Economic evaluation of microalgal processes and products
The commercial use of algae has a long history and many species of algae are used as food, feed and as sources of valuable chemicals. For example, several species of the macroalgae Caulerpa, Porphyra, Zridaea, Gigartina and Ulva are harvested for human food or hydrocolloids, whilst species of Laminaria, Macrocystis, Eucheuma, Graciluria and Chondrus are also farmed (Lipkin, 1985; Tseng and Fei, 1987; Avila and Seguel, 1993; Merrill, 1993; Trono, 1994). A few microalgae such as some species of Nostoc and Aphanizomenon are also harvested from the wild for human consumption (cf. Martinez, 1988; Martinez et al., 1995), however most commercially used microalgae are cultured. These include Dunaliella, Chlorella and Spirulina which are cultured for food and for the extraction of high value chemicals (Borowitzka and Borowitzka, 1989b; Belay et al., 1994), a wide range of species such as Tetraselmis chuii, Zsochrysis galbana, Chaetoceras muelleri, Nannochloropsis spp., Skeletonema costutum, etc., which are used as feed in the aquaculture of fish, shellfish and crustaceans (Liao et al., 1983; Fulks and Main, 1991; Benemann, 1992) and several cyanobacteria for use as biofertilizers (Subrahmanyan, 1972; Roger, 1989; Dubey and Rai, 1995). Many other species of microalgae are being considered for possible commercial production.