Assessing Uncertainties of Life-Cycle CO2 Emissions Using Hydrogen Energy for Power Generation

Abstract

Hydrogen and its energy carriers, such as liquid hydrogen (LH2), methylcyclohexane (MCH), and ammonia (NH3), are essential components of low-carbon energy systems. To utilize hydrogen energy, the complete environmental merits of its supply chain should be evaluated. To understand the expected environmental benefit under the uncertainty of hydrogen technology development, we conducted life-cycle inventory analysis and calculated CO2 emissions and their uncertainties attributed to the entire supply chain of hydrogen and NH3 power generation (co-firing and mono-firing) in Japan. Hydrogen was assumed to be produced from overseas renewable energy sources with LH2/MCH as the carrier, and NH3 from natural gas or renewable energy sources. The Japanese life-cycle inventory database was used to calculate emissions. Monte Carlo simulations were performed to evaluate emission uncertainty and mitigation factors using hydrogen energy. For LH2, CO2 emission uncertainty during hydrogen liquefaction can be reduced by using low-carbon fuel. For MCH, CO2 emissions were not significantly affected by power consumption of overseas processes; however, it can be reduced by implementing low-carbon fuel and waste-heat utilization during MCH dehydrogenation. Low-carbon NH3 production processes significantly affected power generation, whereas carbon capture and storage during NH3 production showed the greatest reduction in CO2 emission. In conclusion, reducing CO2 emissions during the production of hydrogen and NH3 is key to realize low-carbon hydrogen energy systems.

Assessing Commuting Energy and Emissions Savings through Remote Working and Carpooling: Lessons from an Italian Region

“…For this reason, this aspect will gain more importance in the future, with the foreseen rising share of electricity in the total final energy consumption of the transport sector. In addition to electricity, uncertainty on emissions related to other energy carriers [46], especially in the well-to-tank emission factor, due to the different parameters involved in the assessment of their supply chains [47].…”

The Role of Fugitive Hydrogen Emissions in Selecting Hydrogen Carriers

“…The fugitive H 2 emissions were estimated by assuming that the initial step in the production process involves the clean generation of H 2 from electrolytic water-splitting using polymer electrolyte membrane (PEM) or alkaline electrolyzers (Table S2). This process results in approximately 3–10% of H 2 loss, caused during the purging and purification of H 2 to remove impurities, such as water vapor (H 2 O) and oxygen (O 2 ). , Subsequently, the generated H 2 must be cooled and compressed for transportation to industrial H–B plants for NH 3 production, which can result in a further loss of 0.5–1%. , H 2 is then employed in the energy-intensive H–B process to produce NH 3 , which has a net H 2 loss rate of 4–5% . As a result, the effective H 2 after all considered losses is around 0.846–0.926 tons, generating electrical energy of 55.865–61.151 GJ e assuming the employment of a combined cycle gas turbine (CCGT) process with an efficiency (η) of 55%.…”

Materializing International Trade of Decarbonized Hydrogen Through Optimization in Both Economic and Environmental Aspects

“…Brändle et al presented an optimization study in 2021 for an efficient combination of RE sources and electrolyzers in several countries considering country-specific and RE-specific hourly capacity factor profiles and several case studies for H 2 supply chains between various countries including Norway, Saudi Arabia, CHN, AUS, DEU, JPN, and United States, figuring out that the supply chains will become feasible only for countries that can be linked using pipelines due to the cost-intensive ship transportation . In 2021, Ozawa and Kudoh estimated the environmental aspects of H 2 supply chain from AUS, Norway, and ARE to JPN through life-cycle inventory analysis for CO 2 emissions and figured out that key strategies to realize H 2 energy-based system are related to the H 2 production and utilizing NH 3 . In 2020, Ishimoto et al conducted EA for H 2 supply chains from Norway producing H 2 with both NG and RE to both Netherlands and JPN with different sea routes comparing LH 2 and NH 3 as H 2 carriers .…”

“…19 In 2021, Ozawa and Kudoh estimated the environmental aspects of H 2 supply chain from AUS, Norway, and ARE to JPN through life-cycle inventory analysis for CO 2 emissions and figured out that key strategies to realize H 2 energy-based system are related to the H 2 production and utilizing NH 3 . 20 In 2020, Ishimoto et al conducted EA for H 2 supply chains from Norway producing H 2 with both NG and RE to both Netherlands and JPN with different sea routes comparing LH 2 and NH 3 as H 2 carriers. 21 Kim et al conducted an optimization study for H 2 supply chain from seven exporting countries including AUS, QAT, ARE, and CHL to KOR considering country-specific resource capacity and price and verified economically optimal H 2 supply routes for KOR in future 2 decades.…”