[Enthalpy]

The appended drawing illustrates how very little improvised equipment lets trucks load a barge on the Danube if the ports don't suffice. Or drop the load from a bridge or a pontoon where available.

I drew a tipper, but other types of trucks may fit crop better. Maybe geotextiles keep the crop clean and dry.

Many location operating in parallel provide the throughput, and also the needed redundancy, since nobody should expect help from the Russians.

Similar equipment might let cross the rivers in Bessarabia, with redundancy of course.

==========

Ukraine uses the Russian track width while all friendly neighbours use essentially the normal width, as shows the appended map pinched from Wiki
  wikipedia
Moldova is the only exception and can lead indirectly to the seas.

Though, one railway line in Poland and two in Slovakia use the Russian track width and connect with Ukraine
  wikipedia - wikipedia - wikipedia
Operating these lines could be easier than transferring the load between railcars or replacing the axles near the border. At least, the lengthy operations can run in parallel at several locations.

==========

Transporting crop isn't an act of war, so foreign workers and equipment could help that in Ukraine.

Marc Schaefer, aka Enthalpy

[Enthalpy]

[...] nobody should expect help from the Russians [...]

Russia bombed yesterday a tunnel of the railway line to Lviv because it served to introduce weapons in Ukraine.

The consumes long-range guided weapons. How many does Russia still have despite the embargo on chips? 50, 100? More barge loading equipment and floating bridges can be built than that.

I put estimates to export 7.2Mt crop from Ukraine. The present wheat stock is rather 20Mt. Just scale up all figures until this summer to free up storage room. The next harvest leaves more time for transport.

[Enthalpy]

maple syrup contains 2/3 sucrose. Mainly Acer saccharum, nigrum and rubrum, present in North America, let produce 0.08Mt/year, or just 0.05Mt/year sucrose
  wikipedia - quebec.ca - thecanadianencyclopedia.ca
far from the 70Mt/year crop from Ukraine. But could the production increase?

1hm² sugar maple produces 250L syrup or 170kg sugar. The species extend over 1 000 000 km² in the wild. Imagine they make 1/20 of the area (do they?) of which 1/5 is reasonably accessible. Tapping the forests makes potentially 0.17Mt/year. If the bitter taste is removed, sap can be harvested over a longer period to produce 0.5-1Mt/year more sucrose. Nothing brilliant, but this feeds 20M people more.

==========

Or could the fat Europeans and North Americans ingest less sugar and ship it instead to hungry people? Where I live, mustard, chilli, saffron and tomato sauces contain sugar, yuk, and even guacamole did recently. Germans swallow 32kg/year, 3.5× the maximum recommended by WHO, and get sick from it. Much comes from soft drinks that contain 2× as much sugar as in the UK.
  de.statista.com - test.de
Imagine that the consumption shrinks to 25kg/year just from receipe changes, that's 0.5Mt/year for Germany alone, let's say 1.5Mt/year for the EU, as much for North America, and sugar has more feeding value than the same mass of wheat. We can be healthier and save 3Mt/year sugar to feed 80M people more.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Could road trains help move crop out of Ukraine, alone or combined with railways and boats? Trials were conducted in Europe.
  wikipedia - pistenkuh.de - mercedes-benz-trucks.com
Difficulties exist.

Drivers must be hired or trained. Other road users must be aware of such trains. Law in Ukraine, Moldova, the EU may need updates.

The tractor units available here seem strong enough, but Europe lacks the trailers used in Australia, North America and Argentina. If European companies build them, then rather near to the customers, but at least the drawings exist. Or the trailers must be rented and brought quickly from other continents
  wikipedia - wikipedia

[Enthalpy]

Camels and kangaroos in Australia compete with human activities and are culled but not always eaten. Alas, they would feed few humans.

Over 300k Australian camels, 30k/year could be taken
  wikipedia - wikipedia - wikipedia
if each provides 150kg meat, they feed 30 000 humans only. Elsewhere, 3.3M camels are slaughtered yearly for meat.

40M kangaroos bear maybe the removal of 0.8M/year
  wikipedia - wikipedia
if each provides 25kg meat, they feed 1M humans only.

Removing mostly the males and targeting an optimum age may double these figures.

[Enthalpy]

Up to last year, natural gas made fertilizers over hydrogen, ammonia, then urea. In short, 1/4 of our food is natural gas.

Good news, Nigeria will sell the C₃-C₄ fraction obtained from wells instead of torching it
  aljazeera.com
These gases too can provide hydrogen for fertilizers. This depends competing uses.

Also: the conversion of formerly cheap methane to hydrogen burned the rests, but proven reactions convert the rest to valuable liquid fuels.
  chemicalforums
This applies to the C₃-C₄ fraction too.

Research papers propose biological means to fertilize the fields, mostly to inject nitrogen compounds. I can't assess how cheap and efficiently, but this would free agriculture from fossil fuels. I instinctively disbelieve that hydrogen from electricity is cheap enough for fertilizers. But two decades ago, I believed natural gas would stay cheaper than solar electricity: wrong.

[Enthalpy]

Chemists, your ideas, suggestions, remarks, comments are needed!

Before the war in Ukraine, farmers produced 1/4 more food by using fertilizers, essentially ammonia and its derivates urea and ammonium nitrate, where natural gas provided the hydrogen, but now gas is rarer, and we must abandon fossil fuels anyway.

The politicians promote hydrogen from renewables in sunny windy countries, then ammonia etc as before. I disbelieve agriculture can afford that process.

Nitrogen fertilizers outperform phosphates and others. Mines don't cover the needs neither.

So could you propose ways or directions to provide usable nitrogen to the plants? N₂ is too inert, but compounds as diverse as ammonia and nitrates are accepted. Nitrogen oxides aren't the energy maelström of hydrogen production. Introduction and more:
  Noura Ziadi, Utilisation des engrais minéraux azotés en grandes cultures
Nitrous and nitric acids are acid, nitrogen oxides are gases, but maybe we can combine nitrogen compounds with the straw that farmers bury in the fields. It comprises cellulose and many compounds, with alcohol functions and more, that could catch the nitrogen compounds as nitro- or others.

A mixture of straw and cattle dejections is often buried. Nitrogen compounds could react after or before mixing. Urea seems a target for a nitrate.

Straw could produce biomethane before the rests fertilize the fields
  chemicalforums
so a supplementation by nitrogen compounds would usefully be compatible with that step.

Marc Schaefer, aka Enthalpy

[marquis]

Re: maple syrup
The problem with maple syrup is the amount of energy required to concentrate the maple sap to maple syrup. The best maple sap is 4% sugar, but many run of the mill trees run much lower.  Say 2% or even lower. You must consider the energy required to evaporate off the water.  There is another option- to concentrate the sap with the equivalent of an HPLC column.  You should be able to find some refs online. It would t get you all the way to the final 66% sugar, but it will save a lot of energy. Good luck.

[marquis]

The maple sap is not collectively by buckets around here, anymore.  They are using plastic bags.  Going down some of the backroads, you will see all these maple trees with white plastic bags attached to them.  If you didn't know better, you'd guess they were of bags.  The season is usually from about Feb to maybe April, depending on temp.  After that, the sap tastes bad. Whether it could be used, I don't know.  The better places use tubing instead of bags.

[marquis]

This info is pulled from Dow Tech Fact form no 609-00513-1204.  The title is Elements used in maple sap concentration. 
It gives a run down on different reverse osmosis type elements usable for sap concentration.  At one time, they had a product called filmed maple sap Mark I.  As far as is known, that's been discontinued.  They lost other reverse to elements that can be used in place.  8 inch elements biotech nf279-499, biotech nf90-400,Gingrich xle-440.  4 inch elements, nf270-4040, nf90-4040, Gingrich xle-4040.  Sorry, my memory was bad. Thought it was hplc, not RO.  This data sheet is rather old.  Hopefully, something similar is still available.

[marquis]

For whatever reason, the spellchecker thinks filmtec   should be bio tec.  So wherever you saw biotec, replace it with filmtec. That's the trademark for the Dow product.

[marquis]

The reverse osmosis won't get you anywhere close to 66% sugar, but it can significantly concentrate it. Which saves a lot of wood and time.  Some claims it can concentrate to 12% sugar. Unlikely. But significant concentration can occur. This amounts to a significant savings in energy.  A word of warning.  The reverse osmosis columns don't like to go dry.  Good luck.

[marquis]

Apparently, there has been some progress. Dow now markets a maple sap E8  for reverse osmosis.  FYI.

[marquis]

For an interesting rundown of costs,etc, done by Ohio state universities at departmebt. Go to
 u.osu.edu/ohiomaple/tag/reverse-osmosis/

[marquis]

Maple sap flows primarily in the spring.  The best time is when it's below freezing in the morning and above freezing later.  Or do the books say.  If this is true, it will dramatically change your calculations.