Biogas Plant Costs on the Farm: Investment and Operation

A small manure biogas plant (Gülle-Kleinanlage) with around 75 kW of electrical output requires an investment of roughly 600,000 to 1,000,000 euros, depending on specification and existing infrastructure, which is about 8,000 to 13,000 euros per kilowatt. Running costs for maintenance, labour, insurance and reserves come on top. These ranges are indicative as of October 2026. The actual price depends above all on whether storage has to be built new, the distance to the grid connection point and how much of the heat is used.

Why cost figures vary so much

There is no list price for a biogas plant. Every plant is adapted to a specific farm, and starting points differ widely. A dairy farm with a new slurry tank that can be covered and a transformer on site starts from a very different position than a farm that has to build a digester, a digestate store and a long cable route from scratch. Price swings for steel, concrete, engines and electrical equipment in recent years add to the spread.

Guide values for planning and operation are published by the Association for Technology and Structures in Agriculture (KTBL) and the Agency for Renewable Resources (Fachagentur Nachwachsende Rohstoffe, FNR). Use them for an initial check, but not as a substitute for quotes.

Investment cost blocks

The investment in a farm biogas plant is made up of several blocks:

Many suppliers of small manure plants offer standardised complete systems, some in containerised form. This cuts design effort and construction time, but it does not remove site-specific items such as earthworks, bunding and the grid connection. Check carefully which items a quote includes.

Running costs

Operating costs are often set too low at the planning stage. The main items are:

1. CHP maintenance and repairs: many operators sign full-service contracts charged by operating hours or electricity output.
2. Reserves for overhauls: engines need an overhaul or replacement after a certain number of operating hours, so money should be set aside every year.
3. Own electricity use: pumps, mixers and controls consume part of the electricity generated.
4. Labour: inspection rounds, the feedstock log, fault clearance and documentation take time every day, even with a high level of automation.
5. Insurance, inspections and analyses: liability and machinery breakdown cover, inspections under the AwSV and the Industrial Safety Ordinance, feedstock and digestate analyses.
6. Co-substrates and direct marketing: purchased co-substrates and a direct marketer’s fee only arise if you use these routes.

For your planning, list operating costs item by item rather than as a lump sum, and back them up with actual quotes for the maintenance contract and insurance. Talking to operators of comparable plants in your region is also valuable, as they know their real costs from several years of operation. The guide to biogas plant maintenance explains typical service contracts and intervals.

What drives the price

In practice these factors make the biggest difference:

• Existing storage: if an existing slurry tank can serve as the digestate store, a major structure is no longer needed.
• Grid connection: the further away the connection point, the more expensive cabling and trenching become.
• Ground conditions and water law: a high water table or a protection zone calls for more elaborate tanks and leak monitoring.
• Plant size and flexibility: more installed capacity than necessary raises CHP and gas holder costs and can make direct marketing mandatory.
• Heat use: a local heating network to the farmhouse, barns or neighbours costs extra but often improves the business case.
• Own labour: doing earthworks or foundations yourself reduces costs but raises questions of liability and coordination.
• Construction type: steel or concrete tanks, membrane covers or fixed roofs and prefabricated container modules each come with their own costs, build times and maintenance needs. Ask suppliers to explain the differences in their quotes.

Capital cost per kilowatt hour: a worked example

To put quotes into perspective, it helps to look at the capital cost per kilowatt hour generated. A simplified example with assumed figures:

1. Investment of 800,000 euros, financed over 20 years at 4 per cent interest.
2. The annual annuity for interest and repayment is then roughly 59,000 euros.
3. With 657,000 kWh of electricity a year, i.e. 75 kW rated output, that comes to about 9 ct per kilowatt hour.

From a payment of around 21 ct/kWh, roughly 12 ct/kWh is therefore left in this example for maintenance, reserves, insurance, labour and profit. If the plant performs worse than planned, the capital cost per kilowatt hour rises immediately, because the annuity is fixed. It is therefore wise to be cautious about slurry volumes when sizing the plant.

Cutting costs without saving in the wrong places

The main savings come from the starting position: reusing existing tanks, choosing a site close to the barn and the grid connection, and sizing output to the slurry actually available. Saving on safety equipment, controls, leak monitoring or maintenance is risky by contrast. Such savings often backfire through downtime, additional permit conditions or higher insurance premiums. Also check the warranty and service terms in each quote, since a low price with long response times after a breakdown can end up costing more than a higher price with good service.

Putting costs into context

The investment figure alone says little. What matters is whether revenue from EEG payments, heat use and avoided costs covers capital costs and operation over 20 years. On paper, a small manure plant with 75 kW rated output earns electricity revenue in the order of 140,000 euros a year, as shown in the guide to the EEG feed-in tariff. Depreciation, interest and all operating costs have to be paid from that.

You can test your own figures in the biogas calculator. For a sound comparison, obtain at least two or three quotes covering the same scope. Suitable firms are listed in the biogas plant construction directory, and the guide to choosing a biogas contractor offers tips on selection.