Organizers expect tens of thousands of protestors Sunday in Washington in the biggest climate change rally in U.S. history.

The protest is against the Keystone XL pipeline, which would carry Alberta bitumen to Texas refineries.

It follows an earlier rally on Wednesday in Washington, which led to 48 arrests including those of Robert Kennedy Jr. and Daryl Hannah.

The main groups organizing the demonstration are 350.org, the Sierra Club and the Hip-Hip Caucus.

Daniel Kessler of 350.org said he doesn’t expect the kinds of arrests that happened on Wednesday, telling 660News this one will be a positive.

“We have 165 buses coming from 31 different states, so it’s clear that all across the country people are fired up and they’re coming to D.C. to tell the president that they want action,” he said.

There will also be Canadian connections to the protest, including Greenpeace Canada climate and energy campaigner Melina Laboucan-Massimo as a speaker.

As for the controversial pipeline, Kessler said while we do need oil and gas for the foreseeable future, with less and less oil being consumed, Keystone isn’t going in the right direction.

“We’re very much against this pipeline because one it’s symbolic, it shows that we’re willing to look backwards, instead of looking forward when it comes to our energy policy, and two it taps into the tar sands, which contain about enough carbon to cook the planet,” he said.

He added the problem is exacerbated with global temperatures on the rise, much of the U.S. in drought and billions being spent on extreme weather cleanup costs.

U.S. President Barack Obama is not in Washington to see the protest. He is currently in Florida.

The final call on keystone will be made by U.S. Secretary of State John Kerry, who hopes to announce the decision in the near future.

But, Patrick Michaels of the Cato Institute told CNN he thinks a decision has likely been done.

“The White House has probably already made its decision on Keystone,” he said. “The political calculus is obvious, if they come out against it, they’re going to pay a very big price.”