How can the alt be added to this wooCommerce category image?

Something like this?

$image_alt = get_post_meta( $image->id, '_wp_attachment_image_alt', true);

To use in your string:

if ($image) echo '<img src="' . esc_url($image) .'" alt=".$image_alt.">woocommerce-CJD">';

Use it under the $image declaration. In your $image declaration make sure youll get the image attachment via wp_get_attachment_image() function.