In theory, a methanizer can digest all materials as long as they are organic. In practice, you have to think carefully about the different inputs and their quantity to create a balance that will optimize digestion and therefore biogas production. Each methanizer has its own action plan defined according to several criteria that we will describe later in this article.

The different types of inputs that exist are:

• Livestock waste and in particular effluents (slurry and manure)
• Agricultural waste which can be crop/harvest residues (cereals, fruits, vegetables, etc.) or CIVE (Intermediate Energy Crops intended to produce biogas)
• Food waste which is leftover food from households, communities, canteens, restaurants, etc.
• Industrial waste, which is all waste that comes from the food industry: processing residues (from dairy products, flour, breweries, etc.) or even downgraded products (because they are not suitable for human consumption following contamination, for example)
• Green waste such as grass clippings or leaves for example. Whole plants are not a preferred input since they contain lignin which is not digested by bacteria, they would first have to be ground into dust.
• Sewage sludge containing organic residues

The Environmental Code provides for a classification and codification of all waste that may exist, including biowaste. This list can be referred to to check the admissibility of waste in methanization and justify its category.

Faced with these numerous choices of materials, the person responsible for inputs in a methanization unit will define his selection based on 4 main criteria:

• Methanogenic power and cost: Methanogenic power is the capacity of a material to produce biogas. The higher the methanogenic power, the easier the material will fulfill its objective and therefore the more valuable it will be in the eyes of a methanizer. Its cost can therefore be an important selection criterion.
• Nutritional balance : to create the right balance for good digestion, it is generally necessary to create diversity in the composition and texture of the materials. Some structures will need to introduce dry materials to compensate for an excess of liquid volumes. We can also notice the lack of a specific nutrient and therefore move towards a category of material rich in this nutrient.
• Availability of inputs : most methane digesters are created by farmers. They therefore generally have readily available materials that already belong to them. For example, our livestock partners will be able to recover the manure/slurry from their animals, and our cereal customers can secure their inputs thanks to CIVE.
  Apart from these materials of internal origin, the choice of inputs is sometimes limited by their availability (shortage or season for example).
• Capacity of the structure and associated regulations : each methanization unit must respect a maximum volume (called tonnage), pre-defined according to the regime for which it has obtained authorizations. It must also select inputs that are compatible with its storage capacities and equipment (for example: need to have a tank for liquid / obligation to pass certain materials through a hygienizer before methanization). Finally, it must remain faithful as much as possible to the distribution forecasts announced in a file prior to the authorization to launch the operation (ICPE).