Log broken queries

I need to log every broken query to logs file in my application. I can't use hook, because it will log every query, I need to log only broken queries. There's also option $db['default']['db_debug'] = TRUE, but it shows information about queries on user's screen (not in logs file). I need to put somehow in logs file same information which user see in case of use $db['default']['db_debug'] = TRUE. Is there any simple solution to do that?