Exergi

The Approach

Stockholm Exergi is retrofitting KVV8, a combined heat and power plant in central Stockholm, with carbon capture. The plant burns woody residues from forestry and sawmills, such as treetops, branches and sawdust, to heat homes and generate electricity for about 800,000 residents, and its flue gas is about 18–19% CO2. The capture unit uses hot potassium carbonate: under high pressure the CO2 binds to potassium carbonate to form potassium bicarbonate, heating releases the CO2 again, and condensing out the water vapor leaves a pure CO2 stream. The captured CO2 is shipped to permanent storage deep underground.

The Case for Exergi

Near-term tons at scale, with a path below $100 per ton. Once operating in 2028, the facility can capture up to 800,000 tons of CO2 a year. Lower capital and transport costs as the industry scales are expected to bring the price below $100 per ton.

An experienced operator. Exergi has supplied Stockholm's heat and power for more than 150 years and has built large industrial processes before.

Residue biomass, and no extra feedstock. The plant burns waste and residues that would otherwise decay and release their carbon. The retrofit produces more energy than it uses, so it needs no additional biomass, and meeting Frontier's Biomass Sourcing Principles is a contract condition.

A modern plant with demonstrated capture. KVV8 is relatively new, recovers heat efficiently and is expected to run for decades. The hot potassium carbonate system has demonstrated 90% capture efficiency.

Strong regulation and local support. The project operates under Swedish and EU environmental and biomass rules, and the local community was involved in its design.

Pricing and Delivery

Frontier buyers contracted $48.6 million for 179,998 tons in a 2024 offtake, for delivery from 2028 to 2030. The final volume and price depend on a Swedish government reverse auction, and Frontier will publish them once it is finalized.