Cells of the unicellular green alga, "Pseudochoricystis ellipsoidea", were uniformly spread on a cellulosic sheet or on a polytetrafluoroethylene (PTFE) membrane sheet superimposed on a cellulosic sheet at a density of 3.5-5.0 g dry weight per m(2), and the sheet was adhered to an inverted V-shaped acrylic plate of 10 cm in height. Several acrylic plates were placed side by side on a tray containing liquid medium at a depth of 0.6 cm, and illuminated from above with a light intensity of 300-340 mu mol m(-2) s(-1). Water and nutrients were supplied to cells by capillary action through the cellulosic sheet. Footprint biomass productivities of cells grown in atmospheric CO2 on this photobioreactor were 8-10 g m(-2) day(-1). This cultivation system is strongly energy-and labor-saving as it does not require mixing of culture fluid, irrigation of medium, and delivery of CO2-enriched air. (C) 2016 Elsevier Ltd. All rights reserved.