Political consensus was hard to find at last month's Rio +20 Earth Summit but there was at least one group speaking with unity on the planet's environmental and economic future.

Hundreds of activists gathered on the city's Copacabana Beach to make a simple demand of their elected leaders and representatives: Commit to ending fossil fuel subsidies, now.

More than a million people around the world -- including actor Robert Redford and comedian Stephen Fry - were quick to lend their support by backing #endfossilfuelsubsidies, an affiliated online campaign.

But as the summit came to a close it became clear that no new enforceable commitments on the issue were to be included in the final version of the Rio agreement text.

For those behind the protest however, the widespread exposure and support afforded the oft ignored subject ensured their efforts still represented a success.

"This all falls into changing our energy usage patterns, which I believe is the pre-eminent challenge of the 21st century," says Steve Kretzmann, founder of Oil Change International, an environmental advocacy group that backs the #endfossilfuelsubsidies campaign.

"The first place to start is to stop putting public money towards fossil fuels," he adds.

"This is not because anybody has it in for the fossil fuel industry. What we're talking about is what the public's money actually should support."

Estimates as to how much this support equates to vary from study to study, as do methods and standards for calculation.

The International Energy Agency (IEA) reported that internationally $409 billion worth of government money flowed into the coffers of the fossil fuel industry in consumption subsidies (designed to make fuel more affordable and accessible to the consumer) in 2010.

A separate study from the U.S. Natural Resources Defense Council estimates that global fossil fuel subsidies will reach $775 billion this year when producer subsidies (designed to facilitate greater fuel production) are added on.

However Kretzmann believes these figures may only be the tip of the iceberg and could actually top $1 trillion every year.

He says there is often a lack of transparency in how some governments report the incentives, with many transferred as hard-to-calculate tax credits.

Kretzmann similarly laments the comparatively sparse investment in renewable energy subsidies (which stood at $66 billion in 2010 according to the IEA) as a wasted opportunity to create less polluting energy sources whilst encouraging growth in the green economy.

"At the end of the day, not only is this bad policy but its also bad economics," he says.

"Long term, renewables are a better option for the environment and the economy. There are multiple studies that show how much more labor intensive renewables are and how they create more jobs per unit of energy created."

However others are more cautious about the consequences that an about-turn in energy policy could create.

"In certain countries and situations, subsidies are essential to peoples way of life," says Dan Kish the deputy vice-president of policy at the Institute for Energy Research, a Washington D.C. based organization that advocates free market energy policies.

Any alteration to this arrangement could cause prices to balloon, weakening development and in the worst case scenario leading to social unrest, he adds.

Kish points out that a large proportion of subsidies are in fact designed to keep fuel prices artificially low, enabling consumers in some of the world's poorest regions access to basic energy products.