[Digestion] ***SPAM*** Biomethane from cactus

[rex at whitfieldfarm.co.za]

Dear Paul

It is good to see that you are still very much alive and kicking! 

After many years of punting biomass to biogas, I finally got traction last
year. I joined an entrepreneurial company that has lofty goals of reducing
the global CO2 emissions by 1 GTpa. Their principle focus was on using
prickly pear (Opuntia ficus indica) as the biomass of choice. I live in
South Africa where 2/3's of the country has low rainfall and this particular
plant is ideal for the job. It has one of thee highest water use
efficiencies making the requirement for rainfall and irrigation relatively
insignificant.

Effectively what we have managed to achieve is to plant these at high
density to produce in the region of 45 dry tons/ha/year. The plants are
harvested mechanically, macerated and fed to large, mixed lagoon digesters.
The digestate is separated into moist solids and liquid digestate. The
liquid is stored and irrigated to reduce plant heat stress when required.
Manure is added to the solids and composted. Compost is spread over newly
harvested fields.

The cactus is typically 8% to 10% dry solids. This means that no additional
water is required for the anaerobic digestion process. The VS are around 75%
to 80% of DS. The H2S content of the gas is <10ppm by volume. So a really
clean gas to start with.

We are growing the thornless variety at big scale. The typical commercial
unit is 1000 ha and multiples thereof. Anything smaller is not commercially
attractive. Each hectare produces approximately 400GJ/year net after
internal consumption.

The main application is for power with the use of 10MW class gas engines
that have a 50% chemical to electrical energy conversion. They also have
high volumes of exhaust in the 375oC range. In mining in particular, this
heat can be used for drying of ore concentrates.

Having said all that, the company ran into difficulties. A colleague and I
are starting an energy company that will have biomethane as a central
component. Using a mix of PV, wind, biomethane, synthetic diesel, hydrogen,
fuel cells, etc, our aim is to help mining companies in particular on their
drive to carbon neutrality.

I just thought I would let all out there know that there is life yet in the
AD world and that it can be scaled. I am looking forward to any queries. My
private email is rex(at)whitfieldfarm(dot)co(dot)za. I will endeavour to
answer all emails.

Kind regards
Rex Zietsman

On Tuesday, March 9, 2021, 09:07:56 AM EST, Paul Harris
<harrisfm at aapt.net.au> wrote:  
 
   
G'day All,
 
It has been a long time since I have had a message from this list, but we do
occasionally get new subscriptions.
 
Welcome to everybody, particularly anyone who has joined recently. Perhaps
you may like to briefly introduce yourselves (and some of the regulars could
as well to get things rolling along!) - mine is below as an example, Name
and City, Country is the Minimum if you can, but I realise some people may
not want to publicise their existence so anything is OK!
 
My name is Paul Harris, I live in Adelaide, South Australia and I have
moderated this discussion list for quite a while. I set up the Beginners
Guide to Biogas, now available as a historical record
at<https://l.facebook.com/l.php?u=http%3A%2F%2Fweb.archive.org%2Fweb%2F20130
804113535%2Fhttp%3A%2F%2Fwww.adelaide.edu.au%3A80%2Fbiogas%2F&h=AT3tJm_fj9bI
4VNXpiTwTt8Wjf9mk2TbA0I-lUFJzMHSMaIJq4x8zXgDtQOXXcDR_N1RMrLsdX3rWkAOWrOWbFfe
nxiWhDOWRYCVbNy_Kb6MZ5Zql9oSvXQbXWE_H34Rvw>, the Biogas Wiki (now
discontinued, when wikispaces closed down, but I have the files) and more
recently a Biogas Facebook page at
<https://www.facebook.com/groups/1841416559501333> with an associated Biogas
Shop at < https://www.facebook.com/groups/710401156143580>. 
I am an Agricultural Engineer by training, now retired, and my main biogas
interest (outside the WWW) is small, simple digesters for domestic use. From
this basis I have presented Biogas courses in Cameroon and Nauru (Notes are
available on the Biogas Facebook page, "Click Files" under
"More"<https://l.facebook.com/l.php?u=https%3A%2F%2Flookaside.fbsbx.com%2Ffi
le%2FBiogas%2520FB%2520Page%2520Files%2520Screenshot%25202021-03-09%25202250
11.jpg%3Ftoken%3DAWzhRgZzqmRoi8u0t4c6mN5BbrUCJaRuKaEovhWiL7xLb3tuQZsLpiZKIrz
k2P4T6Ad3QGGaU2LLcLL2pM1YGwlycG4UUwnXGr9aHOf9uzoi0rOuaKoP3IGozBTunhKadCNiUDr
p51TEM6_kMMPe7FT5s_udoS7QprMaCU2y-3ASqJxiLgi_q2Xh1eoqnzQg2q81j814G58T3hEn7eY
AOgR4zCMuG615XxCevhB3--db3xJwkdFM7jE9XgmG_w5Z1KeKoe_LEfMcYFfNGC8Z5nmeeSen8df
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H_Ddcs6TroOAR_BXq9sBngORq1geaW_pJOBXBlYL6kpe5hD04k9IOm7PQeiwCcLdteVXLyazxhBk
1ubxzxz1E7ipIwBRwiHFFIrjNaTx1X2Iz9Yd2ryhkdtFUYzwOlb75HZpufwv5m136dZRJNes55Ne
-N3aB2oAhSSh9JpYSItf2346qDJQkGA&h=AT2PI64xIyRcq5rIBRkrUSAl6D76kGgY66QWze25xn
QysZWq_TRpVyy_-jeqlPmEqw68t1gXg2fxQWxDpQg5HGrvslg9WDLB2hDVD-H_FZ0UN67SJtSHPB
FGhr51UtezH-67ouUfSmI&__tn__=H-R&c[0]=AT0NKWrvT8Vy-ADYh3h7rwvZrlPmRyf_zW51d4
r1zpFXv1yM2L0r97vX9IEYymVTqQkjuR29ZUY_AFpb2WltBMCZHgabxFsWbM2t4Zuv0TqyZkTkJ2
LAYr09f2ps2tu2ylEznL6HVXzXFfGopOrI66kNgcj9PRWhE7VGVrDkCSEBlqw4> or e-mail
me).
 
Happy digesting,
 
 HOOROO
Paul Harris _______________________________________________
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