how do you filter co2 from biogas?

[@krzysiekbutowski]

According to Wiki Water solubility is relatively high. At 20 °C and normal pressure, the saturation is in equilibrium with the pure carbon dioxide phase at 1688 mg/l. The easiest way is to change the water filter frequently. Your waste is not hazardous to the environment, unlike lye water.

[@Danishfarmer1]

Water wash systems are a two-stage. The first step is a high-pressure reactor column that works in a counter current fashion. Chilled water flows downward and biogas flows upward under high pressure (150 psig). Soluble gases like CO2 dissolve in the water, much like CO2 stays completely dissolved in a typical carbonated soft drink container. The second tower serves as a depressurization tower where pressure is released from the solution and CO2 degasses much like when pressure comes off an opened carbonated soft drink.

[@BiogasUSA]

I am glad you are here. I have been learning about amine towers (high pressure, low temp) and regen towers (low pressure, high temp). I wonder if there's anything I can do without increasing pressure in my jar. That's going to get very complicated fast.

[@Danishfarmer1]

@@BiogasUSA Biogas CO2 from Biogas and Hydrogen Sulphide Scrubbing Is this how to remove Carbon Dioxide from biogas? Read on! Put a section of 4″ PVC about a foot long in the line. Fill this with steel wool, the type used for scrubbing pots. This will rust away similar to the metal above. It is very efficient because of the high amount of surface area presented by the steel wool. Threaded connections make it easy to replace the wool. The easiest way to determine when to replace the wool is when you can smell the hydrogen sulfide at the burners. For a farm-sized system, probably the best thing to use is a pair of old 200litre/44gallon drums. Fill the drums with steel turnings or bashed up rusty tin cans or anything that is iron or steel. The easiest way to do that is to chop out the 3/4″ bung in the top and weld in a 4″ or larger pipe fitting. The 2″ bung on the other side should have a length of the largest size of steel pipe that you can fit inside a 2″ pipe nipple, and that goes nearly to the bottom of the drum and that is the gas inlet from the gas bag. The new and larger bung should be the gas outlet from the top of the drum with a 2″ reduction to plastic pipe, with which everything is connected. The wet biogas will flow slowly through the drum and the metallic iron and the rust will react with the Hydrogen sulfide. You should have two of these drums made up and rotate them at suitable intervals to make sure that no H2S gas is getting through the system, or your intermediate gas compressor for Biogas CO2 Scrubbing will not last for very long. via Appropedia

[@Victor.McCann]

Use the water for the H2S the put straight lye and filter though it I have never seen anyone say CO2 was a problem just moisture so the washed through water ,cat litter helps that and steel wool for H2S so if the bake soda ,or lye is for CO2 the make 4th wash for it and if you don't get the desired numbers repeat the 4 wash tell you get the results you want

[@martinbonner8626]

I heard the addition of biochar to the fermentation tank helps with the efficiency of methane production .

[@BiogasUSA]

I think this option is fascinating. I haven't heard it anywhere else.

[@youthemask]

A cost effective method i don't know... but if liquid nitrogen is colder than liquid co2 than you may condens that co2 with it. I don't know about the pressures needed to do this....

[@BiogasUSA]

Oh that's an interesting thought.

[@youthemask]

@@BiogasUSA did you get the CNG kit? Or this is the first step? What concentration of CH4 is needed in the cng to run the car?

[@BiogasUSA]

@@youthemask I haven't bought a kit yet. I'm not sure what the minimum concentration is, but I believe pipeline quality gas is 70% methane so this is my goal.

[@ZsOtherBrother]

@@BiogasUSA I'm not a 100% sure, but I think in the US the standard to use biogas as a vehicle fuel is 3 mol.% (max) CO2. Standards aside, I'd run some tests to see if a vehicle or a generator can run on 70% CH4 without problems. ( I plan to do that in the not-too-distant future, although I suspect you'll get there sooner :)