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Contract No. DE-AC36-99-GO10337 

Life Cycle Assessment of 

Renewable Hydrogen 

Production via 

Wind/Electrolysis 

Milestone Completion Report 

February 2004 • NREL/MP-560-35404 

Pamela L. Spath 

Margaret K. Mann 
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Life Cycle Assessment of

 Renewable Hydrogen Production via Wind/Electrolysis

Pamela L. Spath

Margaret K. Mann

Milestone Report for the U.S. Department of Energy’s Hydrogen Program

Process Analysis Task

Milestone Type P (Programmatic)

February 2001
1

INTRODUCTION

Although hydrogen is generally considered to be a clean fuel, it is important to recognize that its

production may have negative impacts on the environment. Examining the resource

consumption, energy requirements, and emissions from a life cycle point of view gives a

complete picture of the environmental burdens associated with hydrogen production. Life cycle

assessment (LCA) is a systematic analytical method that helps identify and evaluate the

environmental impacts of a specific process or competing processes. The National Renewable

Energy Laboratory has performed a life cycle assessment on a renewable hydrogen production

process which employs wind/electrolysis. In order to quantify the emissions, resource

consumption, and energy use, collectively known as environmental stressors, material and

energy balances are performed in a cradle-to-grave manner on the operations required to

transform raw materials into useful products. For the wind/electrolysis system, the material

production processes required to construct the wind turbines, electrolyzer, and hydrogen storage

tanks were taken into account. All resources, emissions, and energy flows were inventoried

within the boundaries of the system so that the total environmental picture of each system could

be determined.

SYSTEM DESCRIPTION/BOUNDARIES

The wind/electrolysis system examined in this study is shown in Figure 1. Material

requirements and design data for this system were taken from electrolyzer and wind turbine

manufacturers. The system incorporates three 50 kW Atlantic Orient Corporation (AOC) wind

turbines with a 30 Nm3

/hr Stuart Energy electrolyzer. The size of the electrolyzer determines

that multiple wind turbines are required because they come in discreet sizes, generally classified

as small, industrial, or utility. Additionally, it is usually better to operate with several wind

turbines to allow for more consistency in the wind distribution, and having multiple wind

turbines will also allow the system to operate at a reduced capacity if one of the turbines is shut

down. The turbine blades, which are currently manufactured in Europe, were assumed to be

transported across the Atlantic Ocean to a major coastal port in the U.S. and then transported by

rail to the upper Midwest. To operate at a higher point on its efficiency curve for a greater

number of hours during the year, the electrolyzer was sized for 75% of the maximum wind

speed. For the wind data used in this analysis, the wind turbines operate at greater than 75% of

the maximum wind speed for only 1% of the year. The amount of hydrogen that is not generated

during this time is very small, 2.6 kg/yr of H2, and is equal to 0.05% of the total amount of

hydrogen produced by the system per year.

The system operation was determined using class 5 wind data from the upper Midwest region of

the United States. The electricity is wheeled from this remote location to a fueling station where

the electrolyzer converts the electricity to hydrogen with an efficiency of 85% (higher heating

value basis). The product hydrogen is compressed to a pressure of 20 MPa, stored, and

dispensed at the fueling station. Several electrical losses were subtracted from the gross amount

of electricity produced by the wind turbines. First, there are the transmission losses, which are

7.03%. Next, there is a small amount of electricity needed to pump the deionized water.

Finally, there is the electrical requirement for compression of the product hydrogen. The amount

of hydrogen produced by this system is enough to fuel 36 vehicles at 3 kg of H2/week.
2

wind turbines

electrolyzer compression &

storage

Figure 1: Wind/electrolysis System

RESOURCE REQUIREMENTS

Fossil fuels, metals, and minerals are used to produce hydrogen in this process. Table 1 shows

the major resource requirements for this system, excluding water. The resources that are

consumed at the highest rate are iron (ore plus scrap) and limestone. The iron, which is mostly

used in manufacturing the wind turbines and hydrogen storage vessels, accounts for 37.4% of the

resources shown in Table 1. The large amount of limestone, 35.5% of the major resources, is

used for the turbines’ concrete foundations. Coal, which is consumed primarily to produce the

steel, iron, and concrete, accounts for 20.8% of the remaining resources. This is followed by oil

at 4.7%, and natural gas at 1.6% which are primarily used in manufacturing the wind turbines.

The wind turbine foundation used in the analysis is a standard design by AOC and depending on

the site specific soil conditions, it is quite possible that less concrete and steel could be used, thus

reducing the required resources. A sensitivity analysis was performed to determine how changes

in this parameter would affect the results (see section labeled Sensitivity Analysis - Wind

Turbine Foundation Requirements). 

Table 1: Average Resource Consumption

Resource

total

(g/kg H2)

% of total

in this table

from wind

turbines

from

electrolysis

from

storage

Coal (in ground) 214.7 20.8% 67.6% 5.6% 26.7%

Iron (Fe, ore) 212.2 20.6% 64.2% 5.9% 30.0%

Iron scrap 174.2 16.9% 52.7% 7.7% 39.6%

Limestone (CaCO3, in ground) 366.6 35.5% 96.4% 0.3% 3.3%

Natural gas (in ground) 16.2 1.6% 72.0% 15.4% 12.6%

Oil (in ground) 48.3 4.7% 76.2% 13.1% 10.7%

Water is consumed not only in the electrolysis operation, but also in upstream processes. For

each kg of hydrogen produced, 26.7 liters of water are consumed by the system. Nearly 45% is

used by the electrolyzer, while 38% and 17% is used in manufacturing the wind turbines and the

hydrogen storage vessels, respectively.
3

Figure 2: Life Cycle GWP (CO -equivalent) 2

GLOBAL WARMING POTENTIAL & GREENHOUSE GASES

The global warming potential (GWP) of the system is a combination of CO2, CH4, and N2O

emissions expressed as CO2-equivalence. For a 100 year time frame, the capacity of CH4 and

N2O to contribute to the warming of the atmosphere is 21 and 310 times higher than CO2,

respectively (Houghton, et al, 1996). The GWP and the contribution from each compound is

given in Table 3.

Table 3: GWP (g CO2-equivalent/kg of H2)

GWP

(g CO2-equivalent/kg of H2)

% contribution to GWP

CO2 CH4 N2O

970 97.9% 0.6% 1.5%

Figure 2 shows how the CO2-equivalent emissions are divided among the different process

blocks for the wind/electrolysis system. Because of the steel and concrete requirements, the

construction and operation of the wind turbines account for 78% of the total GWP. Hydrogen

storage and compression accounts for 18% of the GWP. This is due primarily to the production

of the steel used in the storage tanks.
4

OTHER AIR EMISSIONS

Table 4 is a list of the major air emissions. In terms of total air emissions, CO2 is emitted at the

highest rate, accounting for greater than 95 wt%. Producing concrete and steel for the wind

turbines and hydrogen storage accounts for 77% of the system’s CO2. After CO2, the next

highest air emission is particulates. These come primarily from quarrying the sand and

limestone needed for concrete production. Concrete production for the wind turbines accounts

for 85% of the system’s particulate emissions. For the electrolysis step, the largest air emissions

are SOX at 26% of the system total and NOX at 47%. These come from producing benzene,

which is used to make Ryton© for the electrolyzer. However, in general, the majority of the air

emissions come from the process steps in manufacturing the wind turbines. 

Table 4: Average Air Emissions

Air Emission

System Total

(g/kg of H2)

% of total in

this table

% of total

excluding CO2

from wind

turbines

from

electrolysis

from

storage

Carbon dioxide 950.0 95.5% 78.1% 4.4% 17.5%

Carbon monoxide 0.9 0.1% 1.9% 80.3% 3.5% 16.2%

Methane 0.3 <0.0% 0.6% 92.4% 2.8% 4.8%

Nitrogen oxides 4.7 0.5% 10.3% 45.9% 47.1% 7.0%

Nitrous oxide 0.05 <0.0% 0.1% 67.1% 5.6% 27.3%

Non-methane hydrocarbons 4.4 0.4% 9.9% 62.5% 7.3% 30.1%

Particulates 28.7 2.9% 63.7% 94.2% 0.7% 5.0%

Sulfur oxides 6.1 0.6% 13.5% 61.8% 26.1% 12.1%

ENERGY BALANCE

There are several ways of looking at the energy balance of the system. The first is to examine

the total energy consumption of the system as shown in Table 5. The majority of the energy

consumption, 72.6%, comes from manufacturing the materials required for the wind turbines.

Table 5: Average Energy Requirement (LHV basis)

System

total energy consumption

(MJ/kg H2)

from wind

turbines

from

electrolysis

from

storage

9.1 72.6% 4.8% 31.6%

The net energy ratio, defined in Table 6, provides another means of examining the system’s

energy balance. It illustrates how much energy is produced for each unit of fossil fuel energy

consumed. Because of the nature of the wind/electrolysis system, the net energy ratio is greater

than one indicating that the energy in the product hydrogen is greater than the fossil energy

consumed. For every 13.2 MJ of hydrogen produced, 1 MJ of fossil energy must be consumed

(LHV basis).
5

Table 6: Net Energy Ratio (LHV)

Net Energy Ratio

Definition Result

 EH2/Eff 13.2

where:

EH2 = energy in the hydrogen

Eff = fossil fuel energy consumed within the system

SOLID WASTES

The solid waste produced from the system can be classified as miscellaneous non-hazardous

waste. The total quantity of waste is 223 g/kg of H2. The majority of the solid waste (79%)

comes from manufacturing the wind turbines. Concrete production results in 47% of the total

solid waste for this system and steel production results in 22% of the total waste. In the concrete

manufacturing step, the two major sources of solid waste are grid electricity (42%) and

limestone production (30%). In the steel production step, 61% of the solid waste comes from

converting iron ore to steel and 31% comes from grid electricity. The total amount of solid

waste that is a result of grid electricity is 27% of the system total. Because most of the

electricity in the U.S. is generated from coal-fired power plants, this waste will be in the form of

coal ash and flue gas clean-up waste. After grid electricity, limestone production accounts for

14% of the total system waste and converting iron ore to steel accounts for another 14% of the

system’s total solid waste.

SENSITIVITY ANALYSIS - WIND TURBINE FOUNDATION REQUIREMENTS 

The wind turbine foundation used in the analysis is a standard design by AOC and, depending on

the site specific soil conditions, it is quite possible that less concrete and steel could be used, thus

reducing the resources, emissions, and energy consumption per kg of hydrogen produced. To

test the effect of reducing the material requirements, the concrete and steel needed for the

foundation were decreased by 25% and 50%. The following table, Table 7, summarizes the

results of these reductions compared to the base case.
6

Table 7: Results from Sensitivity Analysis on Wind Turbine Foundation Requirements

Base case

value

25% material reduction 50% material reduction

value change from

base case

value change from

base case

RESOURCES

Coal 214.7 201.3 -6.2% 187.9 -12.5%

Iron ore 212.2 205.3 -3.3% 198.3 -6.5%

Iron scrap 174.2 166.6 -4.3% 159.1 -8.6%

Limestone 366.6 281.8 -23.1% 197.0 -46.3%

Natural gas 16.2 15.6 -4.0% 14.9 -8.1%

Oil 48.3 46.4 -3.8% 44.6 -7.6%

AIR EMISSIONS

Benzene 0.0012 0.0011 -12.8% 0.0009 -25.6%

Carbon dioxide 950.0 845.3 -11.0% 740.6 -22.0%

Carbon monoxide 0.86 0.75 -12.4% 0.64 -24.7%

Methane 0.29 0.25 -13.7% 0.21 -27.3%

Nitrogen oxides 4.7 4.4 -5.5% 4.1 -10.9%

Nitrous oxide 0.046 0.043 -6.1% 0.041 -12.1%

Non-methane hydrocarbons 4.4 4.3 -3.5% 4.1 -7.0%

Particulates 28.7 22.5 -21.6% 16.3 -43.1%

Sulfur oxides 6.1 5.8 -4.6% 5.5 -9.3%

OTHER

GWP 970 864 -11.0% 758 -21.9%

System energy consumption (MJ/kg of H2) 9.1 8.6 -5.9% 8.0 -11.8%

Net energy ratio 13.2 14.0 6.2% 15.0 13.3%

Total solid waste generated (g/kg of H2) 223.8 193.6 -13.5% 163.4 -27.0%

Reducing the amount of concrete and steel results in a decrease in the resource requirements,

most notably the amount of limestone used. Several air emissions decrease by significant

amounts primarily due to the reduction in limestone. The particulates decrease by 21.6% and

43.1% for the 25% and 50% material reduction case, respectively. The reduction in the amount

of CO2 caused by reducing the foundation material requirements, results in a 11.0% and 21.9%

decrease in the GWP for the 25% and 50% material reduction case, respectively. Additionally,

because material manufacturing steps are energy-intensive, reducing the foundation material

requirements lowers the system’s energy consumption and increases the net energy ratio.
7

Finally, the amount of solid waste generated is decreased by 13.5% and 27.0% for the 25% and

50% material reduction case, respectively.

SUMMARY

This study examined the resource consumption, energy requirements, and emissions of a

wind/electrolysis system from a life cycle point of view, giving a complete picture of the

environmental burdens associated with hydrogen production from wind/electrolysis. On a system

basis, CO2 is emitted in the largest quantity, accounting for over 95 wt% of the total air

emissions. The resources required, energy consumed, pollutants emitted, and waste generated

are mostly due to plant construction. The majority of the stressors come from manufacturing

and constructing the wind turbines. Because of the nature of the process, almost no emissions

result from plant operation. The energy balance of each system shows that considerably more

hydrogen energy is produced than the amount of fossil energy consumed. Any increase in wind

turbine or electrolyzer efficiency will result a reduced amount of resource consumption,

emissions, and energy use per kg of hydrogen produced.

FUTURE WORK

This study is being compared to a separate LCA previously performed on a fossil based system,

steam methane reforming (Spath and Mann, 2000). Future work will involve comparisons of

these studies to hydrogen production via other routes such as biomass and photovoltaics.

Additionally, long-term technologies (e.g., photobiological hydrogen production, plasma

reforming/oxidation, and carbon nanotube hydrogen storage) can be examined using life cycle

assessment to explore the possibility of improved environmental consequences.

RELATED LCA STUDIES

Prior to conducting this LCA, a literature search was performed to see what life cycle work had

been done on systems involving wind and/or electrolysis. No publications were found related to

LCAs of systems using electrolysis. However, several papers were found containing information

about LCAs for wind generated power production. The following list is a brief summary of

these documents.

Bates, J.; Watkiss, P.; Thorpe. T. (1997).

This article gives the results of LCAs for three renewable technologies: wind turbines,

photovoltaic systems, and small, stand-alone solar thermal systems. They state that the material

manufacturing steps result in the largest amount of emissions therefore, they look at only these

steps. While their statement is true this does not give the total environmental picture of each

renewable. Specific material requirements are not given. They list only air emission results

obtained from using German and UK data. They do not say if the material requirements were

from specific wind turbines.
8

Kato, S.; Widiyanto, A. (1999).

They examined net energy, resource consumption, and emissions of various electricity

generation systems using an evaluation method called NETS (Numerical Environmental Total

Standard). This method calculates a value which indicates the impact on the environment.

Proops, J.L.R.; Gay, P.W., Speck, S.; Schröder, T. (1996). 

This paper examines only CO2, SOX, and NOX for eight forms of electricity generation: 2 coal

technologies, methane, tide, wave, wind, and solar. They use the input-output approach which

deals with economic activity. Their data sources come from the UK.

Schleisner, L. (1999).

This study examined life cycle energy and emissions for electricity production from both

offshore and land-based wind farms. The offshore wind farm consists of ten 500 kW turbines

and the onshore farm consists of eighteen 500 kW units. The total amount of electricity

produced over a 20 year life was assumed to be the same for both systems at 250 GWh. Danish

energy data is assumed for all materials manufacturing steps. A breakdown of total material

requirements for each system is given. Only CO2, SO2, and NOX emissions are given in g/kWh.

Uchiyama, Y. (1997).

This paper presents the net energy and CO2 emissions for photovoltaic cell and wind power

generation plants. The only material requirements listed are cement, steel, and sand and stone

for four different Japanese wind machines. They state that higher performance advanced wind

turbines can improve the energy ratio and reduce the CO2 emissions by 1/5 to 1/3 of that from

today’s turbines.

Van De Vate, J.F. (1996).

They examined the greenhouse gases for the full energy chain of the following energy sources:

coal, oil, natural gas, hydro, nuclear, wind, solar PV, and biomass. The article talks about the

methodologies and databases for making comparative assessments. Very little data is given.

Wiese, A.; Kaltschmitt, M. (1996). 

They perform an LCA on electricity production from wind examining three system sizes: 100

kW, 500 kW, and 1,000 kW and three different annual mean wind velocities (4.5, 5.5, and 6.5

m/s). They used hourly wind data from several locations in Germany. Ranges of material

requirements for steel cement, non-ferrous metals, and plastic are listed. The only results given

are air emissions for SO2, NOX, and CO2.

REFERENCES

Bates, J.; Watkiss, P.; Thorpe. T. (1997). “Life Cycle Emissions from Renewable Energy

Technologies.” International Atomic Energy Agency advisory group meeting on the

assessment of greenhouse gas emissions from the full energy chain of solar and wind power.

October, 21-24, 1996, Vienna, Austria, pp. 138-175.

Houghton, J.T.; Meira Filho, L.G.; Callander, B.A.; Harris, N.; Kattenberg, A.; Maskell, K., eds.
9

(1996). Climate Change 1995. The Science of Climate Change. Published for the

Intergovernmental Panel on Climate Change. New York: Cambridge University Press.

Kato, S.; Widiyanto, A. (1999). “A Life Cycle Assessment Scheme for Environmental Load

Estimation of Power Generation Systems with NETS Evaluation Method.” 1999 Joint Power

Generation Conference. (FACT - Vol. 23). Volume 1: Fuels and combustion technologies;

Gas turbines; and Nuclear engineering. July 25 - 28. Burlingame, CA. pp. 139-145.

Proops, J.L.R.; Gay, P.W., Speck, S.; Schröder, T. (1996). The Lifetime Pollution Implications

of Various Types of Electricity Generation. An Input-Output Analysis. Energy Policy.

Volume 24. No. 3. pp. 229-237.

Schleisner, L. (1999). Life Cycle Assessment of a Wind Farm and Related Externalities.

Renewable Energy. Volume 20. pp. 279-288.

Spath, P.L; Mann, M.K. (2000). Life Cycle Assessment of Hydrogen Production via Natural

Gas Steam Reforming. National Renewable Energy Laboratory, Golden, CO, TP-570-27637.

Uchiyama, Y. (1997). “Life Cycle Analysis of Photovoltaic Cell and Wind Power Plants.”

International Atomic Energy Agency advisory group meeting on the assessment of

greenhouse gas emissions from the full energy chain of solar and wind power. October,

21-24, 1996, Vienna, Austria, pp. 111-122.

Van De Vate, J.F. (1996). Comparisons of the Greenhouse Gas Emissions From the Full

Energy Chains of Solar and Wind Power Generation. International Atomic Energy

Agency advisory group meeting on the assessment of greenhouse gas emissions from the

full energy chain of solar and wind power. October, 21-24, 1996, Vienna, Austria.

Wiese, A.; Kaltschmitt, M. (1996). “Comparison of Wind Energy Technology with Other

Electricity Generation Systems A Life Cycle Analysis.” 1996 European Union Wind

Energy Conference. May 20-24. Göteborg, Sweden. pp. 169-172.
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Life Cycle Assessment of Renewable Hydrogen Production via Wind/Electrolysis: 

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Pamela L. Spath and Margaret K. Mann 

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13. ABSTRACT (Maximum 200 words)

This report summarizes the results of a lifecycle assessment of a renewable hydrogen production process employing 

wind/electrolysis. Resource consumption, energy requirements, and emissions were determined in a cradle-to-grave manner 

on the operations required to transform raw materials into useful products, including the material production processes 

required to construct the wind turbines, electrolyzer, and hydrogen storage tanks. 

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