[Stoves] Large TLUDs for greenhouse heat and CO2

[Crispin Pemberton-Pigott]

Dear Paul

The dominant factor in using a small TLUD that is batch loaded will be the
CO produced, not anything else. Because people have to work in the space,
and because the CO2 is needed in the daytime (though I agree some could
accumulate in the night) it is likely the TLUD would be running when people
are inside.

The CO limit for a working environment is 50 ppm in most places. The
challenge will be to limit the CO to that value. The natural gas burners
have extremely low CO output because they are perfectly tuned to a highly
predictable fuel. They mentioned 30 ppm in the exhaust but it was not stated
what the dilution level was so it is not that helpful actually. 

Let's assume the CO was factored to an O2 level of 7% or 50% excess air. It
means the CO2 level would be something like 18*2/3 = 12% or 120,000 ppm. The
CO/CO2 ratio would then be 30/120,000 or 1/4000 (0.025% or 0.00025). Only a
few stoves can reach that low a level of CO emission for any period of time
and none of them burn wood. They were indicating that even an oil burner (a
highly predictable fuel) would not work.

If the rate of air turnover is known then a calculation can be made as to
what the peak CO level will be based on a known stove and a known air
turnover in the greenhouse. It might be safer to use the 'digestive'
approach. It was interesting to note the CO2 drops to 200 during the day if
ventilation is inadequate. At that point the plants pretty much give up and
stop growing. At 160 ppm they die. Historically plants developed in much
higher CO2 concentrations and during the last Ice Age and Little Ice Age it
dropped to barely above the lower limit for plant survival. That was close!
A 40% improvement in growth for 1000 ppm is a big improvement over the
current baseline.

Regards
Crispin


-----Original Message-----

Dear Alex, Crispin, Hugh, Paul W., Dale, Christa, Tom and others,

I found the document Alex cited about CO2 in greenhouses to be extremely
interesting.

http://www.omafra.gov.on.ca/english/crops/facts/00-077.htm

There has been occasional discussion at BEF Stove Camps and elsewhere on the
use of larger TLUDs in small greehouses for both heat and for CO2.  With
some proper CO and CO2 or O2 and smoke detectors to provide safety features,
the igniting of quality-checked large TLUDs WITH FAN ASSISTANCE (to assure
best combustion and to help with circulation) would make great sense for
small greehouses.

The document gives some basic numbers that we could use for calculations,
but all the examples are for very large greenhouses and using propane and
natural gas.  But perhaps the "number crunchers" in our group could
calculate the heat and CO2 from a TLUD-FA with perhaps a 30 gallon capacity
burning chips or pellets.  And then match that with a size of greenhouse in
some appropriate climate/temperature zone.

If safe and appropriate, perhaps 5 or more TLUDs could be prepared and
(automatically?) ignited at specific times through the night.  The concept
could be scalable within the range of small to medium greenhouses.

If interested, please respond initially via the Stoves listserv and also to
the addresses of this message.  If there is interest, then a working group
could be created off-line from the Listserv.

Paul
--
Paul S. Anderson, PhD
Known to some as:  Dr. TLUD    Doc    Professor
Phone (USA): 309-452-7072   SKYPE: paultlud   Email: psanders at ilstu.edu
www.gtz.de/de/dokumente/giz2011-en-micro-gasification.pdf   (Best ref.)


Quoting Alex English <english at kingston.net>:

> Crispin,
>
> The current state of CO2 use in 'northern' greenhouses is summarized here.
>
> http://www.omafra.gov.on.ca/english/crops/facts/00-077.htm
>
> I have heard mention of research work on using CO2 from biomass  
> combustion. No specifics though.
>
> Alex
>
>
>
> On 8/24/2011 9:54 AM, Crispin Pemberton-Pigott wrote:
>
>>
>> There was a time (early 80's) when tobacco was grown in the US in
>> greenhouses that were heated by natural gas burners that vented into the
>> greenhouse. It was found that highly carcinogenic compounds were formed
at a
>> higher rate although it was not the higher CO2 that did it, it was an
>> incomplete  combustion product. It was quickly banned as a fertilisation
>> practise about the mid-80's.
>>
>> I had hoped to use the emissions from stoves to fertilise things but so
far
>> I am unconvinced there would be a reliable and clean exhaust stream. If
it
>> doesn't work with something as clean as natural gas it is going to be
more
>> difficult with wood.
>>
>> Regards
>> Your agro-fan Crispin
>> ++++++