Install a valve on the package. If the internal pressure is increasing, it would open the valve. An indicator of opening could be applied. The valve also allows draining the methane.

I suppose the way question was asked does not make much sense. You look confused about the topic you wanted to present.

Nevertheless, there will be no degradation of non-biodegradable materials, since the degree of degradation of biodegradable materials in a functional anaerobic digester for biogas production itself is not absolute and depends on several factors.

Furthermore, if you are talking about a systematic biogas reactors, there are designated inlet and outlet ports for specific substrate and products.

I guess your question is about the biodegradability of any waste.

There are various ways, you can confirm the biodegradibility,

1. just take the waste liquid or leachate from the waste periodically and do plating on the nutrient media, and enumerate the total cell count. If the cell count (biomass) is increasing over time. You can say that the biological growth is happening and hence bio-degradation.

2. You can check the BOD of the waste liquid. If you get acceptable BOD value. Definitely, the waste is biodegradable.

2. Find out the C/N ratio using CHNS analyzer. Check if C/N ratio is decreasing over time. If yes, bio-degradation is happening.

Hope this answer help you.

Your question is a little bit peculiar..........

I think that the best way how to determine biodegradability is use of respirometric tests. They are easy to perform and the results are very accurate.

Best regards

Vit

Considering your waste a plastic as it is non-biodegradable, the degradation of plastic can be measured by an equipment called respirometer. with this you can find out how long a non-degradable substance could be degraded. If you want to know the by-products that are produced then you have to design a reactor.