It's a process that aims to capture carbon dioxide emissions from burning fossil fuels and industrial processes to store them underground so they don't pollute the atmosphere.

To ensure the CO2 is stored long-term, sites deep underground are sought where emissions are kept in small pores or spaces in rocks.

It requires extensive pipeline infrastructure to not only move underground water but to inject the CO2.

* Does it work?

It depends who you ask. The federal government put $60 million towards a multi-billion dollar CCS project at Chevron's Gorgon liquefied natural gas facility and points to it as a success story. As part of the facility's approval Chevron agreed 80 per cent of the offshore gas field's carbon dioxide would be buried.

The project faced delays before starting in 2019, but sand has recently clogged parts of it so emissions will instead be released into the atmosphere.

Critics say it is not successful and is more expensive than investing in renewable energy.

* Where does the money go?

The government has announced a further $263.7 million to help develop CCS projects, hubs and technologies. That is in addition to $50 million in last year's budget for CCS projects, and the $60 million to oil giant Chevron.

* Are other countries looking at it?

The US is planning to enhance tax incentives for CCS and double down on investments and it is also a priority for China and the UK.

* What about hydrogen?

The government has announced another $275.5 million to create regional hydrogen hubs across Australia, with locations to be decided by 2022.

It's separate to 13 hydrogen hubs announced by the National Energy Resources Australia, although some of the potential locations double up.

* What is hydrogen?

Hydrogen produces water vapour and heat when burned, and is close to a zero-emissions fuel when produced from water using renewable electricity, or from coal or methane combined with carbon capture and storage.

* Why is it important?

The government is pinning its hopes on current energy industry workers eventually moving to the emerging industry. The five hub locations will require a skilled workforce, existing infrastructure like ports and gas pipelines, and be close to energy resources.

* Is it a clean energy?

It can be if made with renewables. But it can also be made with coal and gas, an option environmentalists say should not occur.

Australian Associated Press