biogas from biomass

[aag]

I am conducting an experiment with biomass ( manure, banana, vegetables peels) producing biogas. There were three mixtures in bottles setup to see which one generates the most gas. A balloon was attached to see how much gas is being generated in each of the bottles. The balloon with just manure is sucked in the bottle due to the creation of a vaccuum and so the the one with manure and vegetable peels. The one with banana and manure is fine. Any suggestions - is this normal, what went wrong? How can we show the difference in biogas generation.

[kgudger]

Hello and welcome to the forums:

I'm not a chemist, but I do compost a lot of horse manure . I have a couple of suggestions.

First, composting can be anaerobic or aerobic (meaning whether it uses oxygen.) It's possible that having the balloon over the bottle caused some of your composting to go anaerobic. In any case, it's possible that your composting method removed more oxygen from the air (adding it to the nitrogen in the compost) than the composting produced CO2.

You might want to try composting with some air in the balloon to start with. This might keep the process from going anaerobic. If the process is actually removing more O2 than the CO2 produced, you can measure the "loss" in volume of the balloon as well as the gain with some of your other bottles. Be sure to have multiple trials and repeat your experiment.

A good idea would be to monitor the temperature of your compost, if possible. It's one of the best ways to know if your compost is going anaerobic. Also, if it's anaerobic, it will smell bad! You probably want all of your composting bottles to be either aerobic or anaerobic so that that's not another variable.

Keith

[aag]

Thank you for the suggestions, I am going to try them.

[jhardenstine]

I am conducting the same experiment (manure, veggie peeling, banana). Any idea how long it should take to see any results. We are into day 2 and have not produced any measurable gas. According to the paper the conditions need to go anaerobic in order to produce the gas.

[kgudger]

Hello:

I'm sorry for the confusing information about aerobic composting I posted before - in composting manure outdoors, most of us try to keep our piles aerobic so they don't smell. I see that the original experiment depends on anaerobic composting to create methane.

In this experiment the water removes all air (and oxygen) from the system, so it should only digest the manure anaerobically. You should see results in a couple of days.

If you're having trouble, be sure that your manure is VERY fresh. Manure will begin to compost right away.

You might also want to try using more of the biomass, although this experiment has been checked out and should work with the amount of materials specified.

Keith

[jhardenstine]

We are running the biomass to biogas project using the balloon and manure. We set up 9 bottles with different combinations of manure (very fresh) alone, manure and vegetables, and manure and banana. We saw minor results (which took 7 days) in 2 of our manure and banana bottles for one day and now the balloons seem to be going down. There does not seem to be a leak, is this normal or has something gone wrong. Has anyone successfully performed this experiment and could inform us of what to expect. We are running out of time and need to know if we need to set up again. Any help would be much appreciated. Thanks.

[kgudger]

Hello:

I posted your request to the originator of the experiment, and they say that 5 g should be enough manure, and that it can take up to 12 days. The fact that your experiment lost gas sounds like a problem. Are you certain there are no leaks? It sounds to me like the gas is getting out somewhere... and no, the balloons should not be going down. Hopefully we'll hear back from the expert in the next day or so, but I doubt it will be in time to help you with your experiment. Sorry.

Keith

[jhardenstine]

I poured a light soap solution over the ballon and bottles and gave a light squeez and saw no bubbles so i think the system is tight. We are going to set up a second series of bottles tomorrow so any tips between now and then will be much appreciated.