5 Steps to calculate the area for a biogas plant: a detailed expert guide

Biogas is a modern solution for agribusiness, enabling the conversion of organic waste into energy while reducing CO₂ emissions and minimizing environmental impact. It’s not just an alternative to traditional energy sources — it’s a path toward sustainable development and energy independence.

For agribusiness, it is especially important to understand how to calculate the area for a biogas plant in order to avoid excessive costs while preserving the possibility for future expansion. A well-designed plant will help you achieve stable profitability faster and secure a competitive advantage.

In this article, we will explain how to calculate the area for a biogas plant on your own.

Why accurate calculation of a biogas plant’s area is the key to success

When planning a biogas facility, many agricultural owners and investors try to cut costs already at the preparation stage. However, it is precisely at this stage that the foundation is laid for the plant’s stable operation over decades.

An incorrect calculation of the biogas plant’s area can lead to:
❌ inefficient logistics and difficulties with entry and exit;
❌ increased production costs for biogas due to unnecessary transportation;
❌ additional expenses for extending infrastructure;
❌ higher risks in case of accidents, up to and including a complete plant shutdown.

If you plan to build a plant not just for one season, but with a focus on stable income and growth over the next 15–20 years, competent site planning is a must-have.

Step 1: In-depth feedstock analysis

What determines the volume of the reactor? The characteristics of the feedstock — moisture content, organic matter content, C:N ratio, and decomposition rate.

For producing biogas from agricultural feedstock, detailed laboratory analyses are essential. It’s not advisable to rely solely on generalized data from handbooks or the internet, as every farm has its own specifics: animal feeding practices, manure collection methods (bedding, hydraulic flushing, etc.), and the microelement composition of plant-based feedstock, which can vary by harvest region.

💡 Example: Two farms with the same number of cows may produce different volumes of manure if their feeding rations or manure collection systems differ.

The more precise your data at the start — the lower the risks after commissioning.

Step 2: Accurate calculation of reactor volume

Equally important is calculating the reactor’s volume, as this directly determines the size of the main processing structure and the required investment. Without knowing the exact volume, it’s impossible to correctly determine the reactor’s footprint for biogas production and calculate the necessary technical clearances.

Typically, equipment suppliers offer different tank sizes that match the feedstock volume. The reactor’s diameter impacts the construction footprint, and if the available building area is limited, its height becomes an important factor — you can choose tanks with a smaller diameter but greater height to fit within the constraints.

Next, we move on to planning the total footprint required for the biogas plant.

Step 3: Calculating the footprint for key facilities

In addition to the reactor(s), you will need space for:

• Gas holder — where biogas is stored before purification or injection into the grid. Savings are possible by choosing agricultural-style tanks with flexible covers and gas holders mounted on top of the tanks.
• Feedstock storage — both permanent and operational.
• Foundation for digestate separator and storage areas for the fermented residue: liquid and solid fractions of digestate.
• Service and access areas — for maintenance vehicles and biogas plant access routes.
• Administrative building — housing the laboratory, heating unit for the biogas plant, control panel, and operator rooms.
• Gas treatment system — space for activated carbon filters / hydrogen sulfide scrubbers and gas drying equipment, as well as for an emergency flare, CHP unit, or upgrading plant (for purifying biogas into biomethane).

All of this forms the technical zone of the biogas plant, which often occupies up to 50% of the entire site.

💬 When do additional construction costs outweigh the initial savings several times over?

• No operational feedstock storage (for 3–5 days) was provided. In the event of a change in feedstock supplier, having such storage is essential to prevent a drop in the plant’s productivity.
• No gas holder installed — biogas is fed directly to cogeneration or upgrading. As a result, during maintenance periods, daily volumes of biogas are burned off via the flare.
• Decision not to separate digestate and to store it directly in lagoons. As a result, cleaning the lagoon becomes technically more complicated and costly due to sediment from the solid fraction accumulating at the bottom.
• Skipping gas treatment (directly feeding unpurified biogas with hydrogen sulfide into cogeneration). As a result — more frequent replacement of CHP parts and more frequent maintenance.

Another critical aspect is logistics. If during maintenance the specialist cannot maneuver safely, loading/unloading time increases, directly impacting productivity.

When planning, you should also consider the potential installation of additional equipment: new digesters, biomethane purification modules, or backup generators. If you fail to reserve space for these now, in the future you may have to bring in a construction crew again to build foundations — resulting in significant extra costs and lost time.

Step 4: Reserve zones — why they are critical

Reserve space is your “safety cushion.” It allows you to:

• Scale up the plant without a full reconstruction (for example, adding another digester if cattle numbers increase, or installing a biomethane production module if the plant initially operated on electricity only).
• Organize emergency settling tanks.
• Ensure backup power supply.
• Preserve space for logistics and safe maintenance operations.

Another critically important factor is ATEX zones — explosion and fire hazard areas around gas holders and other equipment containing flammable gases. These zones are designed in accordance with Ukrainian building codes (DBN) and European directives, ensuring that, in case of an incident, fire does not spread between structures.

It is generally recommended to leave at least 10–20% of the total site area as reserve space — this ensures compliance with both Ukrainian building codes and European safety requirements.

A common mistake is building over the entire site without accounting for technological clearances, fire access roads, and maintenance zones. Overly dense equipment placement complicates operation and creates the risk of a plant shutdown if an inspection requires deficiencies to be addressed.

All structures and equipment must be located in accordance with current State Building Regulations and Ukrainian legislation.

Step 5: Preparing infrastructure and detailed zoning

The final, but no less important step, is detailed site zoning, which includes:

• Separating technological and administrative zones.
• Properly positioning access roads to minimize fuel consumption.
• Separating traffic flows for machinery and personnel to improve safety and operational efficiency.
• Reserving space for vertical biogas reactors if an increase in capacity is planned for the future.
  

Careful zoning is a way to avoid chaos and improve energy efficiency. Every extra kilometer of transportation within the plant increases production costs and consumes resources.

Main zones and their purpose:

1. Raw material area
Storage of manure, silage, etc.
➡️ 15-25% of the area

2. Fermenters (bioreactors)
Main fermentation area
➡️ 10-15% of the area

3. Gas holder / biogas tanks
Storage of produced biogas
➡️ 5-7% of the area

4. Cogeneration unit (or biogas treatment module)
Electricity/biomethane production
➡️ 3-5% of the area

5. Digestate tanks (liquid/solid)
Digestate product
➡️ 15-20% of the area

6. Technical and service area
Control points, service, laboratory
➡️ 3-5% of the area

7. Buffer zones / fire breaks
Passageways, sanitary breaks, ATEX zones
➡️ 10-20% of the area

8. Reserve area (future expansion)
For additional fermenter / biomethane module
➡️ 10-15% of the area

Want to get a detailed technical assessment for your site?

Order an expert consultation or download our checklist for a preliminary analysis!

FAQ

1. Can you do without a reserve zone?

No. The absence of a reserve zone increases risks and limits development potential.

Always take into account reserve space for the biogas plant, as it becomes critical in case of emergencies, scheduled maintenance, or capacity expansion. It also allows you to respond quickly to market changes, scale up production, or add new modules, such as gas upgrading units or fertilizer production systems.

Don’t forget about the technical zone of the biogas plant — the area where auxiliary installations, engineering utilities, tanks, and service equipment are located. This zone should be designed with reserve capacity in accordance with current construction norms and regulations to ensure safe access for maintenance and monitoring.

2. What are the size requirements for a 1,000 m³ reactor?

If the tank has a volume of 1,000 m³ and a height of 6 m, its diameter would be 14.6 m, and the footprint would occupy 167 m².

3. How is a biogas plant secured?

Mandatory fencing, video surveillance, and controlled entry points are essential. These measures are implemented to ensure the legality of operations and maintain the safety of the facility.

4. Should you plan space for gas purification from the start?

Yes — to avoid costly and time-consuming reconstructions in the future.

5. How to choose a site?

Start with a biogas site assessment checklist — it will help you take into account all technical, logistical, and regulatory aspects.

6. Can you build on a site with challenging terrain?

Yes, but it will require additional costs for earthworks, foundation reinforcement, and may affect the placement of reactors.

7. Do you need to allocate space specifically for maintenance?

Absolutely! Working corridors around reactors, gas holders, and storage facilities are mandatory — even if it seems that “everything will fit.“