Utilizing abundant waste by converting it into usable renewable energy by adopting the third generation green technology development has attracted much attention from the world as a source of the depleting fossil fuels. In addition to the awareness regarding the Carbon Credit and the Clean Development Mechanism promoted to developing countries in the Kyoto Protocol, the development of biochemical transformation of biomass through anaerobic digestion to generate methane gas was also one of the exciting areas. The aim of the project is to develop a working prototype of a digester, which will be used to generate methane gas by applying the concept of biochemical transformation of anaerobic digestion.
After that, a prototype was made and experiments were carried out to observe the operation of the digester. Discussions were held to comment and analyze the results, and suggestions were made to improve the efficiency of the digester. Of the many people who have been of great help in the preparation of this dissertation, I am especially grateful to Mr. Mohd Faizairi Mohd Nor and Dr. Suhaimi Hassan for their help and support that guided me to a successful conclusion.
- Background of Study
- Problem Statement
- Scope of Study
As a general information, methane (CH4) has been more effective at trapping heat in the atmosphere than carbon dioxide (CO2) gas for more than 100 years. Methane gas obtained by anaerobic digestion of POME is often seen as a product of the treatment. Therefore, a study has been made to design a digester based on anaerobic digestion concept for treatment to capture methane gas.
By capturing the methane gas produced from organic waste using the biochemical transformation of anaerobic digestion, the waste could be turned into an energy source. Understand the concept of anaerobic digestion to produce methane gas from POME as a feedstock source. Propose digester size change as preliminary study for methane gas generation for FELCRA Nasaruddin, Bota, Perak.
Palm Oil Mill Effluent (POME)
After the sterilization process, the fruits are stripped and separated from the bunch inside a rotating drum stripper. It can be discharged as the most polluting organic residues generated from palm oil mills. 60% of the total POME came from clarification wastewater generated during the clarification process of the extracted CPO.
From the POME characteristics table, it can be seen that the BOD:COD ratio is approximately 1:2. Due to the high awareness of this issue, comprehensive environmental control of the crude palm oil industry was initiated. The following table presents the current effluent discharge standard, usually acceptable for crude palm oil mills.
Because of the relatively large amount of organic waste that goes into the anaerobic digestion process, it is important to study the bacteria involved, the steps and process that build the whole process, and the operational factors that affected the efficiency of the process. The biological process of acidogenesis results in further degradation of the remaining components by fermentation bacteria (acidogens) [5, 10]. As an overview, the conventional POME treatment technology used in most palm oil mills in Malaysia is a combination of physical and biological treatment.
Ponding system, anaerobic filtration, up-flow anaerobic sludge blanket reactor (UASB) and fluidized bed reactor will be the current POME treatment method discussed further. The main components of the system include an oil tank, acidification ponds, methanogenic ponds, facultative ponds and sand beds. Due to the large system and large collection area, the pond system has one of the highest maintenance requirements.
The fluidized bed reactor exhibits several advantages that make it useful for treating highly resistant wastewater. The highest flow rate of raw POME is maintained for the fluidized bed reactor to allow expansion of the support material bed. The fluidized bed reactor has also been widely used to treat cutting oil wastewater, real textile wastewater, wine and distillery wastewater, brewery wastewater, ice cream wastewater, slaughterhouse wastewater, pharmaceutical wastewater, and POME.
Anaerobic fluid bed can typically remove at least 65% and up to more than 90% of COD. Anaerobic fluidized beds were found to generally be able to operate at higher OLRs, implying that less reactor volume would be required to operate at lower OLRs. In POME treatment, fluidized bed was found to be a better treatment method compared to anaerobic filter due to its ability to tolerate higher OLRs and its better methane gas production.
Shorter HRT (6 hours) was also a plus of fluid bed over anaerobic filter (1.5-4.5 days) in POME treatment.
The literature recommended kinetic coefficient (endogenous coefficient) for a substrate similar in composition to vinasse (fatty acid) was 0.04 d-1 and the flow coefficient was 0.05 lb cell/lb BOD. Further calculations for finding the volume of methane gas produced are based on the following formula . The value 5.62 is a theoretical conversion factor for the amount of methane produced by the complete conversion of one pound of BOD to methane and carbon dioxide, cu ft CH4/lb BOD oxidized.
- Flow Chart
- Project Workflow
- Design Theory & Calculations
- Prototype Design
- List of Material
- Experimental Procedure
The objective of this project is to complete the manufacture and testing of the digester within the given time. The performance of the digester should be monitored to inspect for any error and to monitor the product performance. The specification of the design must be drawn up in advance as it represents the desired outcome expected from the project.
Before the design phase of the prototype using AUTOCAD, studies and calculations were made for the design dimensioning. Based on these values, the digester's area and diameter are then calculated to design the digester in cylinder form. The amount of methane gas expected to be produced in this project is determined as follows;
Before fabricating the prototype, AUTOCAD, engineering software is used to design the structure of the solvent base according to the concept and idea that have been identified earlier. The top view, side view and general view of the prototype drawing is shown in the figure below. Based on the design made, the materials to produce the solvent were listed and the best material was selected.
Mainly, the digester was made from a plastic-based material, while other material such as PVC pipes and tubes are used. After the manufacture of the prototype is completed, the digester is tested to observe its performance. The digester is connected to a gas chamber by a transparent tube to channel the methane gas generated from the digestion process.
The captured gas will eventually push the solution into the tank prepared through one of the chamber's lower outlets.
RESULTS AND DISCUSSION
Therefore, the relationship between pH value and volume of methane gas generated can be identified and analyzed by having these two different pH values tested. Based on the graphs, the general pattern of increasing volume of methane gas for all three tests is clearly seen. Naturally, the rate of methane gas generated is highest on Test 3, followed by Test 2 and Test 1.
Comparing test 1 and test 2 in terms of the starting temperature of POME, test 2 gives a better yield for the rate of methane gas generated than test 1. This is due to the inability of the manufactured digester to maintain the temperature and keep the POME at a high temperature so the amount of methane gas generated is constantly high. We proceed to the comparison between test 2 and test 3 in terms of the volume of methane gas generated.
However, the difference in initial pH value, especially for Test 3 which has an optimum initial pH value, affected the overall volume of methane gas generated. This decrease in pH value somehow affected the rate of methane gas generated. The pattern in rate of methane gas generated versus time for both Tests 2 and 3 is observed.
Microorganisms are able to digest the waste in its optimal state, which results in a higher yield of the methane gas produced. Such care and tedious work must be done to maintain the condition of the bacteria, as this will contribute to the efficiency of the digester in terms of the amount of methane produced. Based on the amount of methane gas produced from the designed digester, further discussion on the potential volume of methane gas produced and the volume of POME released from FELCRA Nasaruddin is studied.
The volume of methane gas generated from the fabricated solvent is expected to be quite low.
CONCLUSION AND RECOMMENDATION . 41
For example, the introduction of thermal insulation of the digester would be helpful in keeping the POME temperature high. However, by adding this thermal insulation outside the digester container, none of the changes POME undergoes during residence time can be visibly seen. The replacement of plastic with metal plates is also being considered, along with the visible part of the digester body and proper insulation of the digester.
Also, introducing a mixing mechanism or a heating element into the prototype would be one of the recommendations to improve the performance of the digester to achieve the desired output. An inducing heating element helps absorb heat loss to the environment, allowing the digester to operate under thermophilic conditions. More features can be added to the existing design to increase the marketability of the product.
Besides the main goal of developing an anaerobic digestion concept of a digester to generate optimal methane gas production, this project also aims to raise awareness of green technology and the importance of utilizing the energy available in the area, especially this abundant agricultural waste. . The digester can be further improvised for use for other types of wastewater, such as sewage sludge. Treatability of palm oil mill effluent (POME) using black alcoholic beverage in anaerobic treatment process. Master's thesis), Universiti Sains Malaysia, Penang, Malaysia.
Biological treatment of palm oil mill effluent (POME) using an up-flow anaerobic sludge-solid film (UASFF) bioreactor. Doctor of Philosophy Thesis), Universiti Sains Malaysia, Penang, Malaysia. Effects of anaerobic palm oil mill sludge (POME) from a closed 500 m3 anaerobic methane digested tank on the composting process of pressed shredded empty fruit bunches (EFB). 17] 2006 SPRI Conference on Sugar Processing Baez-Smith, Anaerobic Digestion of Vinasse 268 Anaerobic Digestion of Vinasse for Methane Production at the Sugarcane Distillery Carmen Baez-Smith, PE, PMP Smith Baez Consulting, Inc. Optimization of anaerobic digestion of sewage sludge using thermophilic anaerobic pretreatment.
A technical and economic analysis of heat and power generation from biomethanation of palm oil mill effluent (POME).