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2 A scheme of the photosynthetic reactions in the chloroplast thylakoid membrane of green algae. Dash–dot line shows excitation migration from the antenna to the reaction center. The major electron transfer pathways are indicated by solid lines. The pathways involved in chlororespiration , cyclic electron flow around PS I, and the Mehler reaction are shown by dash–dot–dot lines. The dashed line designates the oxygen-sensitive electron transport route induced under anaerobic conditions. Reactions coupled to the generation of proton gradient and to the ATP synthesis are depicted by dotted lines. (From Antal, T.K. et al., Applied Microbiology and Biotechnology 89:3–15, 2011.)
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Citations
... Among many alternative energy sources, biofuels, natural gas , hydrogen, and synthesis gas ( syngas ) emerge as four strategically important sustainable energy sources in the foreseeable future . Currently, most of the biofuel production at commercial scale are made using the food crops as raw material, developing serious ecological and socioeconomical concern, e.g., land-use changes and food vs. fuel competition (Rathore et al. 2015 ).Most of the issues related to energy security, production, and consumption can be solved by utilization of biohydrogen as fuel, as biohydrogen is renewable and can be utilized as fuel for electricity , heat , and transportation purposes, with some modifi cations to existing technologies and have potential to improve sustainability and reduce GHG emissions signifi cantly . This chapter is an attempt to bring out the sustainability and future prospectus of utilization of biohydrogen as an energy source. ...
Concern over sustainability of fossil fuel use is raised due to depleting fuel resources and emitting greenhouse gases (GHGs) from it. Among many alternative energy sources, biofuels, natural gas, hydrogen, and synthesis gas (syngas) emerge as four strategically important sustainable energy sources. As hydrogen gas is renewable, it does not evolve GHGs, and releases large amount of energy in combustion of unit weight and hydrogen can also be easily converted into electricity by fuel cell. It could be a strong candidate for future alternate energy resource. Biological H2 production delivers clean H2 in sustainable manner with simple technology and more attractive potential than the current chemical production of H2. Although present industrial hydrogen production system is based on chemical processing units, research trend on biohydrogen promises a deafening potential of industrial biohydrogen production in the near future.
Presently most of the energy demand is fulfi lled by the fossil fuel . Global
petroleum demand has increased steadily from 57 million barrels day −1 in
1973 to 90 million barrels day −1 in 2013 and will continue to increase in line
with the world’s economy . The increasing energy demands will speed up the
exhaustion of the fi nite fossil fuel. United Arab Emirates, one of the major oil
export countries, would fail to meet the share in the oil and natural gas
demands by 2015 and 2042, respectively. The fossil fuel resources in Egypt
would be exhausted within two decades.
Using petroleum-based fuels creates atmospheric pollution during combustion
. Apart from emission of the greenhouse gas (GHG) CO 2 , air contaminants
like NO X , SO X , CO, particulate matter and volatile organic compounds
are also emitted which leads not only to climate change but also to deterioration
of environmental and human health. Continued use of fossil fuel is now
widely recognised as unsustainable. A renewable, carbon-neutral energy
resource is necessary for environmental and economic sustainability . Concern
for exhausting the availability of fossil fuel for fulfi lling future energy demand
and considering changes in global climate by conventional energy resource
has diverted researchers towards exploring a way to environmentally safe and
sustainable energy resources. Finding suffi cient supplies of clean energy for
the future is one of the most daunting challenges for humanity and is intimately
linked to global stability, economic prosperity and quality of life. A
rapid surge in research activities with intensive focus on alternative fuels has
been seen in the past decades in order to reduce the dependency on fossil
fuels, mainly by providing local energetic resources.
Biofuels are considered as the most environment friendly alternative
energy source because they are renewable and also sequester carbon.
Currently, biofuels are commercially produced from the food crops , developing
serious ecological and socio-economical anxiety such as land use changes
and food-fuel competition issue. About 1 % (14 million hectares) of the
world’s arable land is able to produce current biofuels, to supply 1 % of global
transport fuel demand. Between 1980 and 2005, worldwide production of
biofuels increased by an order of magnitude from 4.4 billion litres to 50.1
billion litres. Clearly, increasing the share, it will be impractical due to the
severe impact on the world’s food supply and the large areas of production
land required. This is manifested by the recent increase in grain prices due to
utilisation of maize at large scale as a feedstock for production of fuel ethanol
in the USA . This caused riots in Mexico due to the increase in the price of
Pref ace
viii
tortillas, a staple food. Further, GHG saving is another constraint for developing
a sustainable biofuel. The Intergovernmental Panel on Climate Change
has calculated that reductions of 25–40 % of CO 2 emissions by 2020 and up
to 80 % by 2050 are required to stay within temperature range, i.e. less than
2 °C, to avoid dangerous climate changes worldwide. The production of sustainable
bioenergy is a challenging task in the promotion of biofuels for
replacing the fossil-based fuels to get a cleaner environment and also to
reduce the dependency on other countries and uncertainty of fuel price.
Among the various renewable energy sources, biohydrogen is a strong
candidate for future energy source by virtue of the fact that it is renewable,
does not evolve GHG and ozone layer-depleting chemicals in combustion ,
liberates large amount of energy per unit weight in combution and is easily
converted into electricity by fuel cell. Hydrogen is also harmless to mammals
and the environment. Hydrogen can be produced safely and considered as the
ultimate cleanest energy carrier to be generated from renewable sources.
Progress in the late 1990s contributed to a breakthrough in terms of sustainable
hydrogen production. There are various technologies (direct biophotolysis
, indirect biophotolysis, photo-fermentations and dark fermentation)
available for the production of biohydrogen from biomass/ organic wastes ,
and many of these technologies have some drawbacks (e.g. low yield, low
production rate, etc.), which limit the practical application. Studies on the
biohydrogen production have been focused on photo-decomposition of
organic compounds by photosynthetic bacteria, dark fermentation from
organic compounds with anaerobes and biophotolysis of water using algae
and cyanobacteria. Among these technologies, metabolic engineering is presently
the most promising for the production of biohydrogen as it overcomes
most of the limitations in other technologies. The biohydrogen production
from biomass is particularly suitable for a relatively small and decentralised
system, and it can be considered as an important key for a sustainable renewable
energy source.
The present book is an effort to provide an up-to-date information and
knowledge on the state of the art of biohydrogen production technology by
the internationally recognised experts and subject peers in different areas of
biohydrogen. It is a comprehensive collection of chapters related to choices
of feedstock , microbiology, biochemistry, molecular biology, enzymes and
metabolic pathways involved, bioprocess engineering, waste utilisation , economics
, life cycle assessment and perspectives of the biohydrogen production
in different countries and regions of the world and also include scale-up and
commercialisation issues. The introductory chapter (Chap. 1) gives a general
background for global energy statistics, available sources for energy supply ,
options of renewable energy sources, benefi ts of adoption of biohydrogen and
its sustainability and future perspectives . The following chapter (Chap. 2)
reviews the potentiality of different biomass that can be utilised for biohydrogen
production and also discusses various technologies for production of biohydrogen
and sums up with the required further research. Chapters (3 and 4)
focused on biohydrogen production from agricultural biomass and wastes to
analyse their suitability for biohydrogen production and also point out the
challenges for biohydrogen production from agricultural biomass and wastes.
Preface
ix
A series of chapters (Chaps. 5, 6, 7 and 8) are concentrated on the potential
of microbial biohydrogen production especially from cyanobacteria and
green algae . These chapters discussed on the physiology of biohydrogen production
from microbial biomass , industrial approaches for biohydrogen production
by photoautotrophic microbes, characterisation and identifi cation of
algal strains, mechanism of hydrogen photoproduction by algae, design and
modelling of photobioreactor for algae cultivation and biohydrogen production,
algal engineering for improving photosynthetic effi ciency and hydrogenase
and constraints and challenges for biohydrogen production. The
following chapter (Chap. 9) is an attempt to review the latest fi ndings on
hydrogenase enzyme, responsible for hydrogen production, and also enlighten
the metabolic engineering to increase the enzyme production and activity.
Two chapters (Chaps. 10 and 11) reviewed the present status and future perspectives
of biohydrogen production in Asia and Saudi Arabia. The economics
, a major limitation of biohydrogen popularity for industrial production, is
also covered (Chap. 12). Life cycle assessment (LCA) techniques allow
detailed analysis of material and energy fl uxes on regional and global scales.
LCA studies of renewable energy sources calculate the environmental impact
and can relate the results against sustainability criteria. The comprehensive
LCA of biohydrogen production and its comparison with other biofuels is
covered in the Chap. 13 and can be a tool for sustainability assessment and
policy decisions. Chapter 14 presented a global trend of biohydrogen research
and its future perspectives .
This book is aimed at a wide audience, mainly researchers, energy specialists,
academicians, entrepreneurs, industrialists, policymakers and others
who wish to know the latest development and future perspectives of biohydrogen
production, and also discusses the bottlenecks of the various processes
that currently limit the scale-up and commercialisation . Each chapter
begins with a fundamental explanation for general readers and ends with indepth
scientifi c details suitable for expert readers. The text in all the chapters
is supported by numerous clear, illustrative and informative diagrams, fl ow
charts and comprehensive tables detailing the scientifi c advancements, providing
an opportunity to understand the process thoroughly and meticulously.
Written in a lucid style, the book comprehensively covers each point to give
the reader a holistic picture about biohydrogen production technology and its
sustainability . The book may even be adopted as a textbook for university
courses that deal with biohydrogen and renewable energy sources.
Despite the great efforts of authors and editors along with extensive checks
conducted by many experts in the fi eld of biohydrogen production, mistakes
may have been made. We would appreciate if the readers could highlight
mistakes and make comments or suggestions to improve and update the book
contents for future editions.
New Delhi , India Anoop Singh
Gujarat , India Dheeraj Rathore
