A California-based food tech start-up team has won the annual Liveability Challenge, a global call for companies to come up with innovative solutions for clean energy and sustainability in tropical cities.

The competition saw an intense battle, with over 300 entries from 51 countries fighting for the award sponsored by local non-profit organisation Temasek Foundation.

From hydrogen-powered engines to energy-saving air-conditioning systems, solutions to make cities in the tropics greener were pitted against one another.

The Singapore-registered Sophie's Kitchen was named the winner yesterday at the Sands Expo and Convention Centre at Marina Bay Sands.

The team beat five other finalists to clinch $1 million in funding for its technology to produce food-grade microalgae protein as an alternative to animal-and plant-based protein. It also won a six-month mentorship opportunity with angel investment network Bansea.

The process uses food waste such as spent grains and okara - which are by-products of breweries and soy manufacturers - as feed for the microalgae, which is grown in a fermentation tank.

After three to five days, the microalgae is dried and harvested for its protein - which makes up 60 per cent of the biomass - while the rest of the waste materials such as ashes, oil and fibre are removed. The entire process, including the purification of the protein for human consumption, takes less than a week.

The innovation is expected to save large amounts of arable farmland required in agriculture. About 0.02ha of land is needed to produce a tonne of microalgae protein, compared with 141ha needed for beef.

Over 90 per cent of the water used in the production of the protein can also be recycled, explained Mr Eugene Wang, founder and chief executive of Sophie's Kitchen.

The company expects to supply the protein, which tastes like seaweed, as an ingredient to firms that sell plant-based burgers and seafood. Mr Wang added that cost is often a concern for consumers when it comes to eating foods with plant-based protein. "Even in the lab, we're able to achieve somewhere between $13 and $15 per kilo (of protein produced). We're trying to bring it down further to prices that can compete with those of soy-based protein today."

The annual competition is part of the broader Ecosperity Week 2019 - where businesses and policymakers gather to brainstorm sustainable solutions to tackle climate change - which ended yesterday.

Singapore-based biodegradable technology firm RWDC Industries was the winner in last year's competition for its fully biodegradable drinking straws made from a naturally occurring polymer.

The biopolymer is produced during the bacterial fermentation of plant-based oils or sugar, and is certified to be fully biodegradable in soil, water and marine conditions.

The company launched the biopolymer, an alternative to single-use plastics, on Thursday in conjunction with Ecosperity Week.

Apart from drinking straws, the bioplastic can be used to make cutlery, cup lids and packaging for food and beverage.

The firm is currently in talks with a major personal care company on using the polymer to produce diapers and wet wipes.

Ms Jessica Cheam, managing editor of Eco-Business, which is the co-organiser of the event, said: "Given the climate crisis we are facing, it is ever more crucial for us to effectively allocate capital to the solutions we need to rapidly achieve a low-carbon, sustainable and liveable future."