[Digestion] Compressing of biogas

Alexander Eaton alex at sistemabiobolsa.com
Tue Nov 23 11:29:51 CST 2010


At our scale, CO2 filtration is ruled our because it requires high inputs of
chemicals or energy (which can be justified potentially under large scales),
and the benefit it really just space, as the CO2 does not significantly
hamper the combustion process.  If CO2 filtration were easier, carbon
sequestration projects would have gained more traction by now.

Methane is similar to other gases, but yet so different.  As the most simple
hydrocarbon, it has the most energy per unit of mass, but the least amount
of energy per unit of space.  Picture one carbon with four hydrogens poking
out in all directions, versus a tight string of carbon bonds as found in
other hydrocarbons.  With methane the hydrogens slightly repel each other,
and therefore, methane dose not "like" to be compressed.  Even natural gas,
mostly methane, is not generally compressed to the degree of say, propane,
which is even liquefied.  There are obviously LNG projects, but again, scale
is the key driver.

Maybe there are new technological options, but at my last look, it required
between 2 to 3 units of energy to bottle about 10 units of energy worth of
methane at a pressure that would give you any useful volume.  That math gets
worse with 40% CO2.  Scale changes everything, and there are biogas
transportation projects.  Investing the energy into filtration (high
pressure water systems can take out CO2) and compression will still leave
you energy positive, and the energy was still originated from waste.  So,
here I am specifically talking about being discouraged by smaller systems.

When one looks at the properties of biogas, and the conditions of small
biogas plants, the lowest entropy solution is low-pressure, on-site use.
All options within this range should be exhausted before other options are
considered.  The caveat to this would be micro biogas grids.  Biogas can be
transported readily in pipes, and there are simple blowers that can make
that happen relatively efficiently.  A low pressure simple pipeline being
fed by one medium to large plant, or a few smaller plants could also be a
reality.  The longer pipeline option is less of an option when you have
limited buy-in and must cross other people's land or roads in the process.

Saludos,

Alex

On Tue, Nov 23, 2010 at 10:03 AM, Reuben Deumling <9watts at gmail.com> wrote:

> Can you say a bit more about
> - why separating out the CO2 is ruled out? and
> - why if methane 'does not like to be compressed' so many other similar
> gases are compressed regularly?
>
> Perhaps I'm missing something.
> I do appreciate the transport ideas without compression or a pipeline.
>
> Reuben Deumling
>
>
>
> On Tue, Nov 23, 2010 at 8:58 AM, Alexander Eaton <alex at sistemabiobolsa.com
> > wrote:
>
>> We go around this issue frequently, as end users often come up with the
>> same idea.  It is hard to tell them no, so we always take a fresh look under
>> the circumstances.  At the end of the day filtration of CO2 i always ruled
>> out, and that means 40% of the volume of gas you are compressing serves no
>> energetic purpose.  Add that to the fact that methane does not like to be
>> compressed, and we arrive again at a "no" response.
>>
>> The one option we always examine is the non-compressed transportation of
>> large gas reservoirs.  This we have tried for distances that are too long
>> for a simple gas line, and short enough to be practical by cart.  Since we
>> can make durable gas reservoirs of any size and shape, this is not
>> unfeasible.  Once transported, the gas is connected and used as usual, while
>> a second reservoir is filling.  If you can create value for this use, and
>> the transport logistics to not out-weight the value of the energy provided,
>> you may have an option for success.  Others have used large truck
>> inner-tubes in the same way, that are then rolled down the street to the end
>> use.  I suspect that in certain locations, systems that considered
>> low-pressure distribution could gain some traction.
>>
>> Saludos,
>>
>> A
>>
>> On Tue, Nov 23, 2010 at 6:21 AM, Vianney Tumwesige <
>> trustvianney at gmail.com> wrote:
>>
>>> Hello Harold,
>>>
>>> I completely agree withYvonne, it will be economically expensive to
>>> compress the gas.
>>>
>>> P.S. Yvonne, could you send me a copy of the paper and ppt as well?
>>>
>>> Best regards
>>>
>>>  On Tue, Nov 23, 2010 at 1:49 PM, Harold leffertstra <
>>> haroldleffertstra at yahoo.no> wrote:
>>>
>>>>     hello
>>>> Got a question from the owner of a small biogass plant in Tanzania.
>>>> He is expanding a small existing biogas plant to be able to digest waste
>>>> from 200 households and manure from 100 cows.
>>>> He is interested in using the biogas for fueling vehicles. In our part
>>>> of the world we think it will be necessary with cleaning, uppgrading of the
>>>> gas and compressing.
>>>> Do any of you have experience/ideas about whether this is feasible for
>>>> such a small plant?
>>>> 1)What is necessary to use the biogas for fueling vehicles and 2) what
>>>> are the technical and economical consequences?
>>>> Thank you
>>>> Harold Leffertstra
>>>> Senior Advisor
>>>> Norwegian Climate and Pollution Agency
>>>> Oslo
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>> for more information about digestion, see
>>>> Beginner's Guide to Biogas
>>>> http://www.adelaide.edu.au/biogas/
>>>> and the Biogas Wiki http://biogas.wikispaces.com/
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Vianney Tumwesige
>>> Director - Green Heat (U) Ltd  [image: Picture]
>>> P.O. Box 10235
>>> Kampala-Uganda
>>> 256 (0) 71 237 9889
>>>
>>> "The more people are self sufficient in cooking fuel, the more personal
>>> and financial freedom they have." - Emma Casson
>>>
>>>
>>>  <http://trustvianney.wordpress.com/>
>>>
>>>
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>>> for more information about digestion, see
>>> Beginner's Guide to Biogas
>>> http://www.adelaide.edu.au/biogas/
>>> and the Biogas Wiki http://biogas.wikispaces.com/
>>>
>>>
>>>
>>
>>
>> --
>> Alexander Eaton
>> Sistema Biobolsa
>> IRRI-Mexico
>> RedBioLAC
>>
>> Mex cel: (55) 11522786
>> US cel: 970 275 4505
>>
>> alex at irrimexico.org
>> alex at sistemabiobolsa.com
>>
>> sistemabiobolsa.com
>> www.irrimexico.org
>> www.redbiolac.org
>>
>>
>> _______________________________________________
>> Digestion mailing list
>>
>> to Send a Message to the list, use the email address
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>> to UNSUBSCRIBE or Change your List Settings use the web page
>>
>> http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org
>>
>> for more information about digestion, see
>> Beginner's Guide to Biogas
>> http://www.adelaide.edu.au/biogas/
>> and the Biogas Wiki http://biogas.wikispaces.com/
>>
>>
>>
>
> _______________________________________________
> Digestion mailing list
>
> to Send a Message to the list, use the email address
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> to UNSUBSCRIBE or Change your List Settings use the web page
>
> http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org
>
> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>


-- 
Alexander Eaton
Sistema Biobolsa
IRRI-Mexico
RedBioLAC

Mex cel: (55) 11522786
US cel: 970 275 4505

alex at irrimexico.org
alex at sistemabiobolsa.com

sistemabiobolsa.com
www.irrimexico.org
www.redbiolac.org
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