FERMENTATION BIOLOGY ENZYMES SILAGE INOCULANTS PRESERVATION GLOSSARY

Energy preservation in moist substrates

Bulk and viscous biogas substrates with a high water content, such as moist cereal or CCM are ↓ exposed to a high risk of rotting and energy loss during storage.

↓ Various preservation methods have been developed to improve the storability of these substrates.
↓ Tests with cereal and maize have shown that treatment with acids is highly effective as it ensures that the energy remains contained in the substrate for use in the biogas production process.

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Preservation methods

Study of treatment of moist cereal with acid

Microbes cause energy loss during storage

Freshly harvested cereal grains are covered in bacteria, yeast and mould. As long as the plant is alive, these microorganisms cannot do any damage as they are kept at bay by the cell walls.

Problems only occur after the crop is harvested and stored under aerobic conditions, at a grain moisture content of minimum 14 % and a temperature of more than 15°C. Under these conditions, the microorganisms convert the available energy from the grain in an explosion-like process into carbon dioxide, water and heat.

This decomposition leads to increased moisture content in the substrate while the temperature in the cereal rises. This of course only accelerates the decomposition process.

Cereal storage studies

Studies carried out in grain stores show that cereals stored at an initial temperature of 18°C and an initial moisture content of 23% become unfit for consumption after only one week of storage!

Temperature curve

Temperature increases to 45°C are the result of energy loss during grain storage

Practical study: Comparison of the advantages of different preservation methods

There are a number of different methods aimed at stabilising and preserving moist cereal or maize during storage:

Drying of cereal material to a moisture content of less than 14 %.	→ Most reliable protection against loss; high costs
Cooling by means of cooling units or cold air blowers to a temperature below 10°C.	→ High capital investment required; often too expensive for biogas cereal
Gastight storage under CO₂ cover in vertical or horizontal silos.	→ High capital investment required; often too expensive for biogas cereal
Ensiling with addition of water (requires careful adjustment of the optimum dry substance content, depending on the substrate properties)	→ High capital investment required; the liquid storage method is popular despite the high captial costs, as the cereal prepared in this way can be easily processed.
Ensiling under anaerobic conditions	→ Allows for cost-effective and safe preservation of moist forage cereals and maize, provided that the silo remains sealed; after the silo is opened, the conditions can be maintained by using biological ensiling agents.
Chemical preservation with organic acids, urea or caustic soda	→ Allows for the safe and cost-effective storage and preservation of moist forage cereals and maize without the need for any further treatment.

Comparison of preservation methods - PDF file

Cereal preservation test

Dr. Steinhöfel carried out a series of temperature measurements test silos in Köllitsch.

The study shows that only cereals treated with propionic acid and cereals in silage can be stored without major energy loss. After the silo is opened, silage from cereal remains only stable if biological ensiling agents are added.

Temperature curves of various moist wheat storage methods.

Study of cereal preservation methods - PDF file

Grain maize preservation study

A similar test was carried out with grain maize.

The results show that the loss of dry substrate can best be prevented by adding preserving acids. Chemical preservation results in lower dry substance loss than ensiling with our without ensiling agent.

Grain maize silage in foil hose, with added preservative or stored under aerobic conditions

Grain maize preservation

Preservation with acids - a widely used method

For more than 20 years, the SCHAUMANN Group has been using cereial perservation as a cost-effective yet reliable method in its plants. Our systems for the storage of substrates for biogas production is based on our extensive experience in this field, which is also behind our new BC.ACID product range.

Practice shows that preservation with acids is a well-established method for the storage of cereal and CCMs: Thanks to its low-technology approach and high effectiveness, it offers great security during storage. For these reasons, perseveration with acids has become the standard method for cereal and grain maize storage in many large-scale processing plants.