Algal biomass is the main product in microalgal technology and has various applica­tions. The final biomass product is usually green or orange in color (Pulz and Gross, 2004). Most commercial fertilizers are derived from petroleum; however, rising fuel prices influence the cost price of commercial fertilizers derived from petroleum. A cost-effective alternative would be the use of algal biomass as organic fertilizers (http://www. algaewheel. com).

Microalgae have been used in the agriculture industry as biofertilizers and as soil conditioners (Metting, 1996). Employing microalgae as biofertilizers and soil conditioners is a common agricultural practice in Asian countries such as China and India, where they provide more than 20 kg nitrogen ha-1y-1. Nitrogen-fixing cyanobacteria such as Anabaena, Nostoc, Aulosira Tolypothrix, and Scytonema are used in rice cultivation. Mucilage-producing species of the genus Chlamydomonas have been used as soil conditioners to control soil erosion of pivot-irrigated soils in North America (Metting, 1996). The rationale behind using microalgae as biofertilizers is that they have the ability to increase the water-binding capacity and mineral composition of the soil (Pulz and Gross, 2004). This market generates a turnover of US$5 billion y-1 (Pulz and Gross, 2004).