DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH
DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH
Kretzschmar J.,DBFZ Deutsches Biomasseforschungszentrum Gemeinnutzige GmbH |
Kretzschmar J.,Helmholtz Center for Environmental Research |
Riedl S.,TU Braunschweig |
Brown R.K.,TU Braunschweig |
And 2 more authors.
Journal of the Electrochemical Society | Year: 2017
The aim of the study was to provide experimental proof-of-concept that stand-alone power generation based on microbial fuel cells (MFCs) operated using human feces as the substrate can be achieved. A pit latrine that is typically employed for decentralized treatment of human feces e.g. in regions without access to centralized wastewater infrastructures was installed as sampling site. It was the philosophy that the components, i.e. anodes and cathodes, used in the MFCs had to be based on low-cost precursors. This was achieved by recycling common household materials or waste products and a low-tech/cost production method was developed to convert them into usable electrodes. It is demonstrated that i) pre-tests on using an equivalent to vent-air from ovens or fire-places allowed a low-tech carbonization of e.g. corrugated cardboard to electrode materials; ii) that anodes based on corrugated cardboard can be operated using real human feces as substrate, nevertheless, providing only low current densities (15.09 ± 5.18 μA cm-2) and iii) cathodes - with nitrogen functionalities derived from (artificial) urine - based on corrugated cardboard or as an alternative jeans cloth show a good oxygen reduction reaction (ORR) activity. Introducing nitrogen containing surface moieties to the cathode surface increased the ORR up to factor 5 (chronoamperometry at 0 V vs. Ag/AgCl sat. KCl) compared to the untreated reference. Most importantly, highly valuable lessons for exploiting real and highly heterogeneous and dense substrates like human feces in microbial electrochemical technologies were learned. © The Author(s) 2016.
Seco R.,Autonomous University of Barcelona |
Seco R.,U.S. National Center for Atmospheric Research |
Penuelas J.,Autonomous University of Barcelona |
Filella I.,Autonomous University of Barcelona |
And 7 more authors.
Atmospheric Chemistry and Physics | Year: 2011
Atmospheric volatile organic compounds (VOCs) are involved in ozone and aerosol generation, thus having implications for air quality and climate. VOCs and their emissions by vegetation also have important ecological roles as they can protect plants from stresses and act as communication cues between plants and between plants and animals. In spite of these key environmental and biological roles, the reports on seasonal and daily VOC mixing ratios in the literature for Mediterranean natural environments are scarce. We conducted seasonal (winter and summer) measurements of VOC mixing ratios in an elevated (720 m a.s.l.) holm oak Mediterranean forest site near the metropolitan area of Barcelona (NE Iberian Peninsula). Methanol was the most abundant compound among all the VOCs measured in both seasons. While aromatic VOCs showed almost no seasonal variability, short-chain oxygenated VOCs presented higher mixing ratios in summer, presumably due to greater emission by vegetation and increased photochemistry, both enhanced by the high temperatures and solar radiation in summer. Isoprenoid VOCs showed the biggest seasonal change in mixing ratios: they increased by one order of magnitude in summer, as a result of the vegetation's greater physiological activity and emission rates. The maximum diurnal concentrations of ozone increased in summer too, most likely due to more intense photochemical activity and the higher levels of VOCs in the air. The daily variation of VOC mixing ratios was mainly governed by the wind regime of the mountain, as the majority of the VOC species analyzed followed a very similar diel cycle. Mountain and sea breezes that develop after sunrise advect polluted air masses to the mountain. These polluted air masses had previously passed over the urban and industrial areas surrounding the Barcelona metropolitan area, where they were enriched in NO x and in VOCs of biotic and abiotic origin. Moreover, these polluted air masses receive additional biogenic VOCs emitted in the local valley by the vegetation, thus enhancing O 3 formation in this forested site. The only VOC species that showed a somewhat different daily pattern were monoterpenes because of their local biogenic emission. Isoprene also followed in part the daily pattern of monoterpenes, but only in summer when its biotic sources were stronger. The increase by one order of magnitude in the concentrations of these volatile isoprenoids highlights the importance of local biogenic summer emissions in these Mediterranean forested areas which also receive polluted air masses from nearby or distant anthropic sources. © 2011 Author(s).
Pujan R.,DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH |
Hauschild S.,DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH |
Grongroft A.,DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH
Fuel Processing Technology | Year: 2017
The ambitious targets of the aviation industry to reduce greenhouse gas emissions require the use of biofuels in this transport sector in the short and medium term. While five biogenic aviation turbine fuels have already been certified by the American Society for Testing and Materials (ASTM D7566), the search for suitable alternatives continues, seeking higher possible blending ratios or better fuel qualities. Fluidized-bed catalytic cracking (FCC) of algae oil, followed by hydrotreatment of intermediates, could be such a potential option. This conversion concept has several potential advantages, such as aromatic compounds in the biokerosene and the use of a non-food biogenic oil as feedstock. Material and energy balances are obtained from flowsheet simulation using ASPEN Plus®, with the aim to assess the efficiency of the process. The simulation model contains all relevant conversion and separation steps, and auxiliary components such as a steam reformer and a furnace. Simulation parameters for all unit operations were based on current literature to represent the state-of-the-art of the involved technologies. Additionally, the process was optimized by heat integration and waste heat utilization. The established simulation model is proposed to serve as a concept study and basis for the implementation of future experimental results and perceptions. With an energy efficiency of 95% and a biokerosene yield of 41%, the results emphasize the potential of this conversion process. © 2017 Elsevier B.V.
Farokhi M.,University of Manitoba |
Birouk M.,University of Manitoba |
Tabet F.,DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH
Energy Conversion and Management | Year: 2017
This paper presents a computational study to evaluate the influence of turbulence and combustion models as well as chemistry schemes on the combustion of a 8–11 kW small lab-scale biomass furnace. The analysis is conducted in the zone above the bed (freeboard) where the volatiles are burned. The turbulence models tested are standard k-ε, RNG k-ε and Realizable k-ε; and the combustion models are SFM (Steady Flamelet Model), UFM (Unsteady Flamelet Model) and EDC (Eddy Dissipation Concept). In addition, several chemical mechanisms with different complexity (reduced and detailed chemical kinetics) are considered. The predictions of the velocity, species, and temperature fields are compared with their counterparts’ experimental measurements. The present findings reveal that all tested combustion models (SFM, UFM and EDC) are capable of predicting temperature and major species profiles; whereas only EDC is able to reliably predict slow-chemistry species. © 2017 Elsevier Ltd
Tabet F.,DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH |
Gokalp I.,French National Center for Scientific Research
Renewable and Sustainable Energy Reviews | Year: 2015
Abstract Biomass co-firing within the existing infrastructure of pulverized coal utility boilers is viewed as a practical near-term means of encouraging renewable energy while minimizing capital requirements and maintaining the high efficiency of pulverized coal boilers. Coal/biomass co-firing is a complex problem that involves gas and particle phases, along with the effect of turbulence on chemical reactions. Computation Fluid Dynamic (CFD) simulations can provide insight to design and operational issues, such as co-firing percentage, load swings, injection location, excess air and air/fuel staging, and predictions related to heat release, unburned carbon, and NOx emissions. The CFD based co-firing tools consist of models for turbulent flow, gas phase combustion, particles dispersion by turbulent flow, coal/biomass particles devolatilization, heterogeneous char reaction and radiation. Additional models related to slagging and fouling can also be found. This paper presents a review on CFD based modeling approaches used to predict the combustion characteristics of co-firing biomass with pulverized coal under air and oxy-fuel conditions. © 2015 Elsevier Ltd.
Mameri A.,University of Oum El Bouaghi |
Tabet F.,DBFZ Deutsches Biomasseforschungszentrum Gemeinnutzige GmbH
International Journal of Hydrogen Energy | Year: 2016
This study addresses numerically the influence of several operating conditions on the structure and NO emissions of a biogas diffusion flame. The analysis is conducted at atmospheric pressure in counter-flow configuration and mixture fraction space. CO2 volume in biogas is varied from 25% to 60%, H2 enrichment from 0% to 20% and the scalar dissipation rate from near equilibrium to near extinction. Particular attention is paid to CO2 chemical effect. CO2 contained in biogas can have chemical effects when it participates in chemical reactions and thermal effects when it acts like a pure diluent. Chemical effects of CO2 are elucidated by using the inert species technique. Flame structure is characterized by solving flamelet equations with the consideration of radiation and detailed chemistry. It is observed that flame properties are very sensitive to biogas composition, hydrogen addition and scalar dissipation rate. CO2 increment decreases flame temperature, mass fraction of chain carrier radicals and NO emission index. Blending biogas with hydrogen increases the mixture heating value and makes the fuel more reactive. Hence, chain carrier radicals and NO index emission are all increased. The chemical effect of CO2 is found to be present overall scalar dissipation rate values where it reduces the maxima of temperature and OH mass fraction and increases the maxima of CO and NO mass fractions. H2 enrichment has a weak influence on CO2 chemical effect. Hydrogen-rich biogas flames produce less NO at high scalar dissipation rates. © 2015 Hydrogen Energy Publications, LLC.
Dahlin J.,University of Rostock |
Dahlin J.,Nuertingen-Geislingen University |
Herbes C.,Nuertingen-Geislingen University |
Nelles M.,University of Rostock |
Nelles M.,DBFZ Deutsches Biomasseforschungszentrum Gemeinnutzige GmbH
Resources, Conservation and Recycling | Year: 2015
Managing digestate output and developing a market for the product is a serious challenge for the biogas industry. Without effective strategies for sustainable management, the large volume of digestate produced by biogas plants may cripple the industry and its potential. Through interviews with diverse biogas stakeholders, we examine current approaches to digestate marketing to identify factors that support and those that inhibit its success. We find that marketing to regions with a nutrient demand or into the non-agricultural sector holds promise. Upgraded digestate products offer increased marketability due to their higher nutrient content and lower water content. Fertilizer and soil manufacturers, farmers, horticulturists and private customers all represent markets for digestate. Current disposal prices range from negative to strongly positive, depending on the regional nutrient availability, agricultural structure, season, feedstock and degree of upgrading. Marketers agree that concealing the biogas origin of digestate products is still necessary to avoid negative perceptions by customers. One implication of this is the need for better understanding by marketers of consumer concerns and preferences, and for better education of consumers regarding the safety and benefits of digestate. Overall, we find that opportunities for digestate marketing remain largely unexploited and marketing strategies remain immature. Our findings should prove helpful to current and future digestate marketers. © 2015 Elsevier B.V. All rights reserved.
Safer K.,University of Science and Technology of Oran |
Tabet F.,DBFZ Deutsches Biomasseforschungszentrum Gemeinnutzige GmbH |
Safer M.,University of Science and Technology of Oran
International Journal of Hydrogen Energy | Year: 2016
This paper reports a numerical simulation of turbulent non-premixed counter-flow syngas flames structure and NO emissions at a high strain rate with a special focus on mixing. The analysis is conducted over a wide range of hydrogen percentage (H2/CO ratio between 0.4 and 2.0) and operating pressure (from 1 to 10 atm). Numerical model is based on RANS (Reynolds Averaged Navier-Stokes) technique including k-ε turbulence model. SLFM (Steady laminar flamelet model) is used for flame structure calculations and EPFM (Eulerian Particle Flamelet Model) is applied for NOx predictions. Mixing is described by mixture fraction and its variance. Radiation effects are also considered. Computational results show an improvement of mixing with hydrogen enrichment and ambient pressure rise. Maximum flame temperature decreases with H2 addition and increases with pressure. NO levels decrease towards hydrogen-rich syngas flames and increase with pressure. Zeldovich route is found to be the main NO formation path in the operating conditions considered. © 2015 Hydrogen Energy Publications, LLC.
Mauky E.,DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH |
Mauky E.,University of Rostock |
Jacobi H.F.,DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH |
Liebetrau J.,DBFZ Deutsches Biomasseforschungszentrum gemeinnutzige GmbH |
And 2 more authors.
Bioresource Technology | Year: 2015
Purpose of this work was the evaluation of demand driven biogas production. In laboratory-scale experiments it could be demonstrated that with diurnal flexible feeding and specific combination of substrates with different degradation kinetics biogas can be produced highly flexible in CSTR systems. Corresponding to the feedings the diurnal variation leads to alternations of the methane, carbon dioxide and acid concentrations as well as the pH-value. The long-time process stability was not negatively affected by the dynamic feeding regime at high OLRs of up to 6kgVSm-3d-1. It is concluded that the flexible gas production can give the opportunity to minimize the necessary gas storage capacity which can save investments for non-required gas storage at site. © 2014 Elsevier Ltd.
Butt S.,DBFZ Deutsches Biomasseforschungszentrum Gemeinnutzige GmbH |
Hartmann I.,DBFZ Deutsches Biomasseforschungszentrum Gemeinnutzige GmbH |
Lenz V.,DBFZ Deutsches Biomasseforschungszentrum Gemeinnutzige GmbH
Biomass and Bioenergy | Year: 2013
The usage of biomass by mankind can be traced back to thousands of years. The biomass utilization in developing countries like Pakistan has always played a major role to fulfill energetic demands of poor inhabitants of the country. Pakistan being an agricultural country has a tremendous potential to utilize agricultural by-products like bagasse, rice husk, cotton stalks etc. The major share of biomass utilization in Pakistan comes from household sector i.e. 76%. The small scale combustion systems used in households for cooking and heating purposes consist of different types of stoves. However, a lot more has to be done in order to harness the full potential of this renewable energy resource and change the technology pattern by overcoming different social, economic, cultural and political barriers. This objective can only be achieved by initiating effective R&D projects throughout the country.© 2013 Elsevier Ltd.