Wood dust burner instead of heating oil-fired

Wood dust as an energy source

Previously, the asphalt mixing plant in Aichach used about 600,000 l of heating oil to produce its annual output of around 60,000 l of asphalt. This resulted in emissions of 1,800 t of CO₂ – a figure that Christian Schweiger no longer found acceptable. Looking abroad to Germany’s EU neighbors gave him the idea to use wood dust instead of heating oil as the energy source. In Scandinavia, this alternative fuel is already in widespread use, although not yet available on the German market.

Shoulder to shoulder with a strong partner

Looking for a partner for this project, Schweiger talked to Benninghoven at the bauma 2019 trade show, where his idea was very well-received. Schweiger and Benninghoven have worked together for a number of years now and have completed several Retrofit projects together. Christian Schweiger: “Our teams have got to know each other well over the years: there’s a lot of mutual respect here, and it was clear that we wanted Benninghoven as our partner here.”

As the global market leader for multi-fuel burners, Benninghoven has identified wood dust’s potential as a future fuel and likewise the chance to expand its own burner technology portfolio. A specialist company was brought on board to supply the preprocessing system needed to produce wood dust of the required quality. And with that, the burner project was good to go.

Regulatory requirements

The undertaking was designed as a research and development project from the outset.As a first step, Schweiger set to work on obtaining the government grants, fire safety appraisals, and noise/emissions reports – a time-consuming approvals process due to a lack of experience on the part of regulators.

Legislation from local government included a number of requirements, such as ensuring continuous emissions measurement and restrictions on burner capacity. Taking into account overall plant output, Benninghoven installed a power limiter that would reduce burner performance to 12 MW/h. If the plant was then expanded, the burner still had enough reserve capacity to scale performance to match – an aspect that Schweiger had noted as being especially important.

TA-Luft passed with flying colors

In terms of compliance, the most important regulation was the new TA-Luft, which became law in 2021. Yet just 4 weeks after burner installation, the design engineering team from Benninghoven had got emissions figures to a level 50% below the TA-Luft requirements, with continuous measurement. Follow-up checks from a TÜV appraiser team confirmed these values in full, making Benninghoven the only manufacturer capable of achieving – and guaranteeing – compliance with limit values for a wood dust burner plant.

For Schweiger, the new investment is already paying its way – quite literally, as the carbon tax on fossil fuels has risen significantly. “At the start of the project, we assumed that sustainability will be an important topic for the future. But the fact that switching to wood dust has already cut our costs by around 20% was definitely a pleasant surprise.”

EVO JET: the centerpiece

By extending the EVO JET multi-fuel burner to include wood dust as an energy source, Benninghoven has made it possible to utilize this sustainable fuel for use by its burners in asphalt mixing plants. Wood pellets, chippings or wood dust are the starting raw material, which must be ground to a predefined particle size so as to ensure efficient heating in the burner. A supply fan and dosing unit are then used for high-precision feeding of the wood dust into the burner.

Leading the way in asphalt production

News of this innovative project naturally spread quickly through the industry. Leading asphalt makers visited Aichach to take a closer look at the new burner in action.Nor is Schweiger trying to keep it a secret: “On the contrary – we want to share our results with the industry. Everyone’s looking for ways to cut carbon emissions and this shows how easy it can be.”

Grand opening at Schweiger

The wood dust burner was officially brought online on September 15 2023. Guests from local government and businesses were invited, as were members of the press. For Schweiger, this informal inauguration ceremony also offered a good opportunity to turn the spotlight once more onto sustainability. “The real question is about asphalt procurement: Do I buy from a producer with large carbon emissions going forward or with almost zero – as with us?"

Retrofit pays its way

The plan was successfully implemented, the plant is running smoothly, and its emissions are well below the limit values from TA-Luft with continuous operation and emissions measurement. All of this is a good argument for Benninghoven to offer the EVO JET multi-fuel burner with both wood dust and other energy sources as a Retrofit solution. Changing out a burner takes no more than a week to complete. Thanks to the economic and ecological optimizations achieved, operators of older asphalt mixing plants can now take a major step forward to securing their future – and future competitiveness – as a business. “Using wood as a fuel is obviously only an interim solution,” Schweiger explains, “but I do get the impression that, here in Germany, we tend to approach technical issues as perfectionists rather than just taking the better option, though it might not be perfect.”