[ExI] Trash to Fuel

[Keith Henson]

This is likely too long for the list.

Making synthetic fuel from trash and intermittent renewable energy

H. Keith Henson hkhenson at gmail.com

Nov 16, 2025 Engineering draft notes (please check the numbers)

Abstract

This paper explores making synthetic fuel from trash and coal using
renewable energy. The key reaction, dating back to the 1850s, involves
heating carbon in steam to produce hydrogen and carbon monoxide. This
endothermic reaction requires heating, traditionally done by
alternately burning coke and injecting steam. Using intermittent
renewable electricity for heating is now feasible.

A metric ton of carbon requires 3.03 MWh of heat to produce 13.1 MWh
of syngas; a 4 to 1 energy gain. The gas can be stored, burned, or
converted into methane, jet fuel, or diesel. The water-gas shift
reaction can be used to increase the hydrogen at the expense of CO.
The resultant CO2 (about half) can be sorted out of the gas stream and
sequestered.

Following the water-gas shift, the Fischer-Tropsch (FT) process
converts syngas into hydrocarbons, with water as a byproduct.

An example design uses 9,000 tons of trash daily from the Sylmar, CA
landfill supplemented with coal, to produce syngas. The project would
need significant power and infrastructure, including a 3-GW vaporizer
and new high-voltage DC lines.

The venture could generate over $600 million annually from the sale of
diesel, with costs for coal and power totaling $241 million. The
project addresses landfill overuse and methane leakage, and provides a
renewable energy solution for synthetic fuel production, though it
requires substantial investment and the development of a 3-GW
gasifier.

Background

History

In the early days of the Industrial Revolution, “gas works” made “town
gas” by heating coke (burning it) then shutting off the air and
blowing steam into the white-hot coke. This made CO and hydrogen. The
proposal here is to heat any carbon source in steam with renewable
power and then feed the syngas to a FT plant to make liquid fuels. It
takes 3 MWh to vaporize a ton of carbon in steam. (Making the steam
takes 0.94 MWh/ton of carbon and some of the heat can be recovered
from the hot syngas.) This avoids burning the carbon to provide
process heat.

“Town gas is a more general term referring to manufactured gaseous
fuels produced for sale to consumers and municipalities.

“The original coal gas was produced by the coal gasification reaction,”

https://en.wikipedia.org/wiki/Coal_gas

about 1/3rd of the way into the article.

“The problem of nitrogen dilution was overcome by the blue water gas
(BWG) process, developed in the 1850s by Sir William Siemens. The
incandescent fuel bed would be alternately blasted with air followed
by steam. The air reactions during the blow cycle are exothermic,
heating up the bed, while the steam reactions during the make cycle,
are endothermic and cool down the bed. The products from the air cycle
contain non-calorific nitrogen and are exhausted out the stack while
the products of the steam cycle are kept as blue water gas. This gas
is composed almost entirely of CO and H2, and burns with a pale blue
flame similar to natural gas.”

Chemistry

The chemical reaction upon which this depends is:

H2O + C → H2 + CO (ΔH = +131 kJ/mol)

18 12 2 28

“The reaction is endothermic, so the fuel must be continually
re-heated to maintain the reaction.“ (Wikipedia). Traditionally this
was done by alternately blowing air and steam through the hot coke,
burning a lot of the coke to drive the reaction. The idea of heating
the coke (or other carbon source) with electricity would not have made
economic sense at that time, even if someone had thought of it.

Carbon is 12 g/mol, 83.3 mol/kg; a kg would soak up 10900 kJ. A ton of
carbon evaporated in steam would need 10,900,000 kJ or 3.03 MW hours.

This would produce 1/6th of a ton of hydrogen with a combustion energy
content of 39.4 MWh/ton, about 6.57 MWh. The CO combustion energy is
10.1 MJ/kg. A ton of carbon produces 2,333 kg of CO or about 6.55 MWh.
The reaction makes about 13.1 MWh of syngas from a ton of carbon and
3-4 MWh of renewable electric power, an energy gain of over 3. Most of
the energy in the gas is from carbon sources such as trash or coal.

It’s an efficient way to use intermittent power, though. From this
point, the gas can be stored for winter, burned in combustion
turbines, or made into methane, jet fuel, gasoline, or diesel.

Making Liquid Fuels

“The FT is a collection of chemical reactions that converts a mixture
of carbon monoxide and hydrogen, known as syngas, into liquid
hydrocarbons. These reactions occur in the presence of metal
catalysts, typically at temperatures of 150–300 °C (302–572 °F) and
pressures of one to several tens of atmospheres. The FT process is an
important reaction in both coal liquefaction and gas-to-liquids
technology for producing liquid hydrocarbons.[1]”

https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process

The FT reaction is:

CO + 2H2 → (CH2)n + H2O. Half the CO in raw syngas must be converted
to hydrogen via the water-gas shift reaction.

CO + H2O → CO2 + H2. This CO2, about half, can be sorted out and stored.

Sasol has an FT plant in Qatar which makes 34,000 bbl/day of synthetic
diesel. It has been in operation since 2007.

Development

The only part of this proposal that does not already exist at scale is
the electrically heated gasifier. There is no reason it would be very
expensive per ton of capacity, certainly much less than
platinum-containing electrolytic cells used to make hydrogen.

One problem with using trash a carbon source is that we don’t make
enough of it. Can we collect enough biomass? Possibly. It would reduce
the cost of waste collection if biomass were collected with the trash.

Producing Hydrogen

Optimized for hydrogen production, a ton of carbon can make 1/3rd of a
ton of hydrogen at an energy cost of 3-4 MWh. A ton of hydrogen would
take 10 MWh to make. At $20/MWh, the cost would be $200/ton or 20
cents per kg. To this must be added the capital cost of the plant and
the disposal cost of the CO2, but even so, it should come in less than
the $1.50/kg cost of gray hydrogen. Electrolytic hydrogen takes 50
MWh/ton to make, 5 times as much energy, and requires expensive
platinum.

If the cost of a 9,000-ton per day plant is a billion dollars, written
off in 5 years, the yearly production capital cost of hydrogen would
be $1B/(3,000 t/d x 365 d/y x 5 y) or around $180/ton. That about
doubles the cost of hydrogen to 40 cents per kg, which is still a
bargain.

A Back-of-the-Envelope Example

The closest landfill to Sylmar, CA gets 9,000 tons of trash per day.
Call it 4,000 tons/day of carbon. An installation half the size of
Sasol’s Oryx plant (17,000 bbl/day) would need about 8,500 tons of
carbon (half lost to making hydrogen), so it would need ~4,500 tons of
coal per day in addition. That is around 45 rail cars per day which is
a modest amount, and there is a nearby rail line. Tires or brush could
be fed into the vaporizer in place of coal.

Vaporizing this amount of carbon would take 8,500 t/24h x 3 MWh/t, a
little over a GW. If the peak load (when renewable power is available)
were 3 times the average, the vaporizer would use 3 GW. That just
happens to be the capacity of the nearby Sylmar converter station, so
existing power lines could handle it.

It is about 40 miles from the landfill to a Chevron refinery where the
syngas could be processed into synthetic jet fuel and diesel. There
are several old oil fields along the route. It would take effort to
decide if the oil fields were suitable to store a buffer of syngas,
but they probably are.

Rough Economic Analysis

Income at $100/bbl ($2.40/gal) for diesel, the gross annual sales of
this venture would be 17,000 bbl/day x 365 days/year x $100/bbl or ~
$620 M/year.

Figuring cost, the trash is free, and the coal is $66 million (at
$40/ton). The power would cost 3,000 MW x 365 days/year x 8 hours/day
x $20/MWh or $175 million per year. (The least expensive PV is $13.50
per MWh.) This leaves $405 million gross income per year. Maintenance
and labor might reduce this to $250 M. For a 5-year return on capital,
the project could cost up to $1.25 B. The Sasol plant cost a billion
dollars, but that included a refinery. Is there an unused pipeline
close to the 405 freeway? If not, pipelines cost around $8 million a
mile.

Research and Development

The one part of this project that does not exist at scale is a 3 GW
vaporizer. That’s an awful lot of power but not unprecedented for
industrial processes. A blast furnace for iron production ranges from
1 to 5 GW, most of it from the combustion of coke. Arc furnaces for
mini steel mills are much smaller, typically 50 MW (they are melting,
not reducing the iron). Arc is probably not the right approach to heat
trash or coal, the carbon rods will vaporize in the steam. Induction
heating might be better, though this is 60 times more power than any
existing induction furnace. A complicating factor for induction
heating is that the gasifier shell can’t be a conductor. How much hoop
stress would be needed to contain the pressure needs to be calculated.
It should not be much worse than water though that depends on the
pressure.

Figuring trash at a density of one, and a holding time of an hour, the
interior volume of the gasifier would be 1,000 cubic meters. The
largest blast furnace in the world is 6,000 cubic meters. If the
vaporizer were a 50-meter-tall cylinder, it would be a little over 16
m in diameter or somewhat larger to accommodate the counter current
steam pipes.

The trash and coal or tires need to be loaded through an gas lock.
There are two variations used on blast furnaces, double bell
https://www.youtube.com/watch?v=EfmXzny-TkE and Rotating Chute
https://www.youtube.com/watch?v=SKl87k-7PiI

A third option is a rotating drum. If the drum holds 50 tons, it will
have to cycle 20 times per hour to feed the trash into the vaporizer
at 1000 tons per hour. Steam might be used to purge the air from the
trash going in and to prevent raw syngas from escaping. Alternately, a
vacuum system could be used on the rotating airlock to purge the air
and return the syngas.

One of these or some variation will be needed.

Should the trash run through a grinder? Perhaps, how is the trash
treated for incinerators?

One thing which should be added to a conveyer belt is an X-ray and an
AI up to reading the pictures in real time for human bodies. Tracking
of the trucks dumping on the belt would also be useful in the event
bodies are found. There needs to be provision to stop the belt and
recover a body. As a guess this would happen once a year.

The X-ray could measure the amount of carbon in the trash and a
control computer would determine the amount of coal or tires needed to
use the entire electric heat input. Chlorine in plastics should also
be measured for downstream cleanup.

The belt system will need to be enclosed to prevent wind from blowing
trash off the belt. It should incorporate cleaning provisions.
Depending on the control algorithms the same belt could be used to add
the coal. Coal volume or other carbon like tires should be around ¼ of
the trash.

Gas Flow

The flow of syngas would be 1/6 ton of H2 per ton of carbon. Hydrogen
is 500 mol/kg, 500 k mol/ton; 1/6 ton would be 83.3 k mol. At STP, a
mol of a gas fills 22.4 l, 1/6 ton would have a volume of 1867 kl. The
CO volume is equal, so 3,733 cubic meters of gas flow per hour per ton
of carbon vaporized. For a peak of 1,000 tons per hour, the gas flow
would be 3,733,000 cubic meters per hour, half of that if pressurized
to 2 bar. The proposed vaporizer is 200 square meters in area making
the upward gas flow around 3,733,000 m3/200 m2 per hour or ~5 m/s (11
mph). That does not include the pyrolysis gas or the water vapor from
drying out the trash. This is probably not too fast to lift the trash,
but further research is needed.

Vaporizing 9,000 tons of carbon per day (9 hours) would need about
13,500 tons of steam or 1500 tons per hour or 417 kg of steam per
second. Assuming water at 100 degrees C, and 2,257 kJ/kg to boil, it
would take 940,000 kJ/sec to boil the water or 940 MW, or about 30
percent of the power input to vaporize the carbon in steam. The steam
could be generated in counter current pipes lining the induction
gasifier and blown through or across the pool of slag to react with
the carbon. The shape of the induction gasifier might be like the
upper part of a blast furnace, opening up to channel the syngas along
the steam generator pipes. (The newly made syngas has to be cooled,
and it is hotter than 100 C.)

Steam generation tube area can be calculated from the days of locomotives.

The ASME determines boiler horsepower as: The amount of energy needed
to produce 34.5 pounds (15.65 kg) of steam, per hour, at a pressure
and temperature of 0 Psig (0 bar) and 212oF (100oC), with feed water
at 0 Psig and 212oF. One boiler horsepower is about 33,479 Btu per
hour (about 9,810 watts, 8430 Kcal/Hr).

531,000 /15.65 is 34,000 boiler HP. Area would be 577,000 square feet
or 53600 square meters. (An AI using somewhat higher heat transfer got
19,600 square meters.) The inside of the vaporizer is 56.5 square
meters per meter of height. 30 meters would be short of the needed
area by a factor of 31. This indicates that the water boiler part of
the vaporizer will need many steam pipes around the edges to give
enough heat transfer surface. Keeping the pipes from absorbing the
induction heat will be a problem. They may have to be ceramic.

Induction coil

The external coil for the induction heater requires cooling. At 3 GW
even a 0.1% loss will be 3 MW. Coils are often cooled by circulating
water but this requires high resistivity water and an insulating
section between the ends of the coil. Even though it is not thermally
as good as water, the high voltage across the coil may make silicon
oil a better choice. The turn to turn voltage is high as well. 3 GW is
3000 A at a million volts. Turn to turn voltage for 100 turns would
10,000 volts. The entire coil might be immersed in silicon oil.

The coil is in a resonate circuit with capacitors. These will need to
be cooled as well.

While modeling is essential to the design, a 1/10 scale engineering
test prototype or even a smaller unit might be required. This work is
from first chemistry and physics principles so there is much to learn.

Gas Cleanup

The bottom of the induction gasifier will have a pool of slag (mostly
metal and glass) that must be drained off from time to time. The slag
is useful road construction material.
https://wasterecyclingmag.ca/feature/energy-conversion/ Aluminum and
iron in the trash will probably react with steam to make hydrogen.
Blowing steam through the slag should take out most of the carbon plus
heat the steam to the 1600 C it takes to react with carbon. How
efficient this will be is unknown, but there are a lot of studies
about how much carbon remains in slag.

The gas flow would be up through 40 meters of trash. This should
remove most of the pyrolysis products (smoke, bio-oil) and recycle the
carbon down where it can be reacted with steam. This needs further
study. The remaining gas will be cleaned up with an electrically
heated catalytic grid or alternately a plasma torch. The steam content
of the output gas stream must be controlled to assure enough steam to
react with the carbon.

https://www.sciencedirect.com/science/article/pii/S0306261924019391

The design of this subsystem will need careful consideration and
probably counter current flow to get the smoke containing gas hot
enough to react without requiring excessive power.

One safety issue is apparent. If the syngas is going to be used to
make liquid fuels, about 1/3 would be CO. A leak of the magnitude of
the Aliso Canyon leak could kill a large number of people from the CO.

https://en.wikipedia.org/wiki/Aliso_Canyon_gas_leak

This will have to be addressed. Leaking syngas could be burned to make it safe.

Another consideration is that considerable energy is released in the
FT reaction and the reaction runs away at higher tempature. The
possibility of this happening in a storage reservoir needs to be
addressed. It would be quite embarrassing to have an oil field
explode.

Funding a Study

Modern warfare is completely dependent on jet fuel and diesel.
However, we live at the tail end of the fossil fuels era. While
supplies are currently adequate, this will not be true in the long
term. The US DoD had an experimental project that made 11 gallons of
diesel from a ton of trash. This method, using renewable energy for
heat, would make about 80 gallons per ton of trash supplemented with
coal or other carbon sources.

The proposal which might be presented to DARPA is to use trash and
coal heated by renewable power in steam to make syngas. The syngas can
be turned into jet fuel and diesel by FT plants.

There are lots of engineering and economic problems to solve, but the
point is that intermittent renewable energy can be used to make
synthetic fuel to replace that made from oil.

The induction-heated vaporizer will be a major design effort. It would
take 8-10 of these to make all the Los Angeles trash into diesel. At 5
square km/GW for PV, 15 km2 for one of them, 150 km2 for enough power
to make diesel out of all the Los Angeles trash. The existing Pacific
Intertie is 3 GW, so to get the power into the vaporizers would take
~10 new high-voltage DC lines.

It’s a huge job, but within existing technology.

Other possible sources of funding at least for studies is the airlines
or possibly rail companies.

Environmental Considerations

A problem this solves is that the US has been overrun by landfills.
The EU and China use incinerators that could be replaced by this
method to make syngas.

This proposal would stop landfill leakage of methane. Landfill leakage
is a substantial source of methane.

The process would eliminate persistent chemicals and drugs if sewer
digester sludge were included in the feed. (Included water is not a
problems.)

This process eliminates plastics of all kinds. Unlike incinerators, it
releases no dioxins into the environment from PVC.

Tires and harvested brush could be used in place of coal.

Energy Considerations

A problem with renewables is that the grid cannot absorb them when the
load is smaller than the supply, leading to curtailment.

This is wasteful, but using this energy to make hydrogen is too
expensive. The electrolyzes are expensive largely due to the platinum
in them and using them less than all the time increases the effective
capital cost. (Any capital eqipent used ¼ of the time increases the
capital cost by a factor of 4.)

This proposal would purposely install much more renewable power than
the grid could absorb and use all the power in excess of grid need to
make fuel.

Objections > Trash is “not a resource.”

It is a source of carbon, though. If you have lots of excess renewable
power and a low cost source of carbon, you can make diesel for around
$100/bbl. The big problem is that we don’t make enough trash.

Converting syngas to jet fuel or diesel is around 75 percent
efficient. It is well understood. The Sasol plant in Qatar has been
operating since 2007 and a previous version that ran on coal was
supplying much of the fuel for South Africa during the apartheid era.

> What are the specific challenges in scaling up this process to a commercially viable level, especially in terms of integrating intermittent renewable energy?

The one piece that does not exist at scale is the electrically heated vaporizer.

> What is the most efficient way to store and transport the syngas produced by this reaction?

The only economical way I am aware of for storage is an empty gas or
oil field. Transport is by pipeline.

> How do you plan to address the long-term sustainability of this process, especially in terms of CO2 emissions and air capture?

If you are making hydrogen from coal this way, you can capture and
store all the CO2. In making fuel, half the carbon is in the fuel and
is released when the fuel is used. If half the carbon comes from
biomass or trash, the accounting is more complicated. The fuel might
be rated as carbon neutral. Eventually, all the carbon will have to
come from biomass or be taken out of the air if humans are still using
hydrocarbon fuels. None of these will be problems after nanotechnology
comes along, but who knows how long that will take?

>What are the potential costs and environmental trade-offs compared to other forms of renewable energy storage or synthetic fuel production?

There isn’t any storage out there for renewable energy that scales to
seasons. Such synthetic fuel production that exists is many times as
expensive as oil. All the trash that Los Angeles produces plus about
half that much in coal would supply the US military with fuel.
Alternately, the trash could supply all the jet fuel LAX uses.


Best wishes,

Keith