“It is possible, but only if you really want it,” Fell – widely regarded as the “founding father” of the global renewable energy movement – told the Post in Hong Kong.

He was in the city to receive this year’s prestigious Lui Che Woo Prize in the sustainable development category.

“Yes, Hong Kong has limited space for [large-scale generation] but there are many possibilities,” he said. “It will also need a legislative framework and an energy strategy.”

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Although large-scale onshore wind or solar farms were not feasible in the space-starved city, Fell cited huge opportunities from wave and tidal power, to “carbon-neutral” waste to energy, and biofuels.

Other than capturing methane at landfills – which Hong Kong is already doing – a new German technology, called hydrothermal carbonisation, is also a viable option.

“This turns organic waste – and you have a lot of it – into a form of non-polluting bio-coal for fuel,” he said. “It can be used to fertilise soil in agriculture, in chemical processes to produce plastics, and even as fuel for coal power stations.”

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However, Hong Kong would not be self-sufficient and would inevitably have to import electricity from mainland China or elsewhere.

“Hong Kong does not have its own oilfields, but yet it uses oil from other places. Similarly, it could also buy solar power from the Gobi Desert or Australia.”

This would be made easier as electricity storage and transmission technology improved. Biofuels were another option, but this would hinge on development of electrified transport.

The former lawmaker has been advocating all nations transition to 100 per cent renewables. Mathematical models by his think tank, Energy Watch Group, claim to prove it is possible and cost-effective.

Fell’s suggestions for Hong Kong come as the government embarks on the process of replacing coal plants with natural gas-fired ones and prepares a long-term decarbonisation strategy for 2050.

In its latest climate action plan for up to 2030, the Environment Bureau said renewable energy could only provide 3 or 4 per cent of the energy mix, up from the current 1 per cent.

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It has also just implemented its first feed-in tariff scheme, albeit on a limited scale and without a legislative framework behind it.

Such schemes allow renewable producers to sell power to the grid at higher than market rates to shorten payback periods on an investment.

Fell and his Green Party were key players in Germany’s famous policy of Energiewende, or energy transition. He co-authored the landmark Renewable Energy Sources Act in 2000, which institutionalised the feed-in tariff scheme with variable pricing, rate-lowering mechanisms and participation of utilities.

The model is seen as the international benchmark for promoting renewables and has been replicated worldwide.

It helped lower wholesale electricity prices and increase renewable energy in Germany’s electricity mix from about 6 per cent in 2000 to 32 per cent by 2015, though it is still largely dependent on coal. Fossil fuels grew in proportion after the decision to shut nuclear plants after Japan’s 2011 Fukushima disaster.

Fell said it was a mistake for Hong Kong and the mainland to still be looking at natural gas and nuclear as “clean” fuels, the former being just relatively cleaner than coal and the latter, potentially destructive and highly polluting in terms of radioactive waste.

“New investment into wind and solar is cheaper than new investment into a coal, gas or a nuclear plant,” Fell said. “Every investment into fossil and nuclear now will become a stranded investment. The coal industry will vanish.”

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Solar and onshore wind prices have indeed fallen – by a quarter and 73 per cent respectively since 2010. The International Renewable Energy Agency expects electricity from all renewable sources to be cost competitive with fossil fuels by 2020.

Professor Johnny Chan Chung-leung, director of the Guy Carpenter Asia-Pacific Climate Impact Centre at Hong Kong’s City University, said 100 per cent renewable energy for the city was “theoretically possible”, but the issue was cost and government support.

“[Investment] in the environment can’t be left to the free market. Renewables must be able to reap economies of scale … and that requires government support, including subsidies and tax incentives.”

Dr William Yu Yuen-ping of the World Green Organisation argued that from an energy security perspective, Hong Kong would still have to keep some fossil fuels or nuclear in the mix as a stable “baseload” source. But he agreed the city needed to do more to phase out fossil fuels and be more “receptive to new technology”.

“Right now it’s hard to get government funding for a pilot scheme to test out a new clean energy technology.”