Choate has a very cool environmental immersion program that may appeal to you. It’s in Connecticut, but you can spend a semester living at Choate’s Kohler Environmental center (just down the road from the main campus), so it’s a pretty unique opportunity. More info: https://www.choate.edu/academics/signature-programs/environmental-immersion-program
In terms of admission, there are often fewer spots available for sophomores than freshman, and even fewer openings for juniors. If this is something you really want to do, I’d strongly advise you to apply this year rather than wait another year.
Lawrenceville has more sophomore openings than a lot of other BSs and it checks your New Jersey box. In terms of environmental focus, they do have a Leopald Scholar program where students work on sustainability projects, though I’m unsure of the details. They also have a farm on campus that students where students may work, as well as a solar farm (though I’m unaware of the extent to which students are involved). You can find more info here: https://www.lawrenceville.org/academics/experiential-education/sustainability-at-lawrenceville