Reductions in greenhouse gas emissions are necessary to slow global warming and decrease the likelihood of irreversible climate scenarios. There is thus an urgent need for low‐emissions fuels. This study conducted a techno‐economic analysis of two different industrial plant concepts for producing hydrogen from woody biomass. One was a large‐scale centralized 60 MW_H2 option using dual fluidized bed gasification with CO₂ removal. The other was a small‐scale decentralized 1 MW_H2 option using fixed‐bed gasification without CO₂ removal. Mass and energy balances were calculated by the process simulation software IPSEpro. Key performance indicators, including technical, economic, and environmental parameters, were derived. Overall energy efficiencies of 64.2 and 59.5% and hydrogen yields of 87 and 68 g_H2 kg⁻¹_BM.db were determined for hydrogen production by dual fluidized bed and fixed‐bed gasification, respectively. The levelized costs of hydrogen amounted to 5.6 and 15.0 €₂₀₂₂ kg⁻¹_H2 and agreed quite well with values from the literature. Flexible and decentralized heat, electricity, and hydrogen production based on fixed‐bed gasification within a multiproduct plant were also evaluated. The results show that the multiproduct plant could be economically feasible if at least 63% of the annual operating hours were dedicated to hydrogen production, and assuming a hydrogen selling price of 17.5 €₂₀₂₂ kg⁻¹_H2 in Austria. In conclusion, both of the processes that were evaluated are conceivable technologies for the transition of the energy system towards renewable energy sources from a technical and economic point of view, although small‐scale hydrogen production is considerably more expensive.

In many industrial processes, the climate-damaging gas CO₂is produced as undesired by-product. The dual fluidized bed biomass gasification technology offers the opportunity to tackle this problem by using the produced CO₂within the process as gasification agent. Therefore, a 100 kW_thpilot plant at TU Wien was used to investigate the use of CO₂as gasification agent by converting softwood as fuel and olivine as bed material into high-valuable product gas. A parameter variation was conducted, where the typically used gasification agent steam was substituted stepwise by CO₂. Thereby, the amount of CO and CO₂increased and the content of H₂decreased in the product gas. These trends resulted in a declining H₂/CO ratio and a decreasing lower heating value when CO₂was increased as gasification agent. In contrast to these declining trends, the carbon utilization efficiency showed an increasing course. As second part of this work, a temperature variation from 740 to 840 °C was conducted to investigate the change of the main product gas components. With increasing temperature, CO and H₂increased and CO₂decreased. To determine the degree of conversion of CO₂in the DFB reactor system, two approaches were selected: (1) a carbon balance and (2) a hydrogen balance. This way, it was found out that a certain amount of CO₂was indeed converted at the investigated process conditions. Furthermore, under certain assumptions, the reverse water-gas shift reaction was identified to be the predominant reaction during CO₂gasification.

The present paper focuses on the production of a below zero emission reducing gas for use in raw iron production. The biomass-based concept of sorption-enhanced reforming combined with oxyfuel combustion constitutes an additional opportunity for selective separation of CO₂. First experimental results from the test plant at TU Wien (100 kW) have been implemented. Based on these results, it could be demonstrated that the biomass-based product gas fulfills all requirements for the use in direct reduction plants and a concept for the commercial-scale use was developed. Additionally, the profitability of the below zero emission reducing gas concept within a techno-economic assessment is investigated. The results of the techno-economic assessment show that the production of biomass-based reducing gas can compete with the conventional natural gas route, if the required oxygen is delivered by an existing air separation unit and the utilization of the separated CO₂ is possible. The production costs of the biomass-based reducing gas are in the range of natural gas-based reducing gas and twice as high as the production of fossil coke in a coke oven plant. The CO₂ footprint of a direct reduction plant fed with biomass-based reducing gas is more than 80% lower compared with the conventional blast furnace route and could be even more if carbon capture and utilization is applied. Therefore, the biomass-based production of reducing gas could definitely make a reasonable contribution to a reduction of fossil CO₂ emissions within the iron and steel sector in Austria.