Workshop 3 Modeling of Biogas production

Transcription

1 Workshop 3 Modeling of Biogas production The field Introduction and history The world s oil reserves are getting depleted and more and more concern is given to the effect of fossil fuel usage on the environment. In this context alternative fuels like biogas (methane produced from biological processes) are highly interesting. Biogas is produced using microorganisms that transform the raw material (in Sweden usually waste) into methane and carbon dioxide. The fact that methane origins from microorganisms was first described in an article by Popoff in 1875 (Lubken et al., 2010). In 1884 Louise Pasteur produced biogas from horse dung to power the street lighting of Paris and after that biogas was produced in different ways from different feedstock until the interest more or less died out in 1955 due to large availability of cheap oil. The interest was ignited again in 1970s due to the oil crisis. The interest was further stimulated during the 1990s because of profitability of using biogas and increased cost of waste disposal. Germany is the leading country in biogas production in Europe. In 2000 there were 850 biogas plants in Germany, in 2006 the number was 3500 biogas plants and there are plans to construct biogas plants until year (Dueblein and Steinhauser, 2008) Germany UK Italy Spain France The Netherlands Austria Denmark Belgium Others Figure 1 - Percentage of total biogas produce in Europe (in total 4.9 million tons of oil equivalent). Source: Biogas Barometer 2008 from EuroStat

2 The process The biogas process can be divided into four steps: hydrolysis, acidogenic phase, acetogenic phase and methanogenic phase, see Figure 2. Hydrolysis Acideogenic phase Acetogenic phase Methanogenic phase Figure 2 - The biogas process divided into four steps Hydrolysis The incoming substrate is built of carbohydrates, proteins and fats and these compounds are not water-soluble. These undissovled compounds are broken down into water-soluble fragments (monomers) by exoenzymes produced by bacteria. The bacteria can produce two kinds of enzymes, endoenzymes and exoenzymes. The difference is that endoenzymes brake down substances within the bacteria cell while exoenzymes are released from the bacteria and brakes down substances outside the bacteria cell. Not all bacteria produce exoenzymes and typically one exoensyme only degrade one type of substrate so a large group of bacteria is needed for this process. The products of this stage is some simple sugars, fatty acids and amino acids. (Gerardi, 2003; Dueblein & Steinhauser, 2008) Acidogenesis (acid formation) The monomers that were the products of the hydrolytic phase can now be taken up by the bacteria, even those that do not produce exoenzymes, and be further degraded into short-chain organic acids, alcohols, hydrogen and carbon dioxide. Acetogenesis (acetate formation) Acetogenesis can either be seen as a separate step or as a part of the acetogenic phase. The product of the acetogenic phase is acetate. Acetate is important because it is the primary substrate used by methanogenic bacteria. Methanogenic phase (methane formation) In this step the methanogenic bacteria form methane using mostly acetate, carbon dioxide and hydrogen gas. Methane can also be formed from some other organic compounds but all compounds that are not degraded by the methanogenic bacteria will accumulate in the digester. There is no bacteria species that is the only one responsible for a single step, rather it is a group of different bacteria (even though they have similarities). There are also some bacteria that compete with the good bacteria. One kind of such bacteria are sulfate-reducing bacteria that also uses

3 acetate, hydrogen and carbon dioxide (like the methanogenic bacteria) but produces hydrogen sulfide. There are different temperatures that are optimal for different species and there are also some substances that are toxic for some species. So even though that biogas have a long history the process behind it is quite complex and there is still much to learn about it and good possibilities for improvement and optimization. There are questions concerning the inhibition of different substances, like ammonia, on the process and discussions about different pretreatment (Mata-Alvarez et al., 2000). Reliable mathematical models can be of great assistance to facilitate experiments and improvements of the process and offer greater possibility to control the process. The development of mathematical models for describing the process also has a long history. The first dynamic mathematical model was developed by Andrews in 1969 (Lubken et al., 2010). The model and many following models, was based on the concept of rate-limiting step. The models assumed that the acetoclastic methanogenic process step (acetate being formed into methane) was rate limiting and therefore the models only considers this step. However later studies found this is not always true instead the first step, hydrolysis, was more likely to be limiting (Tomei et al., 2009). Models Models can be classified according to a number of different criteria. For example can models be either dynamic or static. A dynamic model considers time as variable while a static model does not. In the same manner models can be 0-, 1-, 2- or 3-dimensional. A 0-dimensional model is a spaceindependent model; it does not include any spatial variables at all. Furthermore a model can be a theoretical model or an experimental model. A theoretical model is, as the name indicates, based on the theoretical knowledge of how the system works. As such it could be expected to be able to predict the behavior of systems of the same kind. An experimental model is developed by experimentally investigating the correlation between different parameters. An experimental model is therefore only valid for the particular system for which it was developed. When a model is developed there are a number of steps that should be followed. The first step is problem specification. What is the aim of the model? Is it intended for research, operation/control of for design? What is the required degree of accuracy? The next step is model development, in which the equations that should represent the process are established. The third step is preliminary verification, in which a first analysis of the identifiability of the model is made, is there only one result for a set of parameters? An initial study of parameter sensitivity, in which interval does the model behave as predicted? If the model is identifiable or the interval does not match the intended interval then the development returns to the first or the second step. (Sanders et al., 2003) After the first three steps have been concluded some kind of model concept has been developed. The fourth step is experimental design in which optimum set of test that will produce the best data for model fitting and validation is chosen. The step after that is parameter estimation in which the model is fitted to experimental data by adjusting the model parameters. The last step is model validation in which the model is evaluated to see of accurate it really is. The predictions made by the model are compared to actual (experimental) data. (Sanders et al., 2003)

4 Problem specification Model development Model preliminary verification Experimental design Parameter estimation Model Validation Figure 3 - The steps to develop a dynamic model of anaerobic digestion (adapted from (Sanders et al., 2003) When discussing mathematical models of biogas production two terms used for describing the equations are often encountered: first-order and Monod-type. A first-order equation has only one variable. Monod-type equations or equations based on Monod-kinetics are equations that are based on the Monod equation, which is a semi-empirical equation that describes bacteria cell growth. Tomei et al. made a review on the modeling of anaerobic digestion of sludge and divided the models in after three main groups: simple substrate characterization models, intermediate substrate characterization models and advanced substrate characterization models. As the name suggests the models are classified according to how advanced the characterization of the substrate is. The simple substrate characterization models do not distinguish between different components of the substrate, these models are early models (1980s) and are of rate-limiting step kind. The modern models are classified as advanced characterization models. Tomei et al. describes three such models: Angelidaki et al Model, Siegrist et al. Model and Anaerobic Digestion Model No. 1 (described in more detail below). (Tomei et al., 2009) In Angelidaki et al s model the substrate is defined by its organic and inorganic composition. The organic components are carbohydrates, proteins, lipids and their degradation intermediates. The inorganic components included are: ammonia, phosphate, carbonate, hydrogen sulfide, anions and cations. There are six kinetic equations used in the model, one for each step. The steps are: (1) hydrolysis, (2) acidogenic glucose-degrading, (3) lypolytic, (4) LCFA-degrading acetogenic, (5) VFAdegrading acetogenic and (6) aceticlastic methanogenic steps (Angelidaki et al., 1999). The models have become more and more complex but more complex is not necessarily better. The level of complexity needed is dependent on the purpose of the model. For example Sanders et al. (2003) describes that for design of a digester simple models, so called steady state models, are popular.

5 ADM1 In 1998 the International Water Association (IWA) formed a task group called the IWA Task Group for Mathematical Modelling of Anaerobic Digestion Processes to create a common platform for anaerobic process modeling and simulation. The model was first presented in 2001 and is called Anaerobic Digestion Model No. 1 (ADM1). The task group had several members and it can be noted that both Angelidaki and Siegrist (mentioned above as researchers behind two of the more modern models) were members of it. The model considers both biochemical processes (involving living organisms) as well as physico-chemical processes (not involving living organisms). The biochemical processes described are disintegration, hydrolysis, acidogenesis, acetogenesis and methanogenesis. Concerning the physico-chemical processes, liquid-gas processes (liquid-gas transfer) and liquidliquid processes (ion association/dissociation) are described but not solid-liquid processes due to difficulties in describing them. (Batstone et al., 2002). However, Kleerebezem & Loosdrecht have pointed out some weaknesses in ADM1. Their three main points was that there was inaccuracies in the stoichiometry, some problems with the solid retention time and that there is a lack of restrictions for the thermodynamic boundaries (some reaction where predicted to occur at ΔG-values greater than 0. (Kleerebezem and van Loosdrecht, 2006a). The ADM1 has been used by several researchers. Blumensaat and Keller (2005) used it to model a two-stage digester (a digester that has a thermophilic pre-treatment stage and a mesophilic main treatment stage) and needed to make several modifications in order to for the model to be in agreement with the data from their pilot-scale process. They concluded that it became clear that the current understanding of modeling anaerobic digestion processes is insufficient, reflected in the necessity to implement balance terms and that even though the curve fitting resulted in a good agreement, principally, a parameter optimization for a structural model with such a high number of parameters requires proof with data from several dynamic experiments (Blumensaat and Keller, 2005). Derbal et al. used it to model co-digestion of organic waste with activated sludge and found it the model to show acceptable simulating results, regarding the number of parameters involved and processes considered. However the authors mean that the model is limited in simulating complex processes and cannot reproduce intimate variations of the different parameters, but an average trend is exhibited. They however admit that it may be due to that some of the input parameters were obtained from literature. (Derbal et al., 2009) Furthermore, Lübken et al used ADM1 to model an anaerobic digester with cattle manure and energy crops feed stock. They also had some trouble in setting up the parameters for the model and also utilized literature values to some extent (Lubken et al., 2007). Ramirez et al (2009) thought that the first-order kinetics used in ADM1 to describe disintegration and hydrolysis was not accurate enough. They therefore took ADM1 and modified it. The model as well as the original ADM1 was compared to experimental results of anaerobic digestion of a thermally pretreated substrate. They found that their new model could quite accurately (more accurately then the ADM1) describe the effects of the pretreatment. The problems encountered by different authors illustrates one of the greater difficulties with ADM1, that it requires a detailed characterization of the substrate (Daels et al., 2009, Kleerebezem and Van Loosdrecht, 2006b), requiring measurements that are not usually made when investigating a biogas plant or wastewater treatment plant and that might not be possible to do on a regular basis. There

6 have been some attempts to circumvent this problem. Kleerebezem and Van Loosdrecht described one method for waste characterization that only needs measurements of Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), organic nitrogen (N org ) and alkalinity (Alk), that, according to the authors, are usually included in periodic measurements of anaerobic bioreactors. (Kleerebezem and Van Loosdrecht, 2006b). Zaher et al. also created a procedure to characterize waste in order to generate input variables for ADM1. They based their procedure on methods previously created be others, among them Kleerebezem s and Van Loosdrecht s method. The measurements they considered available was: total COD (CODt), soluble COD (CODs), VFA, total carbon (TC), total inorganic carbon (TIC), TKN, TAN, total phosphorous, orthophosphate (orthop), total alkalinity (Scat), total solids, and total volatile solids (TVS) (Zaher et al., 2009a). They later on generalized their procedure and implemented it as a general transformer model that can interface ADM1 to any combination of co-digestion wastes (Zaher et al., 2009b) Artificial neural network models However, ADM1 is not the only model used at present. There are other models as. One such model is a model developed Abu Qdais et al which models biogas production with the aim of optimizing, using an artificial neural network (ANN). The input into their model was temperature, total solids, total volatile solids and ph and the output was the percentage of methane in the gas stream. The input data was gathered from a full-scale biogas plant and there was a good match between the model data and the actual data. (Abu Qdais et al., 2010). There is also an ANN model developed by Kanat & Saral (2008) that studies biogas production in a thermophilic digester. As input parameters they selected organic loading rate, total volatile fatty acids of the effluent (outcoming water), influent (incoming water) effluent alkalinity, influenteffluent ph and temperature of the reactor. The output parameter is the biogas production of the digester. The ANN model was capable of prediciting the amount of biogas produced quite well even though estimation of small change swas abetter then the estimation of large fluctuations. There are been a few other artificial neural networks models in the field but I have seen no other that has been directly aimed at modeling the amount of biogas produced. Other models Nopharantana et al. created a model describing the operation of a sequential leach bed even though the focus was not on biogas production (Nopharatana et al., 2003). Nopharantana et al. also created a model for anaerobic batch digestion of municipal solid waste (MSW). The model is described as a dynamic mass balance. The substrate is represented as two components, an insoluble part and a soluble part, the biodegradable proportions of these parts were determined by experiments. Four bacterial groups were identified and stoichiometry equations were set up for each group as well as rate expressions. The kinetic parameters was then either determined through experiments or from literature. (Nopharatana et al., 2007) Daels et al uses the method for waste characterization and estimation of biogas produced made by Kleerebezem and Van Loosdrecht as a model for digestion of solid waste. They verify their model against an experimental results from a lab-scale set-up. They conclude that the results from the model are not significantly different from experimental set-up but I do not completely agree on that.

7 I have also look what program have been used by the different authors for modeling their system and from where they got the experimental data to which they compare the results of their models, see Table 1. For the selected articles, when it has been stated, matlab has been used for simulations. Furthermore, all the models except for the model by Daels et al. are dynamic and none of them consider more then considers the dimension of space. The most common source for experimental data is either lab-scale or pilot-scale even though there are those who have collected data from a full-scale plant. When it comes to lab-scale or pilot-scale my table might not be completely accurate since different authors seem to denot lab-scale and pilot-scale differently. My idea was that lab-scale was anaerobic digestion in a small glas container (10 litre or less) and pilot-scale was more like a 1000 litre. I have also tried to denote them batch, semi-continous and continous which denotes how the digester have been feed. Authors Program/language used Experimental values from Daels et al. (2009) not stated lab-scale, batch Zaher et al (2009) C/Matlab-Simulink pilot-scale, semicontinous Derbal et al (2008) Matlab/Simulink full-scale, continous Lübken et al (2007) SIMBA software under Matlab-Simulink pilot-scale, continous environment Simeonov & Stoyanov not stated lab-scale (2003) Nopharatana et al not stated lab/pilot-scale, batch (2002) Nopharatana et al Matlab pilot-scale, batch (2007) Blumensaat & Keller (2005) Matlab/Simulink pilot-scale, semicontinous Qdais et al (2010) not stated full-scale, continous Hoh and Cord-Ruwisch (1996) not stated Not stated Angelidaki et al. (1998) not stated lab-scale + full-scale Ramirez et al (2009) Matlab/Simulink lab-scale, batch Kanat & Saral (2008) not stated pilot-scale, continous Table 1 - Examination of the models of the different authors Research community Conferences It is hard to find conferences only related to my field, the only one I found that is only about anaerobic digestion is IWA specialist conference on anaerobic digestion, otherwise, according to my colleagues, there are more general conferences that I can attend. General conferences can be focused on waste handling/utilization or bioenergy or similar. I got the impression that there are no conferences in my department that people generally attend to; rather interesting conferences are found from time to time. The conferences that I found were: Name IWA specialist conference on anaerobic digestion Interval once every 3rd year

8 International conference on Applied Energy once every year* Venice 2010 Symposium Once ever 2nd year Renewable Energy Research Conference? IWA/WEF wastewater treatment modelling seminar once every 2nd year* International Renewable Energy Congress once every year* *= only been held once before IWA specialist conference on anaerobic digestion The only conference of two that I have heard of that is specialized on anaerobic digestion. It seems to be held every 3 rd year in different location. The conference is hosted by the International Water Association (IWA). The conference will be held for the 12 th time this year. One of the topics of the conference is AD (anaerobic digestion) modeling. Of the papers that are submitted and accepted for oral presentation a selection number will be considered through another review process for presentation in Water Science and Technology. International symposium of anaerobic digestion of solid waste & energy crops This conference is also hosted by IWA and it is the second conference I have heard about that is specialized on anaerobic digestion. Furthermore, it also seems to be held every 3 rd year (The years it has been held are 1992, 1999, 2002, 2005 and 2008). It then should be held again in 2011 but I have not seen any announcement yet (it is probably too early). International Symposium on Energy from Biomass and Waste The conference is also called Venice 2010 Symposium this year and it is the 3 rd time this conference is held. The second time was in 2008 (when it was called Venice 2008 Symposium). I don t know which the first time this conference was held was but if there is a pattern to it, it should have been held in 2006 and also in Venice. The conference is organized by International Waste Working Group (IWWG). One of the topics of the conference is anaerobic digestion. The papers will be published on a cd that will be distributed to the attendants of the conference and selected papers will be considered for publication in the IWWG journal Waste Management or included in Monographic volumes edited by distinguished international experts (which I do not know what they mean by that). International Conference on Applied Energy The conference is hosted by Applied Energy (I think), a journal. It was held the 1 st time in 2009 and the 2 nd time Selected papers will be published in a special edition of Applied Energy and a number of other international peer-reviewed journals. Renewable Energy Research Conference A generable conference that might be of interest. It says on the homepage [in] addition to interesting lectures on general issues concerning renewable energy, there will be detailed scientific parallel sessions within wind power, solar cells, hydropower, bioenergy, transport, ocean energy, zero emission buildings, as well as societal aspects of energy production and utilization. It is also described as Norway s largest research conference on renewable energy. It will be held now in 2010 but I do not know if it has been held previously or if it will be held again. IWA/WEF wastewater treatment modeling seminar This conference as the name says is focused modeling of wastewater treatment which is not my field. But I thought that this conference may be of interest anyway since the models for anaerobic

9 digestion of solid waste are usually adaptations of models for wastewater treatment. It was first held in 2008 and it was held for the 2 nd time this year, so at this rate it will be held again in International Renewable Energy Congress This is a general conference that will be held this year and seemed to have been held only once before in The sessions of the conference is wind energy, photovoltaic energy, solar thermal energy, hybrid energy and other renewable energies. My research would then fit into other renewable energies. They also have a number of scopes, one of which is modeling and simulation which would then be the correct scope for me. The best papers that are presented will be selected for possible publication in referred international journals. Researchers One of the names I encountered most is Batstone, since he is one of the front names for ADM1, who is currently a researcher at Advanced Wastewater Management Centre at the University of Queensland, Australia. He wrote a doctoral thesis related to the subject in 2000 and then catalyzed the work on the ADM1. Another frequent name is frequent is Keller, was involved in ADM1 and has written several papers on the subject. Keller is also a researcher at the University of Queensland. Angelidaki wrote together with two other researchers several articles, developing a model in the 1990s, which was a part of a group of models providing the foundation for ADM1. Angelidaki was also a member of the task group behind ADM1. Post ADM1, Angelidaki has only been the main author for one article on modeling. However she appears in a lot of different publications upon biogas and seem to be into most parts of the field. Angelidaki belongs to the Department of Environmental Engineering, Technical University of Denmark. Vavilin, was also involved in the creation of ADM1 and has written several papers on the subject of modeling. Vavilin belongs to the Water Problems Institute, Russian Academy of Sciences, in Moscow but also to some French institute. Lübken, has written several articles in the field and belongs to the Institute of Environmental Engineering, Bochum, Germany Zaher, is another researcher with many publications, belongs to the Department of Biological Systems Engineering, Washington State University, USA. Jeppson, a Swedish researcher who belongs to the Department of Industrial Electrical Engineering and Automation, Lund University and is described as a well recognized professor in the field by one of my colleagues. His Phd thesis is called Modelling aspects of wastewater treatment processes. Journals Journals was also difficult in the same manner as conferences. I looked at 24 articles that I found in the field to see in which journals they had been published. Only one journal had a significant larger amount of published articles and that was the journal Water Research. Otherwise only 1-2 papers had been published in the same journal. The spread for the 24 articles can be seen below, including the impact factor of the journal.

10 Name No. of Impact articles factor Water Research 8 3,587 Bioresource technology 2 4,453 Biotechnology and Bioengineering 2 3,04 Biochemical Engineering Journal 2 1,889 Chemical engineering journal 1 2,813 Applied Microbiological Biotechnology 1 2,569 Waste management 1 2,208 Chemical engineering science 1 1,884 Resources, conservation and recycling 1 1,133 Water Environment research 1 1,12 Water Science & Technology 1 1,005 Environmental Modeling & Assessment 1 0,754 Environmental Technology 1 0,674 Chemical and Biochemical Engineering Quarterly 1 0,353 My Work It is somewhere around here I come in. I will be part of two projects related to biogas production. The first one is called REMOWE (Regional mobilization of waste-to-energy) in which I will only (as it looks now) review the present situation of the modeling of biogas production (and also gasification). In the other project I will model biogas production with the focus on control and optimization. My idea is to see what the best practice according to literature is and utilize that to create a model of the anaerobic digestion but also of the rest of the biogas plant. The model will be validated using real data from a biogas plant here in Västerås but there is also the possibility of using additional data from a wastewater treatment plant in Eskilstuna. There are not many articles that discuss the modeling of anaerobic digestion of municipal waste which is what I wish to look at. Anaerobic digestion of wastewater is what is most commonly discussed even though there seem to be more and more of articles related directly to my project in recent years. What I have done so far I have been trying to use the method by Kleerebezem and Van Loosdrecht for characterization of the waste and for estimation of the amount of biogas produced, the same one as has been used by Daels et al. (2009). I have written the code for the model but I do not yet have a complete set of data for the model. There are five parameters that need to be entered into the model for it to calculate the amount of biogas that should be produced: bicarbonate alkalinity, volatile fatty acids, organic nitrogen, COD (chemical oxygen demand) and TOC (total organic carbon). I can calculate bicarbonate alkalinity from alkalinity test, so then alkalinity needs to be tested. The organic nitrogen can be calculated if the total amount of nitrogen is known as well as the amount of ammonia. COD and TOC have specific measurements test. So the parameters I need measurements of are: Alkalinity

11 VFA Ammonia nitrogen Total nitrogen COD TOC Amount of biogas produced Methane percentage of the produced biogas ph in the reactor The amount of biogas produced and the methane percentage are measured daily at the biogas plant. Alkalinity, VFA, ammonia seemed to be measured once a week while total nitrogen, ammonia nitrogen and ph seemed to be measured by an external lab 2-4 times a month. TOC and COD are therefore missing. I have an average COD from a period of six months that were made during an evaluation of the reactor. TOC I do not have for the reactor at all (I have some literature value though). Another problem that I have encountered is that the model I am looking at is a static model, from a given set of parameters it calculates an amount of biogas produced. The full-scale biogas plant I am looking at is continuously fed, therefore it is hard to say when the incoming substrate will be transformed into biogas and how much what substrate contributes. Daels et al. who previously used the model made lab-scale experiments, in which they put in a certain amount of substrate and they could measure exactly how much biogas came out. But in my continuously feed reactor it is not possible to what input the output biogas is related to. I have submitted an abstract for the Venice 2010 symposium which has been accepted for oral presentation. The next step In order to make a better evaluation of the model I will make measurements of the COD and the TOC of the material going into the digester. I also intend to measure the other parameters at the same time so that I have a matching set of parameters. I intend to measure these parameters over a time period so that I can see how they vary. The measurement over a period of time might be a way of circumventing the problem of batch reactor vs. continuously feed reactor since the trend of biogas output from the model might match the trend of the actual output. When this has been completed I will start writing the article for the Venice 2010 symposium or at least the base of the article. I might have gotten more ideas for the articles or the results might have been so good so that I might want to add something when the basic article has been written. After I am finished with this article I will start working on the next step. I think I want to try another kind of model. Either another simple kind that I have found in literature or it might be of interest to try use the ADM1 but as described by other, the waste characterization is a problem. I do not have enough data for a complete waste characterization. It is possible that the model can be implemented anyway by using data from the literature as some other researchers in the field have done or use one of the interfaces created or the method by Kleerebezem and Van Loosdrecht. If think that the ADM1 or an ANN model are the two kinds of models that are most likely to actually predict the behavior of the digester in such a way that it can be used for diagnosis and control of the system.

12 I hope that the result from the first modeling will give me ideas for how I should proceed. My next step I hope to put into a preliminary short paper that I will submit for poster presentation at the IWA specialist conference on anaerobic digestion. The reason that I really want to submit something for this conference is that is the only way I will be able to go to it since at my department we only attend conferences in which we will present something. Uses of the model Uses of the model is a very important question since it influences the specification of requirements for the model. Ideally, I would like to use it to evaluate different scenarios, like different pretreatments but also evaluate to evaluate economical feasibility. I am not interested in developing a new model just two find some model that works or could be adapted to the process which I am looking at. There is also an interest in my department to study diagnosis and control but it is not my main interest. Research questions How can a biogas production plant with a continuously fed digester be modeled with enough accuracy to evaluate different pretreatments and other changes to the process? o Are existing models capable of predicting the workings of a full-scale continuously feed anaerobic digester? o If not, how can they be altered so that they can alternative, how can a model be created that can predict the behavior of a full-scale continuously feed anaerobic digester? Expected results I do not expect that the first model will make a very good fit with the actual process. It is based on too many assumptions. The process varies a lot and there are many factors that can influence it. I believe that there is a model that could describe the process but there may be need of adjustments for it to fit the process I am looking at. Time plan I have made a preliminary time plan for my work until my licentiate: Tasks/Papers Biogas 1st model Biogas 2nd model REMOWE litt. study Biogas complete cycle May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Be ready to submit Be ready to submit Submitt paper to AD12 Be ready to submit licenciate proposal Submitt paper to Venice 2010

13 Activities Make the measurements I need for the current modeling I am looking at. These measurements I will also use to see how much the different parameters vary and how they correlate to the biogas production. Submission of paper to the Venice 2010 symposium, as I mentioned my abstract was accepted and I now need to prepare and submit the full paper. The deadline for the submission of the full paper is July 31th, including short CV. The investigation of how the amount of biogas produced correlate to the parameters I measure could along with some idea for a model make up a shorter paper. Submission of short paper for the IWA specialist conference on anaerobic digestion (AD12). I want to try to submit some short paper for this conference and I hope to include some preliminary results for my future work. The goal is to be accepted for poster presentation so that I can attend the conference and gain new ideas. The deadline for submission is June 15 th. I will get notification of acceptance on July 15 th. I will try to make a better model of the biogas process. I hope that investigation of the correlations will give me some new ideas. I will either try to go with an implantation of ADM1 or an ANN- model. I will take an online course in microbiology this autumn. If I get accepted for AD12 I will attend the conference October 31th to November 4 th.the last day to register if I get accepted is July 30 th. If they are still okay with my paper I will attend the Venice 2010 symposium November 8 th to November 11 th. Registration for the conference has already been made. Milestones Getting my first accepted abstract (the abstract for Venice 2010 symposium) Submitting my first paper (the paper I submit to Venice 2010 symposium) Going on my first conference (AD12 or Venice 2010 symposium) My first published paper A working dynamic model Having three publications My first published paper in a journal Completing a licentiate proposal Presenting my licentiate Courses So far I have taken 16,5 credits in courses and when I finish the courses that I am taking right now, I will receive another 13,5 credits which will be enough for my licentiate (3 of the credits might not be finished since it is given for a course in which a group is writing a review paper and that review paper might not be finished). Beside the course I will take this autumn I will not do any more courses until after my licentiate.

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