A day after Bernie Sanders claimed he 'introduced the most comprehensive climate change legislation' and said he would tax carbon use, the Democratic presidential candidate chartered a Delta 767 to fly him to Rome and back for less than 24 hours.

After attacking rival Hillary Clinton for her stance on fossil fuels stepped on Thursday, Sanders stepped off the plane on Friday in Rome for the Vatican conference with his wife, ten family members, a group of campaign staff, Secret Service detail and members of the press.

The total group of what is believed to be below 50, flew in a chartered Delta 767 for their trip, which can seat between 211 and 261 people, depending on the model. It is unclear if Sanders' aircraft had flatbed seats.

A 767 aircraft carries up to 23,980 gallons of fuel, which is 'enough to fill 1,200 minivans', according to Boeing.

Bernie Sanders traveled to Rome for the Vatican conference on Friday in a private chartered Delta 767 aircraft

He was joined by his wife, ten family members, a group of campaign staff, secret service detail and members of the press

Sanders traveled 4,435 miles to Rome just hours after Thursday night's debate. He will return to the New York after less than 24 hours

Following their eight-hour flight, Sanders and his wife, Jane, took a car to the Vatican for the conference on Friday

Sanders' wife, who is Catholic and ten of Sanders' other family members joined him for the 8,870 round-trip flight, including four of his grandchildren.

The group of campaign staff that flew with Sanders is believed to be small, as is the group of reporters.

A press officer from the Secret Service told Daily Mail Online that he could not disclose the number of Secret Service members who were with the presidential candidate.

With a range of 6,408 miles on a full tank of gas, it can be calculated that a 767 like Sanders' flying 4,435 miles from New York to Rome uses approximately 16,596 gallons of fuel. The round-trip flight will use approximately 33,193 gallons.

On average, an American flies only 7,500 miles per year, according to AmericanForests.org, 1,360 fewer miles than Sanders' round-trip Rome travel. Thus, an average American releases less carbon emissions via aircraft each year than Sanders did in 24 hours.

In comparison to vehicles, an average American drives approximately 13,476 miles per year, according to the Department of Transportation, 4,606 miles more than Sanders' Friday air travel.

It would take the average American between seven and eight months to drive as far as Sanders traveled.

The amount of carbon dioxide emitted by the flight is unknown.

An average round trip flight from New York to Europe can produce two to three tons of carbon dioxide per person, according to the New York Times.

An average person in the United States normally generates approximately 19 tons of carbon dioxide per year through driving, transportation and disposing of waste.

It is unknown how much it cost Sanders to charter the plane for the one-day trip, but according to a 2012 article from the Wall Street Journal, many sports teams charter similar aircraft and pay as much as $200,000 for one-way domestic flights.

Sanders greets supports while at the Vatican City on Friday during his one-day trip to Rome, an opportunity he said was too meaningful to pass up.

Sanders and his wife were flanked by Secret Service members as they visited the Vatican. A press officer from the Secret Service told Daily Mail Online that he could not disclose the number of Secret Service members who were with the presidential candidate.

Daily Mail Online reached out to Delta for an approximate cost of chartering a 767 flight to Italy and they declined to comment.

Sanders' campaign has raised mass amounts of money as of late. Toward the end of March, Sanders raised more than $4million after his victories in Washington state, Hawaii and Alaska.

Sanders' campaign spokesman Michael Briggs that the fundraising shows that the 'people backing Bernie are charged up'.

Sanders' supporters donate just $27 on average when contributing to his campaign.

At Thursday's debate, Sanders claimed that Clinton's support comes from employees at oil companies and lobbyists for the fossil fuel industry.

'As I understand it, 43 lobbyists for the fossil fuel industry maxed out, gave the maximum amount of money to Secretary Clinton's campaign,' he said during the debate.

He said that he's ready to go further than Clinton on climate change, even implementing a tax on carbon.

'Shen we look at climate change now, we have got to realize that this is a global environmental crisis of unprecedented urgency,' Sanders said. 'And, it is not good enough. You know, if we, God forbid, were attacked tomorrow the whole country would rise up and say we got an enemy out there and we got to do something about it.'

He also mentioned that he has 'introduced the most comprehensive climate change legislation, including tax on carbon'.

'Something I don't believe Secretary Clinton supports,' Sanders added.

Reporters and supporters surrounded Sanders, his wife, and Secret Service members as they visited the Vatican

Just a day before his 8870-mile round-trip journey, Sanders claimed at Thursday's debate that Clinton's support comes from employees at oil companies and lobbyists for the fossil fuel industry.

Clinton pushed back by accusing Sanders of being a perpetual critic, unwilling to support progress. She noted he criticized Obama's climate deal.

She said: 'I really believe that the president has done an incredible job against great odds and deserved to be supported.'

Regardless of his criticism on fossil fuels, Sanders still decided to fly to Rome following the debate on Thursday night, saying the opportunity to address the Vatican conference was too meaningful to pass up.

While in Rome, Sanders issued a global call to action at the Vatican Friday to address 'immoral and unsustainable' wealth inequality and poverty and warn of the consequences to future generations if solutions are not found.

He cited Pope Francis and St. John Paul II repeatedly during his speech to the Vatican conference commemorating the 25th anniversary of a landmark teaching document from John Paul on social and economic justice after the Cold War.

The Vermont senator told the audience of priests, bishops, academics and two South American presidents that rather than a world economy that looks out for the common good, 'we have been left with an economy operated for the top 1 percent, who get richer and richer as the working class, the young and the poor fall further and further behind'.

Sanders warned that youth around the world are no longer satisfied with the status quo, which includes 'corrupt and broken politics and an economy of stark inequality and injustice'.

'They are not satisfied with the destruction of our environment by a fossil fuel industry whose greed has put short term profits ahead of climate change and the future of our planet,' he said. 'They are calling out for a return to fairness; for an economy that defends the common good by ensuring that every person, rich or poor, has access to quality health care, nutrition and education.'

He sat next to the other main guest of honor at the Vatican: Bolivian President Evo Morales, whose is renowned for his anti-imperialist, socialist rhetoric.

Pope Francis apologized that he couldn't personally greet participants at the Vatican conference. No meeting with Sanders was expected.

The Vermont senator discussed the economic issues with an audience of priests, bishops, academics and two South American presidents

Bernie Sanders (left) shakes hand with Bolivia's President Evo Morales during Friday's conference in the Vatican

He sat next to the other main guest of honor at the Vatican: Bolivian President Evo Morales (left), who is renowned for his anti-imperialist, socialist rhetoric

The trip came a day after Democratic presidential candidate Bernie Sanders claimed he 'introduced the most comprehensive climate change legislation' and attacked rival Hillary Clinton for her stance on fossil fuels

His talk was titled 'The Urgency of a Moral Economy: Reflections on the 25th Anniversary of Centesimus Annus'.

The conference was organized by a Vatican advisory group comparable to a think-tank that Francis appointed to guide him on a wide range of public policy issues.

Back home, Clinton holds a significant delegate lead against Sanders, but the senator has vowed to stay in the campaign until the party's July convention.

His message calling for a political revolution to address wealth inequality and the influence of Wall Street on US politics has galvanized many Democrats and independents.

A Sanders rally Wednesday night in New York City drew 27,000 people.

Despite being enmeshed in an increasingly bitter campaign against Clinton, Sanders aides said the trip was not aimed at appealing to Catholic voters who comprise a large share of the Democratic electorate in New York and an upcoming contest in Pennsylvania.

'This is not going to be a political speech,' Sanders senior adviser Tad Devine said. 'We're not looking at this through a political lens.'

The Vatican has been loath to get involved in electoral campaigns and usually tries to avoid any perception of partisanship involving the pope.

Popes rarely travel to countries during the thick of political campaigns, knowing a papal photo opportunity with a sitting head of state could be exploited for political ends.

As a result, the invitation to Sanders to address the Vatican conference raised eyebrows and allegations that the senator lobbied for the invitation.

The chancellor for the pontifical academy, Bishop Marcelo Sanchez Sorondo, has said he invited Sanders because he was the only US presidential candidate who showed deep interest in the teachings of Francis.

Sanders did not meet with the Pope during his 24-hour trip to Rome. The Pope apologized for missing the Vatican conference