Science Buddies: "Ask an Expert"

I'm about to begin a new project in which I compost animal waste and plant material and collect the methane produced. I'll then need to measure the amount of methane I was able to collect. Does anyone have any ideas on how I can construct a bin that will separate the gas from the solids in the compost bin? So far, I'm considering using a closed container with a separate gas chamber, but I'm confused about how I'll measure the amount of gas collected. Should I use volume and gas pressure? If so, how will I measure the pressure? Any ideas or tips would be greatly appreciated, as I haven't yet started the project, and I'm just considering the details of the process. Thank you so much!

Here is a cheapish methane probe. https://www.alibaba.com/product-detail/ ... 333dNiGwlW
Alternatively, you could measure change in overall gas pressure over time, much more simply, but without being able to say that what is produced is entirely methane. As easy as fitting a balloon or syringe over a hole and measuring the volume change.

Is this an experiment, or just an observation? If it needs to be an experiment, you will need to change something: air content, temperature, ratio of plant to animal waste, etc.