Development of Charcoal-Based Nanofluids for Enhanced Oil Recovery

Amid global efforts to combat climate change and transition to renewable energy sources, the importance of oil and gas for meeting current energy demands remains undeniable. As initiatives like the Paris Agreement aim to limit global warming, cost-effective and sustainable methods for oil recovery become increasingly crucial. This study delves into the development of charcoal-based nanofluids for enhanced oil recovery (EOR) flooding. Oil recovery is carried out in stages; The first is the primary stage via natural pressure depletion, which generally drives about 20% of the original oil in place (OOIP) to the oil well. Next is the secondary stage also known as water flooding, at this stage, an incremental recovery of ̴ 30% of OOIP can be achieved from a high-quality reservoir. To further recover the remaining 60-70% OOIP, the tertiary stage also known as the EOR (enhanced oil recovery), is applied, which can recover an additional 10-30% of OOIP at the best case scenario. The fluid flooding of EOR needs to overcome the flow path formed during water flooding and effectively spread to a large volume of the complicated structured reservoir driving out the oil in a mixture of brine and gas. Nanofluids of various metal oxides such as SiO2 and TiO2, Al2O3 and Fe2O3 have been examined for their performance in enhanced oil recovery and have demonstrated an oil recovery capacity of 8-16% of the original oil in place (OOIP) after water flooding for SiO2, Al2O3 and TiO2. Charcoals derived from abundant and agricultural wastes rice husk (RHC), wheat straw char (WSC) as well as active carbon (AC) as a reference sample were selected for this study. The study covers the preparation and characterisation of their aqueous nanofluids for size/size distribution of nanoparticles, nanoparticle surface chemistry and interaction with each other, and more importantly, their enhancement on the viscosity of the aqueous charcoal-based nanofluids. The charcoal nanofluids were prepared by wet milling in water. Size analysis detected the nanoparticle size approximately at 154 nm for RHC, 96 nm for WSC and 210 nm for AC at pH 7.0. These sizes varied with the pH values of the nanofluids according to their surface chemistry. The viscosity of the charcoal-based nanofluids was systematically studied for the effect of charcoal concentration (0.5 - 2.5 wt%) and pH values (pH 2.0-pH 11.0). The viscosity enhancement was observed from the three types of charcoal-based nanofluids in the concentration and pH ranges studied. The enhancement was evaluated by the Dispersion Factor (DF), which is proposed in this study based on Chen et al. (2007) equation to comprehensively evaluate the effect of nanoparticle dispersion in a fluid on its viscosity. The higher the dispersion factor, the stronger the interaction of the nanoparticles to the dispersion liquid, and the higher the viscosity enhancement. The DF values of RHC and WSC nanofluids were slightly higher than those of the nanofluids of TiO2 and SiO2 with 5-10 times smaller particle sizes in the literature. More impressively the viscosity enhancement of AC nanoparticles is comparable to that of carbon nanotubes at concentrations below 0.6 vol.% and surpasses carbon nanotubes when the concentration is higher than 0.6 vol.%. The viscosity study shows the potential of the charcoal-based nanofluids to enhance their oil displacement efficiency in EOR. The EOR flooding tests of the charcoal-based nanofluids were conducted on sand-packed cores to mimic sandstone-dominated oil reservoirs. A sectional flooding method is applied, i.e., the nanofluids equivalent to 20% of the pore volume were injected into the packed cores after water flooding saw a levelled oil recovery rate. Water flooding was restored after the nanofluid injection. The effect of nanoparticle concentrations and pH levels of the nanofluids were examined on the enhanced oil recovery. The results showed that 1) a higher nanofluid concentration recovered more original oil in place in the range of 15.4% - 19.3% of OOIP for AC pH 6.0 1 wt% and 2 wt% respectively; 2) the pH value of the nanofluids had a sensible effect on their EOR performance. At a pH that the nanofluids showed a higher viscosity, the oil recovery rate is higher. 3) Most impressively the active carbon nanofluid at pH 2.0 demonstrated a manipulatable flow pattern by pH value in the side of the packed core and eventually yielded a notable further 34.1% of original oil-in-place at a concentration of 2 wt%. Overall, the findings underscore the promising potential of charcoal-based nanofluids as effective EOR flooding fluids. Their abundant renewable nature, as a by-product of biofuel productions and low-cost position them as attractive alternatives of viscosity enhancement agents for advancing EOR technologies and, meanwhile, storing the carbon-rich nanoparticles in the oil reservoir after utilisation

A viscosity study of charcoal-based nanofluids towards enhanced oil recovery

Research into nanofluids for enhanced oil recovery (EOR) has been carried out for more than a decade. Metal oxide nanoparticles dispersed in water are usually applied and the nanofluids can recover 8–16 % more of the original oil in place after or comparing to water flooding, while the oil recovery capacity of carbon tube nanofluids can be even better. Higher viscosities of nanofluids than that of water are one of the key properties that contribute to their good performance in EOR. This work, for the first time, prepared nanofluids from two charcoal samples as well as an active carbon sample for their possible application for EOR. The relationship of nanofluid viscosities with pH values as well as nanoparticle concentrations of the nanofluids was studied for their viscous behaviour in different shear conditions. Their representative viscosity data measured at 100 rpm were examined for the values of the so-called Dispersion Factor (DF). The determined DF values for the charcoal-based nanofluids are close to those of metal oxide nanofluids that have much smaller nanoparticle sizes. The highly porous active carbon nanofluid showed strong viscosity enhancement that is comparable to the values reported for nanofluids of carbon nanotubes. Due to their significant viscosity enhancement and carbon sequestration feature, the charcoal-based nanofluids are promising to be used for EOR

Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950–2021, and the impact of the COVID-19 pandemic: a comprehensive demographic analysis for the Global Burden of Disease Study 2021

Background: Estimates of demographic metrics are crucial to assess levels and trends of population health outcomes. The profound impact of the COVID-19 pandemic on populations worldwide has underscored the need for timely estimates to understand this unprecedented event within the context of long-term population health trends. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 provides new demographic estimates for 204 countries and territories and 811 additional subnational locations from 1950 to 2021, with a particular emphasis on changes in mortality and life expectancy that occurred during the 2020–21 COVID-19 pandemic period. Methods: 22 223 data sources from vital registration, sample registration, surveys, censuses, and other sources were used to estimate mortality, with a subset of these sources used exclusively to estimate excess mortality due to the COVID-19 pandemic. 2026 data sources were used for population estimation. Additional sources were used to estimate migration; the effects of the HIV epidemic; and demographic discontinuities due to conflicts, famines, natural disasters, and pandemics, which are used as inputs for estimating mortality and population. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate under-5 mortality rates, which synthesised 30 763 location-years of vital registration and sample registration data, 1365 surveys and censuses, and 80 other sources. ST-GPR was also used to estimate adult mortality (between ages 15 and 59 years) based on information from 31 642 location-years of vital registration and sample registration data, 355 surveys and censuses, and 24 other sources. Estimates of child and adult mortality rates were then used to generate life tables with a relational model life table system. For countries with large HIV epidemics, life tables were adjusted using independent estimates of HIV-specific mortality generated via an epidemiological analysis of HIV prevalence surveys, antenatal clinic serosurveillance, and other data sources. Excess mortality due to the COVID-19 pandemic in 2020 and 2021 was determined by subtracting observed all-cause mortality (adjusted for late registration and mortality anomalies) from the mortality expected in the absence of the pandemic. Expected mortality was calculated based on historical trends using an ensemble of models. In location-years where all-cause mortality data were unavailable, we estimated excess mortality rates using a regression model with covariates pertaining to the pandemic. Population size was computed using a Bayesian hierarchical cohort component model. Life expectancy was calculated using age-specific mortality rates and standard demographic methods. Uncertainty intervals (UIs) were calculated for every metric using the 25th and 975th ordered values from a 1000-draw posterior distribution. Findings: Global all-cause mortality followed two distinct patterns over the study period: age-standardised mortality rates declined between 1950 and 2019 (a 62·8% [95% UI 60·5–65·1] decline), and increased during the COVID-19 pandemic period (2020–21; 5·1% [0·9–9·6] increase). In contrast with the overall reverse in mortality trends during the pandemic period, child mortality continued to decline, with 4·66 million (3·98–5·50) global deaths in children younger than 5 years in 2021 compared with 5·21 million (4·50–6·01) in 2019. An estimated 131 million (126–137) people died globally from all causes in 2020 and 2021 combined, of which 15·9 million (14·7–17·2) were due to the COVID-19 pandemic (measured by excess mortality, which includes deaths directly due to SARS-CoV-2 infection and those indirectly due to other social, economic, or behavioural changes associated with the pandemic). Excess mortality rates exceeded 150 deaths per 100 000 population during at least one year of the pandemic in 80 countries and territories, whereas 20 nations had a negative excess mortality rate in 2020 or 2021, indicating that all-cause mortality in these countries was lower during the pandemic than expected based on historical trends. Between 1950 and 2021, global life expectancy at birth increased by 22·7 years (20·8–24·8), from 49·0 years (46·7–51·3) to 71·7 years (70·9–72·5). Global life expectancy at birth declined by 1·6 years (1·0–2·2) between 2019 and 2021, reversing historical trends. An increase in life expectancy was only observed in 32 (15·7%) of 204 countries and territories between 2019 and 2021. The global population reached 7·89 billion (7·67–8·13) people in 2021, by which time 56 of 204 countries and territories had peaked and subsequently populations have declined. The largest proportion of population growth between 2020 and 2021 was in sub-Saharan Africa (39·5% [28·4–52·7]) and south Asia (26·3% [9·0–44·7]). From 2000 to 2021, the ratio of the population aged 65 years and older to the population aged younger than 15 years increased in 188 (92·2%) of 204 nations. Interpretation: Global adult mortality rates markedly increased during the COVID-19 pandemic in 2020 and 2021, reversing past decreasing trends, while child mortality rates continued to decline, albeit more slowly than in earlier years. Although COVID-19 had a substantial impact on many demographic indicators during the first 2 years of the pandemic, overall global health progress over the 72 years evaluated has been profound, with considerable improvements in mortality and life expectancy. Additionally, we observed a deceleration of global population growth since 2017, despite steady or increasing growth in lower-income countries, combined with a continued global shift of population age structures towards older ages. These demographic changes will likely present future challenges to health systems, economies, and societies. The comprehensive demographic estimates reported here will enable researchers, policy makers, health practitioners, and other key stakeholders to better understand and address the profound changes that have occurred in the global health landscape following the first 2 years of the COVID-19 pandemic, and longer-term trends beyond the pandemic

Occurrence of bacteria and endotoxins in fermented foods and beverages from Nigeria and South Africa

In Africa, fermented foods and beverages play significant roles in contributing to food security. Endotoxins are ubiquitous heat stable lipopolysaccharide (LPS) complexes situated in the outer cell membranes of Gram-negative bacteria. This study evaluated the microbiological quality of fermented foods (ogiri, ugba, iru, ogi and ogi baba) and beverages (mahewu and untqombodti) from selected Nigerian and South African markets. The bacterial diversity of the fermented foods was also investigated and the identity of the isolates confirmed by biochemical and molecular methods. Isolate grouping was established through hierarchal clustering and the samples were further investigated for endotoxin production with the chromogenic Limulus Amoebocyte Lysate assay. The total aerobic count of the samples ranged from 5.7 to 10.8 Log CFU/g. Fourteen bacteria genera were detected with most of the isolates being members of the Enterobacteriaceae family. Sphingomonas paucimobilis and Escherichia colt were the dominant Gram-negative bacterial species detected. There were considerable variations in the concentrations of endotoxins produced and the lowest endotoxin concentration was found in ogi (4.3 x 10 EU/g) and the highest in iru (5.5 x 10(4) EU/g) while, 44% of umqombothi samples had endotoxins. Ogi baba samples had better microbial quality than other samples due to its reduced bacterial load and endotoxin levels. There was a strong positive (r = 0.714, r = 0.996) and significant (p < 0.01) correlation between the endotoxin levels and bacterial loads of the samples. Some previously unreported species of bacteria found in the fermented foods included Aeromonas haemolyticus and Rhizobium radiobacter. This is the first comprehensive report on endotoxins in fermented foods and beverages in Africa. Furthermore, the occurrence of pathogenic bacteria and toxins in the foods and beverages is of serious concern that calls for immediate action

Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950–2021, and the impact of the COVID-19 pandemic: a comprehensive demographic analysis for the Global Burden of Disease Study 2021

BackgroundEstimates of demographic metrics are crucial to assess levels and trends of population health outcomes. The profound impact of the COVID-19 pandemic on populations worldwide has underscored the need for timely estimates to understand this unprecedented event within the context of long-term population health trends. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 provides new demographic estimates for 204 countries and territories and 811 additional subnational locations from 1950 to 2021, with a particular emphasis on changes in mortality and life expectancy that occurred during the 2020–21 COVID-19 pandemic period.Methods22 223 data sources from vital registration, sample registration, surveys, censuses, and other sources were used to estimate mortality, with a subset of these sources used exclusively to estimate excess mortality due to the COVID-19 pandemic. 2026 data sources were used for population estimation. Additional sources were used to estimate migration; the effects of the HIV epidemic; and demographic discontinuities due to conflicts, famines, natural disasters, and pandemics, which are used as inputs for estimating mortality and population. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate under-5 mortality rates, which synthesised 30 763 location-years of vital registration and sample registration data, 1365 surveys and censuses, and 80 other sources. ST-GPR was also used to estimate adult mortality (between ages 15 and 59 years) based on information from 31 642 location-years of vital registration and sample registration data, 355 surveys and censuses, and 24 other sources. Estimates of child and adult mortality rates were then used to generate life tables with a relational model life table system. For countries with large HIV epidemics, life tables were adjusted using independent estimates of HIV-specific mortality generated via an epidemiological analysis of HIV prevalence surveys, antenatal clinic serosurveillance, and other data sources. Excess mortality due to the COVID-19 pandemic in 2020 and 2021 was determined by subtracting observed all-cause mortality (adjusted for late registration and mortality anomalies) from the mortality expected in the absence of the pandemic. Expected mortality was calculated based on historical trends using an ensemble of models. In location-years where all-cause mortality data were unavailable, we estimated excess mortality rates using a regression model with covariates pertaining to the pandemic. Population size was computed using a Bayesian hierarchical cohort component model. Life expectancy was calculated using age-specific mortality rates and standard demographic methods. Uncertainty intervals (UIs) were calculated for every metric using the 25th and 975th ordered values from a 1000-draw posterior distribution.FindingsGlobal all-cause mortality followed two distinct patterns over the study period: age-standardised mortality rates declined between 1950 and 2019 (a 62·8% [95% UI 60·5–65·1] decline), and increased during the COVID-19 pandemic period (2020–21; 5·1% [0·9–9·6] increase). In contrast with the overall reverse in mortality trends during the pandemic period, child mortality continued to decline, with 4·66 million (3·98–5·50) global deaths in children younger than 5 years in 2021 compared with 5·21 million (4·50–6·01) in 2019. An estimated 131 million (126–137) people died globally from all causes in 2020 and 2021 combined, of which 15·9 million (14·7–17·2) were due to the COVID-19 pandemic (measured by excess mortality, which includes deaths directly due to SARS-CoV-2 infection and those indirectly due to other social, economic, or behavioural changes associated with the pandemic). Excess mortality rates exceeded 150 deaths per 100 000 population during at least one year of the pandemic in 80 countries and territories, whereas 20 nations had a negative excess mortality rate in 2020 or 2021, indicating that all-cause mortality in these countries was lower during the pandemic than expected based on historical trends. Between 1950 and 2021, global life expectancy at birth increased by 22·7 years (20·8–24·8), from 49·0 years (46·7–51·3) to 71·7 years (70·9–72·5). Global life expectancy at birth declined by 1·6 years (1·0–2·2) between 2019 and 2021, reversing historical trends. An increase in life expectancy was only observed in 32 (15·7%) of 204 countries and territories between 2019 and 2021. The global population reached 7·89 billion (7·67–8·13) people in 2021, by which time 56 of 204 countries and territories had peaked and subsequently populations have declined. The largest proportion of population growth between 2020 and 2021 was in sub-Saharan Africa (39·5% [28·4–52·7]) and south Asia (26·3% [9·0–44·7]). From 2000 to 2021, the ratio of the population aged 65 years and older to the population aged younger than 15 years increased in 188 (92·2%) of 204 nations.InterpretationGlobal adult mortality rates markedly increased during the COVID-19 pandemic in 2020 and 2021, reversing past decreasing trends, while child mortality rates continued to decline, albeit more slowly than in earlier years. Although COVID-19 had a substantial impact on many demographic indicators during the first 2 years of the pandemic, overall global health progress over the 72 years evaluated has been profound, with considerable improvements in mortality and life expectancy. Additionally, we observed a deceleration of global population growth since 2017, despite steady or increasing growth in lower-income countries, combined with a continued global shift of population age structures towards older ages. These demographic changes will likely present future challenges to health systems, economies, and societies. The comprehensive demographic estimates reported here will enable researchers, policy makers, health practitioners, and other key stakeholders to better understand and address the profound changes that have occurred in the global health landscape following the first 2 years of the COVID-19 pandemic, and longer-term trends beyond the pandemic