Biogas

First keep in mind, its an animal, not a machine.  It has a stomach. It can be overfed.

It will then get indigestion.

It will then stop making methane. 

You will be able to tell because the gas won't light (it will be increasingly just CO2). The effluent will begin to smell sour (acidic). Your nose will tell you.

Yes.

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1) Turn off the power to the Arduino (or simply unplug)

2) carefully remove the SD card by pushing in until you hear a click and feel the bounce back, then pull it out, noting the wires (maybe take a picture) in case you accidentally disconnect something.

3) put the SD card in your computer and open the file. Hit save as and change the name from Datalog.txt to KathyBorgNov22Datalog.txt (This will enable us to keep backups of the old data each week and the arduino will start a new log called simply datalog.txt when it powers up again)

The methane released (actually only averaging 65% of the biogas by volume) is ultimately non-anthropogenic in the sense that it is the decay product of organic decomposition that has been going on as part of the carbon cycle for millions of years. 

Puxin bags set the standards. Here are their measurements, from

http://puxinbiogas.en.alibaba.com/product/263927194-220435925/PUXIN_biogas_storage_bag.html

We tend to think in buckets, 5 gallon (20 liter) paint buckets. That is something everybody in the world can relate to.

Figure about 1 bucket per cubic meter each day. That is, if you filled a bucket with food waste.  If you grind it you are adding water as you grind, but because it grinds up and occupies less space and you then add water you are still talking about a bucket (because generally when you grind with water you end up with a bucket having about 50/50 food particles to water).

Psychrophilic  or 'cold loving' microbes don't really love the cold, they just do much much better at low temperatures than "mesophilic" (medium temperatue loving) and certainly than "thermophilic" (heat loving) microbes.  They operate from as low as 0 C (some report as low as -4 C!)  to 25 C.

Once again, we turn to a chart from  David House's Biogas Handbook:

"The chart asumes two critical things: first, that you are digesting food waste, and second, that the digester is at body temp. Given just those two assumptions, it shows you how many 1-gallon buckets of food waste you need to be able to get the outcome you want— and what size of digester you’ll need too. Simple. Clear. Ready? Here it is:

Food waste power!

Yup. They do.  Here is a chart created by David William House, author of "The Biogas Handbook":

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The general rule of thumb is that every liter of digester volume yields its same volume in gas after 24 hours at body temperature.  That is an ideal that is rarely met.  But theoretically the typical 1000 liter (275 gallon) home digester should make 1 cubic meter (1000 liters, 275 gallons) of biogas in a day or so after being fed. The amount of food that usually yields that volume of gas is about a bucket's worth, a bucket being between 20 and 25 liters (5 gallons or so).  We use buckets because people have them and most people were instructed to dislike math.