Can I claim head of household without claiming a dependent? He is an adult and needs to claim himself for college grants.

No. You must have a qualified dependent to file HOH,

 

Am I Head of Household?

https://ttlc.intuit.com/questions/1894553-do-i-qualify-for-head-of-household

https://ttlc.intuit.com/questions/2900097-what-is-a-qualifying-person-for-head-of-household

 

If you qualify as Head of Household, when you enter your filing status (single or married filing separately) into Personal Info, and then enter your qualifying dependent, TurboTax will offer HOH as your filing status.

Thanks, HOH to single is a huge difference in refund to owing federal.