Certainly it is easier to pump HC fuels than H2! The same also goes for 
ammonia. In the US and maybe some other countries there already exists a 
network of ammonia pipelines.

Ammonia fertiliser can indeed release N2O as you say. But that's not a 
new problem - this is already happening. The important thing is that as 
you begin to produce solar ammonia it finds a ready market displacing 
fossil fuel ammonia, and that gets over the 'chicken-egg' problem that 
afflicts for example H2.

NH3 on its own has low flammability but it combusts readily when mixed 
with eg diesel fuel - you can burn 90% ammonia that way. This was done 
in Belgian buses during WW2.

You can also use ammonia to run fuel cells, by first reforming it to H2. 
The NH3 is in effect a stable, non-flammable low pressure vector for H2. 
It carries an energy cost of course - but in many circs one worth paying.

Oliver.

On 06/03/2012 23:23, John Nissen wrote:
>
> Hi Oliver,
>
> A first apology.  I was wrong about H+, I should have said plain 
> hydrogen (H2).  The electrochemist researcher who told me about this 
> scheme on the train had talked about activating hydrogen and using 
> catalysts.  I thought he meant producing H+ which would be 
> particularly reactive.  I was wrong.
>
> A second apology.  I did not mention rock crushing.  But when I said 
> "combine biochar with other methods", I had rock crushing in mind as 
> one of the methods.
>
> The researcher's argument started with the issue of getting solar 
> power from Sahara to Europe.  I suggested producing and piping 
> hydrogen, but he said it was much better to produce and pipe 
> hydrocarbon fuels.  Where was the carbon to come from?  CO2 of 
> course.  Where was the hydrogen to come from?  Water of course - 
> though for the Sahara this entails piping sea water to the Sahara and 
> desalinating it.  The researcher pointed out that you end up with a 
> lot of salt!
>
> However I am intrigued by your alternative idea of making ammonia.  
> But, if this is used for fertiliser, could there be a problem with 
> nitrogenous fertiliser that it releases N2O, which is a potent 
> greenhouse gas?  A benefit of biochar is reducing the need for such 
> fertiliser.
>
> Cheers,
>
> John
>
> ---
>
> On 06/03/2012 10:41, Oliver Tickell wrote:
>>
>> John, it is my view that the lowest cost, most benign in impact and 
>> most scaleable solution is accelerated rock weathering (ARW) using 
>> rock types rich in olivine / Mg silicates. Such rocks are globally 
>> abundant and vast stockpiles exist at mine sites eg for nickel, 
>> diamonds. Using such rocks on land / littoral zones will also send 
>> bicarbonates to ocean as it scrubs CO2 f5rom atmosphere, adding ocean 
>> alkalinity.
>>
>> If we have abundant solar energy in the Sahara we are probably better 
>> off using it directly, displacing fossil fuelled generation, rather 
>> than for CO2 scrubbing. The chemistry as described makes no sense. H+ 
>> is an ion not a radical and H+ = acidity. If we are worried about 
>> ocean acidification the last thing we need is to be producing H+. 
>> What this probably means in fact is producing hydrogen (H2) from 
>> electrolysis which can then be reacted with CO2 to produce liquid / 
>> gaseous fuels. This is possible but expensive. More immediate benefit 
>> can be derived by making ammonia NH3 which can itself be used as 
>> fuel, as hydrogen vector, and more immediately to displace ammonia 
>> made by burning fossil fuels for fertiliser etc.
>>
>> Oliver.
>>
>> On 05/03/2012 20:11, John Nissen wrote:
>>> Hi all,
>>>
>>> Is there an alternative to rapid CDR to reduce the atmospheric CO2 
>>> level and hence slow ocean acidification?  Acidification is 
>>> progressing at the fastest rate for 300 million years, faster even 
>>> than in the PETM [1], and spells catastrophe if not curbed over the 
>>> next decade or two.
>>>
>>> I am supporter of biochar for CDR on a large scale.  But few people 
>>> think biochar can be scaled enough to actually start reducing the 
>>> atmospheric CO2 level in the face of CO2 emissions set to climb for 
>>> decades.  So we need a combination of low to medium cost CDR 
>>> schemes, capable of scaling to the very large.
>>>
>>> Today I heard about a scheme for use of solar energy (e.g. in 
>>> Sahara) to power the scrubbing of CO2 from the atmosphere and the 
>>> production of H+ radicals from H2O.  The H+ would then be combined 
>>> with the captured CO2 to create a carbon-neutral hydrocarbon fuel, 
>>> which could then be cheaply and efficiently piped to countries 
>>> wanting a green energy source, e.g. for cars and electricity 
>>> generation.  Apparently it's much cheaper and more efficient to pipe 
>>> liquid fuel than transmit the equivalent electric power over the 
>>> same distance.
>>>
>>> Cheers,
>>>
>>> John
>>>
>>> P.S. If H+ can be produced from H2O, could the OH- byproduct be used 
>>> for combination with scrubbed methane (CH4) to produce further 
>>> carbon-neutral fuel?  Atmospheric methane levels are rising ominously.
>>>
>>> [1] http://planetark.org/wen/64838
>>>
>