How apparel companies can reduce their environmental impact

With the environment on many consumers’ minds, what’s-new-what’s-next in fashion is no longer quite as fashionable as it used to be. The $2.4 trillion apparel industry accounts for 8% to 10% of the world’s greenhouse gas emissions, more than all international flights and maritime shipping combined, and 20% of the world’s industrial wastewater drains out of the industry, according to the United Nations Alliance for Sustainable Fashion.

Though “fast fashion” often takes the blame, make no mistake, low-cost trendy clothing is not the industry’s only guilty party. Fashion at all price levels drives overconsumption, experts say, and, if business continues as usual, the apparel industry’s climate impact is expected to increase 49% by 2030—almost equal to the current annual United States’ greenhouse gas emissions, according to a Quantis report on the environmental impact of the global fashion industry.

So, what’s to be done? Meet Dr. Linda Greer, a Washington, D.C.-based senior global fellow at the Institute for Public and Environmental Affairs. Greer is an expert in corporate environmental responsibility, with a specialty in textiles and sustainability. From this advocacy perspective, Greer has provided advice on green chemistry (which creates chemicals designed to reduce or eliminate hazardous substances) to companies ranging from Target to Burberry and Stella McCartney. Fortune talked to her about the ways fashion companies can become more sustainable, how consumers can make a difference, and why clothing material is only part of the problem.

The following conversation has been edited and condensed for clarity.

How do you define sustainable fashion?

Sustainable means minimal environmental impact. What impacts are we looking at? The answer starts with energy use, carbon emissions, and water use. This industry operates in places where there’s extreme water scarcity, for example, India. Next, is chemical use and chemical release—that’s water pollution and air pollution. Next, we look at the impact on forestry and biodiversity. The last is how much solid waste it generates. This is an issue because of all the clothing that gets thrown away so it’s taking up landfill space. Driving all of these things is the corrosive effect of fast fashion.

What are some of the challenges non-luxury companies face to make sustainable clothing?

There is no difference between the challenges that non-luxury companies and luxury companies face. They’re all facing the same reality of the impacts of their manufacturing and materials, and this is an important concept for people to understand. For all companies, the way the fabric is manufactured, dyed, and finished appears to be more important than the composition of the fabric.

[The challenges] are sort of like how efficient is the factory’s production practices, are they trying to reduce their impact, do they have efficient manufacturing, do they have new machinery? I have seen a lot of fabric mills all over the world and there’s a huge range in how well they’re operated and how much energy they’re using, how much they’re polluting, and how much impact they’re having.

So how can a company work to become more sustainable?

Bottom line—if there’s a company that doesn’t know the energy and water footprint of their supply chain, they are not a sustainable company. Period. The end. They don’t have the information they need to make better choices. The vast majority of brands still don’t collect that information from their suppliers, let alone use it to make business decisions.

A lot of companies don’t know where their stuff comes from because they have these middlemen who do the purchasing and they call it an ‘opaque supply chain.’ Although luxury tends to know more where their special beautiful fabrics come from, these high-end fashion designers make plenty of cotton T-shirts and often they will not know where the more common materials come from.

In terms of fabric, is shopping for clothing made out of cotton, wool, or silk better for the environment than synthetic materials?

I would call it a small step in the right direction. Rather than just cotton, I would look for organic cotton. If you look for rayon, there is a much better rayon called lyocell. Silk is good, wool is, for the most part, good. For all the synthetics [like] polyester and nylon, I would look for materials that have recycled content.

Materials are only one piece, the rest of it is much more important and more difficult for a consumer to get a handle on because it’s not on a label.

So what can consumers do?

Because none of this information, in terms of how these materials are manufactured, is available for consumers to get, it’s impossible for consumers to shop their way out of this problem. They need to demand their favorite brands put programs in place where they are measuring and reducing their impact and transparently providing information to the public.

We have a large number of apparel companies who have made commitments in reducing their greenhouse emissions, but what we don’t have is a commitment to transparently report to the public how it’s going.

I like to imagine if a CEO of a certain company got 25,000 emails saying I love the stuff in your store but I’m not coming in again until I start to see these assurances, that would really leverage the right type of change in corporate behavior.

Is it possible for mass clothing companies to make sustainable clothing?

Absolutely, yes. Levi’s, Adidas, Nike, Target—these are not luxury companies and they are on the path. They are in the lead on environmental responsibility and sustainability. My dream come true would be to get Amazon on top of this, but they haven’t stepped into this yet as far as I know.

Should consumers try and avoid fast fashion?

The biggest single thing can do is buy less, buy vintage, and buy things that last. The best choice is to do with much less… buy things you really love instead of things you know you’re only going to wear a few times. As people get concerned about climate change, they start to realize consumption is what’s driving this climate change problem. People are starting to put two and two together.