Hydrogen is a promising energy carrier of the future, nevertheless biohydrogen technologies are still in their infancy. If biohydrogen systems are to become commercially competitive, they must be able to synthesize hydrogen at rates that are sufficient to power fuel cells of a sufficient size to carry out practical work [1]. Before the concept of hydrogen economy becomes a reality, a safe, economical, sustainable way of producing it needs to be developed [2]. Biological hydrogen photoproduction by photosynthetic bacteria could be a promising method of solar energy conversion. Advancements in hydrodynamic aspects, bioreactor design, gas separation, light intensity and its distribution inside culture thickness are the key points for improving the hydrogen yield [3]. Besides, the growth strategy could be a relevant way to attain the high hydrogen yield. We investigated the hydrogen photoproduction by Rhodopseudomonas palustris 42OL cultured under both artificial and natural radiation. For indoor experiments, we used four cylindrical photobioreactors (PBR) of different internal diameters (i.d. of 4.0 cm; 7.6 cm; 9.6 cm and 13.0 cm). Indoor experiments were carried out at the irradiance of 480 W/m2 and at a constant temperature of 30 °C; outdoor investigations were performed, in autumn, using an underwater tubular photobioreactor (UwTP) with a pipe i.d. of 4.8 cm. The organic carbon source used was malic acid, which is a compound of wine-distillery waste [4]. Although hydrogen production process that uses cheaper materials would undoubtedly make the system more competitive with the conventional hydrogen generation process in the future [5], the high hydrogen yield remains to be the ultimate goal and challenge for the biohydrogen research and development [6]. We demonstrated that the hydrogen production rate (HPR) is greatly affected by the diameter of photobioreactors and an inverse relationship links the HPR to the diameter of the reactor. We used two growth strategies: (i) batch and (ii) semi-continuous regime. The daily average hydrogen production rate (HPRav) attained under batch-growth operation was 222 ± 18 ml(H2)/l/day, which increased to 655 ± 85 ml(H2)/l/day under the semi-continuous regime, which corresponds to 27.3 ± 3.5 ml(H2)/l/h. This rate reduced drastically outdoors (9.8 ml(H2)/l/h). Peaks of 32.7 ml(H2)/l/h and 15.5 ml(H2)/l/h were checked indoors and outdoors respectively. The hydrogen yield of 3.03 mol H2/mol malic acid was achieved indoors under the semi-continuous regime.
Indoor versus outdoor biohydrogen photoproduction by Rhodopseudomonas palustris 42OL
Padovani Giulia;Pintucci Cristina;Ena Alba;Carlozzi Pietro
2012
Abstract
Hydrogen is a promising energy carrier of the future, nevertheless biohydrogen technologies are still in their infancy. If biohydrogen systems are to become commercially competitive, they must be able to synthesize hydrogen at rates that are sufficient to power fuel cells of a sufficient size to carry out practical work [1]. Before the concept of hydrogen economy becomes a reality, a safe, economical, sustainable way of producing it needs to be developed [2]. Biological hydrogen photoproduction by photosynthetic bacteria could be a promising method of solar energy conversion. Advancements in hydrodynamic aspects, bioreactor design, gas separation, light intensity and its distribution inside culture thickness are the key points for improving the hydrogen yield [3]. Besides, the growth strategy could be a relevant way to attain the high hydrogen yield. We investigated the hydrogen photoproduction by Rhodopseudomonas palustris 42OL cultured under both artificial and natural radiation. For indoor experiments, we used four cylindrical photobioreactors (PBR) of different internal diameters (i.d. of 4.0 cm; 7.6 cm; 9.6 cm and 13.0 cm). Indoor experiments were carried out at the irradiance of 480 W/m2 and at a constant temperature of 30 °C; outdoor investigations were performed, in autumn, using an underwater tubular photobioreactor (UwTP) with a pipe i.d. of 4.8 cm. The organic carbon source used was malic acid, which is a compound of wine-distillery waste [4]. Although hydrogen production process that uses cheaper materials would undoubtedly make the system more competitive with the conventional hydrogen generation process in the future [5], the high hydrogen yield remains to be the ultimate goal and challenge for the biohydrogen research and development [6]. We demonstrated that the hydrogen production rate (HPR) is greatly affected by the diameter of photobioreactors and an inverse relationship links the HPR to the diameter of the reactor. We used two growth strategies: (i) batch and (ii) semi-continuous regime. The daily average hydrogen production rate (HPRav) attained under batch-growth operation was 222 ± 18 ml(H2)/l/day, which increased to 655 ± 85 ml(H2)/l/day under the semi-continuous regime, which corresponds to 27.3 ± 3.5 ml(H2)/l/h. This rate reduced drastically outdoors (9.8 ml(H2)/l/h). Peaks of 32.7 ml(H2)/l/h and 15.5 ml(H2)/l/h were checked indoors and outdoors respectively. The hydrogen yield of 3.03 mol H2/mol malic acid was achieved indoors under the semi-continuous regime.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
