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1.
The use of different input data, functional units, allocation methods, reference systems and other assumptions complicates comparisons of LCA bioenergy studies. In addition, uncertainties and use of specific local factors for indirect effects (like land-use change and N-based soil emissions) may give rise to wide ranges of final results. In order to investigate how these key issues have been addressed so far, this work performs a review of the recent bioenergy LCA literature. The abundance of studies dealing with the different biomass resources, conversion technologies, products and environmental impact categories is summarized and discussed. Afterwards, a qualitative interpretation of the LCA results is depicted, focusing on energy balance, GHG balance and other impact categories. With the exception of a few studies, most LCAs found a significant net reduction in GHG emissions and fossil energy consumption when bioenergy replaces fossil energy. 相似文献
2.
《Biotechnology advances》2017,35(4):466-489
The adverse environmental impacts of the fossil fuel and the concerns of energy security necessitate the development of alternative clean energy sources from renewable feedstocks. Lignocellulosic biomass is a 2nd generation feedstock used in the production of biofuels and bio-based products that are conventionally derived from fossil resources. The biochemical conversion, which entails biomass pretreatment, enzymatic hydrolysis and fermentation, is one major platform used to transform lignocelluloses into biofuels. However, lignin presents many challenges to enzymatic hydrolysis leading to the need of high enzyme dose, low hydrolysis yield, low level of recyclability, high cost of enzymatic hydrolysis (because of the high cost of enzymes), and so on. Therefore, enzymatic hydrolysis, which is not cost effective, becomes one of major cost contributors. To mitigate the negative effects of lignin, extensive research has been conducted to explore the fundamental mechanisms of lignin-enzyme interactions to develop technologies to overcome the negative effects of lignin on enzymatic hydrolysis. Non-productive adsorption, which is characterized by hydrophobic, electrostatic and/or hydrogen bonding interactions, is widely known as the primary mechanism governing lignin-enzyme interactions. In addition, lignin-enzyme interaction is also influenced by steric hindrance (i.e., the physical blocking of enzyme access to carbohydrates by lignin). However, the mechanisms underlying the lignin-enzyme interactions remain unclear. This article aims to present a comprehensive review on the lignin-enzyme interactions (i.e. the mechanism, governing driving forces, modeling, and technologies for mitigating the negative effect of lignin). The current challenges inherent in this process and possible avenues of research in cellulosic biorefinery conclude this article. 相似文献
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4.
Franziska Enzmann Markus Stckl An‐Ping Zeng Dirk Holtmann 《Engineering in Life Science》2019,19(2):121-132
Facing energy problems, there is a strong demand for new technologies dealing with the replacement of fossil fuels. The emerging fields of biotechnology, photobiotechnology and electrobiotechnology, offer solutions for the production of fuels, energy, or chemicals using renewable energy sources (light or electrical current e.g. produced by wind or solar power) or organic (waste) substrates. From an engineering point of view both technologies have analogies and some similar challenges, since both light and electron transfer are primarily surface‐dependent. In contrast to that, bioproduction processes are typically volume dependent. To allow large scale and industrially relevant applications of photobiotechnology and electrobiotechnology, this opinion first gives an overview over the current scales reached in these areas. We then try to point out the challenges and possible methods for the scale up or numbering up of the reactors used. It is shown that the field of photobiotechnology is by now much more advanced than electrobiotechnology and has achieved industrial applications in some cases. We argue that transferring knowledge from photobiotechnology to electrobiotechnology can speed up the development of the emerging field of electrobiotechnology. We believe that a combination of scale up and numbering up, as it has been shown for several photobiotechnological reactors, may well lead to industrially relevant scales in electrobiotechnological processes allowing an industrial application of the technology in near future. 相似文献
5.
Bioconversion of Lignocellulose into Bioethanol: Process Intensification and Mechanism Research 总被引:2,自引:0,他引:2
Biofuels produced from lignocellulosic biomass can significantly reduce the energy dependency on fossil fuels and the resulting effects on environment. In this respect, cellulosic ethanol as an alternative fuel has the potential to become a viable energy source in the near future. Over the past few decades, tremendous effort has been undertaken to make cellulosic ethanol cost competitive with conventional fossil fuels. The pretreatment step is always necessary to deconstruct the recalcitrant structures and to make cellulose more accessible to enzymes. A large number of pretreatment technologies involving physical, chemical, biological, and combined approaches have been developed and tested at the pilot scale. Furthermore, various strategies and methods, including multi-enzyme complex, non-catalytic additives, enzyme recycling, high solids operation, design of novel bioreactors, and strain improvement have also been implemented to improve the efficiency of subsequent enzymatic hydrolysis and fermentation. These technologies provide significant opportunities for lower total cost, thus making large-scale production of cellulosic ethanol possible. Meanwhile, many researchers have focused on the key factors that limit cellulose hydrolysis, and analyzing the reaction mechanisms of cellulase. This review describes the most recent advances on process intensification and mechanism research of pretreatment, enzymatic hydrolysis, and fermentation during the production of cellulosic ethanol. 相似文献
6.
This study examines the energy consumption and environmental degradation nexus at a disaggregated (i.e., fossil fuel energy and renewable energy) level by investigating bibliometric indicators on a global scale. For this purpose, the study considers a number of studies published between 1980 and 2021 that were selected on the Web of Science (WoS) database based on relevant keywords. A bibliometric analysis was done through VOSviewer from a comparative perspective. Thus, 17,298 studies on fossil fuel energy consumption & environmental degradation and 62,002 studies on renewable energy consumption & environmental degradation were identified. Bibliometric indicators and network visualizations were used to present the results, which show: (i) the topic of disaggregated energy consumption and environmental degradation has been a problem since 1991; (ii) the number of renewable energy-related studies has exceeded the number of fossil fuel-related studies regarding environmental degradation; (iii) many of the studies in both disaggregated groups fall under the categories of energy fuels, environmental sciences, and green sustainable science technology, respectively; (iv) most of the studies have been published by Elsevier; (v) most of the researchers are from the United States of America (USA), whereas those from China and Pakistan have recently come to the fore. Hence, this study assesses the emerging trends in the literature on the energy consumption and environmental degradation nexus at a disaggregated level. Moreover, potential issues to be included by future studies are suggested. 相似文献
7.
《Comptes Rendus Palevol》2008,7(2-3):159-184
Advances in technology over the past two decades have resulted in unprecedented access to data from biological specimens. These data have expanded our understanding of physical characteristics, physiological, cellular and subcellular processes, and evolutionary relationships at the molecular level and beyond. Paleontological and archaeological sciences have recently begun to apply these technologies to fossil and subfossil representatives of extinct organisms. Data derived from multidisciplinary, non-traditional techniques can be difficult to decipher, and without a basic understanding of the type of information provided by these methods, their usefulness for fossil studies may be overlooked. This review describes some of these powerful new analytical tools, the data that may be accessible through their use, advantages and limitations, and how they can be applied to fossil material to elucidate characteristics of extinct organisms and their paleoecological environments. 相似文献
8.
Pretreatment and Lignocellulosic Chemistry 总被引:2,自引:0,他引:2
Lignocellulosic materials such as wood, grass, and agricultural and forest residues are promising alternative energy resources that can be utilized to produce ethanol. The yield of ethanol production from native lignocellulosic material is relatively low due to its native recalcitrance, which is attributed to, in part, lignin content/structure, hemicelluloses, cellulose crystallinity, and other factors. Pretreatment of lignocellulosic materials is required to overcome this recalcitrance. The goal of pretreatment is to alter the physical features and chemical composition/structure of lignocellulosic materials, thus making cellulose more accessible to enzymatic hydrolysis for sugar conversion. Various pretreatment technologies to reduce recalcitrance and to increase sugar yield have been developed during the past two decades. This review examines the changes in lignocellulosic structure primarily in cellulose and hemicellulose during the most commonly applied pretreatment technologies including dilute acid pretreatment, hydrothermal pretreatment, and alkaline pretreatment. 相似文献
9.
YS Jang B Kim JH Shin YJ Choi S Choi CW Song J Lee HG Park SY Lee 《Biotechnology and bioengineering》2012,109(10):2437-2459
Platform chemicals composed of 2–6 carbons derived from fossil resources are used as important precursors for making a variety of chemicals and materials, including solvents, fuels, polymers, pharmaceuticals, perfumes, and foods. Due to concerns regarding our environment and the limited nature of fossil resources, however, increasing interest has focused on the development of sustainable technologies for producing these platform chemicals from renewable resources. The techniques and strategies for developing microbial strains for chemicals production have advanced rapidly, and it is becoming feasible to develop microbes for producing additional types of chemicals, including non‐natural molecules. In this study, we review the current status of the bio‐based production of major C2–C6 platform chemicals, focusing on the microbial production of platform chemicals that have been used for the production of chemical intermediates, building block compounds, and polymers. Biotechnol. Bioeng. 2012; 109: 2437–2459. © 2012 Wiley Periodicals, Inc. 相似文献
10.
Modern energy production is required to undergo a dramatic transformation. It will have to replace fossil fuel use by a sustainable and clean energy economy while meeting the growing world energy needs. This review analyzes the current energy sector, available energy sources, and energy conversion technologies. Solar energy is the only energy source with the potential to fully replace fossil fuels, and hydrogen is a crucial energy carrier for ensuring energy availability across the globe. The importance of photosynthetic hydrogen production for a solar-powered hydrogen economy is highlighted and the development and potential of this technology are discussed. Much successful research for improved photosynthetic hydrogen production under laboratory conditions has been reported, and attempts are underway to develop upscale systems. We suggest that a process of integrating these achievements into one system to strive for efficient sustainable energy conversion is already justified. Pursuing this goal may lead to a mature technology for industrial deployment. 相似文献
11.
Nor‐Insyirah Syahira Abdul Latif Mei Yin Ong Saifuddin Nomanbhay 《Engineering in Life Science》2019,19(4):246-269
Currently, fossil materials form the majority of our energy and chemical source. Many global concerns force us to rethink about our current dependence on the fossil energy. Limiting the use of these energy sources is a key priority for most countries that pledge to reduce greenhouse gas emissions. The application of biomass, as substitute fossil resources for producing biofuels, plastics and chemicals, is a widely accepted strategy for sustainable development. Aquatic plants including algae possess competitive advantages as biomass resources compared to the terrestrial plants in this current global situation. Bio‐oil production from algal biomass is technically and economically viable, cost competitive, requires no capacious lands and minimal water use and reduces atmospheric carbon dioxide. The aim of this paper is to review the potential of converting algal biomass, as an aquatic plant, into high‐quality crude bio‐oil through applicable processes in Malaysia. In particular, bio‐based materials and fuels from algal biomass are considered as one of the reliable alternatives for clean energy. Currently, pyrolysis and hydrothermal liquefaction (HTL) are two foremost processes for bio‐oil production from biomass. HTL can directly convert high‐moisture algal biomass into bio‐oil, whereas pyrolysis requires feedstock drying to reduce the energy consumption during the process. Microwave‐assisted HTL, which can be conducted in aqueous environment, is suitable for aquatic plants and wet biomass such as algae. 相似文献
12.
This article aims to estimate the efficiency of 26 different European Countries over 2001 and 2012 comparing their performance. Data Envelopment Analysis technique is used in a first step to evaluate the performance of each European country. The output-oriented model was used with two specifications (Variable and Constant Returns to Scale) including as inputs labour and capital productivity, the weight of fossil energy and the share of renewable energy in GDP (gross domestic product), being the output GDP per GHG (greenhouse gases) emissions. In a second step, the quantile regression technique was used, to explain different efficiency scores through variables as Environmental Taxes Revenues, Resources Productivity and Domestic Material Consumption. Results indicate that share of renewables and non-renewable energy sources are important to explain differences in emissions. They suggest a significant change in the trend of economic and environmental efficiency in European countries and put forward the high disparities existing among them. Policy recommendations point for the need of higher steps if the goal is to equal countries efficiency scores. Moreover, environmental tax revenue effects are negatively stronger in less efficient countries, whereas also exerting negative influence over those more eco-efficient. Transport taxes affect negatively more eco-efficient countries and positively less eco-efficient countries. Energy taxes only seem to positively influence the lower eco-efficient countries. There is also evidence for a negative premium of efficiency considering domestic materials consumption. Finally, resources productivity shows a positive and significant influence independently of the country technical eco-efficiency level. 相似文献
13.
Pursuing More Sustainable Consumption by Analyzing Household Metabolism in European Countries and Cities 总被引:1,自引:0,他引:1
《Journal of Industrial Ecology》2005,9(1-2):259-275
Bringing about more sustainable consumption patterns is an important challenge for society and science. In this article the concept of household metabolism is applied to analyzing consumption patterns and to identifying possibilities for the development of sustainable household consumption patterns. Household metabolism is determined in terms of total energy requirements, including both direct and indirect energy requirements, using a hybrid method. This method enables us to evaluate various determinants of the environmental load of consumption consistently at several levels—the national level, the local level, and the household level.
The average annual energy requirement of households varies considerably between the Netherlands, the United Kingdom, Norway, and Sweden, as well as within these countries. The average expenditure level per household explains a large part of the observed variations. Differences between these countries are also related to the efficiency of the production sectors and to the energy supply system. The consumption categories of food, transport, and recreation show the largest contributions to the environmental load. A comparison of consumer groups with different household characteristics shows remarkable differences in the division of spending over the consumption categories.
Thus, analyses of different types of households are important for providing a basis for options to induce decreases of the environmental load of household consumption. At the city level, options for change are provided by an analysis of the city infrastructure, which determines a large part of the direct energy use by households (for transport and heating). At the national level, energy efficiency in production and in electricity generation is an important trigger for decreasing household energy requirements. 相似文献
The average annual energy requirement of households varies considerably between the Netherlands, the United Kingdom, Norway, and Sweden, as well as within these countries. The average expenditure level per household explains a large part of the observed variations. Differences between these countries are also related to the efficiency of the production sectors and to the energy supply system. The consumption categories of food, transport, and recreation show the largest contributions to the environmental load. A comparison of consumer groups with different household characteristics shows remarkable differences in the division of spending over the consumption categories.
Thus, analyses of different types of households are important for providing a basis for options to induce decreases of the environmental load of household consumption. At the city level, options for change are provided by an analysis of the city infrastructure, which determines a large part of the direct energy use by households (for transport and heating). At the national level, energy efficiency in production and in electricity generation is an important trigger for decreasing household energy requirements. 相似文献
14.
Webster Mavhu Sasha Frade Ann-Marie Yongho Margaret Farrell Karin Hatzold Michael Machaku Mathews Onyango Owen Mugurungi Bennett Fimbo Peter Cherutich Dino Rech Delivette Castor Emmanuel Njeuhmeli Jane T. Bertrand 《PloS one》2014,9(5)
Background
Countries participating in voluntary medical male circumcision (VMMC) scale-up have adopted most of six elements of surgical efficiency, depending on national policy. However, effective implementation of these elements largely depends on providers'' attitudes and subsequent compliance. We explored the concordance between recommended practices and providers'' perceptions toward the VMMC efficiency elements, in part to inform review of national policies.Methods and Findings
As part of Systematic Monitoring of the VMMC Scale-up (SYMMACS), we conducted a survey of VMMC providers in Kenya, South Africa, Tanzania, and Zimbabwe. SYMMACS assessed providers'' attitudes and perceptions toward these elements in 2011 and 2012. A restricted analysis using 2012 data to calculate unadjusted odds ratios and 95% confidence intervals for the country effect on each attitudinal outcome was done using logistic regression. As only two countries allow more than one cadre to perform the surgical procedure, odds ratios looking at country effect were adjusted for cadre effect for these two countries. Qualitative data from open-ended responses were used to triangulate with quantitative analyses. This analysis showed concordance between each country''s policies and provider attitudes toward the efficiency elements. One exception was task-shifting, which is not authorized in South Africa or Zimbabwe; providers across all countries approved this practice.Conclusions
The decision to adopt efficiency elements is often based on national policies. The concordance between the policies of each country and provider attitudes bodes well for compliance and effective implementation. However, study findings suggest that there may be need to consult providers when developing national policies. 相似文献15.
J. Y. Zhu Xuejun Pan Ronald S. Zalesny Jr. 《Applied microbiology and biotechnology》2010,87(3):847-857
This mini review discusses several key technical issues associated with cellulosic ethanol production from woody biomass:
energy consumption for woody biomass pretreatment, pretreatment energy efficiency, woody biomass pretreatment technologies,
and quantification of woody biomass recalcitrance. Both total sugar yield and pretreatment energy efficiency, defined as the
total sugar recovery divided by total energy consumption for pretreatment, should be used to evaluate the performance of a
pretreatment process. A post-chemical pretreatment wood size-reduction approach was proposed to significantly reduce energy
consumption. The review also emphasizes using a low liquid-to-wood ratio (L/W) to reduce thermal energy consumption for any
thermochemical/physical pretreatment in addition to reducing pretreatment temperature. 相似文献
16.
The desire to reduce dependence on the ever diminishing fossil fuel reserves coupled with the impetus towards green energy has seen increased research in biofuels as alternative sources of energy. Lignocellulose materials are one of the most promising feedstocks for advanced biofuels production. However, their utilisation is dependent on the efficient hydrolysis of polysaccharides, which in part is dependent on cost-effective and benign pretreatment of biomass to remove or modify lignin and release or expose sugars to hydrolytic enzymes. Laccase is one of the enzymes that are being investigated not only for potential use as pretreatment agents in biofuel production, mainly as a delignifying enzyme, but also as a biotechnological tool for removal of inhibitors (mainly phenolic) of subsequent enzymatic processes. The current review discusses the major advances in the application of laccase as a potential pretreatment strategy, the underlying principles as well as directions for future research in the search for better enzyme-based technologies for biofuel production. Future perspectives could include synergy between enzymes that may be required for optimal results and the adoption of the biorefinery concept in line with the move towards the global implementation of the bioeconomy strategy. 相似文献
17.
Large-scale heterogeneity of the fossil record: implications for Phanerozoic biodiversity studies 总被引:6,自引:0,他引:6
Smith AB 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2001,356(1407):351-367
Patterns of origination, extinction and standing diversity through time have been inferred from tallies of taxa preserved in the fossil record. This approach assumes that sampling of the fossil record is effectively uniform over time. Although recent evidence suggests that our sampling of the available rock record has indeed been very thorough and effective, there is also overwhelming evidence that the rock record available for sampling is itself distorted by major systematic biases. Data on rock outcrop area compiled for post-Palaeozoic sediments from Western Europe at stage level are presented. These show a strongly cyclical pattern corresponding to first- and second-order sequence stratigraphical depositional cycles. Standing diversity increases over time and, at the coarsest scale, is decoupled from surface outcrop area. This increasing trend can therefore be considered a real pattern. Changes in standing diversity and origination rates over time-scales measured in tens of millions of years, however, are strongly correlated with surface outcrop area. Extinction peaks conform to a random-walk model, but larger peaks occur at just two positions with respect to second-order stratigraphical sequences, towards the culmination of stacked transgressive system tracts and close to system bases, precisely the positions where taxonomic last occurrences are predicted to cluster under a random distribution model. Many of the taxonomic patterns that have been described from the fossil record conform to a species-area effect. Whether this arises primarily from sampling bias, or from changing surface area of marine shelf seas through time and its effect on biodiversity, remains problematic. 相似文献
18.
It has been estimated that the energy captured in one hour of sunlight that reaches our planet is equivalent to annual energy production by human population globally. To efficiently capture the practically inexhaustible solar energy and convert it into high energy density solar fuels provides an attractive ‘green’ alternative to running our present day economies on rapidly depleting fossil fuels, especially in the context of ever growing global energy demand. Natural photosynthesis represents one of the most fundamental processes that sustain life on Earth. It provides nearly all the oxygen we breathe, the food we consume and fossil fuels that we so much depend on. Imitating the reactions that occur at the early stages of photosynthesis represents the main challenge in the quest for construction of an efficient, robust, self-renewing and cost-effective ‘artificial leaf’. In this review we summarize the main molecular features of the natural solar energy converters, photosystem I and photosystem II, that allow them to operate at high quantum efficiencies, and thus inspire the smart matrix design of the artificial solar-to-fuel devices. We also discuss the main challenges that face the field and overview selected recent technological advances that have tremendously accelerated the race for a fully operational artificial leaf that could serve as a viable alternative to fossil fuels for energy production. 相似文献
19.
Based on energy and CO2 emission efficiencies, this paper proposes a definition of the elasticity of the potential of emission reduction to energy saving (Eperes), and measures the elasticity in China’s 30 provincial regions. Although Eperes is a relative definition, it can be used (1) to measure the amount of reduced CO2 emissions per unit fossil energy saving, (2) to reflect the effectiveness of fossil energy saving for CO2 emission reduction in different regions, and (3) to provide decision-making criteria for selecting pathways for emission reductions in different regions. The results show that compared with energy saving, emission reduction is a more serious issue in China. This indicates that energy saving policies have been highly effective since their implementation during the 11th “Five-Year Plan”. With respect to provincial disparities, the emission reductions caused by fossil energy saving are not significant in Beijing, Shanghai, and Guangdong. Fujian province has significant Eperes, indicating that emission reduction causing by fossil energy saving is effective. Eperes has been increasing over time in Hunan and Hubei. Hainan’s Eperes has remained less than 1, indicating that its emission-reduction effect of fossil energy saving is worse than in other provinces. Moreover, the elasticity of Eastern China is greater than that of Central China and Western China. This finding sheds light on pathway selection for energy saving and emission reduction in China: it would be more appropriate to encourage fossil energy saving in Eastern China, and to promote clean energy use (e.g., water electricity and solar energy) in Central China and Western China. 相似文献
20.
Luis Panichelli Arnaud Dauriat Edgard Gnansounou 《The International Journal of Life Cycle Assessment》2009,14(2):144-159