A new approach for sustainable utilization of spent grains to develop a profitable process

Technical Session 21: Spent Grains Session
Benjamin Haeffner, TU München - Chair of Process Engineering of Disperse Systems , Weihenstephan
Co-author(s): Jens Voigt and Karl Sommer, TU München, Chair of Process Engineering of Disperse Systems, Weihenstephan, Germany

ABSTRACT: Energy from waste materials of the brewing process is playing a rising role in breweries. Today and in the future, it will become very difficult for the brewing industry to dispose of their waste materials. Due to new regulations and higher standards for waste treatment, producers are being forced to find new methods of cost neutral discharge of their biological waste that also meet regulatory requirements. Brewery wastes with a high content of cellulose, ligno-cellulose, and hemi-cellulose, like spent grains, have a high potential to become a key factor in cost neutral brewery waste discharge if you know how to gain access to this stored energy. Thus, the use of spent grains as an energy source through anaerobic fermentation is a good solution. The key to solving this problem is the combination of two well-known unit operations: milling and fermentation These application areas are focused on at the Chair of Process Engineering of Disperse Systems. A current research project is biogas fermentation in a multi-step solid bed process to optimize the dwell-time, which is supported by AiF (German Federation of Industrial Research Associations). The grinding process is performed with an agitator ball mill. This task is achieved by changing the parameters of the milling process to reach the highest possible energy utilization. Another advantage is an increased area of particles, resulting in a higher degree of bioavailability, which is expected to have a positive effect on the degradation rate and residence time distribution. In the fermentation process a fixed bed reactor containing filling materials is used, increasing the contact surface between substrate and bacteria and leading to a higher fermentation rate. With these improvements the hydraulic retention time of the reactor can be reduced without changing the performance parameters (biogas yield, degree of degradation). With the results from the work packages, we can achieve the best energy efficiency of the overall process.

Benjamin Haeffner was born in 1979. He apprenticed as a specialist in food technology at the Döhler company. He received a diploma engineer (M.S.) degree in food and beverage technology from TU München-Weihenstephan, Germany, in 2006. After that he started his career at the Chair of Process Engineering of Disperse Systems at TU München as a technical engineer in wet/dry grinding and fermentation processes. He is an expert in comminution of organic materials and gives lectures on engineering science fundamentals of apparatus. Since 2011 he has been working as a Ph.D. student at the Chair of Process Engineering of Disperse Systems and has edited his own project (“Biogasfermentation in Multi-step Solid Bed Process as Optimization for Dwell-Time”), which is supported by the German Federation of Industrial Research Associations (AiF) and the Research Group of the German Food Industry (FEI).