Apple’s Lisa Jackson, who joined Apple in June last year to oversee environmental issues from her previous position as head of the Environmental Protection Agency, sat down for an interview this week with Fortune. As you’d expect, the topic of conversation was all things environmental issues at Apple and Jackson talks about many of the accomplishments the company recently announced for Earth Day. In addition to just stats and Apple’s renewable energy initiatives— Apple’s supply chain is responsible for 60% of its footprint— she also gives some hints at what Apple plans to improve in the future.

Jackson noted that Apple has more work to do getting renewable energy to all of its retail stores, but said its working hard to overcome some of the challenges and reach 100% renewable energy:

We have a lot of work to do at our retail stores to get that number up to 100%… it’s a lot harder to do the retail stores, they’re all over the place. In some places they are in a mall… but where they are on the grid and where they are in the world, the access to clean energy may or may not be a trivial exercise.

Apple previously announced that it reached 100% renewable energy in its corporate facilities and 94% across its data centers. Currently around 120 of its U.S. retail stores are powered by renewable energy.

The full interview is worth checking out if you’re interested in Apple’s environmental efforts.