Biogas Concept for Rice Husk Management in Ghana
Karikari, Pius (2023)
2023
Master's Programme in Environmental Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Hyväksymispäivämäärä
2023-05-30
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202305266184
https://urn.fi/URN:NBN:fi:tuni-202305266184
Tiivistelmä
Biogas production from rice husks has gained significant attention as a sustainable energy and waste management solution. Rice husk, a by-product of rice milling, is abundantly available in rice-producing regions. In addition, digestate, a by-product of anaerobic digestion derived from rice husk, holds the potential for various uses, such as fertilizer application.
This study examined the potential of utilizing rice husk as a feedstock for biogas production. The study identified the optimal operational conditions for rice husk anaerobic digestion (AD) and assessed the quantity and quality of biogas produced from rice husk and its potential for energy generation. The study further explored the potential applications of digestate in Ghana, including its use as a crop fertilizer and soil conditioner. Factors influencing the adoption and diffusion of biogas technologies in Ghana, such as policy frameworks, drivers, barriers, and technological constraints, were also identified and evaluated. In this study, a biogas plant was designed using rice husk as the feedstock. Paddy rice was harvested from 1000 ha of land and processed to obtain 595t rice rusks. The feedstock was first mechanically pre-treated and then anaerobically digested to produce biogas. The two reactors used in this case study were CSTR and batch reactors. During the AD process, digestate was produced, which contained essential nutrients. The digestate was then processed for fertiliser use. However, before the biogas was utilised, it was cleaned and upgraded to remove impurities like H2S.
The CSTR reactor results showed that 5 740 CH4 m3/year was produced. The plant also generated 195 144 MJ/year of energy. In the batch reactor, the methane and energy production of four different reactors, A, B, C, and D, A had the highest methane and energy production, while reactor D had the lowest production levels. A produced 93 m3 of CH4/ batch, with a daily production of 1,5 CH4 m3 and energy production of 3149 MJ per batch. Reactor D, on the other hand, produced only 33 m3 of CH4 /batch, with a daily production of 0,5 m3 and energy production of 1115 MJ per batch. The study found that the total N and P available in the 595t rice husk was 2,0 N t/year and 0,4 P t/year, which is enough to replace all the losses of nutrients in all forms combined within a growing season on 22 ha and 13 ha of land, respectively. In the compost facility, the primary feedstock processed is 520 t/year, equivalent to 10 t/week of input feedstock. The raw feedstock processed was 3 976 m³/year, which indicated the facility's large-scale capacity. The finished compost produced was 1 589 m³/year. Therefore, compost-ing digestate from rice husk could provide a sustainable solution for managing nutrient-rich waste and producing a valuable soil amendment and could be applied to approximately 32 ha of land.
Overall anaerobic digestion of rice husk is a promising renewable energy source with the potential for energy production, and upgrading the biogas to remove impurities is essential to ensure its quality and suitability for different applications. However, co-digestion with other feedstock should be considered to boost methane production. In essence, methane production from rice husks provides a comprehensive solution that addresses waste management, renewable energy generation, emission reduction, and sustainable agriculture and fosters efficient and sustainable resource utilization. The Renewable Energy Master Plan in Ghana provides a framework for promoting the development and utilization of renewable energy resources, including biogas production from rice husks, but the challenges outlined in the plan have implications for biogas production. Further research and development are needed to optimize the process and ensure economic viability. At the same time, nutrient recovery from digestate through technologies such as compositing can play a vital role in replenishing lost nutrients during the growing season and act as a means for managing waste from rice production.
This study examined the potential of utilizing rice husk as a feedstock for biogas production. The study identified the optimal operational conditions for rice husk anaerobic digestion (AD) and assessed the quantity and quality of biogas produced from rice husk and its potential for energy generation. The study further explored the potential applications of digestate in Ghana, including its use as a crop fertilizer and soil conditioner. Factors influencing the adoption and diffusion of biogas technologies in Ghana, such as policy frameworks, drivers, barriers, and technological constraints, were also identified and evaluated. In this study, a biogas plant was designed using rice husk as the feedstock. Paddy rice was harvested from 1000 ha of land and processed to obtain 595t rice rusks. The feedstock was first mechanically pre-treated and then anaerobically digested to produce biogas. The two reactors used in this case study were CSTR and batch reactors. During the AD process, digestate was produced, which contained essential nutrients. The digestate was then processed for fertiliser use. However, before the biogas was utilised, it was cleaned and upgraded to remove impurities like H2S.
The CSTR reactor results showed that 5 740 CH4 m3/year was produced. The plant also generated 195 144 MJ/year of energy. In the batch reactor, the methane and energy production of four different reactors, A, B, C, and D, A had the highest methane and energy production, while reactor D had the lowest production levels. A produced 93 m3 of CH4/ batch, with a daily production of 1,5 CH4 m3 and energy production of 3149 MJ per batch. Reactor D, on the other hand, produced only 33 m3 of CH4 /batch, with a daily production of 0,5 m3 and energy production of 1115 MJ per batch. The study found that the total N and P available in the 595t rice husk was 2,0 N t/year and 0,4 P t/year, which is enough to replace all the losses of nutrients in all forms combined within a growing season on 22 ha and 13 ha of land, respectively. In the compost facility, the primary feedstock processed is 520 t/year, equivalent to 10 t/week of input feedstock. The raw feedstock processed was 3 976 m³/year, which indicated the facility's large-scale capacity. The finished compost produced was 1 589 m³/year. Therefore, compost-ing digestate from rice husk could provide a sustainable solution for managing nutrient-rich waste and producing a valuable soil amendment and could be applied to approximately 32 ha of land.
Overall anaerobic digestion of rice husk is a promising renewable energy source with the potential for energy production, and upgrading the biogas to remove impurities is essential to ensure its quality and suitability for different applications. However, co-digestion with other feedstock should be considered to boost methane production. In essence, methane production from rice husks provides a comprehensive solution that addresses waste management, renewable energy generation, emission reduction, and sustainable agriculture and fosters efficient and sustainable resource utilization. The Renewable Energy Master Plan in Ghana provides a framework for promoting the development and utilization of renewable energy resources, including biogas production from rice husks, but the challenges outlined in the plan have implications for biogas production. Further research and development are needed to optimize the process and ensure economic viability. At the same time, nutrient recovery from digestate through technologies such as compositing can play a vital role in replenishing lost nutrients during the growing season and act as a means for managing waste from rice production.