Crazy CO2 sourcing

[Winterfoot]

Hi guys, I had a thought, and this may be crazy. 

I don't have enough information yet to know if this is viable, but I wanted to collect some thoughts.

So, as another hobby I've started roasting my own green beans for fresh coffee. One of the byproducts of the roasting is CO2 generation off the green beans post roasting period. This should be easy to capture (containing and transferring to a sealed container is a little more challenging, but not insurmountable.) What I don't know is how much CO2 is generated off an 800ml batch of beans, and whether or not there is anything else contained in that gas that could be harmful to fish. (i.e. gaseous sulpher.). 

I know some low tech people will use citric acid and sodium bicarb to generate co2, and there are some challenges in that. Things to learn too. I'm mostly interested in repurposing waste as a byproduct to something useful.

Thoughts?

[CT_]

CO2 is everywhere so it's not worth saving.  If you can figure out how to efficiently store what comes off your beans you could just as easily mix baking soda and acid or burn some lawn clippings or tape into your furnace chimney (if its gas).  It's the storage that's hard. 

 

Coffee or anything burning is full of "toxic" stuff but as far as I've seen (I haven't looked that close) there's no adverse effects from the chemicals made in roasting on humans.  We probably know even less about fish and coffee.

 

[Winterfoot]

Yeah the other byproducts are my primary concern. I just don't know enough and don't want to pay to have it analyzed.

My curing rig should be able to efficiently capture the gas though. It's just a mason jar with a through wall sealed fitting on the lid going to a pressure gauge and a venting check valve set to anywhere from 0.5 psi to 2.5psi. those valves have a push to connect fitting so I can get tubing on it, but where it goes to becomes the challenge. I could probably fit the push to connect up to a sealed co2 tank and fill that, shut it off at the valve, and disconnect losing a little, but I still won't know how full that tank is or how much gas i produce.

[CT_]

pure CO2 is about 2g/L so a single mason jar ("standard" 16oz one) is roughly 1g of co2 when full of pure co2.   a tad more a 2psig.  For perspective, the little CO2's for emergency bike flat repair are 16 or 20g.

 

If you want to know what coffee off-gasses there's actually a lot of information on the web about the biproducts of roasting many are really scary sounding but are only in minute quantities.  IIRC there's some idiotic effort to get a California prop65 warning on coffee.

[Winterfoot]

Oh I know prop 65 intimately. It's a pain! I work with ceramic coatings so everything has to be prop 65 tested. I probably spend around 12k a year just for those tests

It may be about just the Mason jar size I fill with gas, maybe more because I do generate enough pressure for an audible pop after I open it.

 

I know the fluval cartridges I get are 45g. Might not be enough to be worthwhile...

[Frank]

"Dry ice" has to be food grade.

[gardenman]

I doubt that the return would be worth the effort. even if the byproducts were harmless. There are much easier ways to generate CO2. Sugar, yeast, water, and a pinch of baking soda is the classic way. Plop it in a two liter bottle and it'll generate enough CO2 for most tanks for a week. Sometimes longer. When the anti-CO2 crowd talks about we need to move to green energy, they largely ignore the vast amounts of CO2  generated by and used for other means. CO2 is widely used commercially in the soft drink industry. Some/many commercial greenhouses inject CO2 directly into the greenhouses to both help plant growth and kill insects. Every alcoholic drink produces CO2 during fermentation. Every loaf of bread releases CO2 during the rising/baking process. Welders use CO2. Dry ice is CO2 in solid form. Aquarium keepers use CO2. The stuff is everywhere and widely used in vast quantities. I don't know the math, but my guess would be that fossil fuels may produce less than the other sources. It's a very commonly used and produced gas. 

[Winterfoot]

I think you guys are right, though largely to note I wasn't planning on roasting coffee to make CO2 for the tank, I was just curious if I could use my byproducts from a process I was doing anyways. There are definitely easier ways to do it if that was the intent, but I'm also fine just buying in CO2 as I need it.

I will probably continue to test and measure my CO2 production from this roasting out of curiosity, but I don't think I will actually use it. 

[Jungle Fan]

A refill for my 5 lb. CO2 cylinder currently costs me $16 at the local brewer's supply store, and it seems like I usually make one trip per year. Haven't felt nostalgic to return to any kind of DIY in regards to CO2 itself, although I wouldn't mind learning how to build my own solenoid controlled dual stage regulators with bubble counter from high quality parts. Until I find out, my GreenLeaf regulator keeps me restlessly happy.