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Historically, air and water have been considered common property resources and, therefore, over utilized as waste receptors. Dairy waste is a leading environmental concern in the North Bosque River watershed in Texas. Changing societal attitudes are forcing dairies and policymakers to balance environmental concerns with farm profitability. Dairies are entering a realm filled with technologies to combat waste concerns. Anaerobic digester technology may play a role in helping dairies balance profit and the environment. Digesters capture methane from livestock waste and transform it into electricity which can be sold to utilities or used on-farm. Because a digester facility is confined, air and water pollution can be reduced. Technological advancement and institutional factor changes allowing the sale of on-farm produced electricity and green power requirements have increased the economic feasibility of digesters. The study of the economic implications of anaerobic digesters for Texas dairies provides producers and policymakers with information to make good decisions concerning adoption and subsidization of this technology. At the beginning of this study, no digesters were operating in Texas. Dairies operating digesters in four states, therefore, were interviewed on-site to provide necessary data. The expected net present value, E(NPV), of a plug-flow digester is negative with and without selling electricity, indicating it should not be constructed based strictly on its financial contribution. At the current electricity-selling price, digesters are less economically feasible than current waste management strategies, lagoons, even after considering potential environmental penalties. However, selling electricity and capturing by-product heat for cost savings makes the digester's E(NPV) less negative than lagoons. The E(NPV) of a covered lagoon digester is positive. This indicates digesters are a potentially feasible waste management strategy. For plug-flow digesters to show a positive E(NPV), the selling price needs to be approximately 82.38% higher than the current price. The breakeven selling price is 12% higher than the current price. Below the breakeven price, lagoons have a larger E(NPV) than plug-flow digesters, therefore making lagoons the preferred waste management strategy. Results suggest changes in rules and technology efficiency make digesters economically competitive with current waste management systems.

First generation bioethanol generated from feedstocks is a sustainable alternative to fossil fuels, and the demand for fuel ethanol has promoted studies on the use of the grain as feedstock. This thesis describes various process designs and the economic feasibility for producing the main product ethanol and other by-products such as Biogas and DDGS (Distillers Dried Grains with Solubles) from the grain. The techno-economic analysis was performed by the data provided by Agroetanol industry, located in Norrköping, Sweden. The key target of this simulation work was to evaluate the influence of several process designs and the main production factors on the ethanol production process, in terms of energy efficiency, ethanol production cost and plant profitability. The main aim of this work was to simulate the current industrial process and to develop novel alternative retrofits by integrating new technologies and for investigating the effects on the plant profitability. In the base case, the cost sensitivity analysis was carried out on the grain buying price, ethanol and DDGS selling price. Along with the cost sensitivity analysis, the capacity sensitivity analysis was performed on the base case model to check the influence of different capacities on the plant profitability. While coming to the study of developing alternative retrofits, the three retrofits were developed on the base case process and they are as following: Retrofit 1) modifying the distillation and dehydration section of the base case retrofit (current process in Agroetanol), Retrofit 2) checking the impact of ethanol concentration on technical and economic aspects of the plant and Retrofit 3) installing the biogas digester.The modelling effort resulted in developing the base case model with an ethanol production rate of 41,985 ton/ year. The capital cost of the base case process was calculated to be at 68.85 million USD and the aspen economic analyzer calculated the product value of the ethanol and DDGS as 0.87 USD/litre and 0.37 USD/kg, respectively. Through cost sensitivity analysis results, it is identified that the ethanol selling price and the grain buying price have significant effects on the plant economy and it is confirmed that they are the main factors playing on the plant profitability in the base case model.The results of the alternative retrofits clearly demonstrate the importance of higher ethanol tolerant strains in ethanol production, which showed a less payback period compared to the base case. The payback periods of all the cases are showing the following patterns from the least to the highest: Retrofit 2 (17%) > Base case > Retrofit 3 > Retrofit 2 (4%) > Retrofit 1.Further retrofitting analysis results also suggested that using the stillage for biogas production will help in reducing the energy costs of the plant. The energy consumption of all the retrofits in ascending manner is as follows: Retrofit 3 > Retrofit 2 (17%) > Base case > Retrofit 1 > Retrofit 2 (4%). The energy usage result comparison of all the cases shows that, in third retrofit the overall energy consumption is decreased by 40% than the base case model.

Wången is a trotting school located in Alsen region in Mid Sweden. Currently they keep almost 105 horses in their premises, which produce 2 400 m3 of stall waste per year.  Stall waste has always been a concern for those who keep animals, and though composting has been a viable solution to this problem for quite some time, it is no longer the only solution. Stall waste can be converted to energy and there are different techniques and approaches to do so.  In this study the writer compares the viability of two possible techniques (Biogas and heating plant) by collecting data from two existing biogas and heating plant providers for Wången trotting school. The results show that with almost same amount of investment on the reactors, a heating plant can meet 85% of Wången heating demand while Biogas plant could only meet 10 % of Wången’s heating consumption. On the other hand, as a result of nitrogen bound compound existence in horse manure, burning stall waste in the heating plant showed a more acidifying potential compared to the biogas plant. / Investigation for Wången trotting school

Digesters at a biogas plant have high temperatures and poor insulation. There is great potential to save energy by improving the construction. This study has two aims. One is to compare the difference between a simple steady-state calculation and a calculation that uses simulated values from Heat2. The second is to develop an improved insulation method at the concrete digester that can be used in future projects. Ten different insulation scenarios have been simulated to understand how to improve the insulation method to develop an idea of where the insulation has the most impact. Then a combined insulation method was created from the scenarios. That combined method was then simulated with 5 different insulation thickness to find the most profitable design. The conclusion was that there is great value in making more advanced calculations for the walls and floor because the energy losses are very excessive using the simplified calculation, especially on surfaces covered in soil. It was proved difficult to calculate the losses for the roof, this was because the assumption that was needed to perform the calculation does not mirror the reality. Due to this, the roof has been neglected in the suggested insulation method. The insulation method proposed provides an energy saving of 58 MW h/year and a discounted payback time of 4, 3 years if the saved energy can be delivered as 90◦C degree hot water into the district heating network.

Arbetet har mestadels utförts i kokeriet på Domsjö Fabriker i syfte att kartlägga hur processförhållandena hänger samman med koncentrationen sulfatjoner. Detta för att lättare kunna undvika förhållanden i processen som innebär mycket höga värden. Arbetet ingår i examen för högskoleutbildningen: processoperatör vid Umeå Universitet.Vid Domsjö Fabriker har tidigare liknande mätningar gjorts i kokeriet och det har konstaterats att koncentrationen sulfatjoner hänger samman med pH och tid. Syftet är att djupare kartlägga hur processförhållandena hänger samman för att lättare kunna undvika förhållanden som innebär höga koncentrationer sulfatjoner. Målet med examensarbetet och dess undersökning är att sammanställa resultat som visar hur och när under koket som sulfatjoner bildas i stora mängder i kokeriet. Förfarandet av undersökningen har bestått i att prov tas ut i provserier om fyra provtillfällen per kok, fryses in och slutligen analyseras genom titrering och pH-mätning.Efter totalt 22 stycken provserier om fyra prov från de olika kokarna konstaterades att sulfatkoncentrationen är högst i slutet av nedgasningssteget. Det första provtillfället hade de högsta pH-värdena men också de lägsta koncentrationerna sulfat. Inget av dessa värden sticker ur och anses onormalt på något sätt. Om sulfatkoncentrationen påverkas av pH-värdet går inte att fastställa av detta arbete, då det inte är de lägsta pH-värdena som genererar de högsta sulfatkoncentrationerna utifrån resultatet i undersökningen. / This work has been performed in the digester at Domsjö Fabriker in order to clarify the concentration of sulphate-ions comparing to different driving-conditions in the process. The reason to this is to understand and be able to avoid conditions in the digester process that means very high concentrations of sulphate-ions. The work is included in the examination of higher education: process operator at Umeå University.At Domsjö Fabriker similar studies have been done in the digester and from that it has been found out that the concentration of sulphate-ions is connected to pH and over time. The purpose is to approve the understanding of the process conditions to avoid extremely high concentration of sulphate-ions. The mission with this work and the measurements included in the work is to put together results that show when the concentration of sulphate-ions is high. The procedure of the study has consisted in taking samples in series of four, frozen the samples and finally analyzing them by titration and pH-measurements.After 22 evaluated trial-series á four samples each from the boilers it was concluded that the concentration of sulphate-ions was the greatest in the end of this process-step. The pH was upper and the concentration of sulphate lower in the first sample. None of the data is abnormal in any way, and they are all connected and relevant to each other. In this experiment it is not possible to state if the concentration of sulphate is affected by the pH or not.

Anaerobic digester (AD) technology is a form of renewable energy that’s economic feasibility assessment is required site by site. This thesis presents a freely available workbook to determine the financial feasibility of a farm-based AD and to demonstrate its use for the Ontario livestock sector. To assess the profitability of ADs for farmers in Ontario with uncertainty included the theory of real options is used. Investment in an AD is financially feasible only for the largest dairy farms in Ontario under current electricity prices, which are approximately six times greater than the wholesale price. Shifting to a duel fuel continuous system would improve returns, as would the availability of additional substrate material in the form of solid grease waste. The real options approach shows that even higher net returns are necessary, than indicated by more traditional approaches, in order for AD investments to be feasible for Ontario livestock farmers.

Darbo tikslas – nustatyti technologinių rodiklių įtaką Kauno nuotekų valyklos metantanko efektyvumui. Darbo uždaviniai: nustatyti išsiskyrusių biodujų debito priklausomybę nuo temperatūros, organinės medžiagos suirimo laipsnio, palyginti teorinį ir faktinį pagaminamų biodujų kiekį. Tyrimo objektai: Kauno miesto nuotekų valykloje dumblo pūdymui periodiškai naudojami du metantankai. Tyrimo metodika: buvo stebimi pagrindiniai rodikliai, įtakojantys biodujų išeigą metantanke: pirminio dumblo debitas, perteklinio dumblo debitas, temperatūra ir organinės medžiagos suskilimo laipsnis. Apskaičiuotas organinės medžiagos kiekis dumble, nustatytas teorinis biodujų kiekis. Apdoroti 75 dienų tyrimų duomenys. Tyrimo rezultatai: biodujų debitas tiesiogiai proporcingas organinės medžiagos kiekiui, esančiam pirminio ir perteklinio dumblo mišinyje. Dumblas pastoviai susidaro pirminiuose ir antriniuose sėsdintuvuose, todėl negalima reguliuoti tiekiamo dumblo debito į metantanką, nes tai gali sutrikdyti nuotekų valymo proceso eigą. Vidutiniškai per dieną į Kauno miesto nuotekų valyklos metantanką tiekiama 432,5 m3 dumblo. Organinės medžiagos kiekis dumble priklauso nuo nuotekų, atitekančių į valyklą, sudėties. Kauno miesto nuotekų valyklos metantankas dirba mezofiliniu režimu. Pagal tyrimų duomenis metantanko darbo temperatūra svyruoja tarp 32,7 – 35,4 °C. Dėl šio temperatūrinio intervalo išsiskiriančių biodujų debitas yra netolygus. Išsiskyrusių biodujų debitas kinta nuo 4600 m3/d iki 9400 m3/d... [toliau žr. visą tekstą] / The object of the research: the two anaerobic digesters that are used for the sludge digestion in Kaunas wastewater treatment plant. The aim of the research: to determine the influence of the technological indicators on the performance efficiency of the anaerobic digester in Kaunas wastewater treatment plant. The objectives of the research: to estimate the dependence of the amount of biogas on the temperature and the degree of biolysis; to compare theoretical and actual amount of the biogas produced. Research methods: the main indicators, influencing biogas emission from the anaerobic digester, such as: primary sludge discharge, surplus sludge discharge, temperature, and the degree of biolysis, were observed. The amount of the organic material in the sludge was evaluated, theoretical amount of biogas was determined from the chart. Research data acquired in 75 days was processed. The results of the research: biogas discharge is directly proportional to the amount of organic material in the compound of primary and surplus sludge. Sludge is constantly forming in the primary and secondary sludge separators, therefore the sludge discharge added to the anaerobic digester cannot be controlled, as this could disorganize the process of wastewater treatment. On the average, 432,5 m3 of sludge are added to the anaerobic digester in Kaunas wastewater treatment plant. The amount of the organic material in the sludge depends on the composition of the sewage that the treatment plant is... [to full text]

This thesis is comprised of two phases; the first phase concerns the effect of arsenic on the denitrification process in the presence of naturally-produced volatile fatty acids (VFAs); while the second phase evaluates the arsenic removal efficiency of New Zealand Iron Sand (NZIS) by adsorption. To accomplish the first phase of the study, VFAs were first produced naturally in an acid-phase anaerobic digester by using commercially-available soy flour. Secondly, a denitrifying biomass was cultivated in a sequencing batch reactor (SBR) using domestic wastewater as a feed solution. Finally, a series of biological denitrification batch tests were conducted in the presence of different concentrations of arsenic and nitrate. As mentioned, the VFAs were generated from an anaerobic digester using 40 g/L soy solution as a synthetic feed. The digester was operated at a solids retention time (SRT) and hydraulic retention time (HRT) of 10 days. The pH of the digester was measured to be 4.7 to 4.9 while the mean temperature was 31 ± 4 °C; however, both these parameters were not controlled. In the effluent of the digester, a mean VFA concentration of 5,997 ± 538 mg/L as acetic acid was achieved with acid speciation results of acetic (33 %), propionic (29 %), butyric (21 %), iso-valeric (5%) and n-valeric acid (12 %). The specific VFA production rate was estimated to be 0.028 mg VFA as acetic acid/mg VSS per day. The effluent sCOD was measured to be 14,800 mg/L (27.9 % of the total COD), as compared to 9,450 mg/L (16.8 % of total COD) in the influent of the digester. Thus, the COD solubilization increased by 11.1 % during digestion yielding a specific COD solubilization rate of 0.025 mg sCOD/mg VSS per day. The extent of the digestion process converting the substrate from particulate to soluble form was also evaluated via the specific TOC solubilization rate (0.008 mg TOC/mg VSS per day), and VSS reduction percentage (17.7 ± 1.8 %). A denitrifying biomass was developed successfully in an SBR fed with domestic sewage (100 % denitrification was achieved for the influent concentration of sCOD = 285 ± 45 mg/L and NH₄⁺-N = 32.5 ± 3.5 mg/L). A mean mixed liquor suspended solids (MLSS) of 3,007 ± 724 mg/L and a mean SRT of 20.7 ± 4.4 days were measured during the period of the research. The settleability of the SBR sludge was excellent evidenced by a low sludge volume index (SVI) measured to be between 50-120 mL/g (with a mean value of 87 ± 33 mL/g) resulting in a very low effluent solids concentration (in many cases less than 20 mg/L). Several preliminary tests were conducted to estimate the right dosage of VFAs (digester effluent), nitrates and arsenic to be added and to confirm the occurrence of denitrification in an appropriate time frame of 4-6 h. From these tests, an optimum C/N ratio was observed to be somewhere between 2 to 4, somewhat higher than all the theoretical C/N ratios required for a complete denitrification using the four major VFAs identified in the digester effluent. During the denitrification batch tests, it was also observed that some NO₃⁻- N was removed instantaneously by reacting with As (III) (As₂O₃); while an increase in alkalinity of around 5.60 mg as CaCO₃ produced per mg NO₃⁻- N reduction was also observed. This latter number was very close to the theoretical value of alkalinity production (i.e. 5.41 mg as CaCO₃ per mg NO₃⁻- N). The effect of arsenic on the denitrification process was evaluated by observing the specific denitrification rate in series of denitrification batch tests (with different concentrations of arsenic). Results from the denitrification batch tests showed that there was a clear effect for both As (III) and As (V) on denitrification. In particular, the specific denitrification rate fell from 0.37 to 0.01 g NO₃⁻- N /g VSS per day as the concentration of As (III) increased from 0 to 50 mg/L. In contrast, there was comparatively less effect for As (V); i.e. only a 37 % decrease in the specific denitrification rate (from 0.34 g NO₃⁻- N /g VSS per day to 0.23 g NO₃⁻- N /g VSS per day) when the initial arsenic concentration increased from 0 to a very high level of 2,000 mg/L. The effects of both the As (III) and As (V) forms of inorganic arsenic on the denitrification rate were further quantified by constructing exponential equation models. It was suspected that the effect of As (III) on denitrification was more substantial than the effect of As (V) because of the former’s toxicity to microbes. Finally, the fate of arsenic was tracked by examining bacterial uptake. During the normal denitrification batch tests (i.e. designed for evaluation of the effect of arsenic on denitrification), no significant arsenic removal was observed. However, additional batch tests with a comparatively low concentration of biomass revealed that the denitrifying biomass removed 1.35 µg As (III) /g dry biomass and 2.10 µg As (V) /g dry biomass. In the second phase of this research, a series of arsenic adsorption batch tests as well as a column test were performed to examine the arsenic (As (III) and As (V)) removal efficiency of NZIS from an arsenic-contaminated water. The kinetics and isotherms for adsorption were analysed in addition to studying the effect of pH during the batch tests. Breakthrough characteristics for both As (III) and As (V) were studied to appraise the effectiveness of NZIS treating an arsenic contaminated water. Batch tests were performed with different concentrations of arsenic as well as at different pH conditions. A maximum adsorption of As (III) of approximately 90 % occurred at a pH of 7.5, while the As (V) adsorption reached its maximum value of 97.6 % at a very low pH value of 3. Both Langmuir and Freundlich Models were tested and found to fit with R² values of more than 0.92 in all cases. From the Langmuir adsorption model, the maximum adsorption capacity of NZIS for As (III) was estimated to be 1,250 µg/g, significantly higher (about three times) than for As (V) of 500 µg/g. In column tests, arsenic-contaminated water with total As concentration of 400 µg/L (in either form of As) were treated and a pore volume (PV) of 700 and 300 yielded a total arsenic level less than the WHO guideline value of 10 µg/L for As (III) and As (V) respectively; while, the breakthrough occurred after a throughput of approximately 3,000 PV of As (III) and 2,700 PV of As (V) with an average flow rate of approximately 1.0 mL/min.