If an insufficient amount of head space is available, this scum can expand and block the gas collection connection. Feedstocks could include table scraps, cow manure, dog manure, dog food, honey, sugar, or virtually any organic material. Organic materials with simple structures will be more easily converted to acids and the digestion process will occur sooner. If simple organic materials such as honey or sugar is used the initial VS loading should be reduced to prevent acidification of the digester. Very complex organic materials such as wood chips would take and extremely long time to digest and should be avoided.
Water is used to dilute the desired amount of volatile solids to the desired volume.
If an attempt is being made to control the digester temperature, the reactor should be placed in the controlled environment, i.e. in the water bath or hot box. If the designed system is effective and the feed recipe was appropriate, biogas production will most likely be observable the following day. Biogas production may take longer if temperature control is not utilized. The digester could be allowed to go unmonitored for one or two days if necessary. Bear in mind the eagerness of project participants to observe their successful results.