Energy from biomass: sustainable production of biogas and organic fertilizers

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Pan grinder mill for mechanical pre-treatment of agricultural by-products for more efficient biogas production

Biogas is an efficient, environmentally friendly form of renewable energy. However, the cultivation of energy corn, which is used as the main raw material, is controversial. Why not use the leftovers? Organic waste, such as solid manure, straw, and green waste, is a smart alternative for generating sustainable power. With the right processing, more biogas and high-quality fertilizer can be obtained. AMANDUS KAHL plants efficiently crush biomass, increase methane yield, and ensure that fermentation residues are used in secondary applications. It is a closed cycle that benefits both the environment and the economy.

Bioenergy from biomass: efficiency through mechanical pre-crushing

While the cultivation of energy corn takes up valuable farmland and promotes monocultures, alternative raw materials such as harvest residues, green waste, or litter offer great potential for the production of bioenergy. However, to achieve an optimum gas yield, the substrate must be efficiently conditioned through mechanical pre-crushing. The AMANDUS KAHL pan grinder mill is ideal for defibrating biomass, playing an important role in sustainable energy production. It increases the surface area and removes enclosed air. This facilitates access to organic matter for bacteria in biogas plants, reduces foam and floating layer formation in fermenters, and accelerates the microbial degradation of biomass.

Fermentation substrate pellets, which are produced from fermentation residues after biogas production and used as fertilizer.

From straw to electricity: how it works

The pan grinder mill uses a special flat die onto which the substrate falls by gravity. The biomass is defibrated and compacted intensely as the rollers of the pan grinder mill roll over it. A key advantage of the AMANDUS KAHL pan grinder mill is its flexibility in terms of input moisture content, which can range from 15 to 70 percent. The ideal moisture content for optimal processing is between 40 and 50 percent. Dry biomass, such as oat husks, can be added to very moist straw to regulate the moisture content without expending additional energy. After pre-crushing, the conditioned product is mixed with liquid manure in an agitator bin, then pumped into the fermenter of the biogas plant.

According to a study by Aarhus University, defibrated straw can increase the relative gas production of a biogas plant by up to 30 percent. Using this method, the same gas yield that takes 30 days to obtain with untreated straw can be achieved in 17 days. Crushing grass for fermentation can also significantly increase the efficiency of renewable energy production.

A key technology for renewable energies: ten reasons for the pan grinder mill

Small, smaller, smallest: there are many methods for crushing biomass. From hammer mills and cutting mills to shredders, biogas operators have a wide range of equipment at their disposal. What sets the pan grinder mill apart from other processes? AMANDUS KAHL offers twelve different models of the pan grinder mill to ensure suitable throughput capacities for smaller and larger biogas plants. They feature ten unique advantages that make them an efficient and economical choice.

High robustness and a long service life with minimal wear

Low consumption of consumables and low lubricant requirements; thus, there is no lubricant contamination of the product

A large grinding chamber for voluminous biomass products

Uniform processing thanks to product feeding by gravity

Adjustable pressure via a hydraulic system for optimum adaptation to different materials

Compact design for low space requirements

Low-noise operation and low operating costs

Low maintenance, with optional remote diagnostics for fast troubleshooting

High flexibility in processing different raw materials

10.

Optimal defibration for more efficient fermentation

In addition to its many technical advantages, the pan grinder mill increases the efficiency of biogas plants thanks to its low energy consumption, making a valuable contribution to the energy transition. Depending on the model, throughput ranges from a few hundred kilograms to 40 tons per hour. Throughput capacities of five tons or more are relevant for use with biogas plants. This makes the pan grinder mill ideal for sustainably recycling organic waste.

Making clever use of fermentation residues: how by-products become fertilizer for agriculture

Not all waste is the same. After biogas production, fermentation residues remain that can be processed into high-quality organic fertilizer. Rather than transporting them directly to the field, the residues are mechanically drained, dried, and pelleted. The advantages of this conditioning step are obvious.

Higher bulk density of fermentation residues for more efficient transport
Less odor nuisance during fertilizer application
Largely dust-free
Easy dosing thanks to uniform pellet size
Homogeneous nutrient composition without segregation
Specific addition of minerals such as phosphorus, potassium, or nitrogen possible

Using organic fertilizer from fermentation residues reduces the need for artificial fertilizers and improves soil quality. Additionally, it promotes soil life, improves water storage capacity, and reduces nutrient leaching.

Pelleted organic fermentation residues can be used far away from the field as well. In addition to being used as fertilizer, they can be used for alternative energy production technologies, such as pyrolysis.

Pan grinder mill and pellet mill – the winning team for a closed value chain

Integrating pellet mills into the biogas process enables the secondary use of fermentation residues and promotes a circular economy.

The pellets are used as high-quality organic fertilizer in agriculture, promoting crop growth.
After harvesting, the moist straw - a by-product of grain harvesting - is efficiently defibrated in the pan grinder mill, either directly or after prior use as litter, for example.
This defibrated material is then used in biogas plants as a fermentation substrate to produce bioenergy.
After fermentation, residues are produced and mechanically dewatered, then dried.
The dried residues are then pelleted into a form suitable for storage and transport.
The cycle is complete when the pellets are spread on the grain field and new straw is produced, beginning the process again.

This creates a closed value chain that promotes power generation, sustainable agriculture, and the meaningful integration of renewable energies. Biogas plant operators benefit from increased efficiency and the additional economic utilization of their fermentation residues.

Biogas Cycle

Pan Grinder Mill 60-1500 — 2. Efficient crushingFeeding of wet straw into the pan grinder mills

Biogas plant — 3. Feeding of crushed straw into biogas plantsProduction of fermentation substrate

Fabric Belt Drier — 4. Mechanical dewateringSolid-liquid separation of the fermentation residues

Pellet Mill 33-600 — 5. Pelleting of the fermentation substrateIn a gentle and energy efficient way

6. Pellets from fermentation substrateFor use as fertiliser in agriculture

Download biogas cycle as pdf

Efficiency meets sustainability — the key to sustainable agriculture!

The efficient use of biomass and fermentation residues is important for sustainable agriculture and the energy transition. Mechanical pre-crushing and pelleting technologies optimize methane yield and enable a sensible circular economy. AMANDUS KAHL offers customized solutions for these processes and helps farmers and operators of biogas plants utilize renewable raw materials profitably.