Refine
Document Type
- Article (4)
Has Fulltext
- no (4)
Is part of the Bibliography
- yes (4)
Keywords
- Biogas (1)
- Biogasanlagen (1)
- Cover Residual Load Rises (1)
- Environmental impact (1)
- Flexibilisierungskonzepte (1)
- Residuallast (1)
- biogas production (1)
- excess electricity conversion (1)
- methanol (1)
- residual load rises (1)
Institute
In this work, the impact on the environment of a renewable methanol production in combination with a wastewater treatment plant (WWTP) was analysed. Carbon dioxide from biogas and hydrogen from water electrolysis were used as resources for methanol synthesis. Additionally, it was decided to use the available excess of electricity and it was prepared for a small city in North-West of Germany (Emden) to have a realistic scenario. As a consequence, methanol plant was simulated with the use of ASPEN Plus software in order to calculate the mass balance and energy requirement. Subsequently a comparative life cycle assessment (cradle-to-gate) was conducted in order to compare renewable methanol with conventional process and also with methanol produced from biomass. In order to evaluate possible impact on the environment, 11 common impact categories were selected. Results showed that enough excess electricity was already available to utilize the whole CO2 from WWTP in Emden. Subsequently it was found that the production of renewable methanol, without emissions related to windmill construction, has much lower impact on the environment than conventional production according to all impact categories. Furthermore, the combination of power-to-methanol plant with WWTP allowed utilization of the biogenic carbon dioxide and application of the produced via electrolysis oxygen. Therefore, thanks to substitution of air with produced oxygen, a reduction in electricity consumption for the aeration system could be possible. However, taking into account the emissions related to wind electricity, renewable methanol would cause lower emissions according to 5 impact categories (acidification potential, climate change, ozone layer depletion, photochemical oxidation, and primary energy demand from non-renewable resources) than natural gas or biomass based methanol.
The development of systems for energy storage and demand-driven energy production will be essential to enable the switch from fossil to renewable energy sources in future. To cover the residual load rises, a rigorous dynamic process model based on the Anaerobic Digestion Model No. 1 (ADM1) was applied to analyse the flexible operation of biogas plants. For this, the model was optimised and an operational concept for a demand-driven energy production was worked out. Different substrates were analysed, both by batch fermentation and Weende analysis with van Soest method, to determine the input data of the model. The lab results show that the substrates have got different degradation kinetics and biogas potentials. Finally, the ADM1 was extended with a feeding algorithm which is based on a PI controller. Essential feeding times and quantities of available substrates were calculated so that a biogas plant can cover a defined energy demand. The results prove that a flexible operation of biogas plants with a feeding strategy is possible.
Fluctuations in wind and solar energy due to climatic conditions as well as the rising demand of renewable energy puts an increasingly stronger focus on alternative systems like the demand-driven biogas production. Hence, currently examined concepts for flexibilization of biogas plants are described. The biogas storage as well as the demand-driven biogas production by feeding management, variable conversion in electricity, disintegration processes, or packed-bed fermentation belong to these concepts. Also, the combination with power-to-gas or power-to-heat systems seems promising and is discussed.
Aktueller Stand der Flexibilisierungskonzepte von Biogasanlagen zur Abdeckung der Residuallast
(2018)
Durch klimabedingte Schwankungen in der Wind- und Solarenergie und den steigenden Bedarf an erneuerbaren Energien rücken alternative Systeme wie die bedarfsorientierte Biogaserzeugung immer weiter in den Fokus. Daher werden die aktuell untersuchten Konzepte zur Flexibilisierung von Biogasanlagen aufgezeigt. Zu den Ansätzen gehören die Biogasspeicherung sowie die bedarfsorientierte Biogasproduktion durch Fütterungsmanagement, variable Verstromung, Desintegrations- oder Festbettfermenter-Verfahren. Auch die Kopplung mit Power-to-Gas- oder Power-to-Heat-Systemen erscheint vielversprechend.