Ahidra 48


Manure digestion Biogas treatment Digestate treatment Nutrient recovery

Navia, Spain
Processing capacity: 420,000 tons per year
Manure volume: 365,000 tons per year
Co-product volume: 55,000 tons per year
Digestion volume: 26,000 m3
Biogas production: 2,000 m3 per hour
Energy production: 4.5 MW(e)
Fertilizer production (dry): 23,000 tons per year.
Struvite production: 400 tons per year
Surface water discharge: 1,200 m3 per day

Due to its large number of livestock farms, the North of Spain faces a major problem; The region produces so much manure that farm storage tanks are overflowing. The uncontrolled use of manure not only has a detrimental effect on farmers, but also negatively impacts other sectors;

The following Colsen group technologies contributed to this technically and economically viable manure processing system:

Thermophilic manure digestion with DIGESTMIX®
Biogas treatment (BIDOX®) and biogas conditioning
Nitrogen removal and organic matter removal with MBR-NAS®
Phosphate removal (ANPHOS®)

The manure digestate digestion and treatment system was built in Navia, a Spanish municipality in the province of Asturias. The facility is located next to an existing paper factory on a plot of approx. 3 hectares (30,000 m2), where it helps solve one of the biggest threats facing our climate today. Thanks to an intelligent combination of technology and knowledge, complex waste streams are converted into energy, nutrients (in the form of biofertilizers) and clean effluents, fully harmonized with the highest environmental standards.

To achieve the desired result, two key components of the process were combined: thermophilic digestion and digestate treatment.
The system is fed with various incoming products, which generally consist mainly of cow manure enriched with a wide range of co-substrates. Manure is delivered daily and stored in the designated storage tank. The co-products, consisting mainly of primary and secondary sludge from the dairy industry, community water treatment plant and slaughterhouse waste, are stored briefly and introduced into the feed system, where the different products are mixed and introduced in 4 thermophilic digesters.
To create an ideal environment for thermophilic digestion, it is vitally important to maintain a good mixture and a stable temperature. To create this mixture and maintain the temperature at 52°C, the 4 manure digesters are equipped with 3 DIGESTMIX® systems. The biogas produced by this system contains several components, including H2S, but before the biogas can be used as fuel as a CHP system, its H2S concentration must be reduced. To do this, Colsen uses its own biogas treatment system (BIDOX®), based on a biological desulfurization technique that sustainably reduces H2S levels. After this step, the biogas can be used in the CHP system.

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