ETS Mechanics

The EU Emissions Trading System is the world's largest carbon market. It covers roughly 40% of EU greenhouse gas emissions and generated nearly EUR 39 billion in revenue in 2022. Understanding its mechanics is a prerequisite for evaluating every other cap-and-trade system on earth, because most are modeled on it.

An ETS distributes a fixed number of emission allowances (each permitting one ton of CO2). The total cap declines annually. Emitters must surrender allowances equal to their verified emissions each year. Those who emit less can sell surplus allowances; those who emit more must buy. The trading produces a carbon price that fluctuates with supply and demand.

The EU ETS has evolved through four phases since 2005, each fixing design failures from the previous one. Phase 1 (2005-2007) gave away too many free allowances, crashing the price to near zero. Phase 3 (2013-2020) introduced auctioning and a Market Stability Reserve (MSR) that absorbs surplus allowances when the market is oversupplied.

The MSR in action. After the 2008 recession, a surplus of roughly 2 billion allowances accumulated. Prices fell below 5 euros/ton.

If the cap is fixed, why didn't prices recover when the economy recovered?

Banked surplus. Firms had banked allowances from recession years, creating a persistent overhang. The MSR, introduced in 2019, withdraws allowances from circulation when the surplus exceeds a threshold, artificially tightening supply. By 2023, the MSR had withdrawn over 2.5 billion allowances and prices exceeded 80 euros/ton.

The MSR illustrates a broader design lesson: quantity-based instruments require active supply management, or market dynamics undermine the price signal.

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