The long-term objective of the ASP was to develop microalgae liquid fuel production processes. Since its inception, the ASP supported laboratory R&D projects (Section II)
and algal mass culture projects. However, for the most part, the laboratory and outdoor projects were not integrated into a strongly unified program. This reflects in large part the difficulty of such integration. Also, during the early stages of the
ASP, too close an integration would have been restrictive, as it was not yet clear at The extensive work on strain isolation, selection, characterization, etc., carried out by the time which research approaches, production systems or algal strains would be tbhees tA. SP was used to a significant extent by the field projects, through the testing of a number of the isolates in algal mass cultures, specifically in the projects reviewed in this section. Unfortunately, the laboratory-level screening protocols had, in hindsight, relatively little predictive power for the ability of the strains to dominate and perform in outdoor ponds. Similarly, the laboratory work on the biochemistry, genetics and physiology of lipid biosynthesis, was difficult to apply to the goal of increasing lipid productivities in outdoor systems. Greater integration of laboratory and outdoor
R&D is a challenge for any future microalgae R&D program.
The ASP initiated two outdoor projects in 1980, one in California using a paddle wheel-mixed raceway pond design ("high rate pond," [HRP]), and another in Hawaii. The Hawaii project was to demonstrate a patented algal culture system, invented by then-ASP program manager, Dr. Larry Raymond (1981). This "Algal Raceway Production System" (ARPS) used very shallow flumes (<10 cm), rapid mixing by air lifts, covers with CuSO4 filters to screen out harmful infrared radiation, and harvesting of the biomass by foam fractionation, among many other claimed attributes (Figure III.B. 1.). Very high productivities were claimed. But a review of the
work (Raymond 1979), in which P. tricornutum was grown in a 0.5-m system, revealed that this projection derived from a single batch culture, and in fact, the last
PUbfeiatODSnt showed biomass density actually decreasing. Benemann et al. (1982a,b, see Section III.D.5.), carried out a comparative analysis of the ARPS and the HRP Raymond, L. (1979) ''Initial investigation? of a shallow layer, algal production designs, concluding that the ARPS would be too expensive and energy intensive, system." Am. Soc. Mech. Eng., New York.
compared to the HRP design. These two projects in California and Hawaii, carried
Raymond, L. (1981) "Mass a1g?1 culture systems." U.S. Patent 4J253, 271. , out for more than 6 years each, are reviewed in this section, followed by descriptions of the ASP projects in Israel, New Mexico, and related projects.
KFi PATENT CLAIMS
• GAS LIFT PUMP MECHANISM FOR CIRCULATION, CAR80HATI0N AND HARVESTING
. heat exchange for temperature control
. FOAM FRACTIONATION / SKIMMING HARVESTING . EaSO* SOLUTION IN COVER TO REMOVE INHIBITING IR. . MIXING TO ACHIEVE FLASHING LIGHT EFFECT
Figure III.B.1. The algal raceway production system. (Source: Raymond 1981.)
III.B.2. The ARPS Project in Hawaii, 1980-1987 III.B.2.a. Hawaii ARPS Project Initiation, 1980-1981
As mentioned earlier, the concept for the ARPS project derived from the Raymond
(1981) patent. The project was initiated in early 1980s, with construction of a single,
48-m raceway system completed in early 1981 (Laws 1981). During this first year, chemostat experiments using two strains of P. tricornutum were carried out. The tests revealed large differences in protein and lipid productivity between the strains. This laboratory work also investigated cell harvesting by "foam fractionation" in whicidiffrcf°am hcttrdg diiby thhse laborcroryf thbepsuiturh?soiwoff 1tftenlxing cells d°I1?Clied ahdiSvuhd Ccmpnrglh soithe tih0-4t0l gmt? ChporlSl ecynCgillIltit0I°h OcOrtitSiili qUidP SrioyaTver, RgsShOfohgeiIsh||feT1ici(en)(llcred?si(ee31edenaia^y by increasing the pond depth to 0.6 m, rather than 0.1 m as proposed by Raymond (1979). This resulted in other problems (low cell density, shading-see below), and the depth was again reduced to 30 cm. The laboratory experiments were extrapolated to predict an outdoor productivity of
Timor ti?3 wom/iiaCystual els ana Scfechc f bus cP ■ fili3tgr?rre(ctfctn ahf m idttho°u|°t dry Roy¿tucra0itp fidC-gOon? wCUrawbiv TClinItllfl;[email protected] t1}??"?11? oaavitSob iiirrhit1iig APRmpoc ei t wcuiduhhi p1on°felo^yooliffhal!lin|itss tna^Mrur-aeihdiOstpre dicp ooehdccy pai1ldftb}itiviSi-ai^o duct, heat." Finally, the "flashing light" effect was investigated. The time constants (1 s light: 1 s dark), and low light intensities used were quite different from the classic flashing light effect of Kok (1953), which uses approx. 1-5 ^ec high intensity light flashes, followed by about five times longer dark periods. Only small,
Lew? pe9titlfl erio f--icorlíagorll^rlitl:for--folitsitWitih(thf-e4e5-mSeo-6-n° lads p , Stifl-amM frroi3-io?-ySiePsoCf-C[tídi-iís^ili5 Pse(1ictnlf^cln0í0(Wh 3lllhibeai?gT(0rctl!i wllglhobeoonaa■ °f the great depth of the culture, which was later reduced. The report concluded that, assuming $30,000/ha/yr production cost, a biomass production of 180 mt/ha/yr AFDW would allow oil production (with protein byproducts) competitive with fossil fuel. However, this productivity figure was extrapolated from the indoor chemostat work, and increased by one-third, as "effects of modulated blue light on the system will allow the extra production to be achieved," so the reliability of this prediction is questionable.
III.B.2 b. Second Year of the Hawaii ARPS Project, 1981-1982
The second year of this project emphasized the use of "flashing light to enhance algal mass culture production" (Laws, 1982; see also Laws et al. 1983). The basic idea was that a "foil array" in the pond culture would generate a vortex that would create organized mixing in the ponds, expected to result in exposure of the cells to regular dark-light cycles (Figure III.B.2.). Based on data in the literature, this effect would be predicted to increase overall productivity. These a priori arguments were not supported by the algal physiological literature (the flashing light productivity enhancements are observed at much shorter time constants), and neither were the
From November 1981 to January 1982, an average productivity of only about 3,3 hydraulic arguments plausible (organized mixing would be seen only in a small g/amti^ washe coodsdfou mhe .5 0FP^wll%up^e tFeactoyr ,i asuery. eowiv aiue for Haway ,teveihlp wiRM eX]AíriPneenSt^íl::§til0]|®S0f the foils, productivities, from February to March 1982,
increased to about 11 g/m /d. This increase was attributed to the effect of the foils, though lack of a control did not allow isolation of this variable from other effects. Five-day running mean average photosynthetic efficiencies (PAR) are shown in Figure III.B.3. The author stated that productivity could be doubled with semi-continuous operations. One observation was infestation of the culture by algal predators, which could have been one reason for the rather large variability in productivities observed during this operation (Figure III.B.3.). However, day-to-day variability in productivities is a fact of outdoor pond microalgae cultivation, even in the best of cases.
Figure III:B:2: Hawaii ARPs with mixing foils
(Top). Schematic of the 48-m flume, showing heat exchangers, lift box, drain box and airlift mixer.
(Bottom) Schematic of mixing resulting from foils inserted in the shallow flumes. (Source: Laws 1982.)
Figure III.B.3. Five-day running productivity averages for the Hawaii system. (Source: Laws 1982.)
III.B.2.c. Third Year of the Hawaii ARPS Project, 1982-1983
Laws and Terry (1983; see also Laws 1984a) reported on the further development of
the ARPS. Four 9.2 m experimental raceways were built to allow replication of experiments and testing of variables, again using P. tricornutum. These raceways were . uigii|iBie IBO ttfoctorial experimental design testing eight variables at two levels
3. Bight time temperatures (15°or 20
4. ft,w rates (15 and 30 c5m. C/us)S, O 4 filters (present and and 9),
7. N source (ammonia and urea), 8n Sal inity (15 and 35
Sixtepepnt) 'runs (of 256 possible) in four sequential blocks were carried out, with the assumption apparently being that these variables are non-interacting and additive
(probably a poor assumption for biological processes). No block-to-block controls were provided, which could have been affected by light intensity and other variables. The ponds had been equipped with six sets of mixing foils, but rather suprisingly the presence or absence of the foils was not a variable tested. A complex data evaluation, in terms of "factor effects", was presented, but no actual productivity data for any of the experiments are available. The authors concluded that "by far the most significant factor affecting biomass production" was culture depth, arguing that the "self-shading effects were more than offset by higher areal standing crops." This was a rather puzzling conclusion as it is contrary to both theory and experience, which assumes that, everything else being equal, depth should not affect productivity. Of course,
Aephhcas BOfe^ PerrGipIe:reivJKe , paOa, wneiceotregco^agdab^ewvwhilob8i4 ytatiidd Ms'
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