As the error said, look inside /etc/default/saned :
# Defaults for the saned initscript, from sane-utils
# Set to yes to start saned
# Set to the user saned should run as
If directive/variable "RUN" is set to "no", then you must change it to "yes". To do this, open /etc/default/saned file with following command:
sudo -H gedit /etc/default/saned
Set RUN=yes. Now, saned service will be started during start-up of Ubuntu, but to start the service for now, run following command:
sudo /etc/init.d/saned start
If you see a line similar to the below line, it means that the service is running.
[ ok ] Starting saned (via systemctl): saned.service.