The Carbon Cost of Wasted Impressions
December19, the Conscious Advertising Network and IAB
Digital advertising has always been measured in impressions.
But behind every impression is a hidden cost - in carbon emissions as well as pounds and pence. Every wasted impression adds to the environmental footprint of our industry without delivering any value to brands or society.
In an age where sustainability is no longer optional, advertisers need to see waste as both inefficiency and environmental liability.
The Conscious Advertising Network's Sustainability Guide calls on the industry to prioritise low-carbon media, avoid waste, and actively support quality climate content. At December19, our IAB Gold Standard certification required us to turn those ambitions into documented practices—from the tools we use to the policies we adopt.
Why Sustainability in Media Matters
The digital ad ecosystem is vast, complex, and energy hungry.
Servers process trillions of bid requests every day; ad exchanges match impressions in milliseconds; creative assets are served and tracked endlessly. Every step consumes energy.
When those impressions are legitimate, reaching real people in quality environments, that energy has purpose. But when impressions are wasted - through fraud, poor targeting, or intrusive formats - the carbon cost remains while the value evaporates.
The numbers are stark:
· A study by Scope3 found that illegitimate websites generate 52% more emissions per impression compared to trusted publishers.
· According to the Energy and Climate Intelligence Unit, The UK's Net Zero economy grew by 10% in 2024, and advertising has a role to play in supporting that growth, not undermining it.
· Consumer expectations are clear: 92% of people trust eco-friendly brands more, and 81% prefer sustainable advertising approaches.
Sustainability is a business necessity as well as a regulatory issue and moral responsibility. Brands that fail to act risk not only higher costs but also reputational damage with increasingly eco-conscious consumers.
Nafissa Norris, Head of Membership & Engagement, Conscious Advertising Network, explains: "The carbon cost of wasted impressions is a pressing challenge for our industry. CAN's Sustainability Guide gives advertisers a clear, practical path to cut emissions by cutting waste. December19’s commitment (proving their approach through certification) shows how principles backed by action can make advertising both more responsible and more effective."
What December19 Has Done in Practice
Our journey to IAB Gold Standard certification gave us the opportunity to codify our sustainability efforts:
RefSettings adoption: We implemented this IAB Tech Lab feature to ensure programmatic delivery aligns with low-energy requirements, reducing the carbon impact of campaigns at scale.
Creative standards: We updated our creative and brand safety policies to align with the Coalition for Better Ads. This ensures we avoid intrusive formats that frustrate users, increase bounce rates, and consume more energy.
Training & advocacy: We ran internal sessions to educate teams on sustainability standards, ensuring media planners understand both the financial and carbon costs of waste.
Case study success: Our work with Biffa on the "What Iff?" campaign showed the tangible benefits. By reducing wasted impressions and focusing on sustainable media choices, the campaign cut emissions by 63%, increased Attention Per Mille (APM) by 404%, and delivered stronger engagement metrics across the board.
David Lucy, Managing Director, December19, reflects on this approach: "Sustainability is built into how we plan and buy media. The Biffa campaign proved that sustainable choices don't compromise performance—they enhance it. Gold Standard certification formalised our approach, but sustainability is now an instinct in how we deliver value for clients."
How Principles and Certification Reinforce Each Other
The CAN Sustainability Guide and Guiding Principles set out the "why"; the IAB Gold Standard provides the "how." Together they create a framework for both ambition and accountability.
Step 1 (Fundamentals): Update internal policies and risk registers to include sustainability.
Step 2A (Conscious Creative): Challenge briefs to avoid high-emission creative formats; prioritise inclusive, accessible storytelling.
Step 2B (Conscious Media): Invest in low-carbon inventory, ensure inclusion lists favour sustainable publishers, and reduce reliance on MFA (Made-for-Advertising) sites.
Step 3 (Guide): Embed the CAN Sustainability Guide in partner and client briefs.
Step 4 (Conscious Questions): Ask: "What's the carbon footprint of my campaign?" and "Are we investing in climate-positive environments?"
Patrick Hann, Ad Tech Manager, IAB UK, highlights the synergy: "Sustainability is one of the most important frontiers for advertising. Tools like RefSettings give agencies the mechanics to reduce waste,. December19's Gold Standard certification demonstrates how practical actions and guiding principles combine to create measurable impact."
What To Do Next
Here are practical steps to take:
· Audit your supply chain: Remove wasteful intermediaries and sites that add carbon without adding value.
· Use inclusion lists strategically: Prioritise trusted publishers, especially those producing quality climate and sustainability journalism.
· Interrogate formats: Ask whether your creative approach is attention-efficient and energy-conscious.
· Measure impact: Work with partners who can report on campaign emissions as well as performance metrics.
· Train your teams: Make sustainability literacy a core competency in planning and buying.
Closing Thought
The carbon cost of wasted impressions is too high to ignore.
By aligning CAN's Sustainability Guide with IAB Gold Standard certification, advertisers can take practical steps to reduce emissions, cut waste, and build stronger, more trusted brands.
Conscious, sustainable media buying delivers a competitive advantage, not a trade-off.