Biological hydrogen production processes are considered as an environmentally friendly way to produce hydrogen. They offer the chance to produce hydrogen from renewable energy sources, like sunlight and biomass. This study aims the process development for a photo-fermentative hydrogen production by photosynthetic purple-non-sulfur bacteria, Rhodobacter capsulatus, in a large scale (80L) tubular photo-bioreactor, in outdoor conditions, using acetate as carbon source. It was shown that Rhodobacter capsulatus had a rapid growth (mu(max) = 0.025 h(-1)). Moreover, at light intensities below 10000 lx (100W/m(2) solar illumination) the hydrogen production does not occur. It was found that the optimum dry cell weight for hydrogen production was in between 0.8 to 1 g/L in order to increase light penetration. Hydrogen production was not observed for the pH values higher than 8. The productivity in terms of illuminated area and day time was 0.3 mmol H-2/m(ill)(2).hr(ill) in December 2008 in a glasshouse. The yield of hydrogen was 19 mg H-2/g acetate input. The acetate utilization was %87.5 at a feed rate of 10L/day and substrate conversion efficiency was %16. As a result, hydrogen production in a pilot scale tubular photobioreactor for continuous hydrogen production was achieved by R. capsulatus in outdoor conditions. This study showed that photo-fermentation in a pilot scale tubular photobioreactor would provide hydrogen successfully, even in the low light intensity.