I assumed they would use sea water for cooling but that doesn't seem to be the case? Maybe the battery coolant is cooled using some sort of sea water heat exchanger?
Batteries for ships seems really silly but at the same time its the perfect regime for a ridiculous quantity potentially hazardous items. Nuclear obviously works well here too. You have an unlimited amount of water with which to fight any fires or cool off equipment and you could theoretically engineer a way to dump the entire assembly into the ocean in an emergency.
Hydrodynamics are brutal, but the square-cube law works in your favor. The ocean doesn't care about what's inside your ship. Just the surface of it. The mass is mostly irrelevant. This is why cargo vessels are so large. The bigger the boat the bigger the energy density benefit.
The only real problem is the cost. To compete with a supermax you would need something like two billion dollars worth of batteries to survive a transpacific voyage.
More modern battery chemistries are less hazardous as well. LFP for example is both cheaper and more stable, just at the cost of energy density. Which might be fine if you have a giant ship that can handle a large volume and mass of batteries to save on fuel costs.
> You have an unlimited amount of water with which to fight any fires
Fire on a ship is extremely dangerous. Think about what your training and your first instincts both tell you to do if there's a serious fire. Where I am the training starts with four words: "Get out. Stay out". But you can't just leave a ship, in the ocean you will drown. Even lifeboats, if they're available and can be used, are much more dangerous than we'd like.
Nuclear power isn't going to happen for merchant vessels (outside some very limited cases like Russia's state owned icebreakers). Unlike superpower navies, shipping lines can't afford to train and pay nuclear engineers plus the necessary armed security personnel. Many countries refuse to allow commercial nuclear vessels to enter their ports due to fears over terrorist attacks, or environmental catastrophe from an accidental sinking.
Unlike superpower navies, shipping lines can't afford to train and pay nuclear engineers plus the necessary armed security personnel.
Yeah, people are probably better off not knowing how insanely cheap shipping lines are. Shipping is one of those parts of the economy and trade that is simultaneously advanced and very old fashioned (in the rickety sense) at the same time.
It's quite fun to do the math on what it would take to power the largest container ships by batteries. It's not physically impossible but it would displace a good chunk of the usable cargo load.
A single container can contain up to 8mwh of capacity. Just 125 of those gets you to 1gwh. Depending on how quick the ship goes, you might need 1-2 gwh per day. You can conserve energy by going slower. But out of 14K containers, reserving maybe a third for battery could power a ship for quite some time. Enough to e.g. cross the Pacific. There are obvious issues with weight and balance. The volume is doable but the weight creates a lot of issues.
Another challenge is indeed the cost of these batteries. That's about an order of magnitude of where it needs to be to make it financially realistic. But batteries coming down further in cost could make this more feasible. And it's not like these huge container ships are cheap. A couple of tens or even hundreds of millions of dollars worth of battery is reasonable. Billions would be unreasonable.
There are traditionally powered ships carrying many thousands of EVs with batteries already. So, putting a few gwh of battery on a ship is already happening; we're just not using them to move the ship. And batteries made in China are typically shipped to the US and elsewhere for integrating into cars, grid storage, etc. as well. If you can ship it, you might as well use it. And of course battery powered ships are already very popular for lighter short haul like ferries, tug boats, small transport barges on rivers, etc. There are plenty of them operational without major issues. Safety issues seem to be so far not a blocker.
The incentive here is not burning a millions of dollars worth of fuel per journey. Container ships use a lot of fuel. That adds up fairly rapidly to offsetting the cost of the battery. I think the question is not if batteries will be used on ships but how much batteries typical ships will have.
> A single container can contain up to 8mwh of capacity.
That's about 10 months of power for my home and car (gas heating). A 40' container on my drive or buried in the garden would power the house through the winter. It's crazy when you think how solvable season-shifting domestic power use is once you exclude the $1.5m price tag.
a couple of years ago it was $2m to store the same energy in the same way.
Excluding the car and heating, it's $40k for battery to store enough power to run my house for a week. Including heating at a 3:1 ratio for a heat pump compared with gas on the coldest week of the last year and it's $80k. That's less than 20% of the cost of the house. Throw in $10k of solar (about 35kWp) and even this far north - on the coldest days it tends to be clear skies and that would generate enough to recharge the battery without even touching the grid. The 35kWp wouldn't fit on the roof, but certainly would fit in a nearby field for basically zero cost for the land.
It'd be better to build more insulated and air tight homes (bonus if they're not single family - shared walls save on heating). Then it doesn't require so much energy to heat and cool.
Assuming 100$/kWh and those 2G$ (giga/billion), a full charge would be 20 GWh.
Realistically: probably exposed wire like on regular high voltage pylons.
Hooked to a not-too-far (the wires will be on the larger end, but you likely don't want the other end to be anywhere it could get in the way of cargo operations, and given the voltages involved, you can probably get half way across the city before it really begins to matter) grid battery bank that normally takes care of day-to-day scale grid balancing/energy arbitrage.
Then you just run a (group of) wires to the ship and apply basically the same principles as those DC fast charge stations for cars, except that you feed the high power DC link of the charging cable from the shore-side battery through much more efficient and importantly cheaper DC/DC regulators instead of involving transformers and AC.
You obviously have remote-controlled switches and circuit breakers to keep those cables grounded while the workers hook them up.
You'd probably have several DC links that have their own DC/DC regulators and can be split between ships.
Mostly also because there's a limit to how high-current any individual cable/connector is made in practice and because you want to use the current rating on your DC/DC converters and the thick-but-off-the-shelf cables between the battery park and the pier.
Do note that you could go for technology like the 100 hour ("0.01C") iron-air batteries "form energy" works on, especially if you're willing to swap them in port instead of DC fast charging through a temporary high voltage link.
You'd get the benefit of charging them when it's sufficiently convenient (off-peak), and the lower energy density and very low power density don't matter nearly as much on a ship.
Question is can they get enough power to be useful. Marine diesel engines are very fuel efficient, fuel oil is very energy dense, and they need to run for a long time. Electric cars work in part because people expect to refuel few couple hours anyway. Enough batteries to cross the ocean is going to be vastly worse.
The only useful picture in the article is a "solar powered board", which doesn't give a good scale but appears to be barely enough solar power for the rich owner to enjoy their luxuries and will barely move all day while forced to anchor all day. I'm sure it can go really fast on battery power, but not for long. Sails would be a better primary movement source with battery for in harbor navigation or when the wind stops backup only.
> Question is can they get enough power to be useful. Marine diesel engines are very fuel efficient, fuel oil is very energy dense, and they need to run for a long time.
Washington State Ferries refit one of their largest ferries (190-car capacity) as a hybrid recently. They replaced two diesel engines with batteries, leaving the other two engines in place. This provides for significant fuel savings. When shore charging is implemented, fuel use will be reduced even more.
I imagine there are also uses where batteries fully replace engines. I've got a tiny boat for casual fishing, you tend not to use the engine that much, and electric propulsion is likely quieter and can probably modulate to slower speeds which could replace a separate electric trolling motor.
A bigger ferry than that has been fully electric in Norway for five years between Horten and Moss. Probably a shorter route than the Washington State one though.
Probably not bigger... it looks like M/V Wenatchee [1] is wider and likely taller, has a much higher passenger capacity, and travels faster (and I misremembered the vehicle capacity a bit). Some of the routes in the system are similar distance than this Norway route, but most are longer, including the one that usually gets the hybrid ferry.
Also, there's a big chicken and egg problem. Can't have electric ferries without shore charging, can't justify building shore power unless there's boats to use it with. There's several ferry routes and individual ferries need to be able to serve multiple routes to allow for flexibility during maintenance, an electric ferry that can only serve one route is not super helpful.
There’s got to be some setup out there were we are able to harness wind energy (and solar to a smaller extent) to significantly increase the ranges here. Not a hundred years ago, we had cargo ships sail solely on wind power so enough energy is there for the taking.
There are a few that are sailing, they are pretty modest size. There are plans for more and larger vessels but I don't think anyone expects widescale deployment anytime soon.
Batteries will not have the requisite energy density for anything remotely long-journey--notably Panamax+ container ships which, sadly, are also the biggest carbon & sulfur (yes low-sulfer regs/fuel exists, but not everywhere) polluters.
These large ships will likely be de-carbonized either with ammonia turbines or fuel cells. Mann has already been running a PoC ammonia turbine ship for about 4 years--the last 2 undergoing proper blue-water "sea-trials" journeys.
But I have my doubts. There's still no economically viable way to produce "green" ammonia at scale. It's hazardous to handle and less energy dense than liquid hydrocarbons.
Which is why we won't be burning ammonia and shouldn't even try.
We already have an entire, scaled up industry of producing artificial fuel in a non-petrochemical route: It's where the ethanol in your gas tank comes from.
Farming will be easier to electrify than shipping, or it might not even need to be, and then we will have ample supply (at least here in the US) of energy dense fuels produced through non-petrochemical needs
Growing corn to turn into ethanol to burn isn't like, a carbon negative process right now, but it's also viable today to provide energy dense fuels in a sustainable way to feed our needs like long term storage, compactness, emergencies, and things like planes which won't work with batteries very well.
We already supply enough artificial hydrocarbon fuel through that process to make up 10% of all gasoline burned. As american cars electrify, the corn farmers are going to lose their shit about this subsidy being reduced, so we should just turn it around and have them commit to a larger artificial fuel industry. Our corn growing is already basically a fully socialized industry, let's just lean into it more. Put less corn syrup into random foods like burger buns and put more of it into vats to get energy dense fuel.
It's (technically, barely) an energy positive process, is extremely scalable, is fairly old "tech" such that it won't be owned by one company or country, and the hardest part will be replacing the petrochemical fertilizer.
The real solution though is nuclear powered shipping. There's dozens of nuclear powered ships already and they've been running safely for decades. It's just regulatory roadblocks, but if governments wanted to do it they could.
Military ships are "safe", because they can generally defend themselves. Commercial container ships would be the target of hijacking, to steal the reactor / fuel, or use them as 9/11 ship equivalents.
Correct. And military nuclear vessels are also operationally safe because superpower navies are willing to spend a fortune on training and paying qualified nuclear engineers and technicians. Despite those large budgets they still struggle to maintain minimum crewing levels. Merchant lines can't afford the personnel expense.
It has only been two years since the Baltimore bridge was destroyed by that container ship. Had known faulty maintenance, but they kept operating. Now the rest of us have to pay $5 billion to replace the bridge, plus whatever economic damage was done to surrounding industries.
We could find a way to make the reactor so integral to the ship and the fuel so integral to the reactor it’d be almost impossible to remove either. We can compound that with fuel cycles with materials less useful for making bombs.
> We already have an entire, scaled up industry of producing artificial fuel in a non-petrochemical route: It's where the ethanol in your gas tank comes from.
Ethanol as a fuel is mostly a subsidy for US farmers. The net energy gain is low.[1] Ethanol plants need a lot of heat energy to process corn into ethanol. They don't burn their own ethanol for heat; they use natural gas or even coal.[2] If they made their own process heat, which they could, they'd use about half their own output. They wouldn't get the subsidy on that. So they burn other fuels to make ethanol.
That doesn't include the costs of farming the corn.
The point is not an energy positive process. The point is a semi sustainable industry for making high density (liquid) fuels for the few systems that will need that energy density to continue functioning in an electrified future. The goal isn't "Don't burn anything ever". The goal is "Stop adding carbon to the atmosphere"
People talk about that concept like it's the future, but humans have been bulk producing a high energy liquid fuel with good stability and toxicity properties for millenia! The US produces enough ethanol to totally replace our entire commercial aviation usage right now.
Ethanol costs about $2 a gallon at that current industrial production level.
Actually that gives me pause. What stops anyone using it as a primary fuel right now if it's so cheap? I imagine the average airplane jet turbine has done a lot of testing on ethanol of course, and you always have to worry about your employees trying to drink your fuel then.
But my point is; We subsidize corn growth so that the USA will never, ever, ever experience a famine. That's the point. The corn will be grown regardless, and if there isn't a minor societal collapse that year, we should turn more of it into ethanol instead of corn syrup. Electrify agriculture and industrial process heat and you can also use that setup to essentially "Load shift" the high solar output in the summer into the winter.
I wonder why ammonia became the solution that went ahead to prototype and now appears the top candidate for near future low carbon alternative?
You still have to deal with a lot of specialized infrastructure and engine design.
I would have thought something like processing coal or synthesizing ethanol to a more suitable drop in replacement fuel would be easier. Maybe less scalable or outright requires more energy input.
Any carbon-based fuel ultimately depends on a lot of capture infrastructure to be carbon-neutral. In the short term, it's hard to see a path to viability. Ammonia is easy to synthesize, ingredients are literally water and air, liquefies at achievable pressure, and can be directly consumed in a fuel cell or combustion engine. It's corrosive, but only to certain materials (late transition metals and aluminum), and toxic, but only in high concentrations (the body naturally contains a few ppm of ammonia at all times). It's biodegradable, so you don't worry as much about spills. It's flammable, but not extremely so like hydrogen.
> You still have to deal with a lot of specialized infrastructure and engine design.
Is that really such a downside? Ports are full of specialized infrastructure anyway, and the costs of engine design can be amortized over many engines to be quite minimal overall. Once you've done the design work an ammonia engine isn't more expensive than a hydrogen or diesel engine. And the upsides of ammonia are substantial: fairly easy to handle, quite energy dense and most importantly it is already produced worldwide in huge amounts.
> I wonder why ammonia became the solution that went ahead to prototype and now appears the top candidate for near future low carbon alternative?
You should probably check who would control a larger part of the ammonia supply. I can see few other reasons for putting large quantities of something so unforgiving as ammonia on ships.
Ammonia is not going to happen. Sorry. There's no way we're going to allow floating chemical weapons maintained by shipping companies that not just cut corners but angle-grind them.
Methane works perfectly well for shipping. It's cheap, abundant, and we already have all the infrastructure for it.
And to fully decarbonize it, we'll just shift to biogas or power-to-gas.
> Methane works perfectly well for shipping. It's cheap, abundant, and we already have all the infrastructure for it.
>
> And to fully decarbonize it, we'll just shift to biogas or power-to-gas.
There is nowhere close to enough biogas for ocean going vessel. Methane has got into the focus due to methane slip. And fossil methane only allow a limited CO2 reduction vs Marine Diesel oil. It won't be enough to reach 2030 IMO target on CO2 reduction.
> There is nowhere close to enough biogas for ocean going vessel.
The total amount of biogas production is around 2.5 exajoules (2.5*10^18) per year. The amount of diesel used for intercontinental shipping is 213 million tons, or 10^19J (given the 45MJ/kg energy density).
So we need about 4x the current biogas production. That's entirely doable, especially with the power-to-gas transition.
If we are thinking about ammonia as a fuel, why not go with hydrazine? It’s not as immediately lethal as ammonia and is much easier to contain and manipulate.
Hydrazine may not be as immediately lethal by inhalation but it's considered a probable human carcinogen by the EPA. It has more explosion/fire risk. It's also more expensive to synthesize starting from clean primary energy (nuclear or renewables).
60 comments
[ 0.23 ms ] story [ 38.2 ms ] threadHydrodynamics are brutal, but the square-cube law works in your favor. The ocean doesn't care about what's inside your ship. Just the surface of it. The mass is mostly irrelevant. This is why cargo vessels are so large. The bigger the boat the bigger the energy density benefit.
The only real problem is the cost. To compete with a supermax you would need something like two billion dollars worth of batteries to survive a transpacific voyage.
So all the fuel is about 4% of the cargo capacity.
Fire on a ship is extremely dangerous. Think about what your training and your first instincts both tell you to do if there's a serious fire. Where I am the training starts with four words: "Get out. Stay out". But you can't just leave a ship, in the ocean you will drown. Even lifeboats, if they're available and can be used, are much more dangerous than we'd like.
Yeah, people are probably better off not knowing how insanely cheap shipping lines are. Shipping is one of those parts of the economy and trade that is simultaneously advanced and very old fashioned (in the rickety sense) at the same time.
A single container can contain up to 8mwh of capacity. Just 125 of those gets you to 1gwh. Depending on how quick the ship goes, you might need 1-2 gwh per day. You can conserve energy by going slower. But out of 14K containers, reserving maybe a third for battery could power a ship for quite some time. Enough to e.g. cross the Pacific. There are obvious issues with weight and balance. The volume is doable but the weight creates a lot of issues.
Another challenge is indeed the cost of these batteries. That's about an order of magnitude of where it needs to be to make it financially realistic. But batteries coming down further in cost could make this more feasible. And it's not like these huge container ships are cheap. A couple of tens or even hundreds of millions of dollars worth of battery is reasonable. Billions would be unreasonable.
There are traditionally powered ships carrying many thousands of EVs with batteries already. So, putting a few gwh of battery on a ship is already happening; we're just not using them to move the ship. And batteries made in China are typically shipped to the US and elsewhere for integrating into cars, grid storage, etc. as well. If you can ship it, you might as well use it. And of course battery powered ships are already very popular for lighter short haul like ferries, tug boats, small transport barges on rivers, etc. There are plenty of them operational without major issues. Safety issues seem to be so far not a blocker.
The incentive here is not burning a millions of dollars worth of fuel per journey. Container ships use a lot of fuel. That adds up fairly rapidly to offsetting the cost of the battery. I think the question is not if batteries will be used on ships but how much batteries typical ships will have.
That's about 10 months of power for my home and car (gas heating). A 40' container on my drive or buried in the garden would power the house through the winter. It's crazy when you think how solvable season-shifting domestic power use is once you exclude the $1.5m price tag.
Excluding the car and heating, it's $40k for battery to store enough power to run my house for a week. Including heating at a 3:1 ratio for a heat pump compared with gas on the coldest week of the last year and it's $80k. That's less than 20% of the cost of the house. Throw in $10k of solar (about 35kWp) and even this far north - on the coldest days it tends to be clear skies and that would generate enough to recharge the battery without even touching the grid. The 35kWp wouldn't fit on the roof, but certainly would fit in a nearby field for basically zero cost for the land.
Realistically: probably exposed wire like on regular high voltage pylons. Hooked to a not-too-far (the wires will be on the larger end, but you likely don't want the other end to be anywhere it could get in the way of cargo operations, and given the voltages involved, you can probably get half way across the city before it really begins to matter) grid battery bank that normally takes care of day-to-day scale grid balancing/energy arbitrage.
Then you just run a (group of) wires to the ship and apply basically the same principles as those DC fast charge stations for cars, except that you feed the high power DC link of the charging cable from the shore-side battery through much more efficient and importantly cheaper DC/DC regulators instead of involving transformers and AC.
You obviously have remote-controlled switches and circuit breakers to keep those cables grounded while the workers hook them up. You'd probably have several DC links that have their own DC/DC regulators and can be split between ships. Mostly also because there's a limit to how high-current any individual cable/connector is made in practice and because you want to use the current rating on your DC/DC converters and the thick-but-off-the-shelf cables between the battery park and the pier.
Note that these are huge: the largest grid battery plant in operation (according to https://en.wikipedia.org/wiki/Battery_energy_storage_system ) is only 4GWh, so 1/5th of such a ship.
You'd get the benefit of charging them when it's sufficiently convenient (off-peak), and the lower energy density and very low power density don't matter nearly as much on a ship.
only problem i see is all the cells would be in parallel due to the single hull, so the voltage would be very low.
The only useful picture in the article is a "solar powered board", which doesn't give a good scale but appears to be barely enough solar power for the rich owner to enjoy their luxuries and will barely move all day while forced to anchor all day. I'm sure it can go really fast on battery power, but not for long. Sails would be a better primary movement source with battery for in harbor navigation or when the wind stops backup only.
Washington State Ferries refit one of their largest ferries (190-car capacity) as a hybrid recently. They replaced two diesel engines with batteries, leaving the other two engines in place. This provides for significant fuel savings. When shore charging is implemented, fuel use will be reduced even more.
I imagine there are also uses where batteries fully replace engines. I've got a tiny boat for casual fishing, you tend not to use the engine that much, and electric propulsion is likely quieter and can probably modulate to slower speeds which could replace a separate electric trolling motor.
https://www.dailyscandinavian.com/worlds-largest-electric-fe...
https://indre24.no/2021/03/01/verdens-storste-elektriske-fer...
Also, there's a big chicken and egg problem. Can't have electric ferries without shore charging, can't justify building shore power unless there's boats to use it with. There's several ferry routes and individual ferries need to be able to serve multiple routes to allow for flexibility during maintenance, an electric ferry that can only serve one route is not super helpful.
[1] https://wsdot.com/ferries/vesselwatch/VesselDetail.aspx?vess...
https://gcaptain.com/the-return-of-sail-power-cargo-ships-ar...
These large ships will likely be de-carbonized either with ammonia turbines or fuel cells. Mann has already been running a PoC ammonia turbine ship for about 4 years--the last 2 undergoing proper blue-water "sea-trials" journeys.
https://www.wartsila.com/marine/products/engines-and-generat...
But I have my doubts. There's still no economically viable way to produce "green" ammonia at scale. It's hazardous to handle and less energy dense than liquid hydrocarbons.
We already have an entire, scaled up industry of producing artificial fuel in a non-petrochemical route: It's where the ethanol in your gas tank comes from.
Farming will be easier to electrify than shipping, or it might not even need to be, and then we will have ample supply (at least here in the US) of energy dense fuels produced through non-petrochemical needs
Growing corn to turn into ethanol to burn isn't like, a carbon negative process right now, but it's also viable today to provide energy dense fuels in a sustainable way to feed our needs like long term storage, compactness, emergencies, and things like planes which won't work with batteries very well.
We already supply enough artificial hydrocarbon fuel through that process to make up 10% of all gasoline burned. As american cars electrify, the corn farmers are going to lose their shit about this subsidy being reduced, so we should just turn it around and have them commit to a larger artificial fuel industry. Our corn growing is already basically a fully socialized industry, let's just lean into it more. Put less corn syrup into random foods like burger buns and put more of it into vats to get energy dense fuel.
It's (technically, barely) an energy positive process, is extremely scalable, is fairly old "tech" such that it won't be owned by one company or country, and the hardest part will be replacing the petrochemical fertilizer.
Oh, ethanol is a more energy dense fuel too.
Regulation is not always bad.
Also, we’d need to make them impossible to open and impossible to remove without cutting the ship in half.
Ethanol as a fuel is mostly a subsidy for US farmers. The net energy gain is low.[1] Ethanol plants need a lot of heat energy to process corn into ethanol. They don't burn their own ethanol for heat; they use natural gas or even coal.[2] If they made their own process heat, which they could, they'd use about half their own output. They wouldn't get the subsidy on that. So they burn other fuels to make ethanol.
That doesn't include the costs of farming the corn.
[1] https://energy.sustainability-directory.com/learn/how-does-t...
[2] https://www.researchgate.net/figure/Energy-use-in-each-of-th...
The point is not an energy positive process. The point is a semi sustainable industry for making high density (liquid) fuels for the few systems that will need that energy density to continue functioning in an electrified future. The goal isn't "Don't burn anything ever". The goal is "Stop adding carbon to the atmosphere"
People talk about that concept like it's the future, but humans have been bulk producing a high energy liquid fuel with good stability and toxicity properties for millenia! The US produces enough ethanol to totally replace our entire commercial aviation usage right now.
Ethanol costs about $2 a gallon at that current industrial production level.
Actually that gives me pause. What stops anyone using it as a primary fuel right now if it's so cheap? I imagine the average airplane jet turbine has done a lot of testing on ethanol of course, and you always have to worry about your employees trying to drink your fuel then.
But my point is; We subsidize corn growth so that the USA will never, ever, ever experience a famine. That's the point. The corn will be grown regardless, and if there isn't a minor societal collapse that year, we should turn more of it into ethanol instead of corn syrup. Electrify agriculture and industrial process heat and you can also use that setup to essentially "Load shift" the high solar output in the summer into the winter.
You still have to deal with a lot of specialized infrastructure and engine design.
I would have thought something like processing coal or synthesizing ethanol to a more suitable drop in replacement fuel would be easier. Maybe less scalable or outright requires more energy input.
Is that really such a downside? Ports are full of specialized infrastructure anyway, and the costs of engine design can be amortized over many engines to be quite minimal overall. Once you've done the design work an ammonia engine isn't more expensive than a hydrogen or diesel engine. And the upsides of ammonia are substantial: fairly easy to handle, quite energy dense and most importantly it is already produced worldwide in huge amounts.
You should probably check who would control a larger part of the ammonia supply. I can see few other reasons for putting large quantities of something so unforgiving as ammonia on ships.
NH3 has no carbon in it. It has the advantage of not producing CO2. This is a good advantage for public communication.
Methane works perfectly well for shipping. It's cheap, abundant, and we already have all the infrastructure for it.
And to fully decarbonize it, we'll just shift to biogas or power-to-gas.
There is nowhere close to enough biogas for ocean going vessel. Methane has got into the focus due to methane slip. And fossil methane only allow a limited CO2 reduction vs Marine Diesel oil. It won't be enough to reach 2030 IMO target on CO2 reduction.
The total amount of biogas production is around 2.5 exajoules (2.5*10^18) per year. The amount of diesel used for intercontinental shipping is 213 million tons, or 10^19J (given the 45MJ/kg energy density).
So we need about 4x the current biogas production. That's entirely doable, especially with the power-to-gas transition.