Measuring annual emissions of power plants can lead to errors, study says

By only measuring the annual emissions of power plants, policymakers may be underestimating the damage they are causing to the environment. 

According to a recent study, traditionally policymakers have used the annual average emission intensity, across all power plants to estimate the emissions avoided by any intervention.

Emission intensity is the emission rate of a given pollutant relative to the intensity of a specific activity, or industrial process.

According to the study, by measuring the emissions annually it misses the fact that many interventions only affect a certain set of power plants.

Scientists at Stanford’s School of Earth, Energy & Environmental Sciences suggest that instead emissions should be measured by using marginal emissions, that are collected on an hourly basis.

The researchers tested the difference between measurements of average and marginal emissions by analysing emissions from PJM, the largest electricity market in the U.S.

PJM generates enough energy to power a fifth of the U.S and contributes around 20% of U.S. power sector emissions.

The researchers found that by only measuring the average annual emissions it can lead to errors when estimating the emissions that have been avoided by interventions, as well as the associated health, environmental and climate change damages.

They found that when only measuring the average emission intensities the damages avoided by the intervention were underestimated by almost 50%.

The report says that only using average values may cause a policymaker to think an intervention is only half as effective as it really is which as a result might compromise its implementation despite the benefits.

Priya Donti, a PhD student at Carnegie Mellon University and study co-author said: ‘The electric grid is changing rapidly, but annual emissions intensity data is often released with a large lag.’

‘Our study demonstrates the importance of frequently updating the data.’

‘These kinds of tools can help decision-makers to understand the impacts of different policy and investment options.’

‘We want to help them design interventions that provide the biggest benefits when it comes to tackling climate change and improving human health.’

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