At first glance, geothermal energy seems almost too good to be true. It's clean, inexhaustible, provides predictable 24-hour power and you can get it just about anywhere. There is a snag, however. Outside of geologically blessed places like Iceland, Japan and New Zealand, where volcanically active rocks are close to the surface, the Earth's heat is locked away under several kilometres of rock.

The airline industry's insatiable demand for fuel is bad news for the environment. But can biofuels provide the solution, asks David Strahan.

Price is just the start of it. We need to kick the petroleum habit or we'll soon be in real trouble, says Ian Sample.

Don't imagine that pumping more oil will get us out of our current mess, argues Matthew R Simmons - dealing with the addiction is the only option.

Black gold might not be as scarce as we thought. This week oil prices escalated to a record $139 per barrel, but that may partly be because the amount of available oil in known reserves has been significantly underestimated. So says Richard Pike, a former oil-industry adviser and chief executive of the UK Royal Society of Chemistry, who blames flawed statistical calculations.

They call it flammable ice, and it could be the world's last great source of carbon-based fuel - assuming we can mine methane hydrates, crystal lattices of ice that trap methane beneath ocean beds and permafrost. One problem with extracting this methane is that you have to melt the ice to bring the gas to the surface. In 2002, a team of geologists from Canada and Japan tried injecting hot water into the ice beneath the delta of the McKenzie river in northern Canada. While this released some hydrates, it used a lot of energy.

Returning to Africa after a 10 year absence, Chris Reij could barely believe his eyes. On the arid margins of the Sahara in Niger, all he could see were trees.

Late last month the Svalbard Global Seed Vault opened in Longyearbyen, on the Norwegian island of Spitsbergen.

With creationists arguing over its formation, and lengthy disputes over land rights, the Grand Canyon has often been the focus of controversy.

The dream of climate-friendly, petroleum-free motoring is creeping closer - thanks to a clutch of breakthroughs in nanotechnology. Several recently reported lab findings promise to vastly improve the safety and performance of the high-capacity batteries that electric cars will need, at last making them a viable alternative to today's petroleum-powered vehicles. Feb 27, 2008