Working with supply path optimization is one way to reduce the emissions of an impression through improved efficiency. Each additional ad-tech partner comes with a carbon cost; making sure you work with the right partners, and that they add value, will optimize emissions per impression.
However, optimizing for the lowest CO2e per impression in isolation can have strange outcomes too, like advertising in the middle of the night when energy demand is lower, removing high-performing but energy-heavy channels like linear TV, or favoring extremely compressed creative that can barely be seen. And don’t forget—this is largely based on estimates today, so partners will look more similar in terms of their carbon emissions than they really are.
Emissions per dollar
This metric is based on total emissions for a specific campaign budget. Dividing the campaign emissions with the budget in dollars creates a “comparable” KPI—emissions per dollar. It’s a companion to total emissions because, in the advertising industry, there is little incentive to stop a campaign before a given budget is fully spent, even if campaign goals are hit early. So assuming all budget is spent, reducing this metric will reduce total emissions.
The most effective way to optimize for this metric would be to never negotiate rates. This would keep CPMs high, which would limit the number of total impressions per budget, which is obviously unlikely. Comparing the emissions per dollar across channels or partners will make any cost-efficient solution look bad because it’s affordable to run a lot of impressions, with no consideration if money, or emissions, were well-spent or not.
Emissions per dollar is a way to splice total emissions, but it’s not best to optimize for unless the spend is actually connected to value-creating outcomes. Inflation happens and budgets go up, so emissions can increase without being easily detected if the rate of budget increase is higher than the rate of emissions increase.
Carbon cost per outcome
Not all impressions are the same. And not every dollar spent provides the same value. Outcomes can be the great equalizer.
A third measurement that ensures a win-win for sustainability and performance and prioritizes quality over quantity, carbon cost of business outcomes may be less straightforward to measure but should be every advertiser’s ultimate goal. A specific outcome could be ROI, ROAS, attention or brand lift; an easier-to-measure proxy could be used during a campaign, with richer measurement happening afterward to drive future optimization and spend. One channel might deliver the highest ROI but also high emissions, and another lowest emissions but low ROI. Dividing emissions by ROI provides a comparable KPI bringing these two goals together.
An advertiser should use this insight to improve ongoing measurement so that media buyers and partners can optimize for emissions reduction and real campaign performance rather than relying on the flawed optimization metrics described above.
