Hydrocarbon Processing - January 2022 - 40

Biofuels and Alternative/Renewable Fuels
as a source of hydrogen.14 FIG. 4 depicts
the relevant sources of hydrogen and their
associated names. The most common
source of hydrogen is methane/natural
gas, which is called gray hydrogen. Steam
methane reforming is used to convert
methane to hydrogen through the process
of synthesis gas generation, hydrogen
generation and gas purification. CO2
is
the primary dilutant removed during the
purification process. Similarly, brown hydrogen
is hydrogen that is produced from
coal, using the same steam methane reforming
(SMR) process.
Although SMR is the cheapest way to
produce hydrogen, this process emits a
significant amount of carbon, resulting in
emitting CO2
as a byproduct.15
SMR emits
about 10 t of CO2/t of natural gas, while
coal produces 19 t of CO2/t of coal.16
To
minimize the emissions associated with
brown hydrogen, carbon capture technologies
are added to the SMR purification
step to create blue hydrogen. However,
this process relies on fossil fuel sources,
which still have a carbon footprint. Hydrogen
produced via water electrolysis
has the potential to eliminate emissions
from this production step. Water electrolysis
uses electricity to separate hydrogen
and oxygen from water. Electrolysis powered
by fossil-fuel-sourced grid electricity
is called blue hydrogen, while electrolysis
powered by renewable energy is referred
to as green hydrogen. While green hydrogen
is the most environmentally friendly
way of producing hydrogen, it is the most
expensive option. Another production
option-turquoise hydrogen-is still in
the research phase. Turquoise hydrogen is
produced through the process of pyrolysis,
which converts methane to pure solid
carbon and hydrogen.
For hydrogen to be a reasonable fuel
alterative, green hydrogen should be the
primary type used in engines or fuel cells.
Significant investments are required in
renewable energy technology. At present,
only 3.9% of the hydrogen produced
comes from water electrolysis.15
and stringent safety procedures. According
to the IEA, the cost infrastructure is
offset by the cost of fuel when calculated
at a 15 yr-20 yr lifespan.17
Once the fuel
cost becomes competitive, hydrogen may
be a viable fuel alternative in the future.
Hydrogen can be used directly as a fuel
Intervention
is needed to reduce the cost of green
hydrogen, so that it may be used as a fuel.
Fortunately, the cost of green hydrogen has
reduced by approximately 50% since 2015
and is forecast to continue to decrease as
more projects focus on renewable energy.16
Hydrogen
production will also need
to increase significantly to meet the demands
of the marine industry. Most produced
hydrogen is used as a component in
the chemical industry and in oil refineries.
Like LNG, hydrogen has a lower energy
density than conventional marine
fuels. Hydrogen has an energy density of
8.5 MJ/L, which is about 15% less than
the energy density of diesel.16,17
Therefore,
ship capacity becomes a significant disadvantage
for hydrogen's use in the marine
industry. To store the same amount of
cargo on board will require fuel tanks to
be seven times larger than diesel tanks.16
Hydrogen could be ideal for smaller ships
or for shorter trips that have frequent access
to bunkering stations. Larger ships
would need hydrogen storage that takes
up less space on the ship (e.g., ammonia
or liquid hydrogen).
Hydrogen must also be stored at high
cryogenic conditions (-253°C), requiring
expensive bunkering facility requirements
in an ICE and in fuel cells to generate electricity.
Dual-fuel ICEs are a possible route
for hydrogen; whereby, MGO can be used
when the hydrogen inventory on ships
runs out.15
However, there is presently no
hydrogen fuel engine commercially available.
There are also no federal regulations
for design considerations for the use of
hydrogen as a marine fuel, and, therefore,
there is no formal approval for its commercial
use. The U.S. Coast Guard may
approve alternative design proposals for
companies on a case-by-case basis.18
The
knowledge gained from the use of LNG
may bridge to developing design solutions
for hydrogen-fueled vessels. Overall, there
are many projects geared toward developing
hydrogen technologies. For example,
the U.S. Department of Energy (DOE)
has funded many projects that focus on
overcoming hydrogen's shortfalls.
Hydrogen's lifecycle analysis as a fuel
is dependent on the source of production.
Hydrogen production emits 60 MMtpy of
CO2
, primarily from brown/gray hydrogen
production, according to the U.S. EPA.
Brown/gray hydrogen and HFO emit
roughly the same amount of carbon.16
Like
LNG, gray hydrogen has high upstream
emissions that results from the extraction
of natural gas. This includes methane leakage
during the extraction process, along
with methane slips during transportation
and SMR processes. Blue hydrogen captures
approximately 90% of the CO2
ted during the SMR process.19
emitHowever,
this
option still involves major upstream
emissions. Howarth et al. conducted a
study on blue hydrogen and found that it
emits 9%-25% less CO2
than gray hydroFIG.
4. The different types of hydrogen production.15
40 JANUARY 2022 | HydrocarbonProcessing.com
gen. However, since methane is used to
power carbon capture technology, fugitive
methane emissions are much greater than
gray hydrogen. Howarth et al. concluded
that the lifecycle GHG emissions of blue
hydrogen are 20% times greater than with
burning natural gas or coal. Turquoise hydrogen
is still being researched, but it has
the potential of minimizing carbon emissions
from the hydrogen fuel lifecycle. The
process produces solid carbon instead of
CO2
, which eliminates the need for car
http://www.HydrocarbonProcessing.com
Hydrocarbon Processing - January 2022

Table of Contents for the Digital Edition of Hydrocarbon Processing - January 2022
