology, Vol. 5, pp, 47-53.

2. Department of Energy (DOE), 1987, Energy Security: A Report to the President of

the United States, Washington, D.C.: Department of Energy.

3. Neenan, B., D. Feinberg, A. Hill, R. McIntosh, and K. Terry, 1986, Fuels from Microalgae: Technology Status, Potential and Research Requirements, SERI/SP-231-2550,

Golden, Colo.i Solar Energy Research Institute.

4. Weissman, J. C., and R. P. Goebel, 1987, Design and Analysis of Microalgal Open

Pond Systems for the Purpose of Producing Fuels, SERI/STR-231-2840, Golden,

Colo.s Solar Energy Research Institute.

5. Weissman, J. C., D. Tillett, and R. P. Goebel, 1987, "Design and Operation of an

Outdoor Microalgae Test Facility," In: FY 1987 Aquatic Species Program Annual

Report, D. A. Johnson and S. Sprague, Eds., SERI/SP-231-3206, Golden, Colo.s Solar

Energy Research Institute.

6. Whittaker, R. H., 1975, Communities and Ecosystems, 2nd edition, New York:

MacMillian Publishing Co.

10