Since you're asking about this for a class, I'll start by replying with one of my most often used (and probably least liked) answers to questions posed in my ecodesign classes: "it depends."
Though the answer may sound evasive, it's also accurate because there seldom is one correct answer to a question in ecodesign.
To begin with a really unhelpful answer, the most eco-friendly material to choose for any design is usually . . . nothing. Building or buying nothing, arguably, is the only really sustainable thing to do. But, obviously, that's not particularly realistic (especially if your living depends on designing things).
How do you define green
Beyond that somewhat academic point, deciding what is greenest hinges on what your definition of "green" is and what your goals are.
With clients who come to me for eco designs, I sometimes ask them why they want to go green and, if they aren't really sure, I say there are three basic reasons to go green ("the three savings"):
- Saving your and your family's health
- Saving money
- Saving the planet
Usually the answer is some combination of all three. In terms of your query (countertops and floors), some of the selection criteria might look like this.
Saving your and your family's health: materials that don't offgas unhealthy fumes; materials that don't harbor pollutants or bacteria, mold, etc. and/or clean easily.
Saving money:materials that wear well; materials that insulate; materials that require low maintenance or can be maintained with nontoxic cleansers and sealants.
Saving the planet: materials that are (rapidly) renewable, that are low in embodied energy, that minimize ecosystem disruption, that are produced locally.
Flooring and countertop materials I like
Some of the choices that I like and have used for green flooring are cork, linoleum, certified or salvaged wood.
And for green countertops: recycled glass and cement composites, and reclaimed or local stone.There are some other great options for counters as well, such as salvaged wood or recycled-content tiles, but they're not my favorites aesthetically. (That's just me.) A lot of people like concrete counters, which can be beautiful; however, there are mixed opinions on concrete's embodied energy and its maintenance.
The last piece I'd mention is: be inventive. Some of the best and greenest projects I've seen have used either salvaged or unexpected materials in unusual, creative ways.
For more information:
Read "Can you recommend affordable green kitchen cabinets, flooring, and countertops?" a Q&A answered by Cynthia Phakos.