CAPTCHA/reCAPTCHA with no cookies

is there way method, or a plugin, that will help me defeat spammers without leaving cookies on a legitimate visitor’s computer? Neither myself or my client has any need to leave cookies on a visitor’s system, but the Google reCaptcha system we’re currently using leaves cookies.

Please note, this is not about comment spam. The comment system on my client’s site is disabled. We are looking for a way to block spam through the Contact Form 7 to stop spam/threatening messages. However, my clients has no desire to do any kind of tracking or to be responsible for leaving cookies on a visitor’s device.

Thanks in advance!