Optimized CHP plant

Since last year, Ladenburger has focused on the drying of lumber in Kerkingen. The production site has a capacity of 650,000 m³ a year. In the past, drying was spread across three production sites in the Ostalb district, which resulted in additional internal transport, as lumber and fuel were moved between Bopfingen, Aufhausen and Kerkingen. In the fourth quarter of 2025, Ladenburger also commissioned its pellet mill in Kerkingen, which has an annual capacity of 160,000 t. 

“The goals of our centralized drying project were to have carbon-neutral production with high added value at the site, guarantee in-house supply of heat and electricity, reduce internal transport, and optimize material flows,” Steffen Häußlein, who is responsible for the sawmill and log wood division in Ladenburger’s management, explains.

34-MW boiler

Urbas had already supplied the two existing 4-MW and 10-MW hot water boilers. For the integrated site, Ladenburger planned to invest in a new biomass-powered combined heat and power (CHP) plant as an expansion and replacement. “We have had consistently positive experiences with Urbas – from the service and installation teams to the company’s management. Urbas is one of the market leaders in the construction of biomass-fueled CHP plants. It stands for state-of-the-art boiler technology, reliable service, fast and unbureaucratic support, and is quickly on-site when we need them,” Häußlein sums up the reasons behind the decision to build the new CHP plant together with Urbas.

The new CHP plant has a fuel heat output of 33.6 MW. The steam output is up to 35 t/h. Depending on the operating mode, the turbine output can reach up to 9 MWel. This corresponds to the electricity demand of around 13,000 households. If the production site’s heat demand is higher, output can drop to 7.2 MWel. Ladenburger uses the generated hot water for its own production, i.e. mainly for drying lumber and wood chips. It could also be used for district heating in Kerkingen. The maximum operating pressure is 81 bar, and the safety temperature of the steam boiler is 535°C. The new plant will generate 18.3 MWth of thermal energy.

Farewell to the existing boiler

“This meant that a 34-MW CHP plant and the two existing boilers with a total capacity of 14 MW were available. The latter could be activated when additional heat was needed – bringing the total to 48 MW,” Häußlein says, describing the company’s initial considerations. Ultimately, though, a new, innovative alternative has emerged that makes it possible to replace the existing 10-MW boiler. This requires the energetic optimization of the new 34-MW boiler. A heat pump and an additional flue gas economizer will compensate for the output of the existing boiler and will be integrated by the end of 2026. Urbas will handle the installation of the economizer and support the integration of the heat pump into the boiler’s electrical and control systems. The 4-MW boiler will remain part of the system as backup when the CHP plant is shut down, for example, during maintenance.

Heat pump instead of existing boiler

“In terms of fuel, operation and maintenance, using a heat pump in combination with an additional economizer is more cost-effective. It results in a significantly better overall cost balance than operating three boilers, as originally planned,” Häußlein tells us.

Using motive steam and heat recovery from the cooling circuit, the heat pump can generate up to 10 MW of additional heat. The heat pump is low-maintenance and can be flexibly turned on and off. Ladenburger plans to operate it primarily in winter when heat demand is higher. In summer, the power plant and economizer supply sufficient heat. With this increase in efficiency, the new CHP plant, in combination with the aforementioned optimization measures, will produce all of the heat and energy required.

Effective economizer

At Ladenburger’s request, Urbas will integrate an additional economizer (ECO), taking another step towards improved heat utilization. The ECO reduces the flue gas temperature from 160°C to 100°C. These 60°C remain in the system, and an additional 1.5 MW of usable heat can be extracted from the flue gas. This offers the possibility to utilize as much of the potential residual heat in the flue gas as possible, especially since there are no low-temperature absorption points available for a flue gas condensing system.

The combination of flue gas economizer and heat pump ensures optimal heat utilization at Ladenburger’s power plant.

Green and dry fuel

In addition to bark that accumulates during production (1,200 stere per day), Ladenburger uses wood chips from rejected wood and otherwise unusable by-products and waste from further processing, such as cut-off pieces, as fuel. All sawmill by-products are used for pellet production. Urbas recommends a moisture content of 45% for the fuel. “Our boilers can be operated continuously and in compliance with emission limit values even with inhomogeneous fuel quality and a moisture content up to 60%,” Urbas emphasizes. In the fourth quarter, Ladenburger will commission a 5,000-m² bark storage hall directly next to the CHP plant. Material handling is done using two electric front loaders that Ladenburger purchased last year.