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As NH3 has received extra attention expected to play a key role as an H2 carrier with desirable physical and chemical properties, H2 production via NH3 decomposition becomes a promising way to supply H2 in a cost-competitive and eco-friendly manner. In this study, life cycle techno-economic and carbon footprint analysis is conducted to investigate the feasibility of the NH3 decomposition process in terms of economic performance and CO2 emissions. In particular, the life cycle NH3 supply chain for H2 production is considered including production, transportation, and decomposition back to H2. Based on the classification of NH3 into three different types depending on how the chemical is produced, NH3 price and CO2 emissions are evaluated. In addition, using a commercial process simulator, the decomposition process is modeled and techno-economic analysis for the whole process for H2 production reveals that NH3 price is the most influential economic factor and the H2 production cost can compete with renewable-based H2 but it is still higher than fossil fuel-based H2 production. Moreover, H2 supply via NH3 decomposition is projected based on a domestic implementation plan in the Republic of Korea resulting in estimation of NH3 price, H2 production cost, and corresponding CO2 emissions in the future.

For utilization of valuable raw material of landfill gas (LFG), CH4 and CO2 which are the major chemical constituents in LFG can be reacted to produce H2 by so-called catalytic dry reforming of CH4 (CDR). In this study, the impact of applying a membrane reactor (MR) for CDR is investigated in terms of energy, economic, and environmental aspects (3E). Due to the intrinsic limitation of an MR being able to operate at lower temperature than the temperature of a conventional chemical reactor (packed-bed reactor, PBR), two different process configurations are invented for an MR and a PBR separately using a commercial process simulator. Based on different process configurations, comparative techno-economic analysis is conducted for an MR and a PBR at the same temperature as well as different temperature. It is identified that energy efficiency and productivity of the process are related to the operating temperature which directly affects variation of CH4 and CO2 conversion. However, it turns out that operating at higher temperature is not always better than lower temperature due to the additional CO2 emissions and fuel costs. Especially, it is revealed that an MR will overcome its low operating temperature and accomplishes economic viability compared to a PBR by developing its durability and permeability.

Synthetic natural gas (SNG) production from captured CO2 and H2 produced by water electrolysis using renewable energy is of increasing interest for low-carbon fuel production, CO2 utilization technology, and unstable renewable energy storage. In this study, the effect of voltage degradation in a water electrolyzer, a core technology for SNG production, on the unit production cost of SNG production and CO2 emissions, with different water electrolysis types such as alkaline electrolysis (AEL), proton exchange membrane electrolysis (PEMEL), and solid oxide electrolysis (SOEL), was identified through techno-economic and environmental assessment. In particular, the energy efficiency, unit production cost of SNG, and CO2 emissions were identified based on the change in the power consumption caused by voltage degradation. Moderate voltage loss results in a decrease in energy efficiency from 53.8% to 48.8% in AEL, 55.3% to 47.0% in PEMEL, and 76.3% to 51.2% in SOEL. Moreover, respective SNG unit production costs of 140.3–170.2 USD MWh−1, 157.5–203.1 USD MWh−1, and 153.1–353.5 USD MWh−1 for AEL, PEMEL, and SOEL, respectively, were obtained, showing an increase in SNG production cost due to the voltage degradation. Furthermore, total CO2 emissions for the SNG production process were investigated considering voltage degradation as well as electricity generation sources.