Can I put food in the HOTBIN without adding 'browns'?

This is one of those questions where terminology from traditional composting does not work well in HOTBIN.

Browns normally means woody material and relates to mixing greens and browns

Despite being high in nitrogen (a green), food waste will compost without adding browns - but it rarely composts successfully - more often that not it goes anaerobic - this has little to do with the carbon to nitrogen ratio (ie the ratio of green to browns), it relates to water content.

Food waste has a high water content (80%). When released, it creates a wet mush that bocks airflow, which then results in anaerobic conditions.

To avoid this, the HOTBIN uses two techniques - bulking agent (wood chip) is added to maintain airflow. We also add shredded paper or corrugated cardboard - which adds a dry food waste for bacteria to eat. This releases more heat - which drives the excess water off.

So you need to add bulking agent and shredded paper (both of which are browns), but you are not adding them to balance green and browns. Sorry if this is a little pedantic - but to get your HOTBIN working all the time, the two essentials are to understand the need to maintain airflow and to have enough heat to dry of excess water.