Ads Often Run on Websites That Come With High Carbon Emissions but Low Returns, Study Finds

The study examined 116 billion digital display ad impressions valued at $375 million from 43 advertisers in 11 global markets in 2021 and 2022, and estimated the energy it takes to deliver an ad impression by looking at factors such as auctions and emissions from the end-user’s device.

The companies’ goal was to give brands a better sense of how much of an impact they are having on the environment with their digital advertising and to suggest ways to reallocate ad budgets to web publishers with lower carbon footprints, they said. 

Concerns have been growing in some corners of digital advertising about the industry’s carbon footprint. The business consumes a significant amount of energy, leading to carbon emissions, as many websites trigger automated auctions for various ad spaces every time a consumer arrives on one of their pages. Sites often involve ad-tech intermediaries that offer services such as matching marketers with particular target audiences.

It is difficult to calculate just how much electricity online advertising consumes, but a study published in 2018 estimated that 10% of the energy usage of the internet results from online ads.

Industry players have begun exploring ways by which the business could consume less power. Ebiquity and Scope3 say one way of cutting down on emissions would be to work to keep marketers’ ads from winding up on “made for advertising” sites. The consumer experience on these sites is poor, as is the effectiveness of advertising on them, Ebiquity said in a July report. 

“In most cases, either the content is ripped or pirated from genuine sites, or it’s A.I.-generated and it’s just terrible,” said

Ruben Schreurs,

chief product officer at Ebiquity.

The average grams of carbon dioxide and equivalent greenhouse gas emissions per 1,000 impressions for ads was 52% lower on certain news websites—those deemed “trusted” by the Global Disinformation Index, a nonprofit organization that rates news organizations based on the probability that they will publish demonstrably false information—than the made-for-advertising sites, because they are running more auctions and contain more tracking technologies, Mr. Schreurs said. 

The companies said they recommend reallocating investment to high-quality journalism. 

Brian O’Kelley,

an ad-tech veteran who co-founded Scope3 and is its chief executive, said the company is developing benchmarks for brands to help determine where their online-ad emissions sit and how their performance could be improved. 

“This allows brands to cut high-carbon, made-for-advertising sites from their campaigns and influence legitimate publishers with high carbon footprints to clean up their supply chain,” Mr. O’Kelley said.

Publishers can also use that kind of information to reduce the complexity of their supply chains as advertisers try to use more low-carbon publishers in their media planning and buying, he said. 

Ron Amram, senior director of global media at Mars Inc., one of the participants in the study, said the candy and pet-food maker is working with its agencies and partners to identify how much waste or greenhouse gas is created by its digital advertising before creating the tools and capabilities that can help buy and plan advertising in a more environmentally friendly way. 

“You have to understand where the waste is, where the issues are,” Mr. Amram said. “The only way you can do that is to do a broad assessment and sharing that information with experts to create a formal point of view, and that’s the stage we’re at now.” 

Mikko Kotila, one of the researchers for the 2018 study, said evidence that significant amounts of spending are going to wasteful sites that are emitting high amounts of carbon should be meaningful for advertisers. 

“If this is not going to be sufficient for advertisers to become serious about reducing waste, then it is hard to see what will,” he said.

Other groups are working on different approaches to measuring carbon emissions in advertising. Mr. Kotila was formerly a chief technology officer at Cavai, a Norwegian advertising technology company that aims to tell advertisers how much energy it takes to deliver and render each ad. 

But Mr. Kotila and his fellow researcher Tommy Torjesen, founder and chief product officer of Cavai, said marketers should be wary as they wade through the claims of companies offering solutions to carbon emissions in advertising. 

“Everybody has a solution. So there’s a lot of good marketing talk. But if you dig deep into the different claims,” many aren’t legitimate, Mr. Torjesen said. 

Write to Megan Graham at megan.graham@wsj.com