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Co-digestion WWTP sludge with other wastes
Published on 16 May 2020
Spain
This is the good practice's implementation level. It can be national, regional or local.
About this good practice
The mixture of sludge from WWTP process, with other wastes is a good way to get the increase of biogas production and, therefore, a higher production of electricity that will reduce the energy consumption of the plant and make the treatment process more sustainable.Another advantage could be the mixture of sludge and waste could get a final product with better properties for the digestate as fertilizer.
Anaerobic digestion is a part of the treatment process where microorganisms break down the volatile matter of the sludge in the absence of oxygen and biogas is generated. This biogas is burned in an engine to produce electricity for the needs of the plant and with the produced heat in the exhaust gases we can maintain the digester temperature in mesophilic conditions. If the sludge is mixed with other products (usually wastes) with a high carbons matter, we can increase dramatically the produced biogas. If usually we can get between 40 and 50 % of the plant energy from the combustion of digestion, biogas, if we mix the sludge with other products, the energy consumed will be much higher. Of course we need that disaster has capacity excess. In Molina de Segura WWTP we have been mixing sludge with molasses from factory candies, with a high load of sugar, and the production of biogas increased significantly. The sludge will be increased obviously, but, if the management price of sludge is not very high, the process will be very profitable.
Anaerobic digestion is a part of the treatment process where microorganisms break down the volatile matter of the sludge in the absence of oxygen and biogas is generated. This biogas is burned in an engine to produce electricity for the needs of the plant and with the produced heat in the exhaust gases we can maintain the digester temperature in mesophilic conditions. If the sludge is mixed with other products (usually wastes) with a high carbons matter, we can increase dramatically the produced biogas. If usually we can get between 40 and 50 % of the plant energy from the combustion of digestion, biogas, if we mix the sludge with other products, the energy consumed will be much higher. Of course we need that disaster has capacity excess. In Molina de Segura WWTP we have been mixing sludge with molasses from factory candies, with a high load of sugar, and the production of biogas increased significantly. The sludge will be increased obviously, but, if the management price of sludge is not very high, the process will be very profitable.
Expert opinion
Treatment plants that enable the transformation of organic matter such as sewer sludge, food waste and livestock manure through anaerobic digestion offer an optimal solution for waste management in line with the principles of the circular economy. The by-products of this process are biogas and digestate. The first can be used for electricity production, as in the case at hand, or transformed into biomethane to replace fossil gas, which is not good for the climate, for consumption by households or the transport sector. The second can be used as quality compost in agriculture in a way that gives back carbon to the soil and contributes to reducing the use of chemical fertilisers. Other European regions may learn from this transferable good practice.
Resources needed
The resources we need are capacity excess in the WWTP digester and possibility to get wastes with a high organic matter load near the plant.
If the feasibility study is led by a Public Adm, can serve as a general conclusion document for implementing the technology assessing some possible scenarios.
If the feasibility study is led by a Public Adm, can serve as a general conclusion document for implementing the technology assessing some possible scenarios.
Evidence of success
It is a tool to improve the electrical production capacity, due to biogas that has the advantages of sharing treatment facilities, unifying management processses, reducing investment and operating costs, and buffering temporary variations in the management, composition of each waste.
With co-substrates such as molasses, ice cream cream and by-products of the food industry from the manufacture of gazpacho or juices increases the biogas production (23 -26 %), compared to without co-digestion.
With co-substrates such as molasses, ice cream cream and by-products of the food industry from the manufacture of gazpacho or juices increases the biogas production (23 -26 %), compared to without co-digestion.
Potential for learning or transfer
This practice will be very interesting for any region in which there are suitable wastes, the sludge management is not very high and it´s interesting to reduce the cost of wastewater treatment, with excess capacity of digesters.
Further information
Website
Good practice owner
You can contact the good practice owner below for more detailed information.
Organisation
ESAMUR
Spain
Región de Murcia
Contact
AGRICULTURAL ENGINEER