Biogas: understanding how a methanisation plant works and how it filters

The inputs are prepared prior to the methanisation process. These operations vary depending on the type of waste and the facility: removal of unwanted materials, homogenisation and, if necessary, dilution or grinding. The aim is to obtain a sufficiently uniform and pumpable material to feed the process.
Once prepared, the organic materials are fed into the digester. This hermetically sealed, oxygen-free tank is the heart of the process. To function efficiently, digestion takes place under controlled conditions: the temperature is maintained between 40 and 60°C and the material is continuously stirred using an agitator to ensure a homogeneous environment conducive to bacterial activity. Inside, microorganisms naturally present in the inputs gradually break down the organic matter and convert part of it into gas.
Methanisation then produces two streams: a recoverable digestate (the residual material from digestion, liquid and/or solid) and raw biogas (a mixture of CH₄ and CO₂). This biogas naturally contains water vapour, H₂S, siloxanes, VOCs and fine particles, which must be removed before any energy recovery can take place.

Before any recovery, biogas from the digester must be treated in order to protect downstream equipment. This purification process aims to remove the main impurities naturally present in raw biogas. In practice, purification is based on three essential functions.

The cogeneration engines used in anaerobic digestion plants are industrial engines designed to operate at a stable speed over long periods of time. Engine availability is therefore a major issue. Controlled maintenance, based in particular on appropriate filtration, ensures safe operation and limits unplanned downtime.

Beyond the filters mounted on the engine, the ambient environment directly influences the reliability of the cogeneration installation. In a methanisation plant, technical rooms and electrical cabinets are often exposed to dust from agricultural or industrial activity.
If the ventilation air is not filtered, these particles can be sucked in, accumulate on equipment (fans, heat exchangers, grilles) and disrupt cooling. Appropriate air filtration helps to limit clogging and maintain stable operating conditions. HIFI FILTER® offers pocket filters, filter mats, PPI foams and filter strips for the ventilation of technical rooms, containers and electrical rooms.
The protection of electrical cabinets is based on the same principle: a supply of filtered air limits internal clogging and contributes to the reliability of the equipment.

In addition to biogas production, methanisation generates digestate, i.e. the organic matter remaining after the digestion phase. It comes in liquid or solid form, or separated into two fractions.
Rich in fertilising elements (nitrogen, phosphorus, potassium), digestate is mainly used in agriculture as an organic fertiliser, partially replacing mineral fertilisers. Its management and recovery thus constitute an additional outlet for the methanisation process, distinct from energy production.

Methane conversion transforms organic matter into biogas, which can be used in cogeneration or, after additional treatment, into biomethane. It also generates a valuable by-product: digestate.
In all configurations, the reliability of a plant depends on controlled biogas and equipment protection. Filtration occurs at several levels in a methanisation plant in order to protect equipment from fouling, corrosion and premature wear. HIFI FILTER® is used in particular on the biogas line, cogeneration engines, ventilation of technical rooms and electrical cabinets, as well as on machinery and vehicles operating on site.
Beyond these applications directly related to the biogas process and recovery, other filtration needs may arise in anaerobic digestion plants: filtration of industrial liquids, hydraulic circuits, compressed air and vacuum, dust removal solutions, and even fuel distribution. These are all environments where HIFI FILTER®'s expertise can be put to good use.
To find out more and identify the references compatible with your configuration, contact our teams!