Techno-economic evaluation of biohydrogen production from wastewater and agricultural waste

The world is facing serious climate change caused in part by human consumption of fossil fuel. Therefore, developing a clean and environmentally friendly energy resource is necessary given the depletion of fossil fuels, the preservation of the earth's ecosystem and self-preservation of human life. Biological hydrogen production, using dark fermentation is being developed as a promising alternative and renewable energy source, using biomass feedstock. In this study, beverage wastewater and agricultural waste were examined as substrates for dark fermentation to produce clean biohydrogen energy.     

Effect of fuelwood scarcity and socio-economic factors on household bio-based energy use and energy substitution in rural Ethiopia

In Ethiopia biomass is predominantly utilized for household energy needs often using inefficient rudimentary stoves which cause adverse environmental and welfare effects. This paper examined the contribution of biomass resources to rural household energy use and energy substitution. The analysis applied the ordinary least square in the final stage estimation of fuelwood and overall biomass energy consumption by using predicted shadow prices. The paper used Tobit model to estimate charcoal and agricultural fuel consumption due to the presence of censoring. An increase in fuelwood shadow price was associated with reduced household fuelwood consumption with price elasticity of −0.38. The cross price elasticity between fuelwood and agricultural fuels revealed no evidence of energy substitution, which conforms to the findings of previous studies. Household access to electricity was associated with lower household biomass energy utilization but kerosene was not fuelwood substitute. Household energy use conformed to the ‘fuel stacking’ or ‘multiple fuel use’ concept, but households preferred modern energy options as welfare increased in areas where modern energy is available. This suggests that there is a promising prospect for fuel-transition, but access to modern energy and economic growth have key roles. The findings suggest that a concerted policy effort is required that would help diversify rural livelihoods, improve living standards and encourage economic growth, encourage inter-fuel substitution through improved modern energy access and afforestation to increase biomass supply.     

Prioritizing driving factors of household carbon emissions: An application of the LASSO model with survey data

The identification of factors that influence household carbon emissions (HCEs)—a key driver of the national emissions, is an important step in achieving more accurate predictions, as well as better interpretation and more effective policy intervention. In this paper, based on survey data, we first calculated the direct, indirect, and total HCEs per capita for 37,620 households in China in the year of 2012, 2014 and 2016. Then we introduced a LASSO regression model to determine the main driving factors of HCEs and ranked the factors according to their importance. The use of the LASSO regression model addresses the issues of multicollinearity and over-fitting. It also provides two practical benefits: minimizing the number of influencing factors for forecasting and giving more flexibility in policy design. The results showed that fuel type and dwelling type can explain more than 70% of the direct HCEs, while income, urban or rural residency, and fuel type are the three most important influencing factors of the indirect HCEs. To mitigate HCEs while China will continue its rapid urbanization and fast consumption growth, the government needs to provide affordable clean energy, improve the efficiency of household energy consumption, promote green and low-carbon economic recovery, and guide low-carbon lifestyles.     

Rural household energy consumption with the economic development in China: stages and characteristic indices

This paper discusses history variance and general features on rural household energy consumption with the economic development in China. Energy shortage has been a long-standing problem in rural areas of China. The average effective energy consumption was 0.46–0.54 kgce per day per household in the 1960s and 1970s. The reason for this is that the rural household energy supply mainly relies on the available amounts of local natural energy resources. The problem of cooking fuel shortage was basically solved in the early 1980s since more straw and stalks were produced due to the rapid development of agriculture. The process of energy commercialization also started from the early 1980s due to the availability of coal, fuel oil and other energy sources in the market, and the reconstruction of rural power supply network. Energy consumption was 369.8 kgce per capita with 30% of commercial energy consumption and the effective heat per capita per day was 0.64 kgce in 1995. A closer relationship was found between household energy consumption level/structure and family income along with the economic development. This paper analyzed the rural household energy consumption of three typical regions, i.e., out-of-poverty, well-off and rich regions, in terms of effective heat per capita per day, percentage of commercial energy consumption in total effective heat, electricity consumption per capita and room temperature of northern areas in winter.     

Rural household energy consumption pattern in the disregarded villages of Bangladesh

Energy is one of the most important ingredients required to alleviate poverty and realize socio-economic and human development, which is directly interconnected to the prominence of life in rural areas. An extensive survey on household energy consumption pattern interrelating socio-economic and demographic factors was carried out in the disregarded villages of Bangladesh using stratified random sampling technique of 120 households. This paper focuses on household energy consumption, various combinations of fuels and their expenditure in the study area. Biomass, kerosene, electricity, LPG and candle were found as the energy carrier used in the rural households in this study. The study shows that 92% households use biomass, 28% LPG, 89% kerosene, 78% electricity and 27% candle as fuel types. It was found that 56% households collected biomass from their own homesteads and/or agricultural lands. Bamboo, branches, cow dung, firewood, rice husk, leaves & twigs and straw were found as the biomass for household energy use. Average monthly household expenditure for total energy was US$ 9.67 (SE, 0.31) per month while the total monthly income of the household was US$ 123 (SE, 2.53). The ratio of the total monthly energy expenditure to the total monthly income was 7.86%. The study will be helpful to understand the energy consumption system and its expenditure in the rural areas of Bangladesh and to the policy formulation for energy production, consumption and utilization.     

Environmental life cycle assessment of lignocellulosic conversion to ethanol: A review

Bioenergy from lignocellulosic biomass offers the potential to provide a significant source of clean, low carbon and secure energy. In recent years, a number of studies have been carried out to assess the environmental performance of lignocellulosic ethanol fuel. However, the complexity of biofuel systems generates significantly different results due to the differences in input data, methodologies applied, and local geographical conditions. Moreover, much attention has been placed on assessing climate change potential and energy consumption. This study draws on 53 published life cycle assessment of the lignocellulosic ethanol. More than half of the articles reviewed focus on assessing greenhouse gas (GHG) emission or fossil energy consumption or combination of both. All studies but two reviewed conclude that there is a reduction of GHG emission when using lignocellulosic ethanol in comparison to fossil fuel reference system. However, different studies have reported different sources contributing to GHG emission: some reports majority of GHG emissions come from biomass cultivation stage; others argue significant GHG emissions from ethanol conversion process. All articles suggest a reduction of fossil consumption in all cases of ethanol fuel. Contrary results for the impact of acidification and eutrophication potential from lignocellulosic ethanol are also observed—some reports less impact in comparison to conventional gasoline whiles others report significant increase of acidification and eutrophication potential by ethanol production. Studies also show water consumption varies significantly depending on biomass types, irrigation requirement, and regional irrigation practices; with different findings on whether agricultural practices or ethanol conversion being the main sources for water consumption. Contrary findings on emissions contributing to ecotocixity and human health have also been reported with some being favourable while others not. Results from the literature also suggest strong dependency of LCA results on system boundary, functional unit, data quality and allocation methods chosen.     

Comprehending household cooking energy choice in rural India

Energy is essential to attain the quality of life and economic prosperity in a society. In the rural areas of India, cooking dominates the aggregate consumption of energy. This energy demand is mostly met by biomass fuels, which have many associated inherent disadvantages. Hence, it is important to understand the decision making process in rural households regarding the choice of cooking fuels. For this purpose, household information using the 61st round of National Sample Survey is analyzed for the rural parts of India. The logistic regression model is used to explain the determinants of clean fuel use for cooking purposes. The study shows that number of educated females between 10 and 50 years of age, average household education index, regular salary, and monthly per capita consumption expenditure have a positive and significant impact on probability of using clean cooking fuels, whereas possessing a Below Poverty Line ration card, belonging to reserved caste categories, family size and size of farm land have a significant negative linkage.     

Analysis of changes in the structure of rural household energy consumption in northern China: A case study

There is currently a paucity of research examining changes in the structure of household energy consumption in rural areas of northern China. Here, we thoroughly analyze household energy consumption in terms of energy sources and energy end-uses in villages of Huantai County from 1989 to 2005. Results indicated that commercial energy consumption increased, both in the absolute amount and the relative proportion. Non-commercial energy (traditional biomass energy) use decreased greatly but still accounted for a significant proportion of all energy sources. In terms of energy end-uses, cooking and home-heating energy consumptions were of nearly equal importance. While energy for cooking has historically dominated total consumption, energy used for recreational activities increased dramatically in comparison. In addition, we discuss the influence of changes in energy consumption structure on household energy expenditures, environmental effects and supply-demand balance of energy. Results showed the payout of household energy consumption was stable, the environment deteriorated, the fossil fuel supply was unsustainable in the long term. For the sustainable development of local energy sources, the environment, and the economy, it will be imperative to fully exploit suitable, local renewable energy resources.     

Economic growth,fossil fuel and non-fossil consumption: A Pooled Mean Group analysis using proxies for capital

This study employs a Pooled Mean Group estimator to examine the nexus between economic growth and fossil and non-fossil fuel consumption for 53 countries between 1990 and 2012. The global sample was divided into four categories: developed exporters, developed importers, developing exporters and developing importers. The purpose of these categories was to observe whether factors unique to these countries influence the relationship between energy consumption and economic growth. With the exception of developing importers, evidence of bi-directional causality between fossil fuel consumption and real GDP across all subsamples is observed. This leads to the conclusion that efforts to directly conserve fossil fuels may harm economic growth. In terms of non-fossil fuel use, the results are more diverse. Bi-directional causality between non-fossil fuel use and real GDP is found in the long and short run for developed importers; bi-directional causality only in the long run for developed exporters; negative long-run causality from real GDP to non-fossil fuels for developing exporters; and long-run causality from non-fossil fuel use to real GDP for developing importers. These results lead to the conclusion that other factors have been responsible for the progress seen in non-fossil fuel use. Thus it is concluded that economic growth on its own is insufficient to promote clean energy development. There is a need for policy makers to create an environment conducive to renewable energy investment.     

Common factors and major characteristics of household energy consumption in comparatively well-off rural China

Common factors that influence Chinese rural household energy consumption are proposed and major demand characteristics of well-off rural areas are analyzed on the basis of survey data. A system of major characteristic indicators for rural household energy consumption includes effective heat consumption for livelihood per capita per day (EHC), the proportion of commercial energy in EHC (PCE) and annual electricity consumption for livelihood per capita (AEC). Typical values in three economic regions (out-of-poverty, well-off and rich areas) of China are also given.     

我国生物质能源现代化应用前景展望(一)——生物质资源和供给

生物质能除了可以在改善世界一次能源结构、降低化石能源需求量方面做出重要贡献以外,还可在减少温室气体排放、保障能源供应安全、改善贸易平衡、促进农村发展和改进城市废弃物处理方式等方面发挥作用。目前全球每年一次能源消费总量为500EJ,生物质资源的年用量约占一次能源消费总量的10%左右,主要被用于传统的民用燃料和生产第一代生物燃料。第二代生物燃料技术预计将于2020年前后在一些国家实现工业化生产。IEA预测,2050年世界一次能源需求量为670EJ,生物质资源将占一次能源需求总量的20%左右。各方学者预测的2050年全球生物质资源量最低值基本在200~400EJ之间,最高值在400~1500EJ之间。中国的生物燃料产业尚处于起步阶段,不过应该说取得了良好的开端。我国生物质资源相对较少,且分布不均,发展生物质能产品需要依靠能源作物。只有通过合理开发、有效利用,才能在不与粮食和食用油争夺土地的前提下,在一定程度上提供生物运输燃料和生物质发电供热所需的原料,生物质能-农产品和/或生物质能-林产品联合生产系统应成为主要发展方向。美国生物燃料产业的发展模式对我国具有一定的借鉴意义。生物质最有效的利用方式是生产运输燃料,从长远来看,生物燃料可以与石油燃料竞争,尤其是喷气燃料和汽油更具替代优势,但受到生物质资源供应量的制约。     

Energy profiles of rural domestic sector in six un-electrified villages of Jorhat district of Assam

A comparative analysis of the household energy consumption patterns and available biomass energy in six un-electrified villages of the Jorhat district of Assam is presented. This empirical study examines how the energy consumption patterns in six villages (Gariabhonga, Khongia, 8 No. Spur, Na-Jankhona, Upper-Deorigaon and Nam-Deorigaon), each representing different categories, are influenced by the locally available biomass energy resources. The study reveals that the total energy consumed in GJ/capita/year for domestic activities ranges from 7.503 to 12.692. Major findings in the domestic sector are: (1) fuel wood is preferred for domestic energy consumption, (2) easy availability encourages excessive consumption, (3) 21.5 to 42% more energy is consumed in winter than in summer for meeting cooking, water heating and space heating needs, (4) rice residues and dung are present in abundance but go to waste owing to the easy availability of fuel wood, and (5) commercial fuel kerosene is the only alternative for domestic lighting.     

Induction stoves as an option for clean cooking in rural India

As part of a programme on ‘access to clean cooking alternatives in rural India’, induction stoves were introduced in nearly 4000 rural households in Himachal Pradesh, one of the few highly electrified states in India. Analysis of primary usage information from 1000 rural households revealed that electricity majorly replaced Liquid Petroleum Gas (LPG), generally used as a secondary cooking fuel, but did not influence a similar shift from traditional mud stoves as the primary cooking technology. Likewise, the shift from firewood to electricity as a primary cooking fuel was observed in only 5% of the households studied. Country level analysis indicates that rural households falling in lower monthly per capita expenditure (MPCE) classes have lesser access to electricity and clean cooking options than those falling in higher MPCE classes. Again, only three states in India with high levels of rural household electrification report consumption statuses more than 82 kWh per month (the estimated mean for electricity consumption by induction stoves). Overall, the results of the study indicate that induction stoves will have limited potential in reducing the consumption of firewood and LPG if included in energy access programmes, that too only in regions where high levels of electrification exist.     

Effects of future fossil fuel use on CO2 levels in the atmosphere

A model based on fossil fuel use per capita and United Nations population predictions has been developed to predict global fossil fuel use and the resulting levels of CO₂ in the atmosphere. The results suggest levels of CO₂ will increase to between 415 and 421 ppm by 2025. Countries with energy-intensive economies will be responsible for the majority of CO₂ emissions, while nations with large populations but low energy consumption per capita will have less of an effect. A major increase in nuclear power generation will not have a significant impact on CO₂ levels over this time scale.     

Anaerobic fermentation technology increases biomass energy use efficiency in crop residue utilization and biogas production

A biomass energy utilization project (Corn stalk→Cattle→Cattle dung→Biogas digester→Biogas/Digester residues→Soil) was conducted in a typical temperate agro-village of China from 2005 to 2010. The present study focused on two key approaches of the ecological loop: (1) increasing corn stalk use efficiency by improving anaerobic fermentation technology; and (2) enhancing biogas productivity by optimizing fermentation conditions. Our results showed that crude protein and fat of corn stalks significantly increased, while crude fiber content and pH decreased considerably during anaerobic fermentation. The cattle digestion rate, forage consumption and increases in cattle weight were higher in cattle fed fermented corn stalks than in those fed non-fermented corn stalks. The rate of biogas production was higher (78.4%) by using cattle dung as a substrate than using crop residues. Heat preservation measures effectively enhanced the biogas production rate (12.3%). In 2005, only two cattle were fed in this village, with only 1.1% corn stalk utilized as forage. No more than three biogas digesters existed, and the proportion of biogas energy used in total household fuel was only 1.7%. At the end of the 5-year experiment, the number of cattle capita reached 169 with 78.9% corn stalk used as forage. Biogas digesters increased to 130, and the proportion of biogas energy used in total household fuel was up to 42.3%. A significant positive correlation was noted between the increasing rate of farmers’ incomes and the proportion of corn stalks used as forage. Available nutrients were higher in fermented cattle dung than in fresh cattle dung. Our findings clearly suggest that anaerobic fermentation technology is important in enhancing crop residue use efficiency, biogas productivity and soil fertility. Fermentation technology may help reduce the use of fossil fuels and improve the environment in rural areas.     

Biomass boiler conversion potential in the eastern United States

The U.S. is the world's leading consumer of primary energy. A large fraction of this energy is used in boiler installations to generate steam and hot water for heating applications. It is estimated there are total 163,000 industrial and commercial boilers in use in the United States of all sizes.This paper characterizes the commercial and industrial boilers in the 37 states of the Midwest, Northeast, and Southern regions of the U.S. in term of number of units, unit capacity, aggregate capacity, and fuel type. A methodology is developed for evaluating and ranking the potential for converting from existing fossil-fuel boilers to biomass boilers in these states.In total, 3495 oil and coal boiler units in industrial and commercial buildings, and 1067 major wood energy facilities in the 37 eastern states were identified. These represent a subset of existing and potential conversions from fossil fuels to woody biomass. Based on this sample and energy consumption data from the Energy Information Administration (EIA), we estimate that there are currently 31,776 oil, coal, and propane boiler units over 0.5 MMBtus/hour capacity in these 37 states, representing a total energy consumption of 1.7 quadrillion Btus, or roughly the equivalent of 287 million barrels of oil. Were these units all converted to woody biomass fuel, they would consume a total of 121 million dry tons of wood per year, about three times the most recent US DOE estimates of woody biomass availability in those regions. Since only the most economical conversions typically occur, the reality of woody biomass market availability combined with thermal fossil-fuel consumption patterns suggests that roughly one-third of all potential projects could be achieved under sustainable utilization of existing biomass feedstocks in the three regions.Analysis of the results indicates that a targeted response to wood-conversion initiatives will yield the most successful program of fossil-fuel replacement in thermal applications. A ranking index developed in this study through analysis of existing boiler installations and availability of wood feedstocks suggests that the top ten states in the eastern United States on which to focus future messaging, feasibility studies, and policy development for potential woody biomass conversions are:1. Maine, 2. Texas, 3. New York, 4. Florida, 5. Georgia, 6. Alabama, 7. South Carolina, 8. North Carolina, 9. Arkansas, 10. Pennsylvania.     

A comparative study of bioenergy consumption and CO2 emissions in Tibetan region of China

Bioenergy is an important energy source for Tibetans. To compensate for the lack of a comparative study on household bioenergy consumption and CO₂ emissions among farming region, farming-pastoral region, pastoral region, and forest edge zones in Tibetan area, the authors conducted the comparative study through field investigation, literature review and data analysis. The study results reveal that: (1)Bioenergy consumption show regularity from high to low in forest edge zones, pastoral region, farming-pastoral region and farming region, respectively, but the CO₂ emissions change from high to low in forest edge zones, pastoral region, farming region, and farming-pastoral region, respectively in Tibetan area; (2)Remote geographic locations and traditional nomadic system restricts Tibetan pastoral region from use of diversified energy, resulting in higher bioenergy consumption and CO₂ emissions; (3)The energy efficiency could be potentially increased by improving energy structures and by using durable, low cost and easy to carry clean energy facilities.     

Household energy consumption pattern and socio-cultural dimensions associated with it: A case study of rural Haryana, India

A survey of household energy consumption pattern was carried out in a village of Jhajjhar district of Haryana, India in the year 2007. The households surveyed covered heterogeneous population belonging to different income, educational and social groups. There was more availability and utilization of solid biomass fuels as energy resources in domestic sector as compared to the commercial fuels. Dung cakes, crop residues and firewood were found to be the three main fuels used for cooking, though LPG was also used along with biomass fuels. But complete conversion to cleaner fuels has not taken place yet even in households that has been using LPG for many years. Income was an important factor determining the choice of fuel for cooking, but there were some socio-cultural factors which were equally important in making fuel preferences at household level.     

When will fossil fuel reserves be diminished?

Crude oil, coal and gas are the main resources for world energy supply. The size of fossil fuel reserves and the dilemma that “when non-renewable energy will be diminished” is a fundamental and doubtful question that needs to be answered. This paper presents a new formula for calculating when fossil fuel reserves are likely to be depleted and develops an econometrics model to demonstrate the relationship between fossil fuel reserves and some main variables. The new formula is modified from the Klass model and thus assumes a continuous compound rate and computes fossil fuel reserve depletion times for oil, coal and gas of approximately 35, 107 and 37 years, respectively. This means that coal reserves are available up to 2112, and will be the only fossil fuel remaining after 2042. In the Econometrics model, the main exogenous variables affecting oil, coal and gas reserve trends are their consumption and respective prices between 1980 and 2006. The models for oil and gas reserves unexpectedly show a positive and significant relationship with consumption, while presenting a negative and significant relationship with price. The econometrics model for coal reserves, however, expectedly illustrates a negative and significant relationship with consumption and a positive and significant relationship with price. Consequently, huge reserves of coal and low-level coal prices in comparison to oil and gas make coal one of the main energy substitutions for oil and gas in the future, under the assumption of coal as a clean energy source.     

Stochastic convergence in per capita fossil fuel consumption in U.S. states

This study examines the stochastic convergence of per capita fossil fuel consumption across U.S. states (including the District of Columbia) utilizing LM and RALS-LM unit root tests with allowance for endogenously determined structural breaks. Our results indicate that with the exception of Nevada, the evidence from two-break and one-break LM and RALS-LM unit root tests rejects the null hypothesis of a unit root in the relative per capita fossil fuel consumption in the U.S. This finding indicates the presence of stochastic convergence in relative per capita fossil fuel consumption in the U.S. states.