Immer mehr pflanzenbasierte und erdölbasierte Verpackungsmaterialien sind biologisch abbaubar und... more Immer mehr pflanzenbasierte und erdölbasierte Verpackungsmaterialien sind biologisch abbaubar und lassen sich theoretisch vergären. Was für die Verwertbarkeit ein Fortschritt zu sein scheint, muss für die Ökologie keiner sein-wie eine umfassende Studie zeigt. Die neu erschienene Öko-bilanz der Carbotech AG, kombiniert mit Vergärversuchen der Fachhochschule Wädenswil (ZHAW) zeigt, dass fast alle der untersuchten Teller, Becher, Säcke und Folien aus biologisch abbaubarem Material besser in einer Kehrichtverbrennungsanlage mit Energierückgewinnung entsorgt werden.
BFE Projekt-/ 44155 Vertrag-Nummer 84194 Dauer des Projekts (von -bis) Mai-Dezember 2002 ZUSAMMEN... more BFE Projekt-/ 44155 Vertrag-Nummer 84194 Dauer des Projekts (von -bis) Mai-Dezember 2002 ZUSAMMENFASSUNG Bei der Kaffeeverarbeitung und -produktion fällt als organischer Abfall das Fruchtfleisch (Pulpa) an. Bis jetzt wurden kaum Machbarkeitsstudien zur Vergärbarkeit und zum Biogaspotential von Kaffee-Pulpa durchgeführt. Aus diesem Grund wurden in den Labors der HSW mit gezielten anaeroben Abbauversuchen das Biogaspotential ermittelt. Des Weiteren wurde die anaerobe Abbaubarkeit, verbunden mit einer möglichen Hemmung durch Nährstofflimitationen (N-/P-) und/oder durch Inhaltsstoffe, bestimmt. Der biogene Abfall weist einen Trockenrückstand von 16.2% auf. Für den organischen Trockenrückstand konnte ein Wert von 92.7% analysiert werden. Die im Labor durchgeführten Experimente mit Pulpa bei 37 o C zeigten, dass die organischen Inhaltsstoffe gut abbaubar sind, da bei entsprechenden Verdünnungen, über einen Zeitraum von 50 Tagen, Abbaugrade von 70% erreicht wurden. Für einen weitgehenden Abbau der organischen Substanz sind lange Verweilzeiten von über 30 Tagen notwendig. Die Gaserträge in den Laborversuchen sind mit 0.45 -0.70 NL Biogas kg -1 oTRabgebaut im Vergleich mit in der Literatur gefundenen Werten hoch. Es konnte eine Substratinhibition festgestellt werden.
Production of biogas from different organic materials is a most interesting source of renewable e... more Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. Although several norms and guidelines for BMP tests exist, inter-laboratory tests regularly show high variability of BMPs for the same substrate. A workshop was held in June 2015, in Leysin, Switzerland, with over 40 attendees from 30 laboratories around the world, to agree on common solutions to the conundrum of inconsistent BMP test results. This paper presents the consensus of the intense roundtable discussions and cross-comparison of methodologies used in respective laboratories. Compulsory elements for the validation of BMP results were defined. They include the minimal number of replicates, the request to carry out blank and positive control assays, a criterion for the test duration, details on BMP calculation, and last but not least criteria for rejection of the BMP tests. Finally, recommendations on items that strongly influence the outcome of BMP tests such as inoculum characteristics, substrate preparation, test setup, and data analysis are presented to increase the probability of obtaining validated and reproducible results.
Dry anaerobic digestion is considered a promising technology for treatment of organic waste in de... more Dry anaerobic digestion is considered a promising technology for treatment of organic waste in developing countries, mostly due to its simple design which can be constructed and operated at low cost. As real-scale experience is missing, a dry anaerobic pilot digester was developed by Eawag in collaboration with KNUST and ZHAW by converting a second-hand shipping container into a biogas reactor. The digester was filled with organic solid waste from the dumpsite and four batch runs of 4-8 weeks were conducted in Kumasi, Ghana. First batch results revealed insufficient gas tightness of the container and unsatisfactory biogas production. After several modifications and tests, a second biogas digester was built using a shipping container of higher quality. Finally, the fifth batch in this new digester showed an increasing gas production and methane content of 55-60%. However, gas production levels were still much lower than expected.
Composts can influence soil fertility and plant health. These influences can be positive or negat... more Composts can influence soil fertility and plant health. These influences can be positive or negative, depending of the quality of the composts. Some practitioners already make use of the positive effects on plant health. For example, they use composts to protect their plants against soil borne diseases in substrate, or to detoxify and reactivate soil after steaming. In order to estimate the potential of Swiss composts to influence soil fertility and plant health positively, we analyzed one hundred composts representative of the different composting systems and qualities available on the market. The organic substance and the nutrient content of the composts varied greatly between the composts; the materials of origin were the major factor influencing these values. The respiration rate and enzyme activities also varied greatly, particularly in the youngest composts. These differences become smaller when the composts become more mature. Maturity, the degradation stage of the organic matter, depended not only on the age of the compost, but also on the management of the process. The N-mineralization potential from compost added to soil showed that a high proportion of young composts immobilized the nitrogen in the soil. This problem was hardly correlated with the materials of origin, but with the management of the first stage of the composting process. Especially composts which had become too dry in this period lost their ammonia-nitrogen, and hence immobilized nitrogen in the soil. Also composts with a low NO 3 /NH 4 ratio, as a rough indicator for an immature compost, immobilized nitrogen in the soil. By contrast, the phytotoxicity of the composts varied very much also in matured composts, showing that the storage of the compost plays a decisive role. While the majority of compost protected cucumber plants against Pythium ultimum, only a few composts suppressed Rhizoctonia solani in basil. With respect to disease suppression, the management of the maturation process seems to play a major role. In conclusion, big differences in compost quality and of their impact on soil fertility and on plant health were observed. The management of the composting process seems to influence the quality of the composts to a higher extent than the materials of origin or the composting system. More attention should be paid to biological quality of composts, in order to produce composts with more beneficial effects on crops.
Combinations of heat and enzymes gave higher gas yields on sewage sludge, but the energy input wa... more Combinations of heat and enzymes gave higher gas yields on sewage sludge, but the energy input was not always compensated by the increased methane yield. The energy balance for pretreatment is an important factor in biogas production and should be considered carefully in order to improve economic and ecological benefits.
Composts and digestates can influence soil fertility and plant health. These influences can be po... more Composts and digestates can influence soil fertility and plant health. These influences can be positive or negative, depending of the quality of the composts. A currently important question is to know, if digestates differ from composts in these aspects. A Swiss project is concerned with the estimation of the potential of Swiss composts and digestates to influence soil fertility and plant health positively. For this, one hundred composts and digestates representative of the different composting systems and qualities available on the Swiss market were analyzed. The organic matter and nutrient content of the composts varied greatly between the composts and the digestates; the materials of origin were the major factor influencing these values. The respiration rate and enzyme activities also varied greatly; they are particularly important in digestates. The organic matter of digestates is less stable than that of composts. The N-mineralization potential from the majority of the digestates added to soil is high, in comparison to young composts. When digestates are not correctly treated or stored, however, they can immobilize nitrogen in the soil. This problem is hardly correlated with the management of the digestate in the first stage after leaving the fermenter. Especially products which have become too dry during this period lost their ammonia-nitrogen, and hence immobilized nitrogen in the soil. The risk of phytotoxicity is higher in digestates than in composts. This limits the possibility for use of digestate. With a post-treatment of digestate, it is possible to produce high quality compost with a high compatibility with plant growth and with a more stabilized organic matter. In field experiments, digestates increased the pH-value and the biological activity of soil to the same extent than composts. These effects were observable also one season after compost application. No immobilization of nitrogen was observed.
Seit Sommer 2001 ist in Schaffhausen die erste grosstechnische Grasraffinerie der Schweiz in Betr... more Seit Sommer 2001 ist in Schaffhausen die erste grosstechnische Grasraffinerie der Schweiz in Betrieb. Neben der Produktion von Grasfasern wird in einem anaeroben EGSB Reaktor Biogas gewonnen, welches nach Aufbereitung teilweise ins Erdgasnetz eingespiesen wird, teilweise in einem BHKW zur Produktion von Betriebswärme und Ökostrom genutzt wird. Nach einer Einfahrphase von 2 Monaten wurde im Winter 2001/2002 ein Programm zum Monitoring und zur Bilanzierung des Biogasreaktors durchgeführt. Während zwei unterschiedlichen Betriebsperioden von 4 resp. 5 Monaten wurden detaillierte Kohlenstoff-und Stickstoff-Massenbilanzen erhoben und die Leistung des anaeroben Systems anhand von Kennzahlen charakterisiert. Zudem wurde das Langzeitverhalten des granulären EGSB Schlammes ermittelt.
A full quantitative mass flow analysis of all goods of biogenic origin was established with a spe... more A full quantitative mass flow analysis of all goods of biogenic origin was established with a special focus on biomass flows for anaerobic digestion. The data serves as a basis for future decisions related to the production, processing and use of goods and of bioenergy from biomass. Data on materials and flows of goods of biogenic origin in Switzerland were collected from a broad spectrum of sources including official databases and statistics, current and past research and development projects and data collections from industry as well as from private organizations and NGO's. A standardized and comprehensive scheme of 16 processes (such as agriculture, meat processing, food processing, pulp & paper, household consumption, recycling) and the flows in between have been defined. Most flows, incl. import and export were quantified to the most detailed level available. A special focus was laid on a detailed input and output mass flow analysis of anaerobic digestion processes which we...
Anaerobic membrane reactors enable the separation of organics and bacteria and their rejection in... more Anaerobic membrane reactors enable the separation of organics and bacteria and their rejection into the biogas fermenter. At a test site at semi-industrial scale and a laboratory facility, experiments with separated manure, UF retentate and with co-substrates were conducted for more than 1,250 days. With separated manure the MBR produced biogas at a ratio of 610 l/kg OM (63% CH4) at an hydraulic retention time of 10 days and an sludge retention time of 40 days, compared to 270 l/kg OM at an HRT of 20 days in continuous stirred tank reactors (CSTR) using raw manure. A reduction of the retention time to 4 days is possible without affecting the degradation process. With UF retentate loading rates have been achieved up to 8 kg OM/m3 • d. With 7 % crude glycerol as a co-substrate, the gas yield was 700 l/kg OM at a HRT of 16 days and a SRT of 25 days. The gas yield from separated liquid manure and whey at a 20 % fraction was 560 l/kg OM (53% CH4) at 10 days HRT and 25 days SRT. The separ...
This paper evaluates the suitability of a small-scale biogas system as a decentralised treatment ... more This paper evaluates the suitability of a small-scale biogas system as a decentralised treatment option for the organic fraction of market and household solid waste in Dar es Salaam, Tanzania. A research plant was installed and operated for five months to evaluate its performance when fed with food and market solid waste. The system proved to be effective in terms of the reduction of waste volume and organic load. Performance of the digester regarding gas production was found to be good. The plant design may be improved for enhancing its performance. Reliable operation and maintenance were also found to be crucial to ensure long-term and sustainable use of biogas systems. However, for a wider dissemination of this promising solid waste treatment method, the cost of installation has to come down considerably.
Water science and technology : a journal of the International Association on Water Pollution Research, 2005
In 2001 the first green biorefinery started operation in Switzerland with a design load of 5,000 ... more In 2001 the first green biorefinery started operation in Switzerland with a design load of 5,000 tons dm of grass per year and a combined output of fibres (0.4 tons per ton input), protein (160 t/t) and bioenergy (500 kWh/t). Bioenergy was produced in a 570 m3 UASB reactor which has been monitored intensively during its first year of operation. Anaerobic treatment of liquid residues with > 80% degradation of organics was shown up to high f/m ratios and loading rates of 12 -15 kg COD/m3 d and specific biogas production of 0.5-0.65 Nm3 of gas per kg of COD added. A mass flow analysis of solids and pellets leads to the conclusion, that due to a low sludge bed volume of only 16% of the reactor combined with a low actual organic loading of 1.5 kg COD/m3 d there was a restricted adsorption and a low degradation of substrate solids.
Immer mehr pflanzenbasierte und erdölbasierte Verpackungsmaterialien sind biologisch abbaubar und... more Immer mehr pflanzenbasierte und erdölbasierte Verpackungsmaterialien sind biologisch abbaubar und lassen sich theoretisch vergären. Was für die Verwertbarkeit ein Fortschritt zu sein scheint, muss für die Ökologie keiner sein-wie eine umfassende Studie zeigt. Die neu erschienene Öko-bilanz der Carbotech AG, kombiniert mit Vergärversuchen der Fachhochschule Wädenswil (ZHAW) zeigt, dass fast alle der untersuchten Teller, Becher, Säcke und Folien aus biologisch abbaubarem Material besser in einer Kehrichtverbrennungsanlage mit Energierückgewinnung entsorgt werden.
BFE Projekt-/ 44155 Vertrag-Nummer 84194 Dauer des Projekts (von -bis) Mai-Dezember 2002 ZUSAMMEN... more BFE Projekt-/ 44155 Vertrag-Nummer 84194 Dauer des Projekts (von -bis) Mai-Dezember 2002 ZUSAMMENFASSUNG Bei der Kaffeeverarbeitung und -produktion fällt als organischer Abfall das Fruchtfleisch (Pulpa) an. Bis jetzt wurden kaum Machbarkeitsstudien zur Vergärbarkeit und zum Biogaspotential von Kaffee-Pulpa durchgeführt. Aus diesem Grund wurden in den Labors der HSW mit gezielten anaeroben Abbauversuchen das Biogaspotential ermittelt. Des Weiteren wurde die anaerobe Abbaubarkeit, verbunden mit einer möglichen Hemmung durch Nährstofflimitationen (N-/P-) und/oder durch Inhaltsstoffe, bestimmt. Der biogene Abfall weist einen Trockenrückstand von 16.2% auf. Für den organischen Trockenrückstand konnte ein Wert von 92.7% analysiert werden. Die im Labor durchgeführten Experimente mit Pulpa bei 37 o C zeigten, dass die organischen Inhaltsstoffe gut abbaubar sind, da bei entsprechenden Verdünnungen, über einen Zeitraum von 50 Tagen, Abbaugrade von 70% erreicht wurden. Für einen weitgehenden Abbau der organischen Substanz sind lange Verweilzeiten von über 30 Tagen notwendig. Die Gaserträge in den Laborversuchen sind mit 0.45 -0.70 NL Biogas kg -1 oTRabgebaut im Vergleich mit in der Literatur gefundenen Werten hoch. Es konnte eine Substratinhibition festgestellt werden.
Production of biogas from different organic materials is a most interesting source of renewable e... more Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. Although several norms and guidelines for BMP tests exist, inter-laboratory tests regularly show high variability of BMPs for the same substrate. A workshop was held in June 2015, in Leysin, Switzerland, with over 40 attendees from 30 laboratories around the world, to agree on common solutions to the conundrum of inconsistent BMP test results. This paper presents the consensus of the intense roundtable discussions and cross-comparison of methodologies used in respective laboratories. Compulsory elements for the validation of BMP results were defined. They include the minimal number of replicates, the request to carry out blank and positive control assays, a criterion for the test duration, details on BMP calculation, and last but not least criteria for rejection of the BMP tests. Finally, recommendations on items that strongly influence the outcome of BMP tests such as inoculum characteristics, substrate preparation, test setup, and data analysis are presented to increase the probability of obtaining validated and reproducible results.
Dry anaerobic digestion is considered a promising technology for treatment of organic waste in de... more Dry anaerobic digestion is considered a promising technology for treatment of organic waste in developing countries, mostly due to its simple design which can be constructed and operated at low cost. As real-scale experience is missing, a dry anaerobic pilot digester was developed by Eawag in collaboration with KNUST and ZHAW by converting a second-hand shipping container into a biogas reactor. The digester was filled with organic solid waste from the dumpsite and four batch runs of 4-8 weeks were conducted in Kumasi, Ghana. First batch results revealed insufficient gas tightness of the container and unsatisfactory biogas production. After several modifications and tests, a second biogas digester was built using a shipping container of higher quality. Finally, the fifth batch in this new digester showed an increasing gas production and methane content of 55-60%. However, gas production levels were still much lower than expected.
Composts can influence soil fertility and plant health. These influences can be positive or negat... more Composts can influence soil fertility and plant health. These influences can be positive or negative, depending of the quality of the composts. Some practitioners already make use of the positive effects on plant health. For example, they use composts to protect their plants against soil borne diseases in substrate, or to detoxify and reactivate soil after steaming. In order to estimate the potential of Swiss composts to influence soil fertility and plant health positively, we analyzed one hundred composts representative of the different composting systems and qualities available on the market. The organic substance and the nutrient content of the composts varied greatly between the composts; the materials of origin were the major factor influencing these values. The respiration rate and enzyme activities also varied greatly, particularly in the youngest composts. These differences become smaller when the composts become more mature. Maturity, the degradation stage of the organic matter, depended not only on the age of the compost, but also on the management of the process. The N-mineralization potential from compost added to soil showed that a high proportion of young composts immobilized the nitrogen in the soil. This problem was hardly correlated with the materials of origin, but with the management of the first stage of the composting process. Especially composts which had become too dry in this period lost their ammonia-nitrogen, and hence immobilized nitrogen in the soil. Also composts with a low NO 3 /NH 4 ratio, as a rough indicator for an immature compost, immobilized nitrogen in the soil. By contrast, the phytotoxicity of the composts varied very much also in matured composts, showing that the storage of the compost plays a decisive role. While the majority of compost protected cucumber plants against Pythium ultimum, only a few composts suppressed Rhizoctonia solani in basil. With respect to disease suppression, the management of the maturation process seems to play a major role. In conclusion, big differences in compost quality and of their impact on soil fertility and on plant health were observed. The management of the composting process seems to influence the quality of the composts to a higher extent than the materials of origin or the composting system. More attention should be paid to biological quality of composts, in order to produce composts with more beneficial effects on crops.
Combinations of heat and enzymes gave higher gas yields on sewage sludge, but the energy input wa... more Combinations of heat and enzymes gave higher gas yields on sewage sludge, but the energy input was not always compensated by the increased methane yield. The energy balance for pretreatment is an important factor in biogas production and should be considered carefully in order to improve economic and ecological benefits.
Composts and digestates can influence soil fertility and plant health. These influences can be po... more Composts and digestates can influence soil fertility and plant health. These influences can be positive or negative, depending of the quality of the composts. A currently important question is to know, if digestates differ from composts in these aspects. A Swiss project is concerned with the estimation of the potential of Swiss composts and digestates to influence soil fertility and plant health positively. For this, one hundred composts and digestates representative of the different composting systems and qualities available on the Swiss market were analyzed. The organic matter and nutrient content of the composts varied greatly between the composts and the digestates; the materials of origin were the major factor influencing these values. The respiration rate and enzyme activities also varied greatly; they are particularly important in digestates. The organic matter of digestates is less stable than that of composts. The N-mineralization potential from the majority of the digestates added to soil is high, in comparison to young composts. When digestates are not correctly treated or stored, however, they can immobilize nitrogen in the soil. This problem is hardly correlated with the management of the digestate in the first stage after leaving the fermenter. Especially products which have become too dry during this period lost their ammonia-nitrogen, and hence immobilized nitrogen in the soil. The risk of phytotoxicity is higher in digestates than in composts. This limits the possibility for use of digestate. With a post-treatment of digestate, it is possible to produce high quality compost with a high compatibility with plant growth and with a more stabilized organic matter. In field experiments, digestates increased the pH-value and the biological activity of soil to the same extent than composts. These effects were observable also one season after compost application. No immobilization of nitrogen was observed.
Seit Sommer 2001 ist in Schaffhausen die erste grosstechnische Grasraffinerie der Schweiz in Betr... more Seit Sommer 2001 ist in Schaffhausen die erste grosstechnische Grasraffinerie der Schweiz in Betrieb. Neben der Produktion von Grasfasern wird in einem anaeroben EGSB Reaktor Biogas gewonnen, welches nach Aufbereitung teilweise ins Erdgasnetz eingespiesen wird, teilweise in einem BHKW zur Produktion von Betriebswärme und Ökostrom genutzt wird. Nach einer Einfahrphase von 2 Monaten wurde im Winter 2001/2002 ein Programm zum Monitoring und zur Bilanzierung des Biogasreaktors durchgeführt. Während zwei unterschiedlichen Betriebsperioden von 4 resp. 5 Monaten wurden detaillierte Kohlenstoff-und Stickstoff-Massenbilanzen erhoben und die Leistung des anaeroben Systems anhand von Kennzahlen charakterisiert. Zudem wurde das Langzeitverhalten des granulären EGSB Schlammes ermittelt.
A full quantitative mass flow analysis of all goods of biogenic origin was established with a spe... more A full quantitative mass flow analysis of all goods of biogenic origin was established with a special focus on biomass flows for anaerobic digestion. The data serves as a basis for future decisions related to the production, processing and use of goods and of bioenergy from biomass. Data on materials and flows of goods of biogenic origin in Switzerland were collected from a broad spectrum of sources including official databases and statistics, current and past research and development projects and data collections from industry as well as from private organizations and NGO's. A standardized and comprehensive scheme of 16 processes (such as agriculture, meat processing, food processing, pulp & paper, household consumption, recycling) and the flows in between have been defined. Most flows, incl. import and export were quantified to the most detailed level available. A special focus was laid on a detailed input and output mass flow analysis of anaerobic digestion processes which we...
Anaerobic membrane reactors enable the separation of organics and bacteria and their rejection in... more Anaerobic membrane reactors enable the separation of organics and bacteria and their rejection into the biogas fermenter. At a test site at semi-industrial scale and a laboratory facility, experiments with separated manure, UF retentate and with co-substrates were conducted for more than 1,250 days. With separated manure the MBR produced biogas at a ratio of 610 l/kg OM (63% CH4) at an hydraulic retention time of 10 days and an sludge retention time of 40 days, compared to 270 l/kg OM at an HRT of 20 days in continuous stirred tank reactors (CSTR) using raw manure. A reduction of the retention time to 4 days is possible without affecting the degradation process. With UF retentate loading rates have been achieved up to 8 kg OM/m3 • d. With 7 % crude glycerol as a co-substrate, the gas yield was 700 l/kg OM at a HRT of 16 days and a SRT of 25 days. The gas yield from separated liquid manure and whey at a 20 % fraction was 560 l/kg OM (53% CH4) at 10 days HRT and 25 days SRT. The separ...
This paper evaluates the suitability of a small-scale biogas system as a decentralised treatment ... more This paper evaluates the suitability of a small-scale biogas system as a decentralised treatment option for the organic fraction of market and household solid waste in Dar es Salaam, Tanzania. A research plant was installed and operated for five months to evaluate its performance when fed with food and market solid waste. The system proved to be effective in terms of the reduction of waste volume and organic load. Performance of the digester regarding gas production was found to be good. The plant design may be improved for enhancing its performance. Reliable operation and maintenance were also found to be crucial to ensure long-term and sustainable use of biogas systems. However, for a wider dissemination of this promising solid waste treatment method, the cost of installation has to come down considerably.
Water science and technology : a journal of the International Association on Water Pollution Research, 2005
In 2001 the first green biorefinery started operation in Switzerland with a design load of 5,000 ... more In 2001 the first green biorefinery started operation in Switzerland with a design load of 5,000 tons dm of grass per year and a combined output of fibres (0.4 tons per ton input), protein (160 t/t) and bioenergy (500 kWh/t). Bioenergy was produced in a 570 m3 UASB reactor which has been monitored intensively during its first year of operation. Anaerobic treatment of liquid residues with > 80% degradation of organics was shown up to high f/m ratios and loading rates of 12 -15 kg COD/m3 d and specific biogas production of 0.5-0.65 Nm3 of gas per kg of COD added. A mass flow analysis of solids and pellets leads to the conclusion, that due to a low sludge bed volume of only 16% of the reactor combined with a low actual organic loading of 1.5 kg COD/m3 d there was a restricted adsorption and a low degradation of substrate solids.
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