Valorization of waste agricultural residues from north-western Germany - A pathway to biofuels and long-term carbon storage within the UNLOC concept

Kurzfassung

The UNLOC (UNlocking the LOst Carbon potential of agroindustry) concept attempts to compare different process chains for the valorization of underexplored agricultural residues. Maize is the 2nd most relevant crop in Germany in area of production, with substantial production in the northwestern regions in geographic proximity to important export routes. Corn stover, a waste byproduct, offers noteworthy potential for resource recovery, and is understudied in comparison to wheat straw, Miscanthus grass and woody residues. Given the EU’s reliance on energy imports, biofuels and other bio-based commodities fromagricultural residues are gaining traction. Fast pyrolysis yields gas, liquid, and solid products. While the gas can be utilized for process heat and power, the liquid needs further processing for fuel production,targeting air and marine transportation. Notably, the solid product, bio-char, presents marked potential for long-term carbon storage within the BECCUS framework. To enhance process efficiency, autothermal pyrolysis can be considered, allowing for gas valorization through fermentation to ethanol and acetate. Moreover, bio-char can be transformed into activated carbon for enhanced carbon capture. This constitutes a preliminary study of process chain alternatives for corn stover valorization, aiming to produce biofuel precursors, gas fermentation products, and carbon-negative bio-char.