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Plant facility
(example of  500 Sm3/h)

DSA ASAC Anaerobic Digester High-performance anaerobic digester

After hydrolysis, the sludge is sent to a mesophilic anaerobic digestion stage. Compared to a traditional system, the sludge is much easier to be digested because, on the one hand, ASAC hydrolysis has solubilized the COD making it readily available to methanigenic bacteria, and on the other hand, it has also eliminated all the ammonia, a toxic and inhibiting substance for anaerobic bacteria. Finally, the process of anaerobic digestion under these conditions takes place in less time and with a greater efficiency, having as output a digestate with very low COD, BOD and nitrogen values and suitable for direct discharge into the sewer system, after separation of the dry matter by thickening and/or centrifugation or filter pressing. The time required for the entire anaerobic digestion process for the highest possible biogas recovery, can be reduced increase significantly, in case of difficult biomasses such as poultry manure and FORSU. In addition, the methanogenic residue is minimized and in fact more gas is produced than with traditional technologies.

Biomass

Any type of organic matrix even difficult-to-process biomasses such as: poultry manure, FORSU, sewage sludge, industrial sludge, waste with high ammonia conten.

Curva

Recirculation system for minimising water requirements.

Skid cogenerator/Biogas boiler self-consumption

By using this technology, anaerobic digestion volumes are extremely small compared to those required by other technologies, which means, in addition less clutter, lower thermal and electrical consumptions for pumping and mixing. In addition, no downstream energy-intensive treatments such as composting and nitro-denitrogen are required. Throughout the process, the biogas remains at atmospheric pressure, avoiding compression energy costs as needed in membrane or PSA systems. Self-consumption is easily covered by a small cogenerator possibly flanked by a small biogas boiler.

Organic matrices pretreatment basin

At this stage, organic matrices are dosed and prepared by fine grinding, preheating with heat recovered from the process, and mixing them to obtain a pumpable sludge to be sent to the next stages.

Digestate discharge to sewer

ASAC’s patented technology allows for severe nitrogen stripping and complete degradation of organics during anaerobic fermentation. As a result, the liquid digestate output is suitable to be disposed in the sewer system (D. Lgs 152/06) by simple separation of solids and further eventual passage to a small oxygenation tank. It does not require nitro-denitrogen treatment section. It does not require spreading of digestate (digestate can be discharged to sewer).

Biomethane

ASAC’s patented technology makes it possible to obtain high-purity biomethane suitable for feeding into the grid in compliance with current regulations.

Skid ISU ASAC Hydrolysis Ammonia stripping Biomethane Upgrading

In this section, the sludge is treated through an innovative hydrolysis process developed and patented by ASAC where the organics solubilize and are made into a more digestible form. In addition, the nitrogen compounds are converted to gaseous ammonia which is then recovered as ammonium sulfate through a sulfuric acid scrubber. What performed at this stage is not a simple hydrolysis as is usually done in normal pretreatment plants, but it is an hydrolysis especially optimized to strip ammonia and to solubilize organic components, in a very high efficient way. At this stage an initial upgrading step takes place where a portion of the CO2 in the biogas is absorbed and converted to calcium bicarbonate. At this stage the process also allows for the complete purification of H2S and other undesired components in the biogas. The ASAC process last step is the final upgrading and purification of the biogas into biomethane, which occurs through a second step of CO2 convertion into calcium bicarbonate.

1
After hydrolysis, the sludge is sent to a mesophilic anaerobic digestion stage. Compared to a traditional system, the sludge is much easier to be digested because, on the one hand, ASAC hydrolysis has solubilized the COD making it readily available to methanigenic bacteria, and on the other hand, it has also eliminated all the ammonia, a toxic and inhibiting substance for anaerobic bacteria. Finally, the process of anaerobic digestion under these conditions takes place in less time and with a greater efficiency, having as output a digestate with very low COD, BOD and nitrogen values and suitable for direct discharge into the sewer system, after separation of the dry matter by thickening and/or centrifugation or filter pressing. The time required for the entire anaerobic digestion process for the highest possible biogas recovery, can be reduced increase significantly, in case of difficult biomasses such as poultry manure and FORSU. In addition, the methanogenic residue is minimized and in fact more gas is produced than with traditional technologies.
2
Any type of organic matrix even difficult-to-process biomasses such as: poultry manure, FORSU, sewage sludge, industrial sludge, waste with high ammonia conten.
3
Recirculation system for minimising water requirements.
4
By using this technology, anaerobic digestion volumes are extremely small compared to those required by other technologies, which means, in addition less clutter, lower thermal and electrical consumptions for pumping and mixing. In addition, no downstream energy-intensive treatments such as composting and nitro-denitrogen are required. Throughout the process, the biogas remains at atmospheric pressure, avoiding compression energy costs as needed in membrane or PSA systems. Self-consumption is easily covered by a small cogenerator possibly flanked by a small biogas boiler.
5
At this stage, organic matrices are dosed and prepared by fine grinding, preheating with heat recovered from the process, and mixing them to obtain a pumpable sludge to be sent to the next stages.
6
ASAC’s patented technology allows for severe nitrogen stripping and complete degradation of organics during anaerobic fermentation. As a result, the liquid digestate output is suitable to be disposed in the sewer system (D. Lgs 152/06) by simple separation of solids and further eventual passage to a small oxygenation tank. It does not require nitro-denitrogen treatment section. It does not require spreading of digestate (digestate can be discharged to sewer).
7
ASAC’s patented technology makes it possible to obtain high-purity biomethane suitable for feeding into the grid in compliance with current regulations.
8
In this section, the sludge is treated through an innovative hydrolysis process developed and patented by ASAC where the organics solubilize and are made into a more digestible form. In addition, the nitrogen compounds are converted to gaseous ammonia which is then recovered as ammonium sulfate through a sulfuric acid scrubber. What performed at this stage is not a simple hydrolysis as is usually done in normal pretreatment plants, but it is an hydrolysis especially optimized to strip ammonia and to solubilize organic components, in a very high efficient way. At this stage an initial upgrading step takes place where a portion of the CO2 in the biogas is absorbed and converted to calcium bicarbonate. At this stage the process also allows for the complete purification of H2S and other undesired components in the biogas. The ASAC process last step is the final upgrading and purification of the biogas into biomethane, which occurs through a second step of CO2 convertion into calcium bicarbonate.

ASAC Green Gas thanks to decades of experience and the high skills of its staff is able to provide complete turnkey plants for biomethane production from any organic matrix with very high efficiency and complete CO2 trapping/seizing.

Thanks to ASAC’s patented technology, it is possible to build facilities from 25 to more than 1,000 Sm3/h of biomethane fueled even 100% with difficult biomasses such as poultry manure, FORSU or civil and industrial sludge.

If the customer wants to build on its own the delivery systems, the anaerobic digestion and external components, only the supply of the patented ASAC hydrolysis system with upgrading and CO2 sequestration is possible.

A new grass roots facility built with ASAC’s patented technology has many advantages (see page 6), one of the most important being the ability to build a facility with much reduced anaerobic fermentation volumes compared to those required by traditional technologies. The special ASAC patented hydrolysis stage in fact produces a biomass that is much easier for the anaerobic bacteria to digest, guaranteeing much lower retention times within the anaerobic digesters and the complete stripping of ammonia nitrogen. It is able to feed the plant even with 100 percent biomass, that is generally very difficult because it is rich in nitrogen, such as poultry manure, FORSU or civil or industrial sludge with extremely small digestion volumes.

The digestate then has a very low nitrogen concentrations and does not require further composting steps or nitro-denitro treatments.

All above results in a much simpler and smaller facility with very little aesthetic impact, an issue that is particularly sensitive and felt by the stakeholders, which are often against the construction of biomethane plant precisely due to landscape and environmental issues.

The need for transportation, another issue particularly felt by the stakeholders, is also minimized because with ASAC technology there is no need to spread the liquid digestate, which is instead released directly into the sewer system.

To give a term of comparison, the sizing of a 500 Sm3/h plant fed 100% poultry manure is shown where much smaller installation areas can be observed when compared to traditional technologies (membranes, PSA, ecc…)

Finally, it is emphasized that the patented ASAC system is not a simple upgrading system, but it is an integrated system where complete trapping/seizing of CO2 takes place. CO2 is converted to bicarbonates, making the carbon footprint extremely low.

ASAC technology is applicable for:

Plant facility

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Reconversions and upgrading

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Microunits

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Biogas plants in cogeneration

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