Literature review: LCA of different types of hydrogen production

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Background[edit | edit source]

A review on blue and green hydrogen production process and their life cycle assessments^[1][edit | edit source]

• Green hydrogen is created by splitting water molecules into oxygen and hydrogen using renewable energy sources
• Blue hydrogen, on the other hand, is produced by reforming natural gas and capturing and storing the resulting carbon emissions
• green hydrogen production generally shows a lower environmental impact compared to blue hydrogen production
• the environmental impact of green hydrogen production can vary depending on the source of the renewable energy used for electrolysis
• hydrogen odor and colorless
• but the colors are determined by the source of hydrogen and production process^[2]
• Green hydrogen is currently more costly^[3][4]
• LCA can help inform policy decisions related to hydrogen production and use^[5][6]
• process: electrolyzing water(using clean electricity)>> Hydrogen+ oxygen [no co2 emission] (Electrolysers employ an electrochemical process) ^[3]
• Usage of green hydrogen : power heavy-duty vehicles, shipping, and aviation, offering long driving ranges and shorter refuelling times, heating and residential use, exported as an energy source, and contribute to global decarbonization efforts
• For 1 kg of green hydrogen produced, electrolyzers use more than 55 kWh of power^[7]
• blue hydrogen is produced by steam reforming method (steam + natural gas) >> Carbon capture storage^[8][9]
• usage of blue hydrogen: industrial processes, power generation, hydrogen blending, transportation, and energy storage
• Each 1 kg of blue hydrogen produced emits about 12 kg of CO2^[8]
• table1 and table 2

Grey, blue, and green hydrogen: A comprehensive review of production methods and prospects for zero-emission energy^[10][edit | edit source]

• main goal of this study is to describe several methods of producing hydrogen based on the principal energy sources utilized.
• The amount of greenhouse gas (GHG) emissions generated during the production of hydrogen gas (H2) depends on how clean the energy used during the production process^[11]
• Above 40% of gray hydrogen is a by-product of several chemical procedures, mainly used in the petrochemical industry and the production of ammonia
• About 6% of the natural gas extracted in the world and 2% of coal are used each year to produce gray hydrogen, that emits 830 metric tons of CO2 per year ^[3]
• At present, the main electrolysis methods are polymer electrolyte membrane electrolysis (PEM), alkaline water electrolysis (ALK) and solid oxide electrolysis cell (SOEC)
• Global hydrogen production emits around 900 Mt of CO2 into the atmosphere each year
• According to the International Energy Agency (IEA), gray hydrogen production accounted for around 6% of global CO2 emissions in 2020^[12][13]
• Global hydrogen production emits around 900 Mt of CO2 into the atmosphere each year^[14]
• Still, the main problem with electrolyzing alkaline water is that it has low electric densities (0.1–0.5 A/cm2) because the OH− is not very flexible and the KOH electrolytes are corrosive. the KOH electrolyte is very sensitive to ambient CO2, which leads to the creation of salt (K2CO3), causing a reduction both in quantity of (OH−) and ionic conduction^[15]
• Table3

Hydrogen production, storage, utilisation and environmental impacts: a review^[16][edit | edit source]

• The global hydrogen demand is projected to increase from 70 million tonnes in 2019 to 120 million tonnes by 2024
• More than 100 current and planned hydrogen production technologies are reported to date, with over 80% of those technologies are focused on the steam conversion of fossil fuels and 70% of them are based on natural gas steam reforming.
• The higher heating value (HHV) of hydrogen is 141.8 MJ/kg at 298 K, and the lower heating value is 120 MJ/kg at the same temperature.^[17][18]
• as opposed to liquified natural gas, liquified hydrogen contains 2.4 times the energy but takes 2.8 times the volume to store.^{[17] [18]}
• reviewed 24 LCA studies published from 2019 to 2021 on hydrogen
• It was observed that ~ 42% of the reviewed studies used ‘kg of hydrogen produced’ as the functional unit
• The two commonly studied kinds of system boundary for hydrogen production are ‘cradle-to-gate’ or ‘well-to-pump’ that includes processes only until production and ‘cradle-to-grave’ or ‘well-to-wheel’, which incorporates emissions during end use as well.
• table 5

Green, Turquoise, Blue, or Grey? Environmentally friendly Hydrogen Production in Transforming Energy Systems^[19][edit | edit source]

• Global hydrogen use was about 120 Mt/a in 2020, and is expected to rise to 530 Mt/a in 2050^[20][21]
• n 70 Mt/a of hydrogen are used for oil refining (39 Mt/a) and ammonia production (32 Mt/a)
• around 50 Mt/a of hydrogen are used in carbon-containing gas mixtures, syngas, for methanol production (14 Mt/a) and steel manufacturing (5 Mt/a) as well as for electricity and heat generation (30 Mt/a)^[20][22]
• Current hydrogen production, however, is far from being renewable; it relies almost entirely on reforming and gasification of fossil hydrocarbon sources, such as natural gas (76%) and coal (23%) resulting in 830 Mt/a CO2 emissions^[22]
• Alternative hydrogen production technologies such as methane pyrolysis and water electrolysis^{[23][24][25][26][27][28]}
• smr>> gray, smr+ccs >> blue, methane pyrolysis >> tranquoise, PEM >> green
• research question:
  • How sensitive with regard to the energy system transformation
  • Which hydrogen production environmentally most favorable in the long run
  • When and under what circumstances does a certain hydrogen production technology evolve to be the environmentally most favorable option
• methane pyrolysis (MP), also referred to as methane “decomposition” and methane cracking, CH4 is cleaved into gaseous H2 and elemental carbon (C)
• LCA
  • goal and scope: “cradle-to-gate>>resource extraction to the factory gate
    • Subsequent life cycle stages such as hydrogen transport and storage and their associated environmental impacts do not depend on the applied hydrogen production technology
    • functional unit was chosen to be 1 kg H2 at 30 bar pressur
  • by-products: electricity generated from low-pressure steam by SMR, carbon black by MP, and oxygen by PEMEL>> avoided burden method
  • Table 2-3 detailed LCI
  • With electricity supplied from the current grid mix in Germany and without considering the utilization of by-products, the resulting GWI ranges from 3.94 to 34.85 kg CO2-eq/kg H2.
  • Grey: 11kg co2/kg h2 [e process-related GHG emissions with a GWI of 9.00 kg CO2-eq/kg H2 (77.75%) and the supply of natural gas with 2.56 kg CO2-eq/kg H2 (22.13%)]
  • blue hydrogen: 6.87 kg co2/kg ( 56% ccs) >> 60% are caused by process-related emission; 3.97 kg co2/kg h2 (90% ccs)>> 24,9% process related
  • When using electricity, carbon, natural gas, or hydrogen as the heat source, MP-based processes produce "turquoise" hydrogen with a GWI of 9.91, 7.65, 6.45, and 3.94 kg CO2-eq/kg H2, respectively.
  • fig 12 imp**

Green hydrogen: A holistic review covering life cycle assessment, environmental impacts, and color analysis^[29][edit | edit source]

• Methods like water electrolysis, biomass gasification, and methane reforming with carbon capture and storage offer pathways to synthesize hydrogen without greenhouse gas emissions
• , incorporating nuclear energy could reduce emissions by up to 90% compared to conventional methods
• green hydrogen can reduce lifecycle emissions by 60–90% compared to gray hydrogen
• Hydrogen is thought to be able to provide 6% of the total worldwide emission reductions^[30]
• The LCA assessment process normally consists of four key steps, as stated by ISO 14040: inventory analysis, impact assessment, aim and scope definition, and interpretation^{[31][32][33][34]}
• Among the available sources, the terms brown and black hydrogen are also sometimes used to refer to gray hydrogen^[35][36]
• coal gasification (brown h2), particularly prevalent in China due to factors such as the high cost of natural gas and abundant coal reserves, results in the highest CO2 emissions among various hydrogen colors, ranging from 18 to 25 kgCO2eq./kgH2^[37]
• One study found that if 56% of CO2 is captured, the total effect on climate change drops to 6.87 kg of CO2-eq/kg of hydrogen, with 60.0% of that coming from process-related emissions.^[38]
• . Elevated rates of capture, such as 90%, further reduce the impact to 3.97 kg of CO2-eq/kg of hydrogen, reducing the contribution of process-related emissions to 24.9%^[39]
• blue hydrogen only shows an 18–25% reduction in greenhouse gas emissions compared to gray hydrogen^[40]
• it still emits 20% more greenhouse gases than natural gas or coal when used for heating ^[40]

A review on global warming potential, challenges and opportunities of renewable hydrogen production technologies^[41][edit | edit source]

• gray Hydrogen >> Natural gas, Coal >> 7.5-25 kg Co2/ kg H2>> eff: 60-85% (NG), 74-85% (coal gasification)
• blue hydrogen >> NG + CCS >> 3.97-6.87 kg CO2 >> 55-80% (with CCS)
• turquoise hydrogen>> methane >> 3.94-9.91>> not specified
• green hydrogen >> water electrolysis >> ~0 > variable
• pink / red hydrogen >> nuclear >> 0.1-0.6 >> not specified
• yellow hydrogen >> solar energy >> ~0 >> variable
• biohydrogen >> biomass, biowaste >> 6.7-9.8>> notspecified
• white hydrogen >> nuclear energy >> 0.87 (Cu-Cl cycle) >> nor specified [known as white, has been informally assigned by the North American Council for Freight Efficiency to hydrogen produced as a by-product]
• While water electrolysis has almost no direct process emissions, the process is energy-intensive, thus the source of the process energy is directly linked to the overall GHG emissions of the system^{[42][43][44][45][46]}

Insights into low-carbon hydrogen production methods: Green, blue and aqua hydrogen ^[39][edit | edit source]

• Canada is one of the larger hydrogen producers in the world today, making about three million tonnes a year using steam methane reformation of natural gas^[47]
• Western Canada dominates Canadian hydrogen production due to its large fossil fuel resources. Canada's largest hydrogen plants are located in Western Canada without CCS.^[48]
• According to the Paris Agreement on Climate Change, Canada has promised to reduce methane emissions by 40%e45% in the oil and gas sector.

Environmental sustainability assessment of large-scale hydrogen production using prospective life cycle analysis^[49][edit | edit source]

• Prospective life cycle analysis of green and blue hydrogen produced at 500 Mt/yr

Carbon Footprint Assessment of Hydrogen and Steel^[50][edit | edit source]

• Only 0.5% of the global hydrogen production is from renewable sources, the so-called green hydrogen
• Around 6% of global natural gas consumption and 2% of global coal consumption are used for hydrogen production>> 2.5% of global CO2 emissions^[51]
• If a hydrogen production rate of about 70 Mt per year is taken into account, this leads to about 12 kg CO2/kg H2.
• Gray hydrogen >> 11-13 kg co2 / kg h2 [natural gas production and transportation 1.7 kg co2/kg h2]; 19-24 kg co2/kg h2^{[52][53][54][55][56][57][58][59]}
• The carbon footprint of grey hydrogen from electrolysis driven by a fossil-based electricity mix varies between 1.1 and 35 kg CO2eq/kg H2
• blue hydrogen >> 0.6-4.7kg co2/ kg h2; 11-22kg Co2/ kg h2 ^[40]
• green hydrogen >> 1.0-5.1 kg co2/ kg h2
• The focus of this paper lies on hydrogen from electrolysis operated with a grid mix. State-of-the-art grid mixes for Poland, France, Germany, and Europe (EU-28) are modelled.

Life Cycle Assessment of Hydrogen Production^[60][edit | edit source]

• “well-to-tank” LCA of gaseous hydrogen (H2) as an energy carrier, where the H2 is intended for use in the fuel cell of a road vehicle
• Functional unit: 1kg of purified H2 at a pressure of 450kPa available at the vehicle fuelling station pump
• 1kg H2 is able to release 120MJ energy if considering the lower heating value (LHV).
• Electrolysis is the splitting of water molecules into H2 and O2 by passing direct electric current between two electrodes seperated by an ion exchange membrane. Oxygen is produced at the anode and hydrogen at the cathode, both in very pure form.^[61]
• potassium hydroxide (KOH) is added to the water to about 30wt % in order to improve its conductivity as an electrolyte
• In the 2005 scenario, electrolysis requires almost 47kWh electricity per kg H2

A well to pump life cycle environmental impact assessment of some hydrogen production routes^[62][edit | edit source]

• hydrogen production routes of water electrolysis, biomass gasification, coal gasification, steam methane reforming, hydrogen production from ethanol and methanol
• Comparatively higher life cycle Carbon dioxide emissions of 27.3 kg/kg H2 is determined for the water electrolysis hydrogen production route via U.S. electricity mix

Is the Polish Solar-to-Hydrogen Pathway Green? A Carbon Footprint of AEM Electrolysis Hydrogen Based on an LCA^[63][edit | edit source]

• table 1 The color spectrum of hydrogen
• About 9 L of water are needed to produce 1 kg of H2, producing 8 kg of oxygen as a by-product, which can be used on a smaller scale in healthcare or on a larger scale for industrial purposes
• total H2 production 70 Mt, if it has been produced by electrolysis, this would result in a water requirement of 617 million cubic meters, which is equivalent to 1.3% of the global energy sector’s water use today, or roughly twice as much as the current water consumption for the hydrogen produced from a steam methane reformer.
• a green hydrogen plant with 5 MW peak solar power located in Zarzecze, in the southern part of the country.
• The conceptual analysis of the designed green hydrogen plant, annually providing about 80 Mg of industrial-purity hydrogen (99.8%)
• power plant specification:
  • 5MWp
  • 2 transformers with a max power of 2500kVA
  • 34 inverters
  • 18-21.54%
• the tech parameter of AEM
  • 4 devices with 1.25 MW of power
• 56.34 kWh of energy was used to produce 1 kg of hydrogen under normal conditions
• the GWP indicators as 2.73–4.34 kgCO2eq for a plant using AEM electrolysis

Climate change performance of hydrogen production based on life cycle assessment^[64][edit | edit source]

• grey hydrogen had the highest emissions, with the LNG route showing higher emissions, 13.9 kg CO2 eq. per kg H2, compared to the pipeline route, 12.3 kg CO2 eq. per kg H2
• Blue hydrogen had lower emissions due to the implementation of carbon capture technology (7.6 kg CO2 eq. per kg H2 for the pipeline route and 9.3 kg CO2 eq. per kg H2 for the LNG route)
• The production of green hydrogen using wind energy resulted in the lowest emissions (0.6 kg CO2 eq. per kg H2), while solar energy resulted in higher emissions (2.5 kg CO2 eq. per kg H2).

Global Hydrogen Review^[65][edit | edit source]

• Annual production of low-emission hydrogen could reach 38 Mt in 2030, if all announced projects are realised, although 17 Mt come from projects at early stages of development
• Of the total, 27 Mt are based on electrolysis and low-emission electricity and 10 Mt on fossil fuels with carbon capture, utilisation and storage.
• Novel applications in heavy industry and long-distance transport account for less than 0.1% of hydrogen demand, whereas they account for one-third of global hydrogen demand by 2030 in the Net Zero Emissions (NZE) by 2050
• In the NZE Scenario the average emissions intensity of hydrogen production drops from the range of 12-13.5 kg CO2-eq/kg H2 in 2022 to 6-7.5 kg CO2-eq/kg H2 in 2030.
• China has taken the lead on electrolyser
• In 2020, China accounted for less than 10% of global electrolyser capacity installed for dedicated hydrogen production
• In 2022, installed capacity in China grew to more than 200 MW, representing 30% of global capacity, including the world’s largest electrolysis project (150 MW). By the end of 2023, China’s installed electrolyser capacity is expected to reach 1.2 GW – 50% of global capacity – with another new world record-size electrolysis project (260 MW), which started operation this year.
• North America and Europe have taken the lead in implementing initiatives to encourage low-emission hydrogen production.

Towards hydrogen definitions based on their emission intensity^[66][edit | edit source]

• The G7 is a cornerstone of efforts to accelerate the scale-up of the production and use of low-emission hydrogen, ammonia and hydrogen-based fuels. G7 members – Canada, France, Germany, Italy, Japan, the United Kingdom, the United States and the European Union – account for around one-quarter of today’s global hydrogen production and demand.
• The average emissions intensity of global hydrogen production in 2021 was in the range of 12-13 kg CO2‑eq/kg H2. In the IEA Net Zero by 2050 Scenario, this average fleet emissions intensity reaches 6‑7 kg CO2‑eq/kg H2 by 2030 and falls below 1 kg CO2‑eq/kg H2 by 2050.

Comparison of environmental and economic aspects of various hydrogen production methods^[67][edit | edit source]

• nickel >> as catalyst >> grey h2^[68]

Additional[edit | edit source]

• Methane, with an energy density of 55.5 MJ·kg−1, is the simplest hydrocarbon molecule; in reforming it is reacted with steam at 700–1000 °C under a pressure range of 3–25 bar^[69][70]
• gas water shift^{[71][72][73] [69]}
• blue hydrogen, produced from fossil fuels with CO2 capture, is currently viewed as the bridge between the high-emission grey hydrogen and the limited-scale zero-emission green hydrogen.^[74]

References[edit | edit source]