I hate recapthca forms, puts me off filling a form!
You could just try and write a smarter form to detect spam bots!
You could using filter_var($EMAIL, FILTER_VALIDATE_EMAIL)
You can try tricking spammers by putting hidden fields and if they are filled in you know it's a spammer.
most spammers on my website used this "[url]" and "[link]" so i filtered out those results.
Don't name your form fields with obivous words such as "email", "last name", "Subject"
There is a lot more you can do, but i have managed not to go down the route of recaptcha or anything like that, I like to make life easy for my customers.
It took me roughly two weeks to reduce the spam after i had learned how they were using the form.
I have a happy boss again and customers find it really easy to submit forms!
If you need more help show me your form and i can tell you what you can do to reduce spam bots filling it in