Biogas digestate drying with ExergyPSSD®
Biogas production converts organic waste into renewable energy, but it also generates a nutrient‑rich by‑product: biogas digestate. When handled correctly, this digestate can become a high‑value, sustainable fertilizer instead of a waste problem.
Biogas production turns organic waste into renewable energy and produces digestate — a nutrient‑rich byproduct that can become a valuable, sustainable fertilizer.
What is biogas digestate?
Biogas is a renewable fuel produced mainly from biomass residues and organic waste such as food waste, energy crops, and residues from wastewater treatment, agriculture, or forestry. In an anaerobic digestion process lasting about three weeks, bacteria break down the organic matter in an oxygen‑free reactor, producing biogas and a nutrient‑rich digestate.
The digestate retains most nutrients from the original feedstock, especially phosphorus, nitrogen, and potassium, making it a valuable fertilizer when properly treated and handled.
Why dry biogas digestate from biogas plants?
Raw digestate has very high moisture content, causing practical and environmental challenges such as difficult handling, odor emissions, microbial growth, and costly transport of excess water.
Drying biogas digestate helps to solve these issues by stabilizing the material, improving hygiene, and making it easier to store, transport, and apply as fertilizer or other value‑added products.
Thanks to the short and well‑controlled residence time at high temperature, Exergy’s superheated steam drying process completely sterilizes the digestate and efficiently destroys pathogens, while still preserving the valuable nutrients.
Compared with hot air or gas drying, the steam environment reduces oxidation and helps maintain the fertilizing properties of the digestate. The result is a stable, free‑flowing product that:
- Emits significantly fewer greenhouse gases than moist digestate.
- Is easier and safer to store and handle.
- Can be applied more precisely as a fertilizer or soil improver.
Once dried, biogas digestate becomes easier to transport over long distances at a lower cost per nutrient unit. It can be pelletized or granulated and distributed as:
- Organic fertilizer for agricultural crops.
- Soil improver for horticulture or landscaping.
- A nutrient carrier in other value‑added products.
Because the dried digestate is stable and hygienic, it enables new business models around nutrient recycling, circular agriculture and regional fertilizer supply.
Drying biogas digestate is not straightforward. The material’s high moisture content, fiber structure and nutrient composition can make traditional drying technologies inefficient or even harmful to product quality. Traditional hot air or gas systems often lead to:
- Uneven drying and dust formation
- Oxidation and loss of valuable nutrients
- Undesired emissions to the atmosphere
- Higher specific energy use and operating costs
Since drying is one of the most energy‑intensive steps in digestate processing, choosing the right dryer technology is crucial for energy efficiency, environmental performance and final fertilizer quality, making advanced solutions such as pressurized superheated steam drying increasingly attractive for modern biogas plants.
In the ExergyPSSD® system, superheated steam circulates in a closed, pressurized loop where excess steam is recovered and reused to supply energy or heat elsewhere in the plant. This minimizes external energy demand and helps biogas plants increase self‑sufficiency and cut emissions.
ExergyPSSD® can be integrated into new or existing biogas facilities as part of a complete energy and waste management solution, where recovered heat can be used for:
- Pre‑heating of digesters.
- District heating supply.
- Other on‑site thermal processes.
This makes digestate drying a key driver of efficiency and sustainability.
Thanks to the short and well‑controlled residence time at high temperature, Exergy’s superheated steam drying process completely sterilizes the digestate and efficiently destroys pathogens, while still preserving the valuable nutrients.
Compared with hot air or gas drying, the steam environment reduces oxidation and helps maintain the fertilizing properties of the digestate. The result is a stable, free‑flowing product that:
- Emits significantly fewer greenhouse gases than moist digestate.
- Is easier and safer to store and handle.
- Can be applied more precisely as a fertilizer or soil improver.
Once dried, biogas digestate becomes easier to transport over long distances at a lower cost per nutrient unit. It can be pelletized or granulated and distributed as:
- Organic fertilizer for agricultural crops.
- Soil improver for horticulture or landscaping.
- A nutrient carrier in other value‑added products.
Because the dried digestate is stable and hygienic, it enables new business models around nutrient recycling, circular agriculture and regional fertilizer supply.
Drying biogas digestate is not straightforward. The material’s high moisture content, fiber structure and nutrient composition can make traditional drying technologies inefficient or even harmful to product quality. Traditional hot air or gas systems often lead to:
- Uneven drying and dust formation
- Oxidation and loss of valuable nutrients
- Undesired emissions to the atmosphere
- Higher specific energy use and operating costs
Since drying is one of the most energy‑intensive steps in digestate processing, choosing the right dryer technology is crucial for energy efficiency, environmental performance and final fertilizer quality, making advanced solutions such as pressurized superheated steam drying increasingly attractive for modern biogas plants.
In the ExergyPSSD® system, superheated steam circulates in a closed, pressurized loop where excess steam is recovered and reused to supply energy or heat elsewhere in the plant. This minimizes external energy demand and helps biogas plants increase self‑sufficiency and cut emissions.
ExergyPSSD® can be integrated into new or existing biogas facilities as part of a complete energy and waste management solution, where recovered heat can be used for:
- Pre‑heating of digesters.
- District heating supply.
- Other on‑site thermal processes.
This makes digestate drying a key driver of efficiency and sustainability.