SOLAR HYDROGEN PROJECT BIOPHOTOLYTIC HYDROGEN PRODUCTION B. Tamburic*, K. Hellgardt, G. C. Maitland, F. W. Zemichael Department of Chemical Engineering, Imperial College London, SW7 2AZ, UK Conclusion This project links genetic approaches to reactor design and engineering, demonstrating the power of using an integrated, cross- disciplinary approach to address the challenge of carbon-free H 2 production. Improvements in H 2 production efficiency and bioreactor design may allow hydrogen to fulfil its potential as the sustainable fuel of the future. Photobioreactor Design Fig.2 Fig.2 AquaMedic® culture reactors facilitate C.reinhardtii growth Fig.3 Fig.3 Sartorius® photobioreactor used to investigate growth and H 2 production kinetics Algal Growth Control the light intensity, pH, agitation and temperature of the system (Fig.2) Minimise the risk of contamination by using filters and sterilisation procedures Measure optical density of culture Sulphur deprivation Cycle the algal growth medium by: Extracting algal cells by centrifugation/ultrafiltration Heavily diluting the growing culture with a sulphur-replete medium Controlling sulphur content through better understanding of process kinetics (Fig.3) Scientific Background The green alga Chlamydomonas reinhardtii has the ability to photosynthetically produce molecular hydrogen under anaerobic conditions (Fig.1) : Photons are absorbed within the chloroplasts of C.reinhardtii This facilitates photochemical oxidation of water by photosystem II (PSII) proteins The hydrogenase (H 2 ase) enzyme catalyses the process of proton and electron recombination to produce H 2 Hydrogenase activity is inhibited in the presence of O 2 Sulphur deprivation of C.reinhardtii reduces photosynthetic O 2 production below the level of respiratory O 2 consumption, thus creating an anaerobic environment and leading to sustained H 2 production (Fig.4) Fig.1 Fig.1 Photosynthetic electron transport chain during anaerobic H 2 production in C.reinhardtii Why Solar Hydrogen? With the decline in reserves and increasing concern over fossil fuel use, there is a demand for an alternative energy carrier that is CLEAN, RENEWABLE and AVAILABLE HYDROGEN can be the solution – but only if it is produced by a SUSTAINABLE process Aim is to generate CARBON-FREE HYDROGEN using unlimited resources – SUNLIGHT and WATER Imperial College project, funded at £4.2M by EPSRC Unique multidisciplinary approach from genetic engineering to reactor and system design H 2 Production Fig.4 H 2 production commences once anaerobic conditions have been established Measurement Products identified using injection mass spectrometry Gas phase H 2 production measured by water displacement Dissolved oxygen/hydrogen content measured with reversible Clark electrode Dissolved gas extracted using a H 2 -permeable membrane and analysed with a mass spectrometer Optimisation Increase H 2 production rate (Fig.4) by: Controlling light intensity and algal optical density Improving light penetration Preventing H 2 diffusion leaks