No description available.

The research represents a first approach to measure the utilization potential of ultrasonic pretreatment on six different substrates: fat, oil and grease (FOG), paper sludge, ground switch grass, ground hay, ground wheat straw, and cut wheat straw. Several laboratories techniques were applied to determine the influence of ultrasonication on biogas production and yield, biogas quality, and digestibility ratio. With the data, mathematical definitions of Net Energy Balance and Net Economy Balance were computed to draw a first justification or rejection of the use of this pretreatment technology for the specific substrates. Ultrasonic pretreatment has a significant effect on biogas production and yield as well as digestibility ratio (p-value < 0.0001) from the early stages of digestion until as far as 50 days of digestion. Ultrasonication and macro particle size management did not influence significantly the methane (CH4) content in the biogas (p-value = 0.1793). Also, the impact of ultrasonication on the substrate varies between all studied feedstock. Most of the ultrasonicated digestion cases studied provided a negative Net Energy and Economic Balance except for FOG where a certain window of utilization was found. In the context of an ultrasonication process retrofit upgrade, the technology looks to be more useful for substrates that are hard to digest when the retention time is, unfortunately, longer than common retention time. In the context of a new facility, a design that includes an understood ultrasonication technology has yet a small potential success depending on several variables. The ultrasonication technology for anaerobic digestion is hard to recommend due to its energy consumption that, in many cases, overshadows the energy surplus derived from its use. / MITACS

Increasing charges by the private utilities for the treatment of industrial waste water are making on-site effluent treatment more attractive. On-site anaerobic digestion is increasingly being used by food processing factories as a cost effective solution to waste liquid waste disposal. Discharge of treated effluent to sewer or water course requires compliance to a maximum admissible concentration (MAC) value, therefore, there is a need for careful control of on-site waste water treatment. This research investigates the treatment of effluent from instant coffee production. This results in a liquid waste that contains recalcitrant and toxic compounds formed during the roasting process. This waste varies in strength and composition according to the different processes that are performed in the manufacture of instant coffee. Anaerobic filters are particularly attractive for wastes containing recalcitrant or inhibitory compounds requiring a long sludge age. Therefore, this study was aimed at firstly investigating the treatability of coffee waste, using anaerobic filters; and secondly monitoring and control of the digestion process in order to maintain a constant effluent quality.

No description available.

No description available.

Sustainable and environmentally friendly waste-to-energy conversion technologies, such as anaerobic digestion (AD) and gasification, have received significant attention in recent energy research. These technologies have proven their ability to reduce reliance on fossil fuels and greenhouse gas emissions by converting organic waste into products and fuels with market value, such as biomass, biogas, and synthetic gas. Since the syngas produced by biomass gasification contains highly toxic CO and flammable H₂, converting syngas into renewable natural gas has recently gained a lot of interest. By coupling AD with syngas, microbial consortium in the AD reactor converts the syngas into methane through a process known as biomethanation. Feeding syngas into the AD reactor is a method that not only can enhance methane production by conversion of CO₂ to CH₄ during the AD process but also converts syngas into methane as pure energy. This study aims to assess and compare the effect of different syngas compositions on methane production and optimize the SB process by identifying the best syngas composition and gas-biomass ratio under mesophilic temperature conditions. The study was conducted using batch and semi-continuous reactors in a lab-scale setting. The results of this study can contribute to the development of more efficient and sustainable methods for SB. In phase I of this study, syngas biomethanation under different syngas compositions was conducted under three different gas-biomass ratios (0.5, 1 and 1.5) in bench-scale experiments to study the impact on CO and H₂ partial pressure and CO toxicity on operation parameters (e.g., pH and VFA) and syngas conversion efficiency. The results showed that the optimum syngas composition with the highest amount of CH₄ is H₂-rich syngas (CO₂:CO; H₂ 1:1:7) and syngas with stoichiometric ratios between H₂ and CO/CO₂ (CO:H₂ 1:3; CO₂:H₂ 1:4) because of the sufficient available amount of hydrogen in the headspace. Methane content in the produced biogas reached 80.0%, 63.6% and 57.7%, respectively, compared to the control sample with 30.2% methane in the headspace. In phase II, the optimum syngas compositions were selected for experimenting with semi-continuous mode to 1) investigate the effect of injecting syngas in several stages in increasing syngas conversion efficiency, 2) adapt microorganisms to hydrogen and enhance biohydrogen production, and 3) test higher stoichiometric ratio between H₂ and CO/CO₂ to enhance syngas biomethanation efficiency. The data indicated higher methane content and syngas conversion in a semi-continuous mode. The biogas had methane concentration of 82.3, 76.9, 73.8, 84.9 and 81.7% in samples CO₂:CO: H₂ (1:1:7), CO:H₂ (1:3), CO₂:H₂ (1:4), CO: H₂ (1:4) and CO₂:H₂ (1:5). By injecting gas into the biomass in several stages, methane levels in the produced biogas in each stage increased, demonstrating the adaptation of microorganisms to the injected hydrogen and carbon-sourced gases. A higher stoichiometric ratio of H₂ to CO/CO₂ promoted the growth and activity of methanogens, leading to increased methane production.

Acidogenic codigestion of fats, oils, and greases (FOG) was studied at 37"C using suspended sludge digesters operated as sequencing batch reactors (SBRs). Volatile fatty acid (VFA) production was found to increase with larger FOG loading rates, although this increase was insignificant compared the theoretical VFA production from FOG addition. Long chain fatty acids (LCFAs) were found to have accumulated in the reactor vessel in semi-solid balls that were primarily composed of saturated LCFAs. Adding high FOG loadings to an APD not acclimated to LCFAs allowed for a mass balance calculation and resulted in near complete saturation of unsaturated LCFAs and significant accumulation of LCFA material in the digester, which was found to be mostly 16:0, 18:0, and 18:1. While 18:2 and 18:3 LCFAs were nearly completely removed, 18:0 and 14:0 LCFAs were produced, most likely from the degradation of 18:2 and 18:3 LCFAs. The APD pH was found to have a significant impact on the amount of accumulated LCFA material present, with higher pH levels resulting in less accumulated material. Two-phase codigestion of FOG was also studied using an APD followed by gas-phase (GPD) digesters. The two-phase systems were compared by FOG addition to the APD versus GPD. FOG addition to the APD resulted in 88% destruction of LCFAs, whereas FOG addition to the GPD resulted in 95% destruction of LCFAs. Accumulated LCFAs in the APD receiving FOG were composed mostly of stearic acid (18:0). The low pH of the APD is likely the cause of LCFA accumulation due to saturation of unsaturated LCFAs. / Master of Science

Pacific Island Countries (PICs) currently rely heavily on imported, expensive and unsustainable fossil fuels as their primary source for energy production. Establishing an alternative energy source from local resources would therefore have considerable benefits for many Island communities. Coconut copra is high in biodegradable organic carbon and is found growing abundantly in PICs. One alternative use for this local resource would potentially be the conversion of the coconut copra into a valuable and useful energy source through biological processes, such as anaerobic digestion. The purpose of this research was to investigate the biogas generation potential of coconut copra as a carbon source using anaerobic digestion processes. Both batch and continuously stirred reactors (CSTRs) in addition to the environmental and operating variables that affect the production of biogas were investigated in order to optimize methane production and increase the overall conversion efficiencies of organic matter to methane. The results suggest that coconut copra is amenable to anaerobic digestion due to the high theoretical methane yields from the substrate’s high lipid content. However, the optimal organic loading rate (OLR) was limited to within a narrow range of 3.6-6 g VS (2.4 - 4 g VS/L Reactor) for the batch reactors and a maximum of 0.420 L CH4/ g VS was achieved at an OLR of 3.6 g VS. OLRs exceeding 15 g VS resulted in low pH values and negligible methane production due to substrate overloading. High average methane yields of 0.708 L CH4/ g VS•day were also successfully achieved for the CSTRs and increased mixing was observed to have an improved effect on methane production. However, the addition of nitrogen and phosphorus supplements failed to increase biological activity and ultimately resulted in the accumulation of ammonia to concentrations toxic to methanogenic bacteria. The failure of an accelerated CSTR start-up procedure also reinforced the requirement for a gradual and steady acclimated period for anaerobic digestion of this particular substrate.

No description available.

Swedish people today are generally interested in environmental issues. One can assume that this would affect the way people act in their daily lives. However, research has shown that when it comes to attitudes and behavior, there is what has been described as “a gap”. Concern for the environment does not automatically mean that people act in an environmentally friendly way. The fact is that there are many barriers that prevent a so-called pro environmental behavior. This study deals with some of the factors that can influence a specific behavior, namely the sorting of food waste in the City of Lidingö – a municipality in Sweden that works to increase the number of subscribers of food waste collection. The waste is a valuable substrate when producing biogas, which is considered a renewable fuel. By replacing fossil fuels with biogas, the amounts of greenhouse gases that reach the atmosphere can be reduced. A questionnaire was sent out to more than 800 local citizens (of which half of them are subscribers of food waste collection) with questions about values, beliefs, motivation factors and opinions about efforts linked to the sorting of food waste. The results show that sustainability reasons are strong when it comes to why people decide to sort out food waste, and that a number of the subscribers of food waste collection consider it a moral obligation to take action in this matter. Several barriers, especially in the form of economic issues, preclude others from sorting. A need for more information, when it comes to the significance of this behavior, is also evident. As the thesis has its focus on pro-environmental behavior, factors in Stern’s Value-belief-norm theory, are used as the basis for the analysis. Blake’s model of barriers between environmental concern and action is used when studying what it is that prevents people from sorting out their food waste.