China's national carbon market has reached a sizable covered volume, but what keeps refiners awake is the next step: widening the scope. Power ran first, steel, cement and aluminum followed, and petrochemicals were named as the obvious next candidate — the sector's emission intensity leaves no way around it.

The mechanism is straightforward: allowances are allocated against a benchmark, and anything above that is bought on the market. The carbon price now hovers around 90 yuan per tonne, modest on its face, but multiplied by a refiner's emission intensity it becomes real money. A ten-million-tonne refinery could see carbon spend in the tens of millions of yuan per year.

For SNSUC's seven arbitrage grades the effect shows up at the delivered end. Grades like ESPO, Dubai and Oman, if processed at domestic refiners, carry carbon cost into the duty-paid price; if they move as pure transshipment without local processing, the relevant constraint is the counterparty's home carbon regime. The tax gap between the two paths turns into a hard spread in the quote.

Short term it is a cost line; long term it is a ranking game. Capacity with low carbon cost holds a structural edge in export bids. This is the domestic mirror of CBAM — one guards what comes in, the other guards your own.