Microalgal Hydrogen Production

Achievements and Perspectives

Michael Seibert, Giuseppe Torzillo, Michael Seibert, Giuseppe Torzillo

• Verlag: Royal Society of Chemistry
• Jahr: 2018
• ISBN:
  9781788014236
• Auflage: 1
• Thema: Physical Sciences
• Thema: Energy

Hydrogen could be the fuel of the future. Some microorganisms can produce hydrogen upon illumination. Biological methods of production could be greener than chemical or physical production methods, but the potential of biological methods is still being harnessed.
This comprehensive book highlights the key steps necessary for future exploitation of solar-light-driven hydrogen production by microalgae. The highly regarded editors bring together 46 contributors from key institutions in order to suggest and examine the most significant issues that must be resolved to achieve the goal of practical implementation, while proposing reliable methodologies and approaches to solve such issues. This 19 chapter book will be an indispensable resource for academics, undergraduate and graduate students, postgraduates and postdoctoral scholars, energy scientists, bio/chemical engineers, and policy makers working across the field of biohydrogen and bioenergy.

Part I

Biology and Physiology of Photobiological Hydrogen Production

Chapter 1

Photosynthesis and Hydrogen from Photosynthetic Microorganisms

Patrick C. Hallenbeck^a,b, Carolina Zampol Lazaro,^b and Emrah Sagir,^b

^a Life Sciences Research Center, Department of Biology, United States Air Force Academy, USAF Academy 2355 Faculty Drive, Colorado 80840, USA

^b Département de microbiologie, infectiologie, et immunologie Université de MontréalCP 6128, Centre-ville Montréal PQ H3C 3J7, Canada[email protected]

1.1 Introduction

There is a large number of urgent reasons for pushing the development of green fuels, including the finite nature of fossil fuel reserves, impending climate change effects, the perceived need for energy security, and the dangers that the use of petroleum products pose to the environment and human health.¹ The world economy and geopolitical structure has been built upon the use of fossil fuels, so any changeover to new energy sources will bring significant challenges, so daunting that they need to become part of the current public discourse.¹ These include a number of open-ended questions, which should not necessarily be thought of as either/or propositions, but perhaps as multiple paths to a new energy independence. These new energy challenges include: new production processes; the wholesale adoption of conservation measures; implementation of both quick, short-term solutions and smart, long-term solutions; the development of a more resilient energy mix depending on several interchangeable energy sources; and the diversification of the energy production model from essentially a totally centralized one, to a model which includes a greater level of local production.¹

On the political level, a number of central general questions surrounding energy production and consumption need to be answered prior to moving forward with new energy sources, as the energy industry finds itself today at a historical intersection where one has a chance to rethink globally how things should be done. Should industry as a whole continue to conduct its business as usual? Under this scenario decisions are made that ignore the fact that local use has global effects, thus overlooking the impact of anthropogenic activities on common resources such as the atmosphere.^2–5 Will energy demand–supply continue to drive politics and wealth redistribution? Whose resources will be used for whose energy?

It is becoming very clear that one of the significant effects of past and present fossil-fuel use (i.e., climate change) is already upon us, as evidenced by recent extreme weather events.^6,7 Recently, increased global temperatures are being noted year after year.⁸ In addition to terrestrial concerns, which have been fairly well documented, there are also a number of effects of increased atmospheric levels of CO₂ on the world’s oceans. Increased temperature will cause sea levels to rise for several centuries, and this is already causing disturbances in marine ecosystems.^9,10 In addition, rising atmospheric levels of CO₂ will overwhelm the oceanic buffering system, leading to an acidification so severe that it threatens to have devastating effects on marine ecosystems.¹¹

Thus, since the adoption of the Kyoto Protocol in 1997, renewed by succeeding COPs (Conferences of Parties), such as the COP21 in Paris in 2015, where nations agreed to hold the increase in the global temperature to below 2 °C and pursue efforts to keep it below 1.5 °C, the international spotlight has been focused on the urgent need for reducing greenhouse-gas emissions. While all seem to agree that this is necessary, few mechanisms are in place to make the significant adjustments that are necessary, with the exception of a few carbon-trading schemes that have been met with limited success. This is because carbon emissions are a function of the total population, individual consumption (essentially individual income), the energy intensity of production, and the carbon intensity of energy use.¹² Energy production and use thus directly impact GDP (gross domestic product), and it is therefore a highly critical and political matter for every country in search of economic competitiveness, whereas the use of the atmospheric in common remains unregulated. Thus, assuming the current status quo remains unchanged, achieving a sustainable reduction in carbon emissions is nearly intractable since the world population continues to grow, and no country will individually adopt measures that might be perceived as impacting negatively its individual GDP. Under the present status quo, it seems that only small gains in the energy efficiency of current, highly developed production processes of developed nations are possible. Thus, in practical terms, the most realistic approach to reduce carbon emissions is through the “decarbonization” of energy production. In other words, carbon-neutral fuels must be introduced as soon as possible. In fact, even under very optimistic scenarios, maintaining economic growth while remaining at or below the critical 450 ppm CO₂ in the atmosphere will require the introduction of 30 terawatts of carbon-neutral fuel by 2050, as well as requiring a series of strategies for drastic reductions in overall carbon emissions.^13,14

1.2 Developing a Low Carbon Economy

Ancient prehistoric and early historic land clearing initiated recent increases in atmospheric forcing, which was greatly augmented by industrialization driven by the use of fossil fuels as a major energy source. However, industrialization has simultaneously created the modern world, greatly increasing per capita GDP (in developed countries, e.g., the Organization for Economic Co-operation and Development [OECD]). Thus, present energy use is tightly linked to per capita income levels while simultaneously causing disastrous climate change effects. Unfortunately, this creates great tension between the need to change energy use and the desire to maintain high standards of living in the OECD member countries, or the chance for developing countries to achieve a similar lifestyle.

Under almost any scenario, two multiplying factors, population growth and growth in per capita energy usage, will drive significant growth in future energy demand. Per capita energy usage is driven by income growth. This can be seen historically, where since 1900 the world population has increased four-fold, while over this same time frame, real income has increased twenty-five-fold with a concomitant 22.5-fold increase in energy consumption.¹⁵ Obviously this trend will continue as the world population is predicted to reach about 10 billion by 2050, given an annual growth rate close to 1%.¹⁶ At the same time, average incomes will increase with GDP, which is thought to be increasing at an annual rate of 3.2%.¹⁷

These relationships can be directly coupled using the Kaya Identity:¹⁸

1.1

This shows that total anthropogenic carbon emissions are a function of the total population (P), individual consumption (GDP/P, gross domestic product consumed per person), the energy intensity of production (E/GDP), and the carbon intensity of energy use (CO₂/E). However, it is readily apparent that of the four factors involved in total carbon dioxide emissions, only two can realistically be manipulated to effectively slow or stabilize total emissions. This is because changing population growth has been historically difficult and decreasing economic output, or even reducing it to no growth, is a nonstarter, since this directly affects per capita income. While E/GDP can theoretically be reduced by adopting processes with greater efficiency, these measures can only go so far. This is true even for countries with advanced technologies (i.e., OECD countries), where the apparent recent decline in energy intensity is in reality due to the outsourcing of emissions to manufacturing countries as the advanced nations switched to service economies, as well as some contribution from switching energy g...