It is relatively easy to imagine a fully sustainable product, one that has no negative impact on the environment or the social condition. So why does no fully sustainable product exist yet? The answer lies in the most crucial aspect of innovation that people usually forget: people.

Innovation is not an activity that happens in the absence of human beings. It's created by human beings, and more importantly, for human beings. And it is the human element that we most often forget. In order for an innovation to truly be innovative, people must use it. A lot of people. Nothing is more frustrating than to hear a product being called innovative that only a few privileged people can use. That's not innovation, that's obscurity. Technology or creativity are not the most important components of innovation, adoption is.

Consider two ideas that have been brought to market in the world of cleaning products and what they teach us about how innovation creates change. The first idea is the refill station. This is currently being tested at Asda stores in the U.K., and has been attempted at a number of times over the last decade at natural grocers in the States. The idea is simple: After you've used up your cleaner, you bring in the empty trigger sprayer bottle, scan the barcode and, like the push-button coffee machine that fills your cup with the cappuccino or latte you ordered, it refills your existing bottle with the same cleaner you bought before. You get a refill without buying another bottle or trigger, or having to ship a bunch of water around. Seems like a no-brainer.

Another idea is the concentrated "fill yourself" model. Here you are sold an empty bottle with an additional small bottle of concentrate that you pour in, add water, and shake up to make a full bottle of cleaner.

Neither the fill yourself or refill station models have yet to reach beyond a tiny market niche. The reason they haven't worked is not because they weren't cool or green. In fact, they're both. These ideas haven't worked because they weren't designed with adoption in mind.

How many times have you forgotten your reusable shopping bags when you make a trip to the store? Now imagine having to remember to throw your empty bottle of bathroom cleaner in the back of the car too. And say you just got to the store and remembered you're out of cleaner. What are you going to do? Filling your own cleaning product at home seems like a good idea until you realize its work and it makes you doubt whether the product will be effective. These ideas haven't worked because, while interesting, they make it harder, not easier, to do the sustainable thing. In a category like cleaning that people try to think about as little as possible, this is the kiss of death.

The best innovations are self-educating. Their designs make it obvious that the behavior change required will make life better. Method has had tremendous success with its line of refill pouches because the benefit of the product, and how to use it simultaneously, is clear to consumers.

The important thing about this refill pouch product is not so much its sustainability benefits. While it creates an admirable 80 percent reduction in plastic use, one could point out that a refill station does this and also saves on the transport of water.

The important thing is that we have gotten a large group of people off of the habit of buying a new bottle and trigger every time they run out of cleaner. That change of habit allows us to innovate again. Maybe it will allow us to develop a concentrate or refill-at-shelf format that is incrementally more sustainable and adoptable. When we do, we will focus our efforts on solving the convenience issues so that the format is not asking for more effort from the consumer, but rather, making it easier and more delightful to use.

The fascinating part about this phenomenon of serial innovation is that it includes and is dependent on people — and it is exactly these small, intermediary steps that become the steady march toward a more sustainable future. The pundits and dilettantes will stand on the sidelines and critique the market, saying that we need more demonstrably sustainable products and we need people to realize they must use them. But they miss the point. Until someone wants to use something, really wants to, change cannot be created.

For the designer, it means adoption must be built into the product brief. It also means that the designer must get comfortable with the fundamental paradox of sustainable product design: The fastest path to a sustainable endpoint is a less sustainable midpoint.

This article originally appeared on The Huffington Post and is reprinted with permission.