Costa Rica’s new president has announced a plan to ban fossil fuels and become the first fully decarbonised country in the world.

Carlos Alvarado, a 38-year-old former journalist, made the announcement to a crowd of thousands during his inauguration on Wednesday.

"Decarbonisation is the great task of our generation and Costa Rica must be one of the first countries in the world to accomplish it, if not the first," Mr Alvarado said.

"We have the titanic and beautiful task of abolishing the use of fossil fuels in our economy to make way for the use of clean and renewable energies.”

Symbolically, the president arrived at the ceremony in San Jose aboard a hydrogen-fuelled bus.

Last month, Mr Alvarado said the Central American country would begin to implement a plan to end fossil fuel use in transport by 2021 – the 200th year of Costa Rican independence.

"When we reach 200 years of independent life we will take Costa Rica forward and celebrate ... that we've removed gasoline and diesel from our transportation,” he promised during a victory speech.

Costa Rica's renewable energy

Costa Rica already generates more than 99 per cent of its electricity using renewable energy sources, but achieving zero carbon transport quickly - even in a country well-known for its environmental commitment - will be a significant challenge, experts say.

Jose Daniel Lara, a Costa Rican energy researcher at the University of California-Berkeley, said completely eliminating fossil fuels within just a few years is probably unrealistic – though the plan will lay the groundwork for faster action towards that goal.

“A proposal like this one must be seen by its rhetoric value and not by its technical precision,” Mr Lara said.

Oscar Echeverría, president of the Vehicle and Machinery Importers Association, said the transition away from fossil fuels in transport cannot be rushed as the clean transport market is so far undeveloped.

“If there’s no previous infrastructure, competence, affordable prices and waste management we’d be leading this process to failure. We need to be careful,” Mr Echeverría said.

But economist Monica Araya, a Costa Rican sustainability expert and director of Costa Rica Limpia, which promotes renewable energy and electric transport, said that in a country already rapidly weaning itself off fossil fuels, focusing on transport – one of the last major challenges – could send a powerful message to the world.

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“Getting rid of fossil fuels is a big idea coming from a small country. This is an idea that’s starting to gain international support with the rise of new technologies,” she said.

Costa Rica’s push towards clean energy faces no large-scale backlash, in part because the country has no significant oil or gas industry.

But demand for cars is rising, as is use of other transport systems, and that may prove one of the biggest challenges in meeting the new goal, Mr Lara said.

According to data by the National Registry – the country’s records agency – there were twice as many cars registered as babies born in 2016.

Transport is today the country’s main source of climate changing emissions. According to the country’s National Meteorological Institute, 64 per cent of Costa Rica’s emissions come from energy use, and more than two thirds of that is from transport.

According to data from the State of the Region report, put together by a council of Costa Rica’s university leaders, public transport has struggled to meet the transport needs of the country.

As a result, demand for private vehicles has risen dramatically, with the car industry growing 25 per cent in 2015 alone, making Costa Rica one of the fastest growing auto markets in Latin America, according to the report.

The centre-left Mr Alvarado beat hs Christian conservative rival and namesake Fabricio Alvarado, whose campaign had largely centred on his opposition to same sex marriage, with 60 per cent of the vote in second-round elections, and took office on 8 May.