The former Australian of the Year, who has championed CCS and projects such as Santos' $700 million Moomba storage project in South Australia, said he had changed his view on the idea of capturing carbon and storing it underground during a trip to Germany last week.

Professor Flannery, who sits on the sustainability advisory board of Siemens, said he formed the view after talking with lead technicians from the company, which is itself involved in developing a number of trial CCS projects.

''I must say that I was rather shocked by what I heard,'' he said. ''Their view is that sure, carbon capture and storage is technically possible and all of the elements are in place now, and we understand enough to start building full-scale plants. So why aren't people building commercial scale plants with carbon capture and storage? Their argument was that it is economically unfeasible, and if it isn't happening now it simply is not going to happen in the future.

''I have been a great proponent of carbon capture and storage because I believed it was just essential particularly in places like China. But … having come back from that meeting and met the world's experts in this area, I have a less hopeful view of carbon capture and storage.''

Professor Flannery said the federal government should commit funds towards geothermal energy, solar photovoltaic energy and ''possibly even nuclear'' to meet Australia's future energy demands.

''There is still a very significant element in the Labor Party that believes coal is the future. That can still be an acceptable belief … because there is the promise that carbon capture and storage will be developed on time and will start pushing for a responsible coal industry in the future,'' he said. ''But the idea that coal is the future is a big problem for us.''

Nick Otter, the chief executive of the Global Carbon Capture and Storage Institute, which has $100 million a year in funding committed by the federal government, said the major challenges of CCS were not insurmountable: ''The challenge is to address these barriers to create the conditions for the integration of these technologies at commercial scale and across a variety of applications.''