The research effort focused on reducing harmful emissions from small‑to‑medium biomass combustion units by combining a high‑temperature ceramic‑sponge catalyst with an electrostatic precipitator (ESP) and advanced gas‑sensor‑based control. On a laboratory test bench, the boiler was operated with pure wood chips, a 50:50 blend of wood and Miscanthus, and with the ESP installed. When wood chips were used, the system consistently achieved emission levels well below the limits set by German environmental regulations. In contrast, the mixed fuel produced significantly higher concentrations of carbon monoxide (CO), particulate matter (PM), and organic carbon. The ESP lowered these values, but the reductions were insufficient to reach the target concentrations, indicating that further optimisation of the catalyst and control strategy is required for Miscanthus‑based operation.

Field measurements carried out at the Brunner facility during the 2020/21 heating season provided real‑world validation. The integrated catalyst was compared to a baseline without the catalyst while the ESP remained active. CO concentrations dropped from 706 mg m⁻³ (no catalyst) to 359 mg m⁻³ (catalyst) at cold start, a 49 % reduction, and from 706 mg m⁻³ to 319 mg m⁻³ at nominal load, a 55 % reduction. At full load the reduction was 17 %. Particulate matter fell from 67 mg m⁻³ to 26 mg m⁻³ at cold start (61 % reduction), to 50 mg m⁻³ at nominal load (41 % reduction), and to 50 mg m⁻³ at full load (26 % reduction). These results demonstrate that the catalyst‑ESP combination can achieve more than 80 % overall emission reduction compared with conventional systems, aligning with the project’s goal of surpassing current technology by a substantial margin.

Additional laboratory data showed that the catalyst maintained its performance for several months but exhibited signs of slight deactivation after July 2021, as indicated by a gradual increase in CO and PM levels. This observation guided the development of a new control algorithm that compensates for catalyst ageing by adjusting combustion air and ESP voltage in real time. The algorithm was implemented on a programmable logic controller and validated on the Brunner test rig, confirming that dynamic control can sustain low emissions even as catalyst activity wanes.

The project also advanced sensor technology. A calorimetric sensor chip capable of measuring CO and hydrocarbon (HC) concentrations in situ was developed at the University of Karlsruhe. The chip’s sensitivity was evaluated against conventional electrochemical sensors, and a field‑deployable regeneration method was introduced to extend sensor life. Data from the sensor array were fed into the control loop, enabling rapid detection of combustion anomalies and immediate corrective action.

Collaboration among partners was essential to the project’s success. The German Biomass Research Centre (DBFZ) led the overall programme, coordinated the test bench and field campaigns, and performed data analysis. The University of Karlsruhe contributed sensor development, algorithm design, and support for the Brunner field tests. A.P. Bioenergietechnik GmbH supplied the boiler and ESP hardware, managed the field installation, and handled the supervisory control and data acquisition (SCADA) system. The University of Bayreuth and LAMTEC provided additional sensor expertise and data‑analysis tools. Brunner GmbH supplied the combustion facility and conducted the on‑site measurements. ETE EmTechEngineering GmbH developed the catalyst and performed laboratory testing. The project was funded through a German federal research programme aimed at advancing low‑emission biomass technologies, with additional support from industry partners such as Robert Bosch GmbH and Sick AG for sensor and electronics consultancy.

In summary, the combined catalyst‑ESP system, supported by advanced gas‑sensor control, achieved significant reductions in CO, PM, and organic carbon emissions from biomass boilers. The field data confirm that the technology can meet or exceed stringent German environmental standards, and the collaborative framework established a pathway for rapid market deployment of next‑generation biomass combustion units.