Our Hydrogen Future

Our Hydrogen Future

Our Hydrogen Future

Our hydrogen future: a very brief overview
Reprinted from ReNew Magazine Issue 161

Hydrogen from the electrolysis of water
Hydrogen production from natural gas
Types of Hydrogen:
Typical Waste Sequestration Site
A primer on carbon capture and sequestration (CCS)
So where do we stand?

see also Australia as a Major Exporter of H2 Hydrogen - questions that need to be addressed and Hydrogen Energy in Australia – Green or Fossil Fuel ?

Australia is being promoted on several levels as a future major exporter of hydrogen fuel. Not all technologies are equal and CCS (carbon capture and sequestration) is relied upon to contain some greenhouse gas emissions from hydrogen production.

The selling point of hydrogen fuel isthat when it is combusted, water is the only waste product. Hydrogen (H) is also the smallest atom and the simplest element. Containment during storage and transport is an issue.
Hydrogen by weight contains three times the energy of petrol, but because hydrogen is so much lighter (less dense), you need four times the volume of hydrogen to get the same energy as petrol. However, hydrogen has some advantages over fossil fuels:

A fuel-cell car running on hydrogen is 60% to 80% efficient and achieves between five and 11 times the range (per kilogram of fuel) than a similar-size petrol-powered car (which is 18-30% efficient).
Pipeline transport of hydrogen uses three times more volume (and therefore requires a 20% larger pipe diameter) to supply the same amount of energy as natural gas. This simple fuel must be extracted from compounds through processing.

In Australia, some hydrogen fuel is processed from water (H₂O) but most is processed from fossil methane (CH₄, commonly called natural gas). Methane is also found and harvested alongside oil deposits, coal seams, or fracked from shale formations, or from the fermentation of organic material.

Hydrogen from the electrolysis of water

There are a number of different types of electrolysis devices on the market, with varying capacities and efficiencies.

To produce 1 kilogram of hydrogen at 100% efficiency:

add 9 litres of fresh water to a container
heat to 50 °C to 80 °C.
insert two electrodes
place a permeable membrane between the electrodes
Connect DC electricity from renewable sources
Oxygen (O₂) bubbles off the positive electrode and
Hydrogen (H₂) bubbles off the negative electrode.

The process in reality is 70% to 80% efficient, so a kilogram of hydrogen will tend to use up to 12 litres of clean water and consume 50 kWh to 55 kWh of renewable electricity.
By comparison, an average Australian house consumes electricity amounting to 18 kWh per day.

hydrogen from electrolysis of water

hydrogen from electrolysis of water

Hydrogen production from natural gas

Put simply, the fossil fuel methane (natural gas) is extracted from underground.
At high temperature, using pure water, it is converted to hydrogen fuel and carbon dioxide waste.
The carbon dioxide waste is compressed to a liquid/gas state and injected into geological strata deep in the earth.
The hydrogen fuel is converted to liquid ammonia for export then converted back to hydrogen fuel or used to make fertiliser at its overseas destination.
About 7% to 18% of the energy contained in the H₂ is lost in re-conversion.
In the Gorgon Basin of Western Australia, the source natural gas is mostly methane mixed with about 14% carbon dioxide

--> Using the steam methane reforming (SMR) process
A first step reacts steam with methane to produce hydrogen and carbon monoxide and then a second step reacts steam with carbon monoxide to produce hydrogen and carbon dioxide waste (called the watershift conversion). Greenhouse emissions come from both input power and the reaction.

Steam reformation: CH₄ + H₂O (+ heat) → CO + 3H₂
Water shift conversion: CO + H₂O → CO₂+ H₂
So, in total, we have: CH₄+ 2H₂O → CO₂+ 4H₂
Assuming that there are only these reactions and that they are complete:
Four molecules of H₂ are created at the same time as one molecule of CO₂
A mol of H₂ weighs 2 g and a mol of CO₂ weighs 44 g, so...
Producing 8 g of hydrogen fuel therefore automatically releases 44 g of waste CO₂
1 kg of H₂ therefore releases 5.5 kg of waste CO₂ (at 100% efficiency)
In practice, in a large hydrogen plant, due to heat losses and inefficiencies, 1 kg of H2 produces about 9.3 kg of waste CO₂ and quantities of waste CH₄.

--> Using Pyrolysis of (CH₄) Methane
Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere. Methane pyrolysis decomposition produces hydrogen with solid elemental carbon particles as a by-product and no direct carbon emissions.
Under development, it requires high temperatures to break the bonds of methane to produce hydrogen gas and solid carbon:
CH₄ (gas) → C (solid) + 2H₂ (gas)
The elemental carbon particles may be used in tyres, added to concrete, added to agricultural soil or buried in landfill. With further energy and processing it could possibly be converted to more valuable graphene.
Graphene is a material composed of pure carbon, similar to graphite but with characteristics that make it extraordinarily light and strong. A sheet of one square metre of graphene weighs 0.77 milligrams. Its strength is 200 times greater than that of steel and its density is similar to that of carbon fibre.

Types of Hydrogen:

Types of Hydrogen

Typical Waste Sequestration Site

Waste Sequestration Site

A primer on carbon capture and sequestration (CCS)

The idea behind CCS is to capture the waste CO₂ and inject it deep into the earth so it can’t pollute the atmosphere or acidify the oceans.

--> Where to store the CO₂

A good geologic storage formation for CCS must meet four main criteria.

First, for the host formation to receive the CO₂, it must be porous (have spaces) with good permeability (the spaces are connected)
Second, the host formation should be at a depth of about two to three kilometres, with pressures of 200 to 300 bar and temperatures of 60 °C to 100 °C. This keeps the CO₂ in a more compact liquid/gas state
Third, it is essential that above the host formation is a continuous layer of impermeable caprock such as shale. The liquid/gas CO₂ is less dense than the ground water and will continually try to migrate upwards if it is not blocked
Finally, the formation must be able to store large volumes of CO₂.

--> How is the CO2 kept in place?

Four main mechanisms work together to trap the CO₂ in the formation:

structural trapping,
capillary trapping,
solubility trapping, and
mineral trapping

Structural trapping keeps CO₂ beneath the formation’s impermeable caprock. Rising CO₂ encounters the caprock, stopping vertical migration. Lateral migration is contained if the caprock is shaped like an inverted bowl or hat

Capillary trapping is a function of water and CO₂ competing to move though the small pores between sand grains. The more dense water traps the less dense CO₂ in the little tunnels.

Solubility trapping: Some CO₂ dissolves into the ground water. Since CO₂ saturated water is denser than unsaturated water, it will sink, bringing more unsaturated water in contact with the CO₂

Mineral trapping is a very slow process where CO₂ combines with other rock elements to form solid insoluble minerals.

--> How long will the CO₂ stay underground?

The crust of the earth is dynamic. It erupts, quakes, moves, bends, breaks, fractures, faults and erodes over time. Eventually over time the sequestered CO₂ will escape. The IPCC (Intergovernmental Panel on Climate Change) estimates:

after 100 years, 90% to 99% of sequestered CO₂ remains in place, and
after 1000 years, sequestered CO₂ exceeds 66% to 90%
the IPCC will not and cannot guarantee that a fluid injected in the ground will never come out.

So where do we stand?

Hydrogen fuel production from the electrolysis of water is a battery technology which uses lots of fresh water and lots of electricity. It is useful as a fuel “beyond the grid” for bulk transport like ships, trains, trucks and aircraft where bulky fuel tanks are not a design issue. It may have a place in adding power to the grid in times of peak demand, but this begs the question, in a country where fresh water is scarce, why not use better battery technologies? Hydrogen from natural gas is a processed fossil fuel. Extraction, conversion and injection and sequestration processes do not capture all greenhouse gases. How much CO₂ and CH₄ escapes is currently obscured— it would appear at least 15% and more realistically 60% is lost before sequestration. After sequestration, a portion of that which is captured and sequestered will eventually come back through fugitive emissions.

Our hydrogen future?

It’s a gamble whether this kicking the can down the road buys humankind 100 or 10,000 years

Main Sources

Jin Zhong Zhang, Jinghong Li, Yat Li, Yiping Zhao, 2014, Hydrogen Generation, Storage, and Utilization, co-published by John Wiley & Sons, Inc., Hoboken, New Jersey; and ScienceWise Publishing ISBN 978-1-118-14063-5

Garcia L. 2015, Hydrogen production by steam reforming of natural gas and other nonrenewable feedstocks, in Compendium of hydrogen energy, Vol. 1 Hydrogen production and purification, éd. Woodhead Publishing, Kidlington

Herzog, Howard J. 2018, Carbon Capture, The MIT Press Essential nowledge Series, The MIT Press, Cambridge, MA ISBN 9780262535755

Nuttall William J. , Adetokunboh T. Bakenne, 2020, Fossil Fuel Hydrogen Technical, Economic and Environmental Potential, Springer Nature Switzerland AG, ISBN 978-3-030-30907-7 ISBN 978-3-030-30908-4 (eBook)

Havercroft Ian, Macrory Richard & Stewart Richard, 2018, Carbon capture and storage : emerging legal and regulatory issues, Second edition, Hart Publishing, Portland, Oregon, ISBN 9781509909605

www.industry.gov.au/sites/default/files/October%202021/ document/australias-long-term-emissions-reduction-plan.pdf Australian CCS sites map pg 54

climatechangeconnection.org/emissions/co2-equivalents

energy.gov/eere/fuelcells/hydrogen-production-natural-gas- reforming

en.wikipedia.org/wiki/Hydrogen_production
forbes.com/sites/rrapier/2020/06/06/estimating-the-carbon- footprint-of-hydrogen-production

whatispiping.com/colors-of-hydrogen

large.stanford.edu/courses/2010/ph240/chen1

hydrogene.discoverthegreentech.com/en/production/steam- methane-reforming

aph.gov.au/About_Parliament/Parliamentary_Departments/ Parliamentary_Library/pubs/rp/rp9899/99rp05#COMP anz.com/content/dam/anzcom/pdf/institutional/reports/ hydrogen-handbook.pdf

d3n8a8pro7vhmx.cloudfront.net/lockthegate/pages/6525/ attachments/original/1581635517/Fact_sheet_A_tale_of_two_ fuels_-_vs1._pdf.pdf