Slovenian adventurer Matevz Lenarcic successfully concluded a 100-day eco-friendly trip around the world on Thursday in an ultra-light plane boasting super-low fuel mileage.

"I haven't reached a 'goal' because I do not like goals, what matters is the path we cross," Lenarcic said shortly after landing at Ljubljana's airport late on Thursday.

Lenarcic made the trip flying a Pipistrel Virus-SW914 weighing just 290 kilogrammes (640 pounds) some 100,000 kilometres (62,000 miles), circling the world westbound.

During the trip, Lenarcic overflew seven continents, 60 countries, over 100 national parks, the world's highest mountains including Mount Everest, crossed three oceans and the Antarctic, while burning the smallest amount of unleaded fuel per distance flown.

"It would have been nicer if there were no borders, you do not see borders from the air. Borders are in our heads," the 52-year-old biologist and pilot told journalists.

The accomplished aerial photographer also took pictures as well as measured the concentration of black carbon and light absorbing carbonaceous aerosols (LACA) in regions where such measurements have not been made before.

Climatologists are studying the role of these particles in global climate change.

"There is plenty of space in the world, lots of people live on it, but we are incapable of distributing the wealth we have," Lenarcic said.

The project was backed by Slovenian light aircraft manufacturer Pipistrel.

"Considering the length and how demanding the trip was, I can say that there were almost no problems," Lenarcic said referring to the aircraft.

He added, "This is the best aircraft in the world bearing in mind its performance, fuel consumption, and environment friendliness."

In collaboration with Penn State University in the United States, the plane maker was awarded NASA's Green Aviation prize in 2011 after flying a different, electric aircraft 200 miles in less than two hours using the equivalent in electricity of just over a half-gallon of fuel per occupant.

The trip was Lenarcic's second after circling the globe in 2004 using an ultralight aircraft and flying eastbound.