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Industrial Bioprocess Developments for Biogas and Ethanol Production
University of Borås, Faculty of Textiles, Engineering and Business. (Resource recovery)
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Sustainable development
The content falls within the scope of Sustainable Development
Abstract [en]

Current biofuels face a noteworthy misfortune on commercialization because of its economiccomparison with low-cost fuel from the oil reserves. To compete with gasoline as a fuel, thebiofuels need to be economically feasible and demonstrated on a large-scale. Biogas and ethanolhave a great potential as commercial biofuels, even though it has difficulties, for example, highcapitalinvestment, absence of demonstrated innovations, and availability of raw materials and soforth. This thesis focuses on different application-driven bioprocess developments for improvingthe techno-economic feasibility of the biogas and ethanol industries.

The biogas industry was studied from three different perspectives:

1) Modeling approach in which a Process Simulation Model (PSM) model was developed forpredicting the biogas productions, as exploiting new substrates is vital for a biogas industrygrowth. The PSM model was created using Aspen Plus® which includes 46 reactions of differentphases in the Anaerobic Digestion (AD) processes. It also contains certain important processparameters, thermodynamics, rate-kinetics, and inhibitions involved in the AD processes. PSMwas a library model for the AD processes, which was validated against the laboratory andindustrial data. The validation showed that the PSM predicted the biogas production about 5% inexcess, which could ease the biogas industry to predict biogas from new substrates.

2) Simulation approach to study the imperative components affecting the profitability of theplant. For this purpose, a local municipality plant was studied under distinct situations. The choiceof upgrading method, capacity, cost of waste and its processing, number of digesters used, etc.were exploited. The results showed that the collection and transportation fee, landfilling fee, andthe reduced operation of a plant were the main considerations in influencing its profitability.Moreover, it was identified that for bigger cities the decentralization strategy could beat theexpense of collection and transportation of waste, and the plant could obtain a 17.8% return oninvestment.

3) Rethinking digester technology in which the cost of the digester was significantly lessenedusing a cutting-edge textile, which was principally intended for developing countries. The digestercost played an important role in consuming biogas for different applications. The textile digesterwas tested on a laboratory scale, followed by field tests in different countries including India,Indonesia, and Brazil. Textile digesters cost one-tenth of the conventional digesters, and thepayback was more or less between 1–3 years, when replacing the Liquefied Petroleum Gas (LPG)and kerosene as a cooking fuel for households.

When it comes to ethanol, the first generation ethanol production using grains was financiallypossible with a payback of about 13 years. Nonetheless, with the fluctuation of the oil prices, theethanol industries need to look for alternative sources of revenues. Different retrofits wereconsidered, including the effect of thin-stillage/whole-stillage to ethanol and biomass, in additionto the integration of the first and second generation ethanol production. The results revealed that4% additional ethanol could be obtained when the thin-stillage was converted into ethanol andfungal biomass, while the payback was reduced to 11.5 years. The integration of the first andsecond generation ethanol production revealed that it has a positive influence on the overalleconomics of the process with a payback of 10.5 years. This could help the ethanol industries toconsider a revamp for a better environmental, economic, and energy efficient process.

Place, publisher, year, edition, pages
Borås: Högskolan i Borås, 2015. , 64 p.
Series
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 71
Keyword [en]
biogas, ethanol, process design, techno-economic analysis, simulation, modeling
National Category
Environmental Biotechnology
Research subject
Resource Recovery
Identifiers
URN: urn:nbn:se:hb:diva-668ISBN: 978-91-87525-71-1 (print)ISBN: 978-91-87525-72-8 (print)OAI: oai:DiVA.org:hb-668DiVA: diva2:848465
Public defence
2015-11-06, E310, Allegatan 1, Borås, 10:00 (English)
Available from: 2015-10-02 Created: 2015-08-25 Last updated: 2017-05-04Bibliographically approved
List of papers
1. Impacts of retrofitting analysis on first generation ethanol production: process design and techno-economics
Open this publication in new window or tab >>Impacts of retrofitting analysis on first generation ethanol production: process design and techno-economics
2014 (English)In: Bioprocess and biosystems engineering (Print), ISSN 1615-7591, E-ISSN 1615-7605, Vol. 38, no 2Article in journal (Refereed) Published
Abstract [en]

More than half of the bioethanol plants in operation today use corn or grains as raw materials. The downstream processing of mash after fermentation to produce ethanol and distiller grains is an energy-demanding process, which needs retrofitting for optimization. In addition, the fluctuation in the ethanol and grain prices affects the overall profitability of the plant. For this purpose, a process simulation was performed in Aspen Plus® based on an existing industrial plant located in Sweden. The simulations were compared using different scenarios including different concentrations of ethanol, using the stillage for biogas production to produce steam instead of distiller grains as a by-product, and altering the purity of the ethanol produced. Using stillage for biogas production, as well as utilizing the steam, reduced the overall energy consumption by 40 % compared to the plant in operation. The fluctuations in grain prices had a high impact on the net present value (NPV), where grain prices greater than 349 USD/ton reached a zero NPV. After 20 years, the plant in operation producing 41,600 tons ethanol/year can generate a profit of 78 million USD. Compared to the base case, the less purified ethanol resulted in a lower NPV of 30 million USD.

Place, publisher, year, edition, pages
Springer, 2014
Keyword
Resource Recovery
National Category
Industrial Biotechnology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-1929 (URN)10.1007/s00449-014-1278-2 (DOI)2320/14367 (Local ID)2320/14367 (Archive number)2320/14367 (OAI)
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2016-10-07Bibliographically approved
2. Experimental and economical evaluation of a novel biogas digester
Open this publication in new window or tab >>Experimental and economical evaluation of a novel biogas digester
2013 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 74, 183-191 p.Article in journal (Refereed) Published
Abstract [en]

Many developing countries face an energy demand to satisfy the daily needs of the people. Household biogas digesters are among the interesting solutions to meet the energy demands for cooking and lighting, and at the same time taking care of the kitchen wastes. In this study, a novel textile-based biogas digester was developed. The digester was evaluated for biogas production from a synthetic nutrient and an organic fraction of municipal solid waste (OFMSW) as substrates for more than a year. The obtained biogas productivity in both experiments was 570 L/kgVS/day, which indicates that the digester is as efficient in handling of OFMSW as the synthetic nutrients. Based on the obtained biogas production data, the techno-economic evaluation and sensitivity analysis for the process were performed, replacing LPG and kerosene consumption with biogas in households. A 2-m3 digester can supply the fuel needed for cooking for a family of 4–6 people. The sum of investment and 15-years operational costs of this digester was 656 USD, which can be compared with 1455 USD for subsidized-LPG and 975 USD for kerosene, respectively. The results from the sensitivity analysis show that it was a positive investment, unless the price of kerosene goes down to less than 0.18 USD/L.

Place, publisher, year, edition, pages
Elsevier Ltd, 2013
Keyword
Household digesters, Biogas, Cooking fuel, Techno-economic analysis
National Category
Engineering and Technology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-1584 (URN)10.1016/j.enconman.2013.05.020 (DOI)000325302700020 ()2320/12380 (Local ID)2320/12380 (Archive number)2320/12380 (OAI)
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2016-07-13Bibliographically approved
3. Household biogas digesters: a review
Open this publication in new window or tab >>Household biogas digesters: a review
2012 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 5, no 8, 2911-2942 p.Article in journal (Refereed) Published
Abstract [en]

This review is a summary of different aspects of the design and operation of small-scale, household, biogas digesters. It covers different digester designs and materials used for construction, important operating parameters such as pH, temperature, substrate, and loading rate, applications of the biogas, the government policies concerning the use of household digesters, and the social and environmental effects of the digesters. Biogas is a value-added product of anaerobic digestion of organic compounds. Biogas production depends on different factors including: pH, temperature, substrate, loading rate, hydraulic retention time (HRT), C/N ratio, and mixing. Household digesters are cheap, easy to handle, and reduce the amount of organic household waste. The size of these digesters varies between 1 and 150 m3. The common designs include fixed dome, floating drum, and plug flow type. Biogas and fertilizer obtained at the end of anaerobic digestion could be used for cooking, lighting, and electricity.

Place, publisher, year, edition, pages
M D P I AG, 2012
Keyword
Resource Recovery
National Category
Industrial Biotechnology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-1316 (URN)10.3390/en5082911 (DOI)000308241500017 ()2320/11321 (Local ID)2320/11321 (Archive number)2320/11321 (OAI)
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2016-09-29Bibliographically approved
4. A Novel Process Simulation Model (PSM) for Anaerobic Digestion Using Aspen Plus
Open this publication in new window or tab >>A Novel Process Simulation Model (PSM) for Anaerobic Digestion Using Aspen Plus
2014 (English)Other (Other academic)
Abstract [en]

A novel process simulation model (PSM) was developed for biogas production in anaerobic digesters using AspenPlus®. The PSM is a library model of anaerobic digestion, which predicts the biogas production from any substrate at any given process condition. A total of 46 reactions were used in the model, which include inhibitions, rate-kinetics, pH, ammonia, volume, loading rate, and retention time. The hydrolysis reactions were based on the extent of the reaction, while the acidogenic, acetogenic, and methanogenic reactions were based on the kinetics. The PSM was validated against a variety of lab and industrial data on anaerobic digestion. The P-value after statistical analysis was found to be 0.701, which showed that there was no significant difference between discrete validations and processing conditions. The sensitivity analysis for a ±10% change in composition of substrate and extent of reaction results in 5.285% higher value than the experimental value. The model is available at http://hdl.handle.net/2320/12358 (Rajendran et al., 2013b).

Place, publisher, year, pages
Elsevier BV, 2014
Keyword
Resursåtervinning
National Category
Engineering and Technology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-5381 (URN)10.1016/j.biortech.2014.01.051 (DOI)24524857 (PubMedID)2320/12358 (Local ID)2320/12358 (Archive number)2320/12358 (OAI)
Available from: 2015-12-17 Created: 2015-12-17 Last updated: 2016-05-13
5. Uncertainty over techno-economic potentials of biogas from municipal solid waste (MSW): A case study on an industrial process
Open this publication in new window or tab >>Uncertainty over techno-economic potentials of biogas from municipal solid waste (MSW): A case study on an industrial process
2014 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 125, 84-92 p.Article in journal (Refereed) Published
Abstract [en]

In this study, biogas production from the organic fraction of the MSW (OMSW) was simulated in six different scenarios, using Aspen plus® based on industrial data. The economic evaluations were made using the Aspen process economic analyzer, considering the plant size and the upgrading methods. The base case had an annual processing capacity of 55,000 m3 OMSW. The capital costs and the net present value (NPV) after 20 years of operation were 34.6 and 27.2 million USD, respectively. The base case was compared to the modified scenarios, which had different upgrading methods, processing capacities, addition of biogas from wastewater sludge treatment, and variation of the substrate (OMSW) between ±200 USD/ton. The sensitivity analyses were carried out considering the cost of the OMSW imposed on citizens for collection and transportation of wastes and the different sizes of the plant. The result suggests that producing biogas and selling it, as a vehicle fuel from OMSW is a profitable venture in most scenarios. However, there are some uncertainties, including the collection and transportation costs, landfilling fee, and process operation at lower capacities, which affect its profitability.

Place, publisher, year, edition, pages
Pergamon, 2014
Keyword
Process design, Techno-economic analysis, Biotechnology
National Category
Chemical Engineering Industrial Biotechnology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-1852 (URN)10.1016/j.apenergy.2014.03.041 (DOI)000336778900008 ()2320/13657 (Local ID)2320/13657 (Archive number)2320/13657 (OAI)
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2016-03-15

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