Fraunhofer Institute for Interfacial Engineering and Biotechnology IGBOrganic waste that cannot be recycled or utilized for other purposes is particularly suited for conversion by means of anaerobic digestion. In this process, anaerobic microorganisms decompose organic carbon compounds through various intermediate stages to produce biogas, a mixture of methane and carbon dioxide. For the digestion of sewage sludge, Fraunhofer IGB has developed a particularly efficient high-load process, which can also be used to efficiently convert other organic wastes, such as food waste and kitchen scraps or agricultural residues, into biogas.
The two-stage high-load anaerobic digestion system in Edenkoben allows the wastewater treatment plant to cope with a higher effluent load during the wine harvest
© Photo Verbandsgemeindewerke Edenkoben
Bioenergy.
Schwerzen sewage treatment plant. High-load digestion is also economical for smaller sewage treatment plants (10 000 P.E.).
Production of biogas through high-load digestion of sewage sludge, manure, and organic waste
Challenge: Efficient utilization of organic waste and recovery of usable components
Given the limited availability of fossil and biological raw materials, it is becoming increasingly important for companies, municipalities, and governments to use existing resources more efficiently and intelligently and to recover substances for material or energy use in line with the circular economy approach.
Sludge digestion at wastewater treatment plants – an alternative to sludge stabilization
Wastewater treatment plants remove organic matter from wastewater. When the sludge produced in this process is digested, biogas is generated as a byproduct. However, only about one-tenth of the more than 10,000 wastewater treatment plants in Germany have a digestion tower.
Another challenge is the disposal of the resulting sludge, the use of which has already been severely restricted.
Our solution: high-load digestion for maximum biogas yield and increased energy efficiency
Anaerobic Digestion to Produce Biogas
Anaerobic biogas technology has long been used, even on an industrial scale, for example in the stabilization of sewage sludge or manure. However, this technology for converting organic waste from municipal or industrial sources offers even greater potential if the current level of partial waste disposal – which aims to minimize residual waste – is improved.
High-load digestion for improved degradation and more biogas
Fraunhofer IGB has developed a particularly efficient high-load process for the digestion of sewage sludge into biogas. It was first implemented at the Leonberg wastewater treatment plant as early as 1994 and is now being successfully operated at various municipal wastewater treatment plants.
The results show that high-load digestion converts sludge into biogas much faster and more cost-effectively than conventional digesters. Even larger wastewater treatment plants, whose digesters are now outdated, could produce more biogas with this modern technology and thus improve their cost and energy efficiency.
Suitable for organic residues and agricultural biogas plants as well
High-load digestion has also been successfully used for the anaerobic treatment of industrial biomass residues or kitchen waste, as well as in agricultural biogas plants. This allows organic residues that cannot be further utilized to be converted into biogas through digestion, thus adding value.
Key advantages of high-load digestion
- Shorter retention times (5–10 days) with a smaller digestion space
- Higher degradation rate, resulting in higher biogas yield and improved energy efficiency
- No foaming problems on sewage treatment plants
- Improved dewaterability of the digested sludge/fermentation residue, also for further use (e.g., nutrient recovery and drying as a peat substitute)
- Lower operating and disposal costs
Plant technology
In terms of plant technology, modern bioreactors, in combination with membrane-based or mechanical separation technology, are currently emerging as forward-looking strategies. For some types of waste, a combination of aerobic and anaerobic techniques may also be appropriate to achieve the most complete degradation possible.
High-load digestion
The process
Schema der Hochlastfaulung
The process was developed for increasing the efficiency of sewage sludge digestion and has been the subject of intensive research work at Fraunhofer IGB. The high-load process is characterized by significantly improved efficiency, short retention times, and a high degradation rate.
It is used for the anaerobic conversion of organically degradable substrates such as sewage sludge, but also of liquid manure, biowaste, or other organic residues. Due to its significantly increased biogas yield compared to other processes, it is becoming increasingly attractive.
Operational data
Single-stage plant in Ilsfeld
Pilot plant for the comparative investigation of the digestion of renewable raw materials with high-load and conventional operation.
Excellent operational data compared with conventional digestion
Shorter retention time
Even with a high solid content the sewage sludge only has to remain approx. 5–10 days in the digestion tower instead of 20–30 days up till now. Thus organic load rates of 8–10 kg TVS / m3· d are achieved instead of only 1–2 kg TVS/ m3· d.
High biogas yield
The high-load digestion can produce up to 23 liters of biogas per PE and day, depending on the quality of the raw sludge. Conventional digestion plants in contrast achieve a maximum of only 19.7 liters of biogas per PE and day on average [Haberkern et al; Steigerung der Energieeffizienz auf kommunalen Kläranlagen Umweltbundesamt Texte Nr. 11 / 08, Dessau-Roßlau, March 2008].
The gas can be used to supply the plant with energy or can be delivered as a technically and commercially usable energy carrier.
Less organic residues
In the course of enhanced biogas production the high-load digestion also reduces the organics – by 50 to 70 percent, depending on the specific combination of processes. The organic share of the dry residual matter is now only 50 percent. As a result, far lower amounts of sludge occur, as they can be dewatered and disposed of more effectively.
Benefits for operators
Benefits for operators
Contribution to energy efficiency
The high-load digestion process developed at Fraunhofer IGB transforms sewage sludge digestion into a process that can make a significant contribution to the economic viability and energy efficiency of wastewater treatment plants by efficiently converting the components of sewage sludge into biogas.
In the AmmoRe pilot plant, ammonium is recovered from the sludge water as an ammonium sulphate solution at the Erbach wastewater treatment plant as part of the RoKKa project.
Dewatering of digested sludge provides nutrient-rich filtrate for nutrient recycling
For further use or recovery of ingredients, the digested sludge is dewatered in a solid-liquid separation plant, such as a chamber filter press or centrifuge. This yields a particle-free sludge water that contains most of the dissolved nutrients (nitrogen and phosphorus) and thus can be used directly for fertilizer irrigation.
Alternatively, nitrogen and phosphorus can be recovered as fertilizer. Fraunhofer IGB has developed various technologies for nutrient recovery. The deloaded organic substrate can then be dried and, if desired (in the case of uncontaminated source materials), used as a humus-rich soil conditioner.
Benefits of anaerobic digestion of organic waste: Biogas as a versatile product and a contribution to the energy transition
Digestion processes take place under anaerobic conditions – that is, in the absence of atmospheric oxygen – such as in the rumen of a ruminant or in rice paddies. There are several stages of digestion, each involving different types of bacteria.
At the end of the anaerobic microbial food chain, the carbon content of the organic matter always produces a mixture of carbon dioxide (CO2) and methane (CH4) – biogas. Due to its high net energy yield, it is the most important bioenergy source and has a wide range of applications.
Biogas: renewable energy with versatile application potential
In combined heat and power plants, biogas supplies electricity and heat. Along with combined heat and power generation, biogas production is considered a technology with very high CO2 reduction potential. On sewage treatment plants, high-load digestion helps reduce external electricity demand through the production of biogas. Power generation from biogas, which is produced in biogas plants primarily from ensiled renewable raw materials, is a key pillar of renewable energy.
Baseload-capable: continuous generation
Among the renewable energies, biogas, as “bioenergy” or “green gas,” plays a special role in the energy transition: While electricity generation from solar and wind is highly dependent on the weather, biogas can be produced continuously, stored for a certain period of time, and converted into electricity and heat in a combined heat and power plant as required. This makes electricity generation from biogas capable of meeting base load and stabilizes the power grids.
Upgrading to biomethane as a fuel and chemical feedstock
When biogas is upgraded to biomethane, it can be fed into the natural gas grid, serve as fuel for appropriately equipped vehicles, or be used as a chemical feedstock. In this way, it links the energy and chemical sectors.
Tabbed contents
Range of services and collaboration
Range of services and collaboration
For more than 40 years Fraunhofer IGB has been developing biotechnological processes for the treatment of water and waste – from the microbiological fundamentals to a technical and pilot scale plant.
Integrated approach: energy generation and nutrient recovery
One focus here is materials recycling. This makes us the partner of choice for municipalities and industrial companies wishing to combine waste disposal and wastewater treatment with the use of organic residues. We have also developed various technologies for nutrient recovery from the liquid and solid residues produced during high-load digestion.
We will be glad to advise you on how to make optimum and holistic use of your residual materials! To this end, we work together with other research and development departments at Fraunhofer IGB.
Scaling from pilot plant up to industrial scale
In our pilot plants, we investigate the fermentability of various biogenic residues on a laboratory and pilot plant scale and develop concepts for large-scale implementation. Basic and detail engineering based on Fraunhofer patents is carried out by our industrial partners from the plant engineering sector.
Pilot plant for know-how transfer
To ensure a smooth transfer of know-how to the operators and a successful implementation, we can also always implement the high-load process initially on a pilot scale and operate it on site.
The range of our services extends from digestion tests on laboratory scale to determine the degradability and the biogas yield, to investigations on pilot plant scale to determine design parameters for biogas plants, to the realization of plants on technical scale in cooperation with engineering offices. All developments are carried out with the aim of providing optimal and specific solutions for the user.
- Feasibility studies: Investigation of the fermentability, quantification of the biogas yield of substrates / cosubstrates
- Characterization of solids and substrates: Qualitative and quantitative biogas analysis, analysis of substrate ingredients
- Specific analysis of processes with the aim of process improvements: elimination of faults, increase of efficiency, process optimization
- Anaerobic processes as an alternative to aerobic processes
- Determination of potential for increasing the performance of processes, e.g. wastewater treatment, biogas plants, sewage sludge digestion
- Process development for anaerobic treatment of organic residues, e.g. from agriculture, food processing, production
- Technical implementation up to pilot scale
- Scientific support during the commissioning of processes on a technical scale
Services at a glance
- Analytical measurements
- Comprehensive analysis (chemical and biological parameters)
- Characterization of solids and substrates: Qualitative and quantitative biogas analytics, analytics of constituents of substrates
- Studies
- Feasibility studies for the production of biogas from residues
- Analysis of wastewater treatment plants and biogas plants to increase energy efficiency
- Specific analysis of processes with the aim of process improvements: Elimination of malfunctions, increase of efficiency, process optimizations
- Determination of potential to increase the performance of processes, e.g. wastewater treatment, biogas plants, sewage sludge digestion
- Laboratory tests
- Investigations of sewage sludge digestion for the determination of design parameters
- Performance of fermentation tests (investigation of fermentability)
- Quantification of the biogas yield of substrates/cosubstrates
- Process development for the anaerobic treatment of organic residues, e.g. from agriculture, food processing and production
- Process development for the production of recyclables/biogas from residues: Determination of design parameters at pilot plant scale.
- Industrial implementation
- Development of planning concepts for the realization of high-load digestion on a technical scale
- Scientific support for the start-up of processes on a technical scale
- Technical implementation on pilot scale and operation on site
- Technical-scientific consulting for process improvement or commissioning of plants
- Individual, cost-saving expansion of wastewater treatment plants
equipment
Infrastructure and technical equipment
- Bioreactors of different types and sizes (laboratory, pilot and technical scale)
- Pilot plant for environmental and bioprocess engineering
- Mobile pilot plants in m3 scale for the generation of design data on site for the planning and construction of innovative demonstration plants
Publications
Publications
| Jahr Year | Titel/Autor:in Title/Author | Publikationstyp Publication Type |
|---|---|---|
| 2015 | Anaerobe Batch-Fermentation mit Mais- und Amaranthsilagen: Biogasproduktion und molekulare Charakterisierung mikrobieller Gemeinschaften Kempter-Regel, Brigitte; Grumaz, Christian; Wiese, Franziska; Scherge, Katharina; Birk, Carolin; Schließmann, Ursula; Stevens, Philip; Sohn, Kai; Bryniok, Dieter |
Konferenzbeitrag Conference Paper |
| 2014 | Power generation based on biomass by combined fermentation and gasification - A new concept derived from experiments and modelling Methling, T.; Armbrust, N.; Haitz, T.; Speidel, M.; Poboss, N.; Braun-Unkhoff, M.; Dieter, H.; Kempter-Regel, B.; Kraaij, G.; Schliessmann, U.; Sterr, Y.; Wörner, A.; Hirth, Thomas; Riedel, U.; Scheffknecht, G. |
Zeitschriftenaufsatz Journal Article |
| 2011 | Potencial de otimização da produção de biogás gerado por uma digestão anaeróbia em etes Waelkens, B.E.; Sternad, W. |
Zeitschriftenaufsatz Journal Article |
| 2009 | Mehr Energieeffizienz für kleinere Kläranlagen - Hochlastfaulung mit Mikrofiltration Kempter-Regel, B.; Trösch, Walter |
Zeitschriftenaufsatz Journal Article |
| 2008 | Anaerobe Abwasserreinigung in Membranbioreaktoren unter -Verwendung des Rotationsscheibenfilters Krischke, W.; Mohr, M.; Kempter-Regel, B.; Trösch, Walter |
Zeitschriftenaufsatz Journal Article |
| 2003 | Integration einer Hochlastfaulung in die herkömmliche Technik Kempter-Regel, B.; Oehlke, M.; Weber, J.; Trösch, Walter |
Zeitschriftenaufsatz Journal Article |
| 2002 | Erfahrungen zur Ammoniakentfernung mit Membrankontaktoren Chaumette, C.; Walitza, E.; Kempter, B.; Sternad, W. |
Zeitschriftenaufsatz Journal Article |
| 2001 | Verfahren zur Reinigung von Abwasser Kempter, B.; Sternad, W.; Trösch, W. |
Patent |
| 2000 | Optimiertes Vergärungsverfahren steigert Umsatz von organischen Abfällen Kempter, B.; Trösch, Walter |
Zeitschriftenaufsatz Journal Article |
| 2000 | Verbesserter Abbau von kommunalen Klärschlämmen in einer zweistufigen Hochlast-Vergärungsanlage Kempter, B.; Schmid-Staiger, U.; Trösch, Walter |
Zeitschriftenaufsatz Journal Article |
| 1996 | Aerober und anaerober Abbau von Abwässern aus der Wasserlackverarbeitung Kempter, B. |
Dissertation Doctoral Thesis |
Diese Liste ist ein Auszug aus der Publikationsplattform Fraunhofer-Publica
This list has been generated from the publication platform Fraunhofer-Publica
Comprehensive utilization of waste materials through nutrient recovery
With the BioEcoSim process, livestock manure can be converted into valuable phosphorus fertilizers (rear), nitrogen fertilizers (right) and soil conditioners (front).
Municipal wastewater, liquid manure, digestion residues, and byproducts from the food industry are also rich in nutrients such as nitrogen, phosphorus, potassium, and calcium. In addition to utilizing the organic content (carbon), we also develop technologies and processes to recover these valuable nutrients.