Hi Tony; Welcome to Permies!
I would say all of the things you mentioned are fine other than liquid fuel. Liquid's are generally to volatile.
I doubt your food would pick up a bad smell, lets say cow pie. Folks have been cooking with similar things for a very long time!
What style is your rocket? All metal?
After you use your rocket stove for a while you just might consider a rocket mass heater as your next step into the wonderful world of rocket science!
These guns usually run on heating oil, (read overpriced offroad diesel) but they have natural gas, and propane, versions too, and there are many forums devoted to burning used motor oil and vegetable oil with them.
I've rigged them to be the backup heat source in outdoor boilers and been very pleased with their performance and trouble free nature.
By adequate controls I mean flame sensors, automatic shutdowns if burn parameters are not standard, automatic shudown if CO alarms are triggered, and thermostatic control as every source has notable BTU content.
The downfall of these burners are;
Fuel must be kept scrupulously clean, if your trying to re-purpose an old 55 gallon drum you found in a neighbors field ......this is not the project for you!
Parts are hard to get locally, most hvac shops and supply houses will not sell you components unless you are a licensed contractor.
Advice on setup and tuning parameters will be "hire a professional".
If you do hire a professional, he will want you to scrap the project out of hand and get a U.L. listed appliance.
Inadequate, uneducated, or incompetent, execution of work will result in toxic gasses being leaked into your home, or catastrophic fire.
If you are an able artificer, then an even more trouble free appliance is the Babington burner, owing to its self clearing nature, fuel does not have to be so pristine.
But........many a property has burnt to the ground from overestimated competence.
As I mentioned in my first post I would like to burn more types of fuel.
I would like to expand a bit on that.
I could buy a different setup for each fuel type. Propane, alcohol, diesel, etc
I understand the power of a rocket stove over a normal wood stove is how efficiently it burns wood and that technology has no advantage when burning propane in it.
But I think it may still be more efficient in burning propane compared to a regular stove with a flame that loses a lot of heat to the environment.
The rocket stove has insulated walls and the heat transfer to the pan/pot is maximized due to it's skirted design.
That said I think a skirted pan on a regular propane stove may be more efficient than a regular pan.
I've been looking for liquid fuel burners, they seem to come in many types, for various fuels. Some have/need a wick others don't.
Finding a gas (propane, butane, natural gas) burner, is more of a challenge than I thought it would be. If I understand things correctly different types of gas require a different nozzle.
Another problem for all types (liquid/gas) burners is it's size.
The rocket stove opening is only 70mm high and 120mm wide.
I have a very hard time finding burners of that size.
For example I've looked as bunsen burners that are used in labs. They are quite small but always to high and most often also to wide.
Maybe I should abandon the whole idea using my rocket stove.
But even then questions remain.
I want to be able to cook on, say, 10 types of fuel without buying 10 stoves.
On top of that I want the stoves to be as energy efficient as possible.
So... can someone guide me a bit in the right direction?
To be clear, I'm looking for something small to cook just 1 pot/pan
Fumes are not good, you are right about that.
I think often the fumes are less if the burn in clean.
But yeah, well ventilated is often required.
Electric is by far the cleanest/fumeless way to cook for sure, but electricity is not always available. (off-grid, camping, emergency)
Not entirely sure, but I think for electric emergency cooking 12v rice cookers are a good option. Not suitable to boil potatoes and stuff but suitable for rice, bulgur etc. Not optimal, but a emergency never is.
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rocket mass heater risers: materials and design eBook