BioGasPlants Consulting
Consulting and Planning

Substrate Management

 

Biogas plants use renewable raw materials (Nawaro) as well as livestock maintenance residue and biogenic waste as substrate.

The Renewable Energy Sources Act provides a fixed feed-in tariff (EEC-compensation), plus Nawaro bonus for biogas plants which ferment renewable resources for their electricity input. This makes the cultivation of energy crops to be used as substrate especially appealing. Maize, whole plant silage, sugar beets, and grass silage are among the most commonly used substrates. Some energy crops (e.g. sunflowers) are used occasionally or regionally. Currently, the suitability of numerous plants for use as substrate is being explored.

Renewable Resources:

Maize - 202 m³/t FM - 52% Methane Content
Maize is the most important renewable resource in biogas production. The reasons are: high yields per hectare which will be improved further through the cultivation of so-called energy maize; efficient harvesting with field choppers; and its good shelf-life as maize silage. Additionally, it can be easily transported to the biogas plant. Its high starch content makes it easily degradable. It contains no long fibers which could disrupt the plant’s machinery. As maize silage, it is used year-round.

Whole Plant Silage - 163 m³/t FM - 52% Methane Content
Whole plant silage (WPS) is an increasingly important substrate, primarily made from rye and triticale. The drymass yield per hectare is about 20% lower than that of maize. Cultivating a following crop, such as millet, can increase the annual yield per hectare significantly. Harvesting winter rye early – as forage rye – facilitates a subsequent cultivation of maize.

Sugar Beets - 111 m³/t FM - 65% Methane Content
Sugar beets can produce high yields per hectare. Additionally, they degrade well in biogas plants. Earth clinging to the beet creates problems, as it can disrupt the biogas plant’s operation. Sugar beets can only be stored until Spring, as they cannot be preserved by silaging.

Gras Silage - 172 m³/t FM - 54% Methane Content
Often, biogas plants use a small percentage of grass silage. It contains long fibers that require a suitable mixing process. In addition to grass from agricultural areas, greenery cuts from landscape conservation are available. The use of clover-grass silage can be especially attractive for organic farms which do not maintain livestock, since the green manuring is used profitably and the digestate yields a durable fertilizer.

Biological Waste - 100 m³/t FM - 61% Methane Content
Biological waste is organic waste of animal or plant origin, which accumulates in a household or business and can be decomposed by microorganisms, ground dwelling organisms, or enzymes. Among these are food scraps and lawn cuttings, for example. Generally, biological waste is gathered in so-called bio-waste bins; it is specially treated through composting and fermentation. The resulting compost and digestate is often returned to the environment, for example in gardening and farming.