Two years ago, Kate Mara watched a rough cut of “The Smell of Money” – a documentary about Elsie Herring’s decades-long fight to stop a multibillion-dollar corporate hog farm from spraying animal waste on her family’s land in North Carolina – and signed on to become an executive producer alongside David Lowery. Directed by Shawn Bannon, “The Smell of Money” examines not only how and why hog waste is killing innocent people, but also environmental racism, corporate malfeasance and global warming. The docu follows Herring and other residents as they wade through a nine-year legal battle against Smithfield Foods, whose facilities process tens of thousands of pigs per day, making the company the largest producer of pork in North America.

After debuting at the Sarasota Film Festival in March, the doc is making its international premiere at Canada’s Hot Docs film festival on April 30. Mara and Bannon spoke to Variety about why they wanted to make “The Smell of Money,” the role of high-profile supporters including Elliot Page in getting the film made after Herring’s death, and what they hope its impact will be.

Kate, why did you decide to sign on as executive producer of this docu?

Mara: After watching the film, I couldn’t stop thinking about it. It’s a very haunting thing to learn about. I also felt this immense responsibility to the people (in the doc) and to their story. I wanted to work with Shawn to find a way to get their story out there because we want justice for them.

Is this the first documentary that you have produced?

Mara: Yes. It’s been a really interesting experience. I’m definitely learning a lot as we go along.

Shawn, was it difficult to convince Elsie, who died last year, to be the main subject of the doc? Or was she always on board?

It was almost impossible to convince her to do it because she was so private. But she was also so passionate about this issue. It took time to gain her trust and the community’s trust. We had to be very respectful of people’s time. It was challenging because I never wanted to inconvenience Elsie – a person who was going through a lawsuit for nine years and had been fighting the (pig) industry for 30 years. I began to question what I was doing all the time. But ultimately, we ended up really connecting.

Current hog farmer, Tom Butler is a key character in the doc. He sheds light on factory farming but is still part of that industry. Why did he want to participate in the doc?

Bannon: Tom is all about telling the truth. He doesn’t like that big corporations are lying about stuff. He feels like they should say what they are doing and do something about it. Come up with the solution. Tom has tried to do things and has admitted that his farms have impacted neighbors. But I think he really believes in changing the way food is raised in America.

Were you surprised when Rene Miller, a plaintiff, said that she wouldn’t move even if she wins the lawsuit against Smithfield Foods?

We decided to not put more information about that in the film because it could take up so much time, but it’s like, why should she have to move? She and her family have lived on this land since the Civil War and then a huge corporation moves in, and she has to move. It doesn’t make any sense. Why can’t they clean up with her doing? That’s one reason. But also, most of these people in these areas do not have the resources to move.

You cover a lot of topics in 83 minutes. What was your approach in the edit?

Mara: Shawn sent me a bunch of different edits of the film over the last couple years, but one of the things that we both thought would be useful to the movie would be to show it to people that we really respect and trust as either filmmakers, producers, or actors. So, I gave my own personal notes, but then we also looked at what people that we really admire had to say about it. That was what the process has been for us over the last couple years.

In the credits Jessica and David Oyelowo, Joaquin Phoenix, your sister Rooney Mara, Werner Herzog and Elliot Page are thanked. Are they some of the people who watched rough cuts for you?

Mara: Yes. We chose specific people to watch it. We didn’t just give it to anybody. Elliot Page, for example, directed a documentary. Just hearing how they all reacted to the film was really helpful.

Bannon: After Elsie died, I was in a catatonic state. I could not work on the movie. But sending it out to those people and getting their notes was really motivating. We couldn’t have made this film without them.

You have taken the film to two festivals so far. What are your distribution plans?

Mara: Our goal is to have it seen by as many people as humanly possible.

Bannon: We are hoping to start talking to distributors during or after Hot Docs. But like Kate said, we want to find the biggest audience we can for this movie. We will use every resource and every connection that we can to get this film out there to audiences.

What do you hope happens after this film is released?

Bannon: Getting Elsie and or Rene’s story out there for people to hear is so important to me. To motivate change from that and to have people realize that the food we are putting in our bodies is impacting people in communities all over the world – not just in North Carolina – would be amazing.

Mara: It’s hard question to answer because there are so many things that need to change. We have to have an open mind about what our goals are and what our hopes are for this documentary and just in general for our planet.

Bannon: We need to end factory farming.

Mara: But when you say that a lot of people automatically go, ‘Oh it’s a vegan activism film,’ and it’s not. This is about human activism.