At first glance, clean technology, which either improves the efficiency or reduces the environmental impact of energy-related products, appears to be a booming industry. It is estimated to be worth $150bn now but will reach $600bn by 2020, a United Nations report says.
Investments are being made in a huge variety of concepts and technologies. In one high-profile example, Sapphire Energy, a San Diego-based company that aims to make biofuel from algae, said last month that it had raised more than $100m from investors. New backers include Cascade Investment, owned by Bill Gates, Microsoft’s founder.
