To establish an environmentally sustainable biohydrogen technology, multidis­ciplinary research approach is vital. Process engineering and optimization of operational factors govern the performance of any biological system and also have considerable influence on fermentative H2 production. The persistence of an acidic microenvironment due to production of soluble acid metabolites as end-products inhibits the process leading to low substrate conversion efficiency to H2. Apart from lower conversion efficiency, one of the important aspects to be paid signifi­cant attention is the non-utilized organic fraction that usually remains as a soluble fermentation product from acidogenic process. Various routes to utilize residual organic fraction of acidogenic process as substrate can be explored. Integration of multiple processes possible for additional revenue generation in the form of addition energy (H2, bioelectricity, methane, etc.) and wastewater treatment utilizing acido — genic effluents are depicted in Fig 7. Application of genetic engineering aspects to stimulate conversion process efficiency is one potentially promising research area.

Design and development of bioreactor systems for H2 production is one of the areas where considerable focus is required. Scaling up of the process to pilot or large scale to generate baseline engineering data will sustain the technology with respect to commercialization. Interaction between the research community and industry from time to time to understand the requirements and design the technology accord­ingly holds the key to the successful commercialization of this process. Moreover, the process to convert existing/operating anaerobic reactors producing methane to

H2 production will pave the way for large scale implementation of this technology and helps to achieve continuous H2 production.

Acknowledgments I acknowledge Dr. J. S. Yadav, Director, IICT and Dr. P. N. Sarma, Head, BEEC, IICT for their encouragement and inputs of V. Lalit Babu, G. Mohanakrishna, S. Veer Raghuvulu, S. Srikanth, B. Purushotam Reddy, M. V. Reddy, M. Prathima Devi, R. Kannaiah Goud and M. Lenin Babu. Biohydrogen and bioelectricity research in BEEC is supported by Department of Biotechnology (DBT), Government of India in the form of research grants (BT/PR/4405/BCE/08/312/2003 and BT/PR8972/GBD/27/56/2006).