Advanced Biofuels and Bioproducts

The field of advanced biofuels and bioproducts may play an increasingly significant role in providing renewable energy and ensuring environmental health for a sustainable future of human civilization on Earth. This chapter as an introduction for the book provides a quick overview of advanced biofuels and bioproducts by highlighting the new developments and opportunities in the bioenergy research development arena in relation to the global energy and environmental challenges. The topics include: (1) Brazils sugarcane ethanol as an early and still encouraging example of biofuels at a nationally significant scale, (2) smokeless biomass pyrolysis for advanced biofuels production and global biochar carbon sequestration, (3) cellulosic biofuels, (4) synthetic biology for photobiological production of biofuels from carbon dioxide and water, (5) lipid-based biodiesels, (6) life-cycle energy and environmental impact analysis, (7) high-value bioproducts and biomethane, and (8) electrofuels.

Presently, ethanol from sugarcane replaces approximately 50% of the gasoline that would be used in Brazil if such an option did not exist. In some aspects, ethanol may represent a better fuel than gasoline and to a great extent a renewable fuel contributing little to greenhouse gas emissions in contrast with fossil-derived fuels. Production of ethanol increase from 0.6 billion liters in 1975/1976 to 27.6 billion liter in 2009/2010. Although production costs in 1975/1976 were three times higher than gasoline prices in the international market, such costs declined dramatically thanks to technological advances and economics of scale becoming full competitive (without subsidies) with gasoline after 2004. This was achieved through appropriate policies of the Brazilian government. These policies and the rationale for them as a strategy to reduce oil imports are discussed here with the possibilities of replication in other countries.

Smokeless (emission-free, clean, and efficient) biomass pyrolysis for biochar and biofuel production is a possible arsenal for global carbon capture and sequestration at gigatons of carbon (GtC) scales. The worlds annual unused waste biomass, such as crop stovers, is about 3.3 GtC y

1

. If this amount of biomass (3.3 GtC y

1

) is processed through the smokeless pyrolysis approach, it could produce biochar (1.65 GtC y

1

) and biofuels (with heating value equivalent to 3,250 million barrels of crude oil) to help control global warming and achieve energy independence from fossil fuel. By using 1.65 GtC y

1

of biochar into soil and/or underground reservoirs alone, it would offset the 8.5 GtC y

1

of fossil fuel CO

2

emissions by 19%. The worldwide maximum capacity for storing biochar carbon into agricultural soils is estimated to be about 428 GtC. It may be also possible to provide a global carbon thermostat mechanism by creating biochar carbon energy storage reserves. This biomass-pyrolysis carbon-negative energy approach merits serious research and development worldwide to help provide clean energy and control climate change for a sustainable future of human civilization on Earth.

This chapter reports a technological concept for producing a partially oxygenated biochar material that possesses enhanced cation-exchanging property by reaction of a biochar source with one or more oxygenating compounds in such a manner that the biochar material homogeneously acquires oxygen-containing cation-exchanging groups. This concept is based on our recent experimental finding that the O:C atomic ratio in biochar material correlates with its cation-exchange capacity. The technology is directed at biochar compositions and soil formulations containing the partially oxygenated biochar materials for soil amendment and carbon sequestration.

In this chapter, we first briefly reviewed the knowledge of biochar chemical structures based on solid-state NMR. Then, the reason why the widely applied

13

C cross polarization/magic angle spinning (CP/MAS) technique is inappropriate for biochar characterization was explained. Afterwards, advanced solid-state NMR techniques for the characterization of biochars were introduced.

13

C direct polarization/magic angle spinning (DP/MAS) and DP/MAS with recoupled dipolar dephasing to quantify biochars are used to obtain quantitative aromaticity and nonprotonated aromatic fraction. The recoupled

1

H

13

C dipolar dephasing technique is applied to distinguish different aromatic carbons in biochars. Combined with the data from

1

H

13

C recoupled long-range dipolar dephasing, the information on the fraction of aromatic edge carbons can be used to obtain the structural models of aromatic cluster sizes. Finally, a case study on a slow-pyrolysis biochar produced from switchgrass was demonstrated.

Use of biochar fertilizer is potentially an attractive approach for soil amendment and carbon sequestration possibly at giga tons of carbon (GtC) scale. Cation exchange capacity (CEC) is an important parameter in retaining inorganic nutrients, such as K

+

and NH

4

+

in soil. This experimental study showed that the CEC value of biochar is related to the biomass pyrolysis temperature. Biochar materials made from the pelletized peanut hulls at pyrolysis temperature of about 400C yield the best CEC value. As the pyrolysis temperature increases over 400C, the CEC value decreases. The biochar produced from the 400C pyrolysis possesses certain binding affinity for ammonium bicarbonate (NH

4

HCO

3

) probably because of the presence of more biochar surface functional groups. Addition of ammonium bicarbonate to biochar can help neutralize the pH of biochar material potentially beneficial for certain agricultural soil applications in relation to soil amendment and carbon sequestration.

The US Southeastern Coastal Plains have a long history of agricultural production. However, poor quality sandy soils hamper productivity. Soils have depleted organic carbon contents that lead to poor nutrient retention, reduced aggregation, and low plant-available soil water retention. Past soil management used reduced tillage to increase organic carbon but it deteriorated quickly in the hot, humid environment. Biochars can provide an alternative recalcitrant carbon source. Since biochar varies widely in characteristics, it must be designed to fit the needs of the soil increased carbon, aggregation, nutrient retention, and plant-available water retention. Biochar design characteristics depend mainly on feedstock characteristics and method of pyrolysis. This review offers guidelines for designer biochar manufacture through feedstock selection and pyrolysis technique; it outlines potential usage to improve specific soil quality problems.

Well-engineered, slow-pyrolysis technology, optimized for the production of bioenergy and biochar from sustainable feedstocks, could deliver significant environmental and economic advantages to industry. Utilization of biochar products as a soil amendment could contribute to ongoing food security and agricultural productivity. Biochar production and sequestration can result in the net removal of greenhouse gases from the atmosphere, making the technology a potentially valuable tool for climate change mitigation. It is essential that the emerging industry is well regulated and that quality assurance and sustainability mechanisms are adopted. This will optimize the net benefit of the technology. Biochar products produced from different industries will vary greatly in characteristics. Equally, the drivers for different industries to adopt slow-pyrolysis technology will vary. Significant advantages provided by the technology across multiple industries may result in extensive adoption. The development of a biochar market is required, with the uncertainty in biochar price and market size, being a major contributor to lack of confidence in the business case for the technology. Markets for biochar as a product are diverse, ranging from broad acre agriculture to niche applications such as roof gardens, where its unique properties give it significant competitive advantages over alternatives.

Converting lignocellulosic biomass into biofuels compatible with the existing petroleum refinery infrastructure requires removal of oxygen from the carbohydrate and lignin-derived molecules. The necessary deoxygenation can be achieved through the rejection of water and carbon oxides which occurs at 4000-600C in the presence of catalysts. The yield of hydrocarbons could theoretically reach 35% of the biomass feedstock. So far, the highest yields achieved were in the range of 12-18%. The most promising deoxygenation catalysts belong to the group of medium-pore size zeolites such as ZSM-5. This chapter reviews the research in the field and provides numerous references to the original work in the area of catalytic pyrolysis of biomass. It also reports on some recent experimental results obtained at National Renewable Energy Laboratory.

Selective fast pyrolysis, differed from traditional fast pyrolysis which is usually aimed at the maximum bio-oil yield, is to selectively control or alter biomass pyrolytic pathways for obtaining specific products (high-grade liquid fuels or special chemicals). Fast pyrolysis of biomass can be regarded as the pyrolysis of its three major components, mainly including the following three pathways. The decomposition of lignin mainly produces various monomeric phenolic compounds as well as oligomers (pyrolytic lignins). The depolymerization of holocellulose (cellulose and hemicellulose) mainly generates anhydro-oligosaccharides, monomeric anhydrosugars (mainly levoglucosan), furans, and other products. The pyrolytic ring scission of holocellulose obtains various light products, such as hydroxyacetaldehyde and acetol. The pyrolytic pathways and the subsequent products are influenced by a number of factors, including the biomass type, feedstock properties, pyrolysis conditions (pyrolysis temperature, heating rate, vapor residence time, pressure, gaseous environment), catalysts, vapor filtration, and condensation. Therefore, selective fast pyrolysis can be achieved via proper control of these factors, such as biomass pretreatment or catalyst utilization. This chapter reviews the mechanisms and pathways of biomass pyrolysis, as well as the properties and applications of crude bio-oils. It also summarizes the recent advances in the selective fast pyrolysis of biomass, aiming at how to produce quality-improved liquid fuels, and specific chemicals such as levoglucosan, levoglucosenone, acetic acid, hydroxyacetaldehyde, furfural, 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one, and phenolic compounds.

One of the major challenges in utilization of biomass is its high moisture content and variable composition. The conventional thermochemical conversion processes such as pyrolysis and gasification require dry biomass for production of biofuels. Sub- and supercritical water (critical point: 374°C, 22.1°MPa) technology, which can utilize wet biomass, capitalizes on the extraordinary solvent properties of water at elevated temperature for converting biomass to high energy density fuels and functional carbonaceous materials. Here, water acts as reactant as well as reaction medium in performing hydrolysis, depolymerization, dehydration, decarboxylation, and many other chemical reactions. One of the advantages is that the large parasitic energy losses that can consume much of the energy content of the biomass for moisture removal are avoided. In sub- and supercritical water-based processes, water is kept in liquid or supercritical phase by applying pressure greater than the vapor pressure of water. Thus, latent heat required for phase change of water from liquid to vapor phase (2.26 MJ/kg of water) is not needed. For a typical 250°C subcritical water process, the energy requirement to heat water from ambient condition to the reaction temperature is about 1 MJ/kg, equivalent to 6–8% of energy content of dry biomass.

This chapter briefly reviews the state of art on the conversion of biomass to biofuels by gasification followed by the gas to liquid conversion of biosyngas via Fischer–Tropsch and related syntheses. An integrated process to produce heat, electricity, or fuel by gasification and Fischer–Tropsch synthesis is analyzed. The present state of gasification reactor technology is outlined. The strategies for syn-gas cleanup are delineated. The catalysis and processes for methanol, Fischer–Tropsch, and isosynthesis are briefly evaluated. Finally, various approaches to an integrated process design depending on the desired end results (heat, electricity, or fuel) and the associated economics for each approach are outlined and briefly discussed.

The gasification of biomass followed by a Fischer–Tropsch Synthesis (FTS) is a good alternative for synthesis of gasoline and/or diesel. However, this process may be considered as a high-cost technology, depending on crude oil and biomass raw material prices. The viability may be increased depending on the value of biomass, cost of transportation of biomass and the separation (conditioning) of gases produced in the gasification (elimination of CO

2

, CH

4

, N

2

and others). Nevertheless, this gas mixture “called biosyngas” may be used in the FTS without pre-conditioned for producing gasoline and/or diesel. The main focus of this chapter will be on the latest investigations in the FTS carried out in a microreactor from a simulated biosyngas (without conditioning), as an alternative to decrease the cost of this process. This chapter reports results of catalytic activity and characterization of Fe/SiO

2

and Co/SiO

2

catalysts and Cu, Re, Ru and Zn promoted Co/SiO

2

ca

t

alysts.

Fischer–Tropsch (FT) synthesis is an effective method to produce liquid fuels from biomass. This chapter reports the study on precipitated Fe catalysts for conversion of CO

2

-containing syngas to liquid fuels. The influences of promoter Zn, K, and Cu on CO

2

activation were analyzed by CO

2

temperature-programmed- desorption (CO

2

-TPD). Cu has no strong effect to activate CO

2

. K increases mainly CO

2

adsorption and is inferior to Zn in producing CO. The catalysts with high Zn/K ratio or low K content possess desorbed CO peak around 930 K in CO

2

-TPD and decreased CO

2

selectivity resulted from CO

2

addition in FT synthesis. The Fe catalyst with high Zn/K ratio shows high C

2

+ hydrocarbon selectivity for CO

2

hydrogenation, too. It indicates that the CO

2

contained in syngas is able to be activated by suitable promoter(s) for hydrocarbon synthesis at low temperature. The correlation between promoter composition and catalyst reactivity found for SiO

2

-free Fe catalysts is effective for SiO

2

-added Fe catalysts.

This chapter details the recent advances made on bioconversion of lignocellulosic biomass to butanol, a superior biofuel that can be used in internal combustion engines or transportation industry. It should be noted that butanol producing cultures cannot tolerate or produce more than 20–30 g/L of acetone-butanol-ethanol (ABE) in batch reactors of which butanol is of the order of 13–18 g/L. This is due to toxicity of butanol to the culture. In order to overcome this challenge, two approaches have been applied: (1) developing more butanol tolerant strains using genetic engineering techniques and (2) employing process engineering approaches to simultaneously recover butanol from the fermentation broth thus not allowing butanol concentrations in the reactor to accumulate beyond culture’s tolerance. By the application of the first approach, a number of butanol producing strains have been developed; however, none of these accumulated greater than 1,200 mg/L (1.2 g/L) butanol, while using the second approach total ABE up to 461 g/L has been produced. Attempts to improve the newly developed strains are continuing. Lignocellulosic substrates have been used to produce butanol due to their abundant availability and economical prices usually in the range of $24–60/ton as opposed to corn prices which have been in the range of $153–218/ton during recent months. It should be noted that lignocellulosic substrates require separate hydrolysis prior to fermentation. In a more recent approach, hydrolysis and fermentation (and simultaneous recovery) have been integrated or combined to reduce the cost of butanol production from cellulosic substrates. Using such an approach, up to 192 g/L ABE was produced from 430 g/L cellulosic biomass/sugars. Additionally, this chapter provides details of process integration and simultaneous product recovery technologies for butanol production.

The production of ethanol and other biofuels through the biochemical conversion of lignocellulosic biomass represents a promising path towards sustainably achieving the immense global demand for liquid transportation fuels. While numerous cellulosic ethanol production process configurations exist, the one known as Consolidated Bioprocessing (CBP) stands alone in combining all biologically mediated events into the action of a single organism (i.e., production and secretion of saccharolytic enzymes, hydrolysis of cellulose and hemicellulose, and fermentation of six-carbon and five-carbon sugars into biofuels such as ethanol). We discuss here the major issues with developing CBP technologies including the promises and challenges, the two prominently pursued routes to achieve this technology and several of the most promising candidate organisms. CBP represents a low-risk, high-reward proposition and its pursuit by researchers is most certainly warranted as we look to the future.

Most of the plant biomass is cell wall and therefore represents a renewable carbon source that could be exploited by humans for bioenergy and bioproducts. A thorough understanding of the type of cell wall being harvested and the molecules available will be crucial in developing the most efficient conversion processes. Herein, we review the structure, function, and biosynthesis of lignocellulosic biomass, paying particular attention to the most important bioresources present in the plant cell wall: cellulose, hemicellulose, and lignin. We also provide an update on key improvements being made to lignocellulosic biomass with respect to utilization as a second-generation biofuel and as a resource for bioproducts.

To date, most ethanolic fuel is generated from “first generation” crop feedstocks by conversion of soluble sugars and starch to bioethanol. However, these crops exploit land resources required for production of food. On the other hand, utilization of “second generation” lignocellulosic biofuels derived from the inedible parts of plants remains problematic as high energy inputs and harsh conditions are required to break down the composite cell walls into fermentable sugars. This chapter reviews and discusses genetic engineering approaches for the generation of plants modified to increase cellulose synthesis, enhance plant growth rates, cell wall porosity and solubility, as well as improve cell wall sugar yields following enzymatic hydrolysis. Strategies focusing on increased accessibility of cellulose-degrading enzymes to their substrates have been developed. These approaches reduce cell wall crystallinity or alter the hemicellulose–lignin complexes. A novel approach to cell wall modification involving the introduction of noncrystalline, soluble polysaccharides into cell walls is also presented. The use of such approaches may promote and accelerate the future use of lignocellulosic feedstocks for the bioethanol industry.

Biofuels hold significant promise as an environmentally friendly means to displace a significant amount of fossil fuel from the global liquid transportation fuel mix. Compared with current corn and sugarcane-based feedstocks, which are agriculturally intensive, lignocellulosic feedstocks are abundant, can be produced cheaply, and have a much smaller carbon footprint per unit energy output. However, conversion of cellulosic materials into simple sugars (an intermediate step in biofuel production) is a significant challenge, owing to the rigidity and high resistance of cellulose to degradation. Recent efforts to improve enzymatic breakdown of cellulose have taken advantage of expanding genome sequence databases, advances in structural biology of cellulose degradation enzymes (cellulases), biochemical studies of enzymatic breakdown of cellulose, and protein engineering studies. In this chapter, the structural features of cellulose and cellulose-degrading enzymes will be reviewed, along with methods used to determine cellulase activity. We will focus on models for synergistic effects among enzymes, strategies used by bacteria and fungi to increase reactivity through synergistic enhancement, and approaches by which synergistic enhancement can be engineered into artificial enzymes to be used for large-scale cellulose-based biofuels production.

This chapter reports two inventions: designer proton-channel algae (US Patent No. 7,932,437 B2) and designer switchable photosystem-II algae (US Patent No. 7,642,405 B2), for more efficient and robust photobiological production of hydrogen (H

2

) from water. Use of these inventions could eliminate the following six technical problems that severely limit the yield of algal H

2

production: (1) restriction of photosynthetic H

2

production by accumulation of a proton gradient, (2) competitive inhibition of photosynthetic H

2

production by CO

2

, (3) requirement of bicarbonate binding at photosystem-II (PSII) for efficient photosynthetic activity, (4) competitive drainage of electrons by O

2

in algal H

2

production, (5) oxygen sensitivity of algal hydrogenase, and (6) the H

2

–O

2

gas separation and safety issue. By eliminating these six technical problems that currently challenge those in the field, the designer algae approach could enhance photobiological production of hydrogen with a yield likely over ten times better than that of the wild-type.

This chapter describes an invention on photosynthetic ethanol production through application of synthetic biology. The designer plants, designer algae, and designer plant cells are created such that the endogenous photosynthesis regulation mechanism is tamed, and the reducing power (NADPH) and energy (ATP) acquired from the photosynthetic water splitting and proton gradient-coupled electron transport process are used for immediate synthesis of ethanol (CH

3

CH

2

OH) directly from carbon dioxide (CO

2

) and water (H

2

O). This photobiological ethanol-production method eliminates the problem of recalcitrant lignocellulosics by bypassing the bottleneck problem of the conventional biomass technology. The photosynthetic ethanol-production technology is expected to have a much higher solar-to-ethanol energy-conversion efficiency than the conventional technology. Furthermore, this approach enables the use of seawater for photobiological production of ethanol without requiring freshwater or agricultural soil, since the designer photosynthetic organisms can be created from certain marine algae that can use seawater.

This chapter presents an invention on creating biosafety-guarded designer photosynthetic organisms for photobiological production of butanol and related higher alcohols. The designer photosynthetic organisms are created such that the endogenous photobiological regulation mechanism is tamed, and the reducing power (NADPH) and energy (ATP) acquired from the photosynthetic process are used for synthesis of butanol and/or related higher alcohols from carbon dioxide and water. This photobiological biofuels-production method eliminates the problem of recalcitrant lignocellulosics by bypassing it. This technology is expected to have a much higher solar-to-biofuels energy-conversion efficiency than the conventional biomass technology. Furthermore, this approach enables the use of seawater and/or groundwater for photobiological production of higher alcohols (such as 1-butanol and 2-methyl-1-butanol) without requiring freshwater or agricultural soil, since the designer photosynthetic organisms can be created from certain marine algae and/or cyanobacteria that can use seawater and/or certain groundwater.

Different processes for transesterification of

Jatropha

biodiesel production are currently available. Among them are homogeneous catalysis, heterogeneous catalysis or enzyme catalysis alcohol treatment, supercritical alcohols, lipase-catalyzed in situ reactive extraction, and homogenous-catalyzed in situ transesterification. High cost of biodiesel production is the major impediment to its large-scale commercialization. Methods to reduce the production cost of biodiesel must be developed. One way to reduce production costs is to increase the added value of protein-rich

Jatropha

seedcakes, the by-product of oil extraction, through detoxification process. Development of integrated biodiesel production process and detoxification process results in two products, namely biodiesel and protein-rich seedcakes that can be used for animal feed. This chapter provides information concerning

Jatropha

potential, current development of biodiesel and nontoxic seedcakes production from

Jatropha curcas

and implication of biodiesel production on global warming, environmental impact, and energy efficiency.

Continued reliance on fossil fuel reserves as the primary energy resource is increasingly becoming unsustainable, owing to the need for: minimal exposure to the associate price volatility, reduction of greenhouse gas emissions by energy conservation, and deployment of cleaner and locally produced energy feedstock (including recovery from waste). Based on current knowledge and technology projections, third-generation biofuels (low input-high yielding feedstock) specifically derived from microalgae are considered to be viable alternative energy resource. They are devoid of the major drawbacks associated with first-generation biofuels (mainly terrestrial crops, e.g. sugarcane, sugar beet, maize and rapeseed) and second-generation biofuels (derived from lignocellulosic energy crops and agricultural and forest biomass residues). This chapter focuses on technologies underpinning microalgae-to-biofuels production systems, and evaluates the scale-up and commercial potential of biofuel production, including benchmarking of fuel standards. It articulates the importance of integrating biofuels production with the production of high-value biomass fractions in a biorefinery concept. It also addresses sustainability of resource deployment through the synergistic coupling of microalgae propagation techniques with CO

2

sequestration and bioremediation of wastewater treatment potential for mitigation of environmental impacts associated with energy conversion and utilisation.

Rapid increase of atmospheric carbon dioxide together with depleted supplies of fossil fuel has led to an increased commercial interest in renewable fuels. Due to their high biomass productivity, rapid lipid accumulation and high carbohydrate storage capacity, microalgae are viewed as promising feedstocks for carbon-neutral biofuels. This chapter discusses process engineering steps for the production of biodiesel and bioethanol from microalgal biomass (harvesting, dewatering, pre-treatment, lipid extraction, lipid transmethylation, anaerobic fermentation). The suitability of microalgal lipid compositions for biodiesel conversion and the feasibility of using microalgae as raw materials for bioethanol production will also be evaluated. Specific to biodiesel production, the chapter provides an updated discussion on two of the most commonly used technologies for microalgal lipid extraction (organic solvent extraction and supercritical fluid extraction) and evaluates the effects of biomass pre-treatment on lipid extraction kinetics.

A variety of high value products have so far been produced with algae and the transition to algae mass cultures for the energy market currently arouses the interest of research and industry. The key to efficient cultivation of microalgae is the optimization of photobioreactors that does not only allow for efficient light capture but also takes account of the specific physiological requirements of microalgae. Three fundamental reactor designs (bubble columns, flat plate reactors, and tubular reactors) are common and are discussed together with some elaborate derivatives in the following. Every concept excels with specific advantages in terms of light distribution, fluid dynamics, avoidance of gradients, and utilization of the intermittent light effect. However, the integration of all beneficial characteristics and simultaneously the compliance with energetic and economic constraints still imposes demanding challenges on engineering.

Lipid extraction is a critical step in the development of biofuels from microalgae. The use of toxic and polluting organic solvents should be reduced and the sustainability of the extraction procedures improved in order to develop an industrial extraction procedure. This could be done by reducing solvent amounts, avoiding use of harmful solvents, or eliminating the solvent at all. Here we describe two new processes to extract hydrocarbons from dried and water-suspended samples of the microalga

Botryococcus braunii

. The

first

one is a solvent-based procedure with switchable polarity solvents (SPS), a special class of green solvents easily convertible from a non-ionic form, with a high affinity towards non-polar compounds as

B. braunii

hydrocarbons, into an ionic salt after the addition of CO

2

, useful to recover hydrocarbons. The two SPS chosen for the study, based on equimolar mixtures of 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) and an alcohol (DBU/octanol and DBU/ethanol), were tested for the extraction efficiency of lipids from freeze-dried

B. braunii

samples and compared with volatile organic solvents extraction. The DBU/octanol system was further evaluated for the extraction of hydrocarbons directly from algal culture samples. DBU/octanol exhibited the highest yields of extracted hydrocarbons from both freeze-dried and liquid algal samples (16 and 8.2%, respectively, against 7.8 and 5.6% with traditional organic solvents). The

second

procedure here proposed is the thermochemical conversion of algal biomass by using pyrolysis; this process allowed to obtain three valuable fractions, exploitable for energy purpose, fuel production, and soil carbon storage: a volatile fraction (37% on dry biomass weight), a solid fraction called biochar (38%) and, above all, a liquid fraction named bio-oil (25%), almost entirely composed by hydrocarbon-like material, thus directly usable as fuel.

The increased demand for biodiesel and the difficulties in obtaining enough quantities of raw materials for its production are stimulating the search for alternative feedstocks. Among the various possibilities, the utilization of residual fatty materials, in particular waste frying oils and animal fat residues from the meat and fish processing industries, are increasingly seen as viable options for biodiesel production. This work reviews the state of the art regarding the utilization of waste oils and animal fats as feedstocks for biodiesel production, which are characterized by the presence of high levels of impurities such as high acidity and moisture content. The relative advantages and disadvantages of the different routes for biodiesel production are presented and discussed in this chapter, focusing on their chemical and technological aspects. Also discussed are the questions related to the viability and potential economic advantages of using this type of feedstocks in biodiesel production for road transportation.

We describe a new procedure for conversion of algal biomass into biodiesel using a single step process through the use of tetramethylammonium hydroxide (TMAH). The dried algae is placed in a laboratory-scale reactor with TMAH reagent (25% in methanol) under a blanket of flowing nitrogen gas and converted to a condensable gas-phase product (biodiesel) at temperatures ranging from 250 to 550°C. The condensed biodiesel is freed of methanol and analyzed by gas chromatography/mass spectrometry. Fatty acid methyl esters (FAME) are the main products of the reaction at all temperatures studied. Residues from the one-step conversion exhibit varying levels of transformation which may likely affect their end use.

With the current global drive towards a low-emission economy, countries need to take a stance. For example, Australia, which is one of the world’s largest polluters, has made a commitment that before 2020 its overall emissions would be reduced by 5–15% below the levels registered in the year 2000. To realise these targets, processes which capture carbon dioxide will prove critically important. One of such emerging processes is carbon dioxide capture for microalgae cultivation and subsequent downstream biomass processing for biodiesel production. This chapter will entail engineering scale-up, economic analysis and carbon audit to ascertain the viability of an industrial scale microalgal biodiesel production plant. This will involve the development of an industrial scale model to determine the feasibility of a real large-scale plant. Data from each process step (cultivation, dewatering, lipid extraction and biodiesel synthesis) will be presented individually and integrated into the overall process framework.

This chapter describes how to perform a sustainability evaluation of microalgae biodiesel through its supply chain. A framework for selecting sustainability indicators that take into account all three dimensions of sustainability: economic, societal and environmental, is presented. Special attention is given to a useful definition of the boundary for the system and to the identification of the relevant impacts associated with the biodiesel supply chain stages. A set of sustainability indicators is proposed for quantitative sustainability assessment, based on the impacts deemed relevant for each supply chain stage. Some qualitative arguments are also presented to support the evaluation. Although microalgae appear to be superior in some respects to other currently used feedstocks, the development of large-scale microalgae production systems still needs further research.

Algae-derived bioenergy is being widely discussed as a promising alternative to bioenergy produced from terrestrial crops. Several life cycle assessment (LCA) studies have been published recently in an effort to anticipate the environmental impacts of large-scale algae-to-energy systems. LCA is a useful tool for understanding the environmental implications of technology, but it is very sensitive to modeling assumptions and techniques. In this chapter, the methodological issues surrounding LCA of algae-to-energy systems are reviewed in the context of several of the recent papers with a particular focus on system boundaries, cultivation techniques, metrics, coproduct allocation, and uncertainty. The issues raised here are useful in two regards: (1) they enable an understanding of the differences between the published studies and allow LCA practitioners and others to more directly interpret the results and (2) they serve as a good starting point for future analysis of algae-to-energy technologies.

This chapter comments on fed-batch cultivation of

Arthrospira platensis

under different carbon and nitrogen sources, pH, temperature, light intensity, type of photobioreactor and typical parameters of the fed-batch process, such as feeding time, addition protocol and flow rate. Inexpensive nitrogen sources, such as urea, ammonium salts and nitrogen-rich wastewaters can be used for

A. platensis

cultivation, with results that can be comparable to those with classical nitrate sources. Closed photobioreactors are useful for preventing ammonia loss. The use of organic carbon sources needs to be carried out under aseptic conditions, and it is necessary to evaluate the best supplying conditions when using fed-batch process. The addition of CO

2

ensures the control of pH and, at the same time, supply of the carbon source into the culture medium. The fed-batch process can be useful for the production of

A. platensis

using CO

2

from industrial plants, particularly from industrial alcoholic fermentation.

Chlorophyll, a green pigment found abundantly in plants, algae, and cyanobacteria, plays a critical role in sustaining life on earth and has found many applications in pharmaceutical, food, as well as cosmetic industries. Because of their high intracellular chlorophyll accumulations (up to 10% of cell dry weight), green microalgae are recognized as promising alternative chlorophyll sources. Successful co-production of a high value product such as chlorophyll in a microalgal bio-refinery is desirable as it will alleviate the overall cost of producing microalgal biodiesel. This chapter evaluates the bioprocess engineering required to recover and to purify chlorophyll molecules from microalgae. The use of organic solvents and supercritical fluids to extract microalgal chlorophyll on a commercial scale is examined. The use of chromatographic techniques to purify the recovered chlorophylls is also reviewed. Finally, the chapter ends by presenting a case study which investigates the use of organic solvents (acetone and methanol) to extract chlorophyll from

Tetraselmis suecica

on a laboratory scale.

At present, functional foods are seen as a good alternative to maintain or even improve human health, mainly for the well-known correlation between diet and health. This fact has brought about a great interest for seeking new bioactive products of natural origin to be used as functional ingredients, being, nowadays, one of the main areas of research in Food Science and Technology. Among the different sources that can be used to extract bioactives, algae have become one of the most promising. Algae have an enormous biodiversity and can be seen as natural factories for producing bioactive compounds since either by growing techniques or by genetic engineering approaches, they can improve their natural content of certain valuable compounds. In this book chapter, a revision about the different types of bioactives that have been described in algae is presented including compounds, such as lipids, carotenoids, proteins, phenolics, vitamins, polysaccharides, etc. Also, the modern green techniques used to achieve the selective extraction of such bioactives are presented and the methods for fast screening of bioactivity described.

Anaerobic digestion is a common process for the treatment of a variety of organic wastes and biogas production. Both, macro- and microalgae are suitable renewable substrates for the anaerobic digestion process. The process of biogas production from algal biomass is an alternative technology that has larger potential energy output compared to green diesel, biodiesel, bioethanol, and hydrogen production processes. Moreover, anaerobic digestion can be integrated into other conversion processes and, as a result, improve their sustainability and energy balance. Several techno-economic constraints need to be overcome before the production of biogas from algal biomass becomes economically feasible. These constraints include a high cost of biomass production, limited biodegradability of algal cells, a slow rate of biological conversion of biomass to biogas, and high sensitivity of methanogenic microorganisms. The research opportunities include a variety of engineering and scientific tasks, such as design of systems for algae cultivation and anaerobic digestion; optimization of algae cultivation in wastewater, nutrients recycling and algal concentration; enhancement of algal biomass digestibility and conversion rate by pretreatment; deep integration with other technological processes (e.g., wastewater treatment, co-digestion with other substrates, carbon dioxide sequestration); development and adaptation of molecular biology tools for the improvement of algae and anaerobic microorganisms; application of information technologies; and estimation of the environmental impact, energy and economical balance by performing a life cycle analysis.

Gas hydrates are a vast energy resource with global distribution in the permafrost and in the oceans, and its sheer size demands evaluation as a potential energy source. Here we discuss the distribution of natural gas hydrate (GH) accumulations, the status of the international R&D programs. We review well-characterized GH accumulations that appear to be models for future gas production, and we analyze the role of numerical simulation in the assessment of their production potential. We discuss the productivity from different GH types, and consistent indications of the possibility for production at high rates over long periods using conventional technologies. We identify (a) features, conditions, geology, and techniques that are desirable in production targets, (b) methods to maximize production, and (c) some of the conditions and characteristics that render GH deposits undesirable. Finally, we review the remaining technical, economic, and environmental challenges and uncertainties facing gas production from hydrates.

Biofuels are by now a well-established component of the liquid fuels market and will continue to grow in importance for both economic and environmental reasons. To date, all commercial approaches to biofuels involve photosynthetic capture of solar radiation and conversion to reduced carbon; however, the low efficiency inherent to photosynthetic systems presents significant challenges to scaling. In 2009, the US Department of Energy (DOE) Advanced Research Projects Agency-Energy (ARPA-E) created the Electrofuels program to explore the potential of nonphotosynthetic autotrophic organisms for the conversion of durable forms of energy to energy-dense, infrastructure-compatible liquid fuels. The Electrofuels approach expands the boundaries of traditional biofuels and could offer dramatically higher conversion efficiencies while providing significant reductions in requirements for both arable land and water relative to photosynthetic approaches. The projects funded under the Electrofuels program tap the enormous and largely unexplored diversity of the natural world, and may offer routes to advanced biofuels that are significantly more efficient, scalable and feedstock-flexible than routes based on photosynthesis. Here, we describe the rationale for the creation of the Electrofuels program, and outline the challenges and opportunities afforded by chemolithoautotrophic approaches to liquid fuels.

Isobutanol (IBT) can be used as a 100% replacement for gasoline in existing automobile engines, has >90% of the energy density of gasoline and is compatible with established fuel distribution infrastructure. The facultatively autotrophic bacterium

Ralstonia eutropha

can utilize H

2

for energy and CO

2

for carbon and is also employed in industrial processes that produce biodegradable plastics. Using a carefully designed production pathway,

R. eutropha

, a genetically tractable organism, can be modified to produce biofuels from autotrophic growth. Microbial production of IBT can be achieved by directing the flow of carbon through a ­synthetic production pathway involving the branched-chain amino acid biosynthesis pathway, a heterologously expressed ketoisovalerate decarboxylase, and a broad substrate specificity alcohol dehydrogenase. We discuss the motivations and the methods used to engineer

R. eutropha

to produce the liquid transportation fuel IBT from CO

2

, H

2

, and O

2

.

We are developing an integrated Microbial-ElectroCatalytic (MEC) ­system consisting of

Ralstonia eutropha

as a chemolithoautotrophic host for metabolic engineering coupled to a small-molecule electrocatalyst for the production of biofuels from CO

2

and H

2

.

R. eutropha

is an aerobic bacterium that grows with CO

2

as the carbon source and H

2

as electron donor while producing copious amounts of polyhydroxybutyrate. Metabolic flux from existing

R. eutropha

pathways is being diverted into engineered pathways that produce biofuels. Novel molybdenum electrocatalysts that can convert water to hydrogen in neutral aqueous media will act as chemical mediators to generate H

2

from electrodes in the presence of engineered strains of

R. eutropha

. To increase the local concentration of H

2

, we are engineering

R. eutropha

’s outer-membrane proteins to tether the electrocatalysts to the bacterial surface. The integrated MEC system will provide a transformational new source of renewable liquid transportation fuels that extends beyond biomass-derived substrates.