In the wastewater treatment plant the sludge produced is mixed with organic waste, a co-digestion process is produced that generates biogas and recovered waste.
Sewage treatment plants are high demanded energy installations. On the other hand, waste with a high contend in organic matter is a common waste in food industry in Andalusia. Moreover Andalusian soils have a very low content in organic matter.
This good practice is an example of industrial symbiosis between Sewage treatment plants, local industries, waste managers and farmers.
Through the process of anaerobic co-digestion of sludge with some organic waste or by-products, the following benefits are achieved:
• Energy self-sufficiency of wastewater treatment plants.
• Recovery of waste with a high organic matter content
• Obtain compost for agricultural soil improvement
The treatment of wastewater in sewage treatment plants produces a large quantity of by-products known as sludge, which must be properly managed and which represent a high percentage of the operating cost associated with sewage treatment plants.

The process can be resumed in this way:
• Sludge from water-treatment plants +  organic wastes = Biogas +  digested sludge
The Biogas feeds combustion engines and generate energy

• Digested sludge + Biomass = Compost for agricultural soil improvement
Main Beneficiaries:
• Professionals from the sector involved in the management and exploitation of wastewater treatment processes.
• Food industries in the area
• Sludge managers from wastewater treatment
• Farmers

Resources needed

55.000 euros for facilities
1 skilled person

Evidence of success

In 2017 more than 78.000 Tn of wet matter (4.775 Tn of dry matter) were treated and 11.052 kWh were produced.

Difficulties encountered

To find by-product and non hazardous waste to be digested. To design a control system which could assure the right management. It has been difficult to change the way of thinking, the transition between to be producer and to be a waste management.

Potential for learning or transfer

Biogas production helps to decrease the greenhouse gas emissions. The company has estimated a savings of CO2 emissions of 16,962 tons, plus verified reductions in CH4 and N2O emissions. In addition, there are other advantages such as the production of a waste of great value for composting and others such as reduction of odours.
The company makes a transfer by conducting training courses about co-digestion, also participation in conferences giving dissemination to their experience.

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Main institution
Andalucía, Spain (España)
Start Date
December 2015
End Date


RAUL EMILIO VEGA Please login to contact the author.