What are the specific grounding and lightning protection requirements for H2 vent stacks?

CGA G-5.5 states: All vent stacks shall be grounded and meet the requirements of NFPA 70, National Electrical Code, for integrity and system design and also references NFPA 77, Recommended Practice on Static Electricity, and NFPA 780, Standard for the Installation of Lightning Protection Systems. 

For lightening refer to NFPA 780 and for grounding of the Hydrogen equipment, refer to NFPA 70 (Article 250 and Article 510 are good starting points). 

Best practices in the past have used large stranded wire for grounding connected to a grounding grid. Lightening typically has a larger grounding current requirement than grounding and bonding of nonelectrical equipment for static electricity.