More should be done to encourage investors to support clean energy firms, an industry expert has suggested.According to Jonathan Bryers, an investment partner with Carbon Trust Investments, it will be difficult for people to reduce their carbon footprint until renewable energy companies become more mainstream."For fledgling clean energy companies to get into the marketplace and start making revenues and therefore deliver carbon savings, they need to build compelling investment propositions that can attract early stage investors," he claimed.However, he added investing in a rapid-growth start-up is sometimes a risky venture, but that investing in a company endorsed by a firm such as Carbon Trust Investments could be a safer option.Mr Bryers continued that investment in such a firm is a long-term undertaking with the possibility to last between five and seven years.Meanwhile, RenewableEnergyWorld.com announced this week that the UK is the leading global donor to the Renewable Energy and Energy Efficiency Partnership.The UK has committed around £9 million to the programme since its inception in 2003 and is set to contribute an additional £2.5 million over the coming year.