The cream of low-carbon ideas

Xunlight's lightweight solar modules

It is easy to get depressed about global warming. All the scientific evidence is that the situation is getting rapidly worse; even most politicians would agree that so far their actions to combat climate change have been too little, too late. Against that view the optimists have always contended that man's ingenuity will get us out of the mess we have created. The crisis and the threat to civilisation will lead to rapid technological advance.

If there was ever a moment for the optimists, this is it. The scientists are telling us that carbon dioxide emissions must be reduced immediately. This must be done to avoid the temperature getting above the 2C rise that would be dangerous for human populations and too warm for many of the planet's natural systems to thrive.

So the crisis is here. Is the technology available to meet it? The answer probably lies in the following pages. Here are 100 companies offering technological breakthroughs that will make a large dent in the carbon problem. There is no single silver bullet - there never was going to be - but within this amazing range of scientific ideas turned into products there is room for enormous hope that disaster may be averted.

In these pages are companies offering well researched and ingenious new methods of producing power from the sun, wind, tides and waves. There is a new generation of biofuels that do not use food crops or land needed to feed the world's growing population. There is also a raft of companies developing energy efficiency in appliances and technologies relevant to all aspects of human activity - in the home, factory and farm, providing clean water and dealing with human and commercial waste.

There were thousands of companies with many diverse ideas considered, whittled down to 100 with the help of 35 experts. One of the central issues in the judging was not just whether the technology was promising, but that it had a wide application across the world and frequently that someone with capital had already shown enough faith to put money into its development. Saving the planet by this method is not a sentimental business - new technology is a calculated gamble. Entrepreneurs know the market for cleantech is now so vast that the right investment will make a fortune.

Exciting developments

However, there are no guarantees that everyone will be a marvel. If all 100 companies named thrived then the world's carbon addiction would be on the way to a cure, but some will not do so. As it is, some are already successful, employing hundreds of people and doing excellent business, but looking to expand faster. These are often the companies in the more mature markets like energy efficiency and wastewater management. The greater uncertainty lies in energy generation, the biggest single category, with solar the largest sector. There are, however, exciting developments, for example, a concentrated solar power plant that uses mirrors to boil water and a series of super-thin solar panels, some even printed on a roll like newspapers.

There is also a lot happening in the field of biofuels. One produced from pond scum has already been used to fly commercial airliners, while rivals use other algae grown on waste which, it is claimed, also provide high grade oil for planes and cars.

Another large and promising sector is energy storage, which poses one of the greatest problems of the renewable revolution and is the greatest barrier to turning road and sea transport away from fossil fuels to batteries and fuel cells. Ten companies believe they have found at least some of the answers.

With less than three months to go before the Copenhagen climate talks, when a new deal must be signed by politicians to cut carbon emissions, world leaders will be looking to these technologies to reduce the political pain of the necessary transition to a low-carbon economy. Knowing the challenges they face, politicians are at last finding the political will and the money to foster this sector and in the process create new jobs in the recession.

"As we enter a new era of innovation, driven by the emerging low carbon economy, we must ensure bright ideas are getting the funding they need to become viable commercial propositions... ," says Lord Mandelson, secretary of state for business, innovation and skills, when referring to his department's new initiatives. "We cannot let ground-breaking ideas fail simply due to a lack of business know-how."

In the recession the investors' view of cleantech has become more cautious, as even the best ideas and new products have been taking longer to get a return on capital. But despite setbacks the venture capitalists are still expecting three to five times more back than they invested.

Opportunities abound

Scott MacDonald, a partner with Emerald Technology Ventures in Montreal, Canada, is reviewing hundreds of companies in the field. He says times have been tough but he is optimistic that there are lots of opportunities out there to get back five times his planned investments and is looking for companies with billion-dollar markets.

"We have weathered the worst of the storm and now we expect things to pick up. When the recovery does happen, it will move fast ... It's a time of opportunity for green tech in particular."

But perhaps the most eloquent advocates for the Cleantech 100 companies are the technologies themselves, beacons of ingenuity and optimism. The publicity the companies gain from being in the list gives a world-wide audience the chance to be cheered up and see that there is still all to play for in the battle to survive climate change. At the same time the investors get the chance to get in on the ground floor.

Paul Brown is the Guardian's former environment correspondent and author of eight books on the environment