About Axpo Biomasse

We make the most of bio-waste and use it to generate renewable energy and natural resources for the future. Biowaste contains CO2-neutral, renewable energy. Fermentation in one of our fermentation plants produces methane-containing biogas and digestate from the biowaste. We use the biogas for electricity and heat production or feed it into gas grids. The digestate can be used as fertilizer and is thus returned to agriculture. At our composting sites, we produce top-quality compost products from biogenic waste with lower energy content but a high proportion of wood. The mobile services in the field of green waste processing and post-processing round off the diverse and comprehensive portfolio.

The completed ecological cycle

We have been active in the sustainable recycling of biowaste for over 20 years and have experience and know-how in all areas from waste separation to green waste collection, processing, energy production and fertiliser. We complete ecological cycles by recycling valuable materials and create energy and resources for future generations.


During fermentation, biogenic waste is processed into biogas, electricity, heat and fertiliser. Axpo uses the Kompogas process for this purpose. This is based on constant dry fermentation of biowaste under the exclusion of oxygen. This process produces CO2-neutral methane, which is converted into green electricity and heat in cogeneration plants or processed into biogas of natural gas quality. Thanks to proven technology, Kompogas plants make maximum use of the energy potential of biowaste: Depending on the type of biowaste, up to 1000 kilowatt hours of energy can be generated from one tonne. Around 900 kilograms of natural fertiliser in solid and liquid form remain as a by-product.

Private customers can purchase the natural fertilizer from our plants. Bring your own containers and fill up the natural fertiliser yourself.

Delivery and preparation

The first step in the operation of a Kompogas plant is receiving the collected biowaste. It is unloaded in the deep bunker and transported to the shredder by an electronically controlled crane. The waste is shredded  to a maximum grain size of 60 mm. After sifting, the shredded material is fed into the fermenter via the conveyor belt and auger.

The plug-flow fermenter is the heart of the plant. Uniform conditions must prevail here to ensure a successful  fermentation process:

  • gentle and continuous mixing of the biomass with the microorganisms by a robust agitator
  • continuous, fully automatic feeding into the fermenter around the clock
  • the fermentation process in the fermenter based on anaerobic-thermophilic dry fermentation at a constant temperature of approx. 55°C, optimal for the growth of microorganisms

The biomass remains in the fermenter for about 14 days. Combined with a temperature of 55°C, the material is reliably hygienised (sterilised) and weed seeds are destroyed.


Biogenic waste with a high wood content and low energy content is recycled with the addition of oxygen. The process, which takes several months, produces high quality compost products for a wide variety of uses in horticulture and agriculture. The soil receives valuable nutrients and the ecological cycle is completed.

Delivery and processing

In a first step, the biogenic material is unloaded and sorted on the sites. Foreign matter is then sorted out. In a second step, the green waste is separated and shredded so that the shredded material can be spread out in long rows, known windrows. 

Management and processing

Structural material and old compost are added to the windrows. They are regularly turn so that oxygen and water can get into the material, which is essential for the decomposing process. Depending on the desired end product, this process is carried out for various lengths of time. Fresh compost takes about six months. Well-matured compost takes about ten months. In a final step, the compost is sifted to the desired grain size and, depending on the use, additives are mixed in. The addition of humus or low lime sand produces substrates for a wide variety of uses. 

Composting at a glance

Mobile services

As a specialist in biomass treatment, our subsidiary Berom SAS offers various services for professional processing of green waste on site as well as in compost site management. Our services are designed for communities, composting sites, sawmills, industrial cogeneration plants, wood-fired power plants and earthworks.

Mobile services at a glance

Garden products

Private customers can dispose of biogenic waste at our sites and purchase high-quality compost, fertiliser and wood products.

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Contact us

We would be pleased to advise you on our products and services.