LK2BM: Upgraded lime kilns for cleaner industrial processes

Lime kilns play an essential role in pulp and paper production. They regenerate chemicals used in the Kraft pulp process that converts wood into cellulose fibers, which comprise the bulk of the raw material for paper and cardboard. Kilns operate at very high temperatures and often rely on fossil fuels such as natural gas for power. The LK2BM project plans on changing this by introducing a new way to run an existing lime kiln that uses residual biomass instead of fossil fuels. The LK2BM kiln uses process fines from wood-chipping and locally sourced eucalyptus sawdust, thus converting residue into a primary energy source and eliminating reliance on fossil fuels. 

The project is led by The Navigator Company, an international Portuguese industrial group managing integrated forest and pulp value chains. LK2BM marks the first successful implementation of transforming an existing lime kiln to run mainly on sustainable hardwood biomass in Europe.

Repurposed energy 

Rather than building entirely new infrastructure, the project focused on adapting conventional kilns to operate with alternative combustion feedstock.  Using mainly waste from forestry and wood processing instead of natural gas, its simply replacing fossil fuels with renewable energy.

The heart of its innovation is a newly engineered, multi-fuel biomass burner capable of sustaining the required flame stability and temperature for powering a lime kiln. The burner is complemented by a fuel preparation system designed to manage the natural variability of biomass residues. 

Thanks to the learning of the LK2BM project, the Navigator Company has extended this approach to other sites in Portugal. At the Figueira da Foz pulp mill, a new lime kiln is designed to run mainly on biomass, using natural gas only during start-up. At the Aveiro mill, an existing kiln is being converted to operate with biomass burners using sawdust and pellets, primarily sourced from the company’s own production. Together, these developments are expected to reduce emissions by up to 29,000 tonnes of CO₂ per year.

Challenges and breakthroughs 

A large obstacle that was overcome was ensuring a steady fuel supply to the kiln, given that hardwood powder behaves less predictably than natural gas. Engineers, operators and maintenance experts worked closely together to adjust the system and ensure reliable operation.

As the project involved a first-of-its-kind retrofit, it carried technical and financial risks that had been mitigated thanks to the €4.5 million grant from the Innovation Fund, sourced by EU Emission Trading System revenues. CINEA also provided structured monitoring and technical follow-up in addition to boosting the project’s visibility across Europe. 

The coordinated efforts culminated in the biomass-fuelled lime kiln reaching operational readiness on 30 September 2025. By the end of October, the project had achieved more than 24 hours of continuous operation using over 75% biomass, demonstrating that the upgraded system can run safely and reliably with the new fuel.

Multifaceted impacts 

By replacing natural gas in lime kilns, LK2BM is expected to substantially cut greenhouse gas emissions preventing the release of about 14,292 tonnes of CO₂ annually. This reduction is equivalent to removing approximately 10,000 passenger cars from European roads each year, based on average emission factors reported by the European Environment Agency¹. Over ten years, the project could avoid emitting more than 142, 000 tonnes of CO₂, delivering significant environmental gains.

What lies ahead

As the projects moves on, the focus will be on consolidating the retrofit kiln performance. The team will monitor hardwood biomass fuel behaviour and consistently refine operating parameters to ensure stability over long periods of time.

With Innovation Fund support, LK2BM will embark on a three-year reporting phase, during which annual carbon emission avoidance will be recorded to validate the technical solution and its green benefits.

The experience gained is expected to support the deployment of similar solutions in other lime kilns operated by The Navigator Company and across the wider pulp and paper sector in Europe. By demonstrating that existing kilns can be successfully converted to run on renewable biomass, the project also opens the door for replication in other energy-intensive industries that rely on high-temperature processes, such as the lime and cement sectors. 

Learn more about the Innovation Fund. 

_{1 Average CO2 emissions from new cars and new vans slightly increased in 2024 | Press releases | European Environment Agency (EEA)}

Article published on 30 March 2026