Why SpaceX isn’t YET synthesizing methane in Boca Chica but IS using solar

[Robotbeat]

To make 1 Joule of methane synthetically requires about 2 Joules of solar/wind electricity. But if you took that 2 Joules of solar/wind electricity & exported it to the grid, you’d be displacing about 4 Joules of natural gas from being burned plus you saved the capital cost of electrolysis & Sabatier reactors & CO2 capture and some of the maintenance on the natural gas plants. So even from a climate perspective it’s way better to use that gas directly as propellant and exporting (to the grid) the electricity you WOULD have used to synthesize it.

Once the grid becomes clean enough, then adding more solar and wind electricity tends to just lead to solar and wind curtailment (even with storage), but not quite enough to change that equation until almost all fossil fuels are removed from the grid. So let’s say once the grid is 75-90% clean or better (currently 40% in the US), then it may make sense to synthesize methane versus just using fossil methane and exporting (to the grid) the electricity you would’ve used to make Sabatier methane.

Similar math (but in the other direction) is partly why it may make sense to liquefy the methane and oxygen with solar and wind. Flare gas generators aren’t cheap, require about 1.5¢/kWh of maintenance and require about 3 Joules of gas (HHV) to make 1 Joule of electricity, so if you want to maximize the gas in the field for propellant usage, you’ll use solar and wind to run the liquefaction instead of burning gas in a generator (although they may still do that sometimes).

The gas in that field in Boca Chica is worth more to SpaceX than gas other places (or than exporting that gas to the pipeline infrastructure) because of lower logistics costs. So it makes sense for them to use plentiful solar and wind electricity instead of burning that limited gas supply inefficiently in an on-site generator.

[Robotbeat]

Just to do a bit more quantitative math, industrial gas in Texas has an average cost over the last decade (which has been very low by historical standards but seems reasonable for our purposes) of about $3/MMBTU, or 1¢/kWh-thermal. But that’s thermal energy. To convert that to electricity using a generator at 33% HHV efficiency (that’s for a big generator. Smaller ones are less efficient) means 3¢/kWh-electric worth of gas and another 1.5¢/kWh-electric in marginal maintenance costs (not counting the capital cost of the generator as you might want that for backup, potentially) for a total of 4.5¢/kWh-electric.

SpaceX has a gas well on-site which makes it potentially more valuable (once cleaned) than industrial gas due to logistics costs but it is small, and therefore finite. So its value to SpaceX is at least the industrial gas price and perhaps even higher.

Wind costs 2.5¢/kWh in Texas, perhaps even lower. https://nawindpower.com/innergexs-griffin-trail-wind-project-achieves-financial-close

Solar in similar climates in the US can even be lower than 2¢/kWh, even with some storage: https://www.utilitydive.com/news/los-angeles-solicits-record-solar-storage-deal-at-199713-cents-kwh/558018/

So I think it is reasonable that SpaceX has decided to use solar/wind/storage primarily for electricity requirements as the price for that is about half the cost as it would be if you valued their gas price as the same as industrial gas in Texas. And it’s practice for what they’ll need on Mars eventually and it’s better for the climate.

[Nomadd]

 Wind production is already going surplus on certain days because the transmission network can't handle all of it all the time. It would be pretty inefficient storage, but anything that could use that surplus, including CH4 synthesis, wouldn't cause more fossil juice usage.
 But batteries or other storage schemes would no doubt be a lot cheaper and way more efficient.
 Most jobs touting a "Green power source" would be much more efficient in preventing or removing carbon from the air if they used the money needed to build the source to replace generation in areas where it would reduce fossil fuel usage the most and claim the credit where they're using grid power for their project.

[Robotbeat]

Wind production is already going surplus on certain days because the transmission network can't handle all of it all the time. It would be pretty inefficient storage, but anything that could use that surplus, including CH4 synthesis, wouldn't cause more fossil juice usage.
 But batteries or other storage schemes would no doubt be a lot cheaper and way more efficient.

Yeah, the problem of relying on excess wind electricity is it’s only available like 5-10% of the time. If a new wind turbine has 33% capacity factor and costs $1.3/watt, whereas the electrolysis equipment has a capital cost of $2/Watt, then the useful average cost for using “free extra” electricity is ($2/Watt)/(10%) = $20/Watt while the directly wind coupled electrolysis is ($1.3/W+$2/W)/(.33) = $10/Watt average, or half the price. And you can do even better if you mix in a little solar and storage, too, perhaps bringing the average capacity factor up to 67% or so. (Could get to 100% capacity factor by over sizing the wind, solar, and battery, but that’s not usually worth it until your grid is totally clean.)

If electrolysis capital costs get low enough, though, then maybe it’d be worth it (like 10¢/Watt).

[Robotbeat]

SpaceX’s installation in Boca is getting big enough that they could have enough scale to use utility-scale solar and storage and cut down on transmission costs.

[Nomadd]

  What ever happened to Pons and Fleischmann?

 There is always the possibility that CH4 synthesis is for ISRU research. I'd think the air on Mars for that will be compressed to more than 1 Earth atm, so it should be easy to reproduce Martian conditions.

[Robotbeat]

As far as I know, SpaceX has no CH4 synthesis going on at Boca Chica, just liquefaction equipment like used to produce liquid oxygen, nitrogen, and methane (from the air and their well). This is still a kind of ISRU and would be needed as part of any ISRU plant on Mars as well. It also makes sense economically and climate-wise to do this liquefaction using solar (and maybe wind) with a little bit of storage.

I actually think it’d be cool if they did CH4 synthesis demonstration there anyway, but from what I can tell, they’re not doing it yet. Correct me if I’m wrong, Nomadd.

CH4 synthesis is extremely energy intensive. Need hydrogen (produced typically at 50-67% HHV plant-level efficiency), plus about 1/3rd of the hydrogen’s energy is thrown away when making CH4 using the Sabatier reaction, and you typically need about 8.8MJ per kg of CO2 captured from the air (although you could get down to half that).

CO2 + 4*H2 = CH4 + 2*H2O

44kg CO2 + 8kg H2 = 16kg CH4 + 36kg H2O.

8.8MJ/kgCO2
213MJ/kgH2
55.6MJ/kgCH4

387MJ for CO2 + 1704 MJ for H2 = 890 MJ of CH4 and 246MJ of waste heat from Sabatier and another 955 MJ of waste heat from hydrogen electrolysis.

But some of that CO2 energy could actually be provided from the waste heat from Sabatier, and so if you improve CO2 capture efficiency enough (below 246MJ) it may not add to the extra cost. Also, could improve hydrogen electrolysis hydrogen efficiency to like 75-80% HHV. So roughly 50% overall efficiency of electricity to CH4 if you try.

[DreamyPickle]

Methane production on Mars needs to work for years at a time without any hands-on maintenance or even live monitoring. A good step towards this is to build a couple of methane plants on earth and run them non-stop in order to stress-test the equipment.

It doesn't matter if the resulting methane is more expensive, they need to prove the technology.

[spacenut]

I have said before that I was an engineer for 40 years with a natural gas company.  Here are some of the problems with alternative natural gas production:

1) We tried feed stall gas by collecting cow manure from feed stalls.  This was put into a covered pond to retrieve the natural gas (95% methane) and it cost about 3 times what drilling/fracking cost, but it was doable. 

2) We tried seaweed in holding areas offshore that grew 6' a day.  It too cost over 2-3 times what drilling/fracking costs.

3) We drilled into the old Birmingham land fill and got 5 psi pressure of gas from a 1950's landfill.  Cost was cheap, but gas ran out after a couple of years. 

4) Algae has been tried by Exxon.  It is also 3-4 time more expensive than drilling/fracking. 

5) Sewer gas was tried, but humans do not generate enough methane for any real use. 

All of the above were considered "carbon neutral" by taking CO2 out of the air, making natural gas, then putting it back into the air. 

The number 1 producer of CO2 is China right now with a huge amount of cheap coal burning.

We in America are slowly switching to natural gas from coal.  This cuts over 50% of CO2 from a power plant. 

The next biggest CO2 producer is automobiles.  This is being reduced by hybrids and electrics.  Eventually electrics will take over. 

It is also more efficient (80%) to burn natural gas for heating, water heating, cooking, and clothes drying in the home vs burning the gas to produce electricity and send it to the home (33%).  So using natural gas in homes in America (50% of homes) reduces the need and of transmission of power to the home thus less CO2 in the end. 

Back in the 1970's a study was done to switch the natural gas distribution system in the US to hydrogen gas.  This would require almost all the electricity to be produced using nuclear power to make hydrogen gas during the electric off peek periods.  This could take years.  Also all of the existing natural gas appliances would have to have steel wool pads placed over to burners to glow red as hydrogen invisible when burning.  This would have to be done starting in Maine and working all the way back to the original natural gas sources.  This would take years and billions of dollars. 

Again, all of the above is carbon neutral, but costs far far more than people are willing to pay for.  Why should their $50 natural gas bill or cheap electric bill more than triple to pay for this. 

The number one thing that actually could be done quicker is to install some of these new nuclear power plants around the country to replace the coal and even the natural gas burners.  Fully one third or more of natural gas is being used to make electricity, while 1/3 goes to homes, and the other 1/3 goes to business and industry. 

The second is using more solar and wind in areas where wind is high and or there is far more sunny days.  Storage here is the problem. 

The third best thing is to get a hybrid or electric vehicle when you buy a new vehicle. 

I say all this to say using natural gas to extract the methane for the rocket fuel is the least expensive most way to go for now.  These rockets aren't going to use produce enough CO2 to change anything drastically.  One Superheavy/Starship launch is the equivalent gas that a small town would use in about a week.  Now a lot of launches would be a lot of CO2.  However, this can be offset by SpaceX selling solar or wind electric production. 

Nuclear power plants, especially the smaller ones could be installed quickly around the country, IF tax incentives were given to the power companies.  This would release a lot of natural gas for rocket use.  More than a rocket and hour.  There is also about a 200 year supply of natural gas already drilled and tapped in the US. 

[cdebuhr]

While they'll clearly want to set up pilot plants on Earth to produce CH4 and O2 from CO2 and water, it makes no sense whatsoever to attempt this using captured atmospheric CO2 (beyond the obvious eco brownie points), as it would have no real relevance to CO2 capture on Mars (which  is really mostly just a matter of compression).  Its not to say Terran CO2 scrubbers wont be needed at some point (and at the rate were going, we'll need 'em), but right now, you'd be MUCH better off using the (presumably) renewable power that would be needed to extract atmospheric CO2 to displace fossil fuel generation, and just buy liquid CO2 delivered by truck.

[Robotbeat]

Spacenut:

you’re assuming electrical heating would be resistive. But in the parts of the US that use natural gas for heating, heat pumps would be competitive. They offer a 3-4 times increase in heat output for electricity input, meaning even if you’re using natural gas fired combined cycle power plants, that is Still more efficient than burning the natural gas for heat directly. It seems like you’re cheating the laws of thermodynamics but you aren’t. (Combined cycle plants achieve a combustion temperature far higher than room temperature so there’s a lot of useful work that can be done).

Secondly, all your examples are different types of biogas, not actual Electrolysis and synthesis.

I agree nuclear is good (& also benefits a lot from storage, BTW), but solar and wind and storage are now so cheap and nuclear has become so expensive due to being locked in the courts for so long and also the inexperience of contractors that now you’re better off in the US just using solar, wind, and a bit of storage. Even with the curtailment necessary to get to a 100% capacity factor, still cheaper than nuclear has become (unfortunately). Even so, I’ll defend any nuclear power plant in the US. We should keep them all running until we stop using hydrocarbons.

[born01930]

Cold fusion fell by the wayside when Fleischmann's yeast business took off.

33% efficiency is for a steam plant, gas turbines with HRSG are well north of 60%

[Robotbeat]

Cold fusion fell by the wayside when Fleischmann's yeast business took off.

33% efficiency is for a steam plant, gas turbines with HRSG are well north of 60%

I don't think so. Combined cycle plants are above 60% LOW heating value (I believe 62.something is the record, and not a long-term number... 63% may be a newer record), which is cheating (whenever folks are going for efficiency records, they always use a denominator that makes their numbers look the best). The High heating value efficiency even for the best combined cycle plants is only 50-55% (and those are large, over 100MW with a fairly high capital cost). 33% HHV efficiency is typical for ~500-1000kW natural gas generators.

SpaceX isn’t going to build a 400MW advanced combined cycle plant with a $1.1/Watt capital cost just for refrigeration needs, so we’re comparing solar and wind and storage with 33% HHV efficiency natural gas generators.

[CameronD]

I say all this to say using natural gas to extract the methane for the rocket fuel is the least expensive most way to go for now.  These rockets aren't going to use produce enough CO2 to change anything drastically.  One Superheavy/Starship launch is the equivalent gas that a small town would use in about a week.  Now a lot of launches would be a lot of CO2.  However, this can be offset by SpaceX selling solar or wind electric production. 

Nuclear power plants, especially the smaller ones could be installed quickly around the country, IF tax incentives were given to the power companies.  This would release a lot of natural gas for rocket use.  More than a rocket and hour.  There is also about a 200 year supply of natural gas already drilled and tapped in the US.

ISTM, when most rocket folks today speak of using "methane" for rocket fuel, a goodly percentage of the time they're launching with liquified natural gas (LNG).. so, you're right, it's not only the least expensive way to "extract" methane - it's actually the same thing. 

For the folks fussy enough to insist on pure methane because they like to use their engines more than once (eg. SpX), it's not a huge ask to separate out the liquid CO2 fraction (for sale to the nearest soft drink manufacturer) and the rest of the nasties (like H2S and the occasional acid) once you've compressed your natural gas stream enough to fill your fuel tank.
   

[ZChris13]

I say all this to say using natural gas to extract the methane for the rocket fuel is the least expensive most way to go for now.  These rockets aren't going to use produce enough CO2 to change anything drastically.  One Superheavy/Starship launch is the equivalent gas that a small town would use in about a week.  Now a lot of launches would be a lot of CO2.  However, this can be offset by SpaceX selling solar or wind electric production. 

Nuclear power plants, especially the smaller ones could be installed quickly around the country, IF tax incentives were given to the power companies.  This would release a lot of natural gas for rocket use.  More than a rocket and hour.  There is also about a 200 year supply of natural gas already drilled and tapped in the US.

ISTM, when most rocket folks today speak of using "methane" for rocket fuel, a goodly percentage of the time they're launching with liquified natural gas (LNG).. so, you're right, it's not only the least expensive way to "extract" methane - it's actually the same thing. 

For the folks fussy enough to insist on pure methane because they like to use their engines more than once (eg. SpX), it's not a huge ask to separate out the liquid CO2 fraction (for sale to the nearest soft drink manufacturer) and the rest of the nasties (like H2S and the occasional acid) once you've compressed your natural gas stream enough to fill your fuel tank.
 

Vulcan, New Glenn, and Starship all use the same stuff, which is cryogenic purified NG, which is almost entirely pure methane. ULA call it LNG because of marketing or something.
Is there anybody else using it?

[spacenut]

Spacenut:

you’re assuming electrical heating would be resistive. But in the parts of the US that use natural gas for heating, heat pumps would be competitive. They offer a 3-4 times increase in heat output for electricity input, meaning even if you’re using natural gas fired combined cycle power plants, that is Still more efficient than burning the natural gas for heat directly. It seems like you’re cheating the laws of thermodynamics but you aren’t. (Combined cycle plants achieve a combustion temperature far higher than room temperature so there’s a lot of useful work that can be done).

Secondly, all your examples are different types of biogas, not actual Electrolysis and synthesis.

I agree nuclear is good (& also benefits a lot from storage, BTW), but solar and wind and storage are now so cheap and nuclear has become so expensive due to being locked in the courts for so long and also the inexperience of contractors that now you’re better off in the US just using solar, wind, and a bit of storage. Even with the curtailment necessary to get to a 100% capacity factor, still cheaper than nuclear has become (unfortunately). Even so, I’ll defend any nuclear power plant in the US. We should keep them all running until we stop using hydrocarbons.

I live in the Deep South.  I have a fairly large house with gas heat/electric air on one side, and a heat pump/strip heat on the other side.  The gas is hot faster and the strip heat comes on when the temperature drops below 35-40 degrees which it does quite often between December and February.  Gas cooks better and faster, especially if you are canning or need more precise heat.  Gas heats water faster and cheaper over the life of the water heater than solar.  Our local housing project put in solar water heaters with gas back up.  They determined the solar wasn't worth it after about 5 years.  They had constant problems keeping enough hot water without the gas.  It didn't save the housing project any money and actually cost more in the long run.  So they took out the solar and used gas water heaters only.  Even clothes drying in cheaper.  I changed out my old gas heating and air conditioning units.  The heating was still working, but the air conditioning side compressors burned up after about 25 years.  New air is cheaper on bills, but the heat pump in it's second year is giving trouble, but still in warranty.  Heat pumps sound good on paper and the power company gives kickback money for HVAC people to install them.  However, they are more troublesome and the life expectancy on them is about 1/3 less than a standard air condition/gas heat system. 

I have kept up with my bills.  Gas is much less expensive.  2/3rds of electricity is lost in the transmission from the generator to the power meter at your house.  This is the main reason electricity cost's more than natural gas.  Only 20% of the cost of gas at your home is lost in the pumping and transmission via pipeline to your house.  You see the problem.  You loose efficiency in burning gas to produce power, then in the transforming up and down to get to your house, and the resistance in the powerlines.  It is more efficient to take the gas directly and use it at your house.  It doesn't matter how efficient the electrical appliances are, you still loose 2/3rds of the power in the transmission to your home. 

As far as nuclear.  The small tractor trailer size completely self contained nuclear power plants are what should be installed around the country.  They do not melt down and are designed to last about 20 years without human hands touching them.  They can be controlled remotely to adjust power as demands change.

Wind is about the same cost as natural gas, if you live in the plains states where you have a constant wind, for producing power.  Solar is only competitive in the Southwest where you have more sun.  You also have to factor in the battery storage costs and lifetime maintenance of any type of energy.  Natural gas can be cheaply stored as LNG during summer months to be released in winter.  Solar can easily help with air conditioning bills in the Southwest during the day, while using conventional energy at night when demand is less.  One thing I don't like is the power company in Massachusetts was going to install windmills off Cape Cod a few years ago.  The people voted it down because they didn't want to look out at sea and see windmills.  They installed a fuel oil power plant.  However, most coastal areas have a constant breeze where windmills can be installed and 90% of the worlds people live within 300 miles of an ocean.   Killing birds is the biggest problem. 

From what I have experienced in life.  Homes should be built semi-underground.  In my area 3' deep is a constant 60 degrees F year round.  I personally know a man who built his house semi-underground near me.  He faced is open side north (Deep South).  He went a year without heat or AC.  He got up to 85 degrees in the summer on a 102 degree day.  He got down to 62 degrees on a 14 degree day.  Humidity was his biggest problem.  He ended up having to install a HVAC system.  He only needed a wood fire place to take the chill off on real cold days in winter.  He needed the air conditioning to take out the humidity.  He said between cooking, showers, clothes washing, the humidity built up in the house.  He did use a dehumidifier most of the time. 

Manufacturing metals uses a lot of heat from either coal or natural gas.  Natural gas is now used mostly on soft metals and glass making.  Coal on iron and steel making as it gets hotter.  Right now electricity costs way too much to smelt metals.  Recycling metals uses far less energy. 

I know this is all kind of off topic, but again, using natural gas for rocket fuel is not going to change much.  Changing the way we produce power and drive cars is going to make the biggest dent in CO2 emissions. 

[Robotbeat]

Why are people liking that post? 2/3rds of electricity is lost from generation to your meter? Nope. Try 5% according to the EIA. You’re off by LITERALLY more than an order of magnitude. With massive incorrect statements like that, I stopped reading there. Not worth responding to any of the rest, spacenut.

[CameronD]

The gas in that field in Boca Chica is worth more to SpaceX than gas other places (or than exporting that gas to the pipeline infrastructure) because of lower logistics costs. So it makes sense for them to use plentiful solar and wind electricity instead of burning that limited gas supply inefficiently in an on-site generator.

Getting back to the original question, you missed one option:  burning a little of the natural gas to compress the remaining gas stream - which, come to think of it, is what happens at most natural gas wells anyway.  http://www.solarturbines.com

The next step (which isn't a big one) is to liquify it.. although the infrastructure, permits, operating and maintenance costs to do all that are probably a lot higher than spending the money on a few solar panels and concentrating on your core business: flying rockets... and so it makes sense for them to use plentiful solar and wind electricity instead.
 

[Robotbeat]

The gas in that field in Boca Chica is worth more to SpaceX than gas other places (or than exporting that gas to the pipeline infrastructure) because of lower logistics costs. So it makes sense for them to use plentiful solar and wind electricity instead of burning that limited gas supply inefficiently in an on-site generator.

Getting back to the original question, you missed one option:  burning a little of the natural gas to compress the remaining gas stream - which, come to think of it, is what happens at most natural gas wells anyway.  http://www.solarturbines.com

The next step (which isn't a big one) is to liquify it.. although the infrastructure, permits, operating and maintenance costs to do all that are probably a lot higher than spending the money on a few solar panels and concentrating on your core business: flying rockets... and so it makes sense for them to use plentiful solar and wind electricity instead.
 

Absolutely it’s normal to use some of the gas to compress the rest. I’m saying why it doesn’t necessarily make sense for SpaceX to do that. And liquefaction is basically just compression & expansion with some heat exchangers thrown in for good measure.

[spacenut]

I was always told it was 66%.  This is the heat loss from burning coal or gas, making steam, friction turning a generator, then transmission.  Lots of transference of power from one form to another.  Heat loss, friction, etc. 

The pure product going straight to the house is a better transference.  It is only 20% directly from the well head to the house meter.  Pure natural gas only has to be filtered, go through a vertical separator to removed liquids at the bottom like ethane and butane and some water and helium at the top.  Then it is about 95% pure methane.  Most is already under pressure coming out of the ground.  One well in Mobile bay was 1,400 psi coming out of the well for several years.  It only has to be pressurized near the end of the transmission systems. 

Thus the more efficient method of transference of power.  Even nuclear power has efficiency losses making steam and turning a turbine.