Source for small engine catalytic converter?

[Number21]

I am interested in playing with the idea of CO2 enrichment in a greenhouse for increased plant growth. A lot of people use propane burners for this, mostly just a torch in a box. I would like to instead experiment with using the exhaust gas from a propane powered engine to generate the CO2. Unfortunately a lot more than CO2 comes out, and I need some sort of catalytic converter to convert the CO to CO2.

Does anybody know a source of a small catalytic converter that would work on an engine running in the 2-5hp range? I've found a bunch of industrial "scrubbers" for small engines through a google search, but no actual sources to buy them, or $500+. Are there any cheap OEM cats I might be able to find a modify that would work on an engine that small? Would anything from a small car engine be too large? (not enough exhaust heat?)

[Tom Reed]

In the US I believe most of the new small engines do have built in cats.

[Number21]

In the US I believe most of the new small engines do have built in cats.

Got any more specifics on that? I've heard of some forms of "catalyst muffler", but I'm not sure if that is just "a little cleaner than before" or a full catalytic exhaust treatment, like a modern car? I looked at the Briggs and Stratton website for any info about a catalyst but couldn't find anything.

[glort]

Do you also need to heat the greenhouse?
I helped a guy make a heater for his greenhouse using a Veg oil burner like this. Not sure if he used the CO2 but there would be plenty of it generated.

Using veg oil you would avoid any nasties being discharged and could use a burner with a cat converter from a car for extra insurance.  The gas temp straight out of the Burner would be too high but you could tap off some air from the blower for the burner and feed that into the exhaust to regulate the temp. With a cheap Pyro you could set the exhaust temp right where you wanted it to get optimal temp in the cats.  I'd think you would want to use more than one cat due to the burner flow requirements but that wouldn't be a major expense.

You may be able to kill 2 birds with one stone this way and do it far more economically than anything else.

[Tom Reed]

In the US I believe most of the new small engines do have built in cats.

Got any more specifics on that? I've heard of some forms of "catalyst muffler", but I'm not sure if that is just "a little cleaner than before" or a full catalytic exhaust treatment, like a modern car? I looked at the Briggs and Stratton website for any info about a catalyst but couldn't find anything.

Well a clue is they require unleaded fuel. A friend had a tiller in need of an engine, so we put a Harbor Freight 6.5 hp engine on it. It stunk just like a car when started.

[Number21]

Do you also need to heat the greenhouse?

More of a need for power for some artificial lighting, depending on the season used for a few hours/day. I would really like to use a standard 120v generator, feeding a grid tie inverter. If my math is right I think I would need to burn somewhere between 15,000 and 50,000 BTU/hour of propane to get enough CO2, that could support roughly 2-3kw or so generator. I could add controls to start/stop based on CO2 concentration and maybe some sort of emergency cut off in case of too much CO.

Heat can be useful but the unfortunate problem is that the plants want CO2 during the day, and heat at night. Would need to have a heat storage system to make much use of the heat. They do this in giant commercial greenhouses but not sure if that would be worth the effort/cost in my case.

[Thob]

Several years ago I bought a generic CAT at the auto parts store for our Toyota. The original was $$$$ and I had to rod it out and patch in the new one (the original is a big cast iron housing hanging off the exhaust manifold).  It passed inspection afterwords.

The only question I would have about using one is if it requires a certain flow or temp to operate.

And I would definitely have multiple CO detectors.

[Number21]

The only question I would have about using one is if it requires a certain flow or temp to operate.

That would be my concern with an automotive style cat. Then again, I guess a small economy car engine at idle probably puts out less than 3kw, and they seem to work fine. I wonder if simply wrapping it in insulation would help? Also I'm guessing the exhaust gas from an air cooled engine is hotter than a water cooled engine.

I do plan on spending a few hundred bucks on a gas analyzer to see exactly what is coming out the exhaust when I'm done. Probably run the engine a bit lean.

[glort]

2-3Kw Veg fueled engine with Induction motor generator feeding a grid tie inverter:

I have to admit I have become more partial to that engine than my roid. If I can come across a 10+ Hp water cooled Changfa type I'll sell the roid and just keep the china horizontal.

As for heat storage, I don't see why it would need be at all expensive.  I would just use some IBC's full of water and circulate it through the watercooled engine.
You could either just let the IBC's radiate their heat naturally at night, Put a small fan behind them ( wouldn't need much air circ) or use a circulating pump  on a radiator if you needed to dump more heat.

I helped a guy in the US last year set up a heating system for his greenhouse with one on my Burner designs.
He was running his heater 24/7. Spent a couple of nights sleeping in there with the thing till he was confident with it and also  pretty much fire proofed where it was and installed a couple of safety cutoffs. No chance anything was going to burn.  That would give you the heat and Co2 if not the power.

The other alternative for an engine is a car engine.  Don't believe the Crap about having to run fully loaded and will foul up if run at a fast Idle. I have a merc engine that I have run at 1500 rpm for a good hundred hours now and while not forever, I have compression checked it and there is no difference to when it was in the car.  I run on wvo with 5% Ulp and a water drip into the intake of about 1L Hr. Runs fine and starts possibly better than when it was in the car.  At low speed diesel run with plenty of excess air and have slow combustion cycles so give more time for complete combustion.

You could run a 5 or 10 KW motor as a generator  tied direct back to the mains ( with an isolator of course) to give you a grid tie which would either supply your power needs or run the meter backwards if it was supplying excess.  Again a cheap and effective   .

I'd sure be looking at WVO/WMO before I would be looking at LPG.

[Number21]

I'd sure be looking at WVO/WMO before I would be looking at LPG.

Isn't propane much cleaner burning though? I know a cat works with a diesel engine, but a modern diesel truck still smells like diesel exhaust when it runs. I wouldn't want the inside of the greenhouse to smell like that. The only reason I started thinking about this project is because of the fact they use propane forklifts indoors, never really heard of using a diesel forklift indoors. I am interested in making use of WMO, but, the fumes from that seem extra toxic in this situation. WVO can be hard to find around here.

Here in Oregon, marijuana growers are everywhere, though, I'm only growing vegetables.   It is very common for them to use propane burners to generate CO2 for their big grows. Propane is also relatively cheap, if I get a bulk tank like I want to. I suppose the cost might not be as effective for what I'm growing, but I'm just doing this for fun mostly.