Mohd Afifi Hashim - Academia.edu (original) (raw)
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Papers by Mohd Afifi Hashim
Ecological Indicators, 2013
The primary objective of this study was to provide an insight into sustainable production indicat... more The primary objective of this study was to provide an insight into sustainable production indicators used by the petrochemical industry in Malaysia to measure the sustainability of the industry's operations. In achieving the research objective, the case study method was employed. The petrochemical industry was selected because of its major contribution to the Malaysian economy (market share and total investment), its significant impacts to the environment and, high societal and occupational risks. The sector is also highly dependent on non-renewable fossil fuels such as natural gas, LPG and diesel; and is energy intensive. Utilising the five-tier framework developed by the Lowell Centre for Sustainable Production (LCSP) and indicators identified by the Global Reporting Initiative (GRI) Guidelines 3.1, an analysis of indicators used by the petrochemical sector was carried Out. The LCSP framework was selected as it is an established framework and has been successfully used in sim...
This study evaluated anaerobic hydrogenation performance and microbial ecology in bioreactors ope... more This study evaluated anaerobic hydrogenation performance and microbial ecology in bioreactors operated at different hydraulic retention time (HRT) conditions and fed with glucose-peptone (GP) and starch-peptone (SP). The maximum hydrogen production rates for GP-and SP-fed bioreactors were found to be 1247 and 412 mmol-H 2 /L/d at HRT of 2 and 3 h, respectively. At HRT > 8 h, hydrogen consumption due to peptone fermentation could occur and thus reduced hydrogen yield from carbohydrate fermentation. Results of cloning/sequencing and denaturant gradient gel electrophoresis (DGGE) indicated that Clostridium sporogenes and Clostridium celerecrescens were dominant hydrogen-producing bacteria in the GP-fed bioreactor, presumably due to their capability on protein hydrolysis. In the SP-fed bioreactor, Lactobacillus plantarum, Propionispira arboris, and Clostridium butyricum were found to be dominant populations, but the presence of P. arboris at HRT > 3 h might be responsible for a lower hydrogen yield from starch fermentation. As a result, optimizing HRT operation for bioreactors was considered an important asset in order to minimize hydrogen-consuming activities and thus maximize net hydrogen production. The limitation of simple parameters such as butyrate to acetate ratio (B/A ratio) in predicting hydrogen production was recognized in this study for bioreactors fed with multiple substrates. It is suggested that microbial ecology analysis, in addition to chemical analysis, should be performed when complex substrates and mixed cultures are used in hydrogen-producing bioreactors.
Ecological Indicators, 2013
The primary objective of this study was to provide an insight into sustainable production indicat... more The primary objective of this study was to provide an insight into sustainable production indicators used by the petrochemical industry in Malaysia to measure the sustainability of the industry's operations. In achieving the research objective, the case study method was employed. The petrochemical industry was selected because of its major contribution to the Malaysian economy (market share and total investment), its significant impacts to the environment and, high societal and occupational risks. The sector is also highly dependent on non-renewable fossil fuels such as natural gas, LPG and diesel; and is energy intensive. Utilising the five-tier framework developed by the Lowell Centre for Sustainable Production (LCSP) and indicators identified by the Global Reporting Initiative (GRI) Guidelines 3.1, an analysis of indicators used by the petrochemical sector was carried Out. The LCSP framework was selected as it is an established framework and has been successfully used in sim...
This study evaluated anaerobic hydrogenation performance and microbial ecology in bioreactors ope... more This study evaluated anaerobic hydrogenation performance and microbial ecology in bioreactors operated at different hydraulic retention time (HRT) conditions and fed with glucose-peptone (GP) and starch-peptone (SP). The maximum hydrogen production rates for GP-and SP-fed bioreactors were found to be 1247 and 412 mmol-H 2 /L/d at HRT of 2 and 3 h, respectively. At HRT > 8 h, hydrogen consumption due to peptone fermentation could occur and thus reduced hydrogen yield from carbohydrate fermentation. Results of cloning/sequencing and denaturant gradient gel electrophoresis (DGGE) indicated that Clostridium sporogenes and Clostridium celerecrescens were dominant hydrogen-producing bacteria in the GP-fed bioreactor, presumably due to their capability on protein hydrolysis. In the SP-fed bioreactor, Lactobacillus plantarum, Propionispira arboris, and Clostridium butyricum were found to be dominant populations, but the presence of P. arboris at HRT > 3 h might be responsible for a lower hydrogen yield from starch fermentation. As a result, optimizing HRT operation for bioreactors was considered an important asset in order to minimize hydrogen-consuming activities and thus maximize net hydrogen production. The limitation of simple parameters such as butyrate to acetate ratio (B/A ratio) in predicting hydrogen production was recognized in this study for bioreactors fed with multiple substrates. It is suggested that microbial ecology analysis, in addition to chemical analysis, should be performed when complex substrates and mixed cultures are used in hydrogen-producing bioreactors.