How green is Greta Thunberg's transatlantic trip?

Greta Thunberg has set sail for New York, avoiding a plane journey for environmental reasons, but will her transatlantic trip really be 100% zero carbon?

The Swedish climate activist, 16, is crossing the Atlantic in a racing yacht to join protests in the US and take part in a United Nations summit.

She is making the non-stop two-week voyage in a 60ft Malizia II yacht - one of the fastest ocean sailing boats on the planet.

On board with her are two highly experienced skippers, Boris Herrmann and Pierre Casiraghi (the grandson of Monaco's late Prince Ranier III and actress Grace Kelly), her father Svante and cameraman Nathan Grossman.

The boat has been fitted with solar panels and underwater turbines that produce electricity on board, with the aim of making the journey zero-carbon.

It has no toilets, kitchen or privacy - so Greta is in for an uncomfortable voyage.

As it stands, the journey Greta is about to make is the lowest-carbon option to cross the Atlantic.

And as far as environmentally friendly companies go, Malizia is up there in terms of actively contributing to ocean research and the impacts of climate change on marine environments.

The boat makers recently joined the UN-Iniative Sports for Climate Action and recycle its used sails while avoiding the use of plastics.

:: Will an engine be used at any point?

All Malizia yachts carry an emergency combustion engine on board in accordance to essential safety measures.

However, for Greta's translantic trip, the engine will not be used at all so as to be consistent with her message of sustainability and environmental protection.

The engine has been officially sealed, so Greta and team can only rely on the sails for the whole voyage.

While the engine will stay turned off at all times, it will remain fully operational and ready to use in case of an emergency.

But the journey will not be 100% engine free, as the yacht will be assisted by Torqeedo RIBs powered by electric engines during docking manoeuvres at the start and finish to tow it out of and back into port.

The yacht will not have any support vessels travelling with it during the crossing.

:: How will electricity be generated on board?

In terms of generating electricity, Malizia is equipped with a state-of-the-art 1,3kW solar system and two additional hydro-generators which are permanently installed on the stern of the boat.

With these two independently working systems, Greta and crew will have more electricity than they need on board.

Both energy sources will allow the yacht to run all the systems and electronics on board continuously, including navigation instruments, autopilots and watermakers - ensuring the transatlantic trip will be fully emission-free.

:: Is the trip 100% zero-carbon on a carbon fibre racing yacht?

That's what many sailing experts are wondering.

Malizia say that building this type of racing boat needs three tonnes of carbon fibre, moulds for hull and deck, a number of construction materials and various resins.

It says the boatyards that construct the yachts are aware of the resulting and indisputable environmental impact during boat construction and attach great importance on a sustainable building process.

Therefore moulds are made with recycled dry carbon fibre and reused for building the hulls and decks of several new boats.

Old carbon fibre material is also turned into powder and reused in resins for further construction, and all sorts of construction materials are recycled and reused on new boats.

So in short, the answer is technically no, the trip is not 100% zero-carbon.

:: How has Greta's boat been modified for the trip?

Greta's boat has been minimally modified for the upcoming translantic trip, with the interior kept very bare to reduce the weight of the boat for a high-speed journey.

The only alterations include fitted curtains in front of the bunk and comfortable mattresses for better sleeping.

Malizia say the boat's interior is characterised by lack of comfort and that Greta and her team are fully aware of the living conditions to be expected on board.

:: Could the average traveller afford this trip?

In short, no. Most of us don't have access to such luxury vessels as the Malizia II.

Malizia told Sky News that they had not calculated the total cost of the trip.

The company states on its website that it has not received any additional funding for the voyage and has not asked Greta's team to pay for it.

However the boat's construction cost is upwards of €4m (£3.7m), according to RT.