Electrofuels is a newly created biofuel technology concept that may have significant potential in producing transportation fuel from non-biomass feedstocks such as CO2, H2 and/or electricity. One of its key features is the application of certain chemolithoautotrophic organisms with synthetic biology to synthesize biofuel(s), such as butanol through fixation of CO2 using H2 and/or electrons as a source of reductant. Potentially, this approach could become quite attractive for biofuels pro­duction, since large quantities of inexpensive electricity (thus H2 from electrolysis of water) and CO2 feedstock could foreseeably become available in the near future. With advanced photovoltaic cells, the solar-to-electricity energy conversion efficiency can now reach more than 20%. A solar electricity-based electrofuel process with certain chemolithoautotrophic CO2 fixation pathways [21] could have a combined solar-to-biofuels energy conversion efficiency higher than that of a photosynthesis-based biofuel technology. Therefore, the electrofuels approach merits serious exploration also. In 2009, the United States Department of Energy (DOE) Advanced Research Projects Agency-Energy (ARPA-E) created the electrofuels program to explore the potential of non-photosynthetic autotrophic organisms for the conversion of durable forms of energy to energy-dense, infrastructure-compatible liquid fuels. Chapter 38 reports the US DOE/ARPA-E Electrofuels program efforts, including its rationale, approach, potential benefits, and challenges. Chapter 39 dis­cusses the motivations and the methods used to engineer Ralstonia eutropha to pro­duce the liquid transportation fuel isobutanol from CO2, H2, and O2; and Chap. 40 reports the development of an integrated Microbial-ElectroCatalytic (MEC) system consisting of R. eutropha as a chemolithoautotrophic host for metabolic engineering coupled to a small-molecule electrocatalyst for the production of biofuels from CO2 and H2, which extends well beyond biomass-derived substrates.

As illustrated in Figs. 1 and 2 , photosynthesis captures more CO2 from the atmo­sphere than any other process does on Earth. Each year, land-based green plants capture about 440 gigatons (Gt) CO2 (equivalent to 120 Gt C y-1) from the atmo­sphere into biomass [16]. However, biomass is not a stable form of carbon material with nearly all returning to the atmosphere in a relatively short time as CO2. Because of respiration and biomass decomposition, there is nearly equal amount of CO2 (about 120 GtC y-1) released from the terrestrial biomass system back into the atmo­sphere each year [17]. As a result, using biomass for carbon sequestration is limited. Any technology that could significantly prolong the lifetime of biomass materials would be helpful to global carbon sequestration. The approach of smokeless biomass pyrolysis can provide such a possible capability to convert the otherwise unstable biomass into biofuels, and, more importantly, biochar which is suitable for use as a soil amendment and serve as a semipermanent carbon-sequestration agent in soils/ subsoil earth layers for hundreds and perhaps thousands of years [4].

Biomass pyrolysis is a process in which biomass, such as waste woods and/or crop residues (e. g., cornstover), is heated to about 400°C in the absence of oxygen and converted to biofuels (bio-oils, syngas) and biochar—a stable form of solid black carbon (C) material (Fig. 3). Although its detailed thermochemical reactions are quite complex, the biomass-pyrolysis process can be described by the following general equation:

Biomass(e. g., lignin cellulose) ^ biochar + H2O + bio — oils + syngas

The yield and characteristics of biochar produced varies widely depending on the feedstock properties and pyrolysis conditions, including temperature, heating rate, pressure, moisture, and vapor-phase residence time. Typically, biochar contains mainly carbon (C) with certain amounts of hydrogen (H), oxygen (O), and nitrogen (N) atoms, plus ash. As reported in one of our previous studies [4], a typical compo­sition of biochar on an ash — and nitrogen-free basis can be 82% C, 3.4% H, and 14.6% O. Biochar has been produced throughout recorded history in energy-wasteful earthen pits, kilns, and steel drums releasing smoke. Advances in technology allow the organic volatiles (bio-oils) and syngas (CO, CO, , and H, , etc.) from biomass

More fabric, paper,
wooden furniture,
houses, and buildings

pyrolysis to be used as a biofuel for clean energy production. Typically, through a 400°C slow-pyrolysis process, about 50% of the dry biomass C (carbon) can be converted into biochar while the remaining 50% C in the biofuel portion provides part of its energy to sustain the process.

Terrestria Biomass

Biochar Geologic Storage

As Carbon Energy Reserves

(Capacity: Limitless)

Fig. 2 The global carbon cycle and envisioned “carbon-negative” biomass-pyrolysis energy tech­nology concept for biofuel and biochar production, and carbon dioxide capture and sequestration (reproduced from ref. [5])

In perspective of the global carbon cycle, as shown in Fig. 1, this biochar-producing biomass-pyrolysis approach essentially employs the existing natural green-plant photosynthesis on the planet as the first step to capture CO2 from the atmosphere; then, the use of a pyrolysis process converts biomass materials primarily into bio­fuel and char—a complex but stable form of solid carbon material that can enhance plant growth when used as soil amendment. The net result is the removal of CO2 from the atmosphere through the process of capturing CO2 from the atmosphere and placing it into soils and/or subsoil earth layers as a stable carbon (biochar) while producing significant amount of biofuel energy through biomass pyrolysis. Therefore, this is a “carbon negative” energy production approach.

The world’s annual unused waste biomass such as crop stovers is about 6.6 Gt of dry biomass [18], which is equivalent to about 3.3 GtC y-1 since dry biomass typically contains C as 50% of its total mass. If this amount of biomass (3.3 GtC y-1) is processed through controlled low-temperature pyrolysis assuming 50% conversion of biomass C to stable biochar C and 35% of the biomass energy to biofuels, 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 as a beneficial soil amendment, it would offset the 8.5 GtC y-1 of fossil fuel CO2 emissions by 19%. Therefore, the envisioned biochar-producing biomass-pyrolysis approach (Figs. 1 and 2) should be considered as an option to mitigate the problem of global green­house-gas emissions.

The capacity of carbon sequestration by the application of biochar fertilizer in soils could be quite significant since the technology could potentially be applied in many land areas, including croplands, grasslands, and also a fraction of forest lands. The maximum capacity of carbon sequestration through biochar soil amendment in croplands alone is estimated to be about 428 GtC for the world. This capacity is estimated according to: (a) the maximal amount of biochar carbon that could be cumulatively placed into soil while still beneficial to soil environment and plant growth; and (b) the arable land area that the technology could potentially be applied through biochar agricultural practice.

Using charcoal collected from a wildfire, Gundale and DeLuca recently showed that the amount of charcoal that can be applied can be as much as 10% of the weight of soil to increase plant Koeleria macrantha biomass growth without negative effect [19]. The composition of a biochar material depends on its source biomass material and pyrolysis conditions. Typically, biochar material produced from low-temperature (about 400°C) pyrolysis contains about 70% (w) of its mass as the stable carbon (C) and the remainder as ash content, oxides, and residual degradable carbon (such as bio-oil residue). The density of bulk soil is typically about 1.3 tons m-3. With this preliminary knowledge, we calculated that the maximum theoretical biochar seques­tration capacity is about 303.8 ton C per hectare (1 ha=2.47 acres; 123 ton C per acre) in a 30-cm soil layer alone. From the size of the world’s arable land (1,411 million hectares), the worldwide potential capacity for storing biochar carbon in agricultural soils was estimated to be 428 GtC (Table 1). This estimate (428 GtC), which is somewhat higher than that (224 GtC) estimated by Lehman et al. [20] ,

probably represents an upper limit value. The maximal amounts of biochar carbon that could be cumulatively placed into soil while still beneficial to soil environment and plant growth are probably dependent on a number of factors, including the specific biochar properties, topography, soil type, weather, and plant species. Worldwide biochar soil field tests are needed to obtain more accurate information on the capacity of biochar carbon sequestration in soils.

The world currently faces a systematic energy and environmental problem of increased CO2 emissions, decreased soil-carbon content, and global-climate change. To solve the massive global energy and environmental sustainability problem, it likely requires a comprehensive portfolio of R&D efforts with multiple energy technologies.

J. W. Lee (*)

Department of Chemistry & Biochemistry, Old Dominion University,

Physical Sciences Building, Room 3100B, 4402 Elkhorn Avenue, Norfolk, VA 23529, USA

Johns Hopkins University, Whiting School of Engineering,

118 Latrobe Hall, Baltimore, MD 21218, USA e-mail: jwlee@odu. edu; JLee349@JHU. edu

J. W. Lee (ed.), Advanced Biofuels and Bioproducts, DOI 10.1007/978-1-4614-3348-4_1, © Springer Science+Business Media New York 2013

The field of advanced biofuels and bioproducts, such as photosynthetic biomass energy, may represent one of the major R&D areas that have the potential to provide renewable clean energy, in additions to the other renewable energy technologies, including nuclear energy, geothermal, wind, solar, and hydropower. Photosynthesis captures more CO2 from the atmosphere than any other processes on Earth capture. Each year, land-based green plants capture about 440 gigatons (Gt) CO2 (equivalent to 120 GtC y-1) from the atmosphere into biomass [1]. That is, about one-seventh of all the CO2 in the atmosphere (820 GtC) is fixed by photosynthesis (gross primary production) every year. Theoretically, if there is a technology that could translate as small as 7.5% of the annual terrestrial gross photosynthetic products (120 GtC y-1) to a usable biofuel to substitute fossil fuels that would be sufficient to eliminate the entire amount (nearly 9 GtC y-1) of CO2 emitted into the atmosphere annually from the use of fossil fuels. The success of Brazil’s sugarcane ethanol reported in Chap. 2 has demonstrated that with the advancement of science and technology and coupled with proper policy support, it is possible for the field of advanced biofuels and bioproducts to make a significant contribution to enrich the energy market at a national and/or possibly global scale. Presently, ethanol from sugarcane replaces approximately 50% of the gasoline that would be used in Brazil if such an option did not exist. Therefore, Brazil’s sugarcane-ethanol success may be regarded as an early but still encouraging example of biofuels at least at a national scale. However, understandably, Brazil’s sugarcane-ethanol technology per se may or may not be applicable to the other parts of the world such as the United States because of the differences in climates, crop ecosystems, and various other factors. Development and deployment of other innova­tive biofuels technologies are essential to achieve the mission of renewable energy production. The following highlights some of the bioenergy R&D areas that may be of special significance.

Electrofuels is a newly created biofuel technology concept that may have significant potential in producing transportation fuel from non-biomass feedstocks such as CO2, H2 and/or electricity. One of its key features is the application of certain chemolithoautotrophic organisms with synthetic biology to synthesize biofuel(s), such as butanol through fixation of CO2 using H2 and/or electrons as a source of reductant. Potentially, this approach could become quite attractive for biofuels pro­duction, since large quantities of inexpensive electricity (thus H2 from electrolysis of water) and CO2 feedstock could foreseeably become available in the near future. With advanced photovoltaic cells, the solar-to-electricity energy conversion efficiency can now reach more than 20%. A solar electricity-based electrofuel process with certain chemolithoautotrophic CO2 fixation pathways [21] could have a combined solar-to-biofuels energy conversion efficiency higher than that of a photosynthesis-based biofuel technology. Therefore, the electrofuels approach merits serious exploration also. In 2009, the United States Department of Energy (DOE) Advanced Research Projects Agency-Energy (ARPA-E) created the electrofuels program to explore the potential of non-photosynthetic autotrophic organisms for the conversion of durable forms of energy to energy-dense, infrastructure-compatible liquid fuels. Chapter 38 reports the US DOE/ARPA-E Electrofuels program efforts, including its rationale, approach, potential benefits, and challenges. Chapter 39 dis­cusses the motivations and the methods used to engineer Ralstonia eutropha to pro­duce the liquid transportation fuel isobutanol from CO2, H2, and O2; and Chap. 40 reports the development of an integrated Microbial-ElectroCatalytic (MEC) system consisting of R. eutropha as a chemolithoautotrophic host for metabolic engineering coupled to a small-molecule electrocatalyst for the production of biofuels from CO2 and H2, which extends well beyond biomass-derived substrates.

Since this technology concept of smokeless biomass pyrolysis with biochar soil application is still in its early developing stage, much more research and development work is needed before this approach could be considered for practical implementation. To achieve the mission, a number of technical issues still need to be addressed. First, as pointed out previously, the process technology must be smokeless (emission — free, clean, and efficient) to avoid negative impact on air quality with such a large (GtC)-scale operation. Therefore, it is essential to fully develop a smokeless bio­mass-pyrolysis process to achieve the mission. As illustrated in Fig. 4, one of the possible productive ways to achieve the smokeless (emission-free, clean, and efficient) feature is by converting the pyrolysis syngas “smoke” into clean energy, such as liquid biofuels. Currently, there are a number of Fischer-Tropsch process­ing technologies that might be helpful for conversion of biomass-derived syngas into advanced (drop-in-ready) liquid biofuels, such as biodiesel, to replace petroleum — based transportation fuels. However, significant R&D efforts are needed to fully develop and demonstrate this approach since the currently existing refinery technologies cannot cost-effectively convert biomass-derived syngas and/or bio-oils into liquid transportation biofuels.

Second, there are significant R&D opportunities to improve biofuels products in relation to proper utilization of the biomass-pyrolysis-derived syngas and bio-oils that currently cannot be used as a liquid transportation fuel. For example, one of the problems here is that the biofuel fractions (syngas and bio-oils) from biomass pyrolysis are not in a desired form that could be used as a transportation fuel for cars. In other words, although the amounts and the heating value of the syngas and bio-oils from the envisioned biomass pyrolysis approach could potentially be very large (with heating value equivalent to that of about 3,250 million barrels of crude oil for the world), it is not clear how much they could really replace crude oil because the efficiency for conversion of the syngas and bio-oils into the advanced liquid biofuels has not been fully established. Additional refinery technology is needed to convert the biomass-derived syngas and/or bio-oils into certain desirable advanced liquid biofuels such as biodiesel for use in cars in order to replace the petroleum-based transportation fuels. It is possible to catalytically convert the biomass-derived syngas into liquid transportation fuels through the Fischer-Tropsch synthesis of hydrocar­bons [21-23]. It is also possible to convert the liquid bio-oils by different refinery processes, such as catalytic processing into biodiesel for use as a transportation fuel. Therefore, it is probably worthwhile to explore the use of a proper refinery process, such as the Fischer-Tropsch process, to couple with a continuous biomass pyrolysis for production of advanced liquid biofuels and biochar. However, since most require expensive catalysts, other viable options (such as using bio-oils as a heating oil and noncatalytic fuel production) remain to be examined to determine trade-off between energy efficiency and costs. Significant research efforts are needed to develop inno­vative technologies, such as catalytic bio-oils-hydroprocessing and/or an updated Fischer-Tropsch process, to convert the syngas into advanced (drop-in-ready) liquid biofuels to replace petroleum-based transportation fuels. This also reflects the need of developing tools for optimizing the entire process in relation to feed­stock, energy, greenhouse gases, and economics.

Third, significantly more research efforts are needed on the aspects of biochar production and biochar soil applications. Biochar typically is a spectrum of sub­stances produced from biomass pyrolysis. In order for biochar to serve as an effective soil amendment and carbon sequestration agent, the biochar product must possess certain required properties and quality standards, such as its cation exchange capacity and stability. More research is needed to further optimize the biochar cation exchange capacity [24] while still retaining its carbon stability. It has also been reported that biochar occasionally shows inhibitory effects on plant growth, especially, when biochar soil application exceeds about 5-10% by weight [25-27]. So far, very little is known about the true identity of the biochar inhibitory factors. If biochar were to be globally used as a soil amendment and carbon sequestration agent at GtC scales, the release of potentially toxic compounds into soil and associated hydro­logic systems might have unpredictable consequences in agroecosystems. These characteristics of biochar, including both its beneficial features (e. g., cation exchange capacity) and possible harmful factors need to be systematically studied, since they are directly related to its application impacts (benefils and risks) on soil and the environment. Rigorous biochar-soil studies at large scales across the world are needed to systematically assess the effects of biochar applications on soil fertility, including plant growth, on soil carbon storage (sequestration) and on the associated soil and hydrological ecosystems. Additional work is needed also on how to employ this approach in helping to utilize various waste biomass materials, including (but not limited to) dead leaves, waste woods, and various agriculture stovers, such as cornstovers and rice straws to produce both biochar and biofuels in a distributed manner across the world. It is also worthwhile to explore beneficial utilization of certain sewage solid waste, such as, on what fraction of sewage sludge could be added to waste biomass to produce a higher nutrient dense slow-release biochar and safely recycle the valuable nutrients currently lost in waste processing. With these studies and added knowledge, it should be possible to produce “fil-for-purpose” biochars to address specific soil and environmental constraints and maximize the benefits of biochar soil application at the national and international scales.

Fourth, systematic lifecycle impact-assessment on energy, carbon, land, water, air, and environmental health, including toxicology and ecology studies, must be carefully conducted to fully evaluate the potential benefits and possible risks in rela­tion to biomass pyrolysis and biochar application as soil amendment for global carbon sequestration at GtC scales.

Furthermore, the maximum capacity of carbon sequestration through biochar soil amendment in world agricultural soils (1,411 million hectares) is estimated to be about 428 GtC, assuming maximally 10% biochar C by soil weight for the first 30-cm soil layer alone. To verify this potential capacity and demonstrate its feasibility, soil pot studies and field trials of biochar applications in relation to soil fertility and carbon sequestration are needed in all of the world regions and different soil types. For the immediate future, biochar should be used to revitalize barren degraded land.

This will improve the world’s capacity for growing biomass thus naturally removing more CO2 from the atmosphere.

Another question to answer is whether it is possible to provide a global carbon “thermostat” mechanism to control the atmospheric CO2 concentrations by creating large reservoirs underground (and/or above ground) for any biochar not used for soil restoration. Since the capacity of biochar storage reservoirs could be so large (limit­less), the envisioned photosynthetic biomass production and biochar-producing biomass-pyrolysis approach (Figs. 1 and 2) could be used for many years to reduce the atmospheric CO2 concentrations to any desired levels if the world population is mobilized to implement the approach. This is different from the application of bio­char as a soil amendment where biochar particles are mixed with soil particles in such a diluted manner (such as 10% by soil weight) that recovering of biochar mate­rials from the mixed soils would be very difficult. The biochar materials in reser­voirs are preferably in a pure and concentrated form so that they could be readily retrieved at any time when needed for use of its energy by combustion. Therefore, global use of biochar reservoirs in a regulated manner could provide a global carbon “thermostat” mechanism to control global warming (climate change) in a desirable manner as well.

As a conclusion, this smokeless biomass-pyrolysis “carbon-negative” energy — production approach merits a major program support for serious research and devel­opment worldwide. With further research and development, this approach could provide more efficient and cleaner biomass pyrolysis technology for producing bio­fuels and biochar from biomass as a significant arsenal to help achieve indepen­dence from fossil energy and to control climate change for a sustainable future on Earth.

Biomass utilization through smokeless (emission-free, clean, and efficient) pyrol­ysis is a potentially significant approach for biofuels production and biochar car­bon sequestration at gigatons of carbon (GtC) scales. One of the key ideas here is to use a biomass-pyrolysis process to produce certain biofuels and more impor­tantly to “lock” some of the unstable biomass carbon such as dead leaves, waste woods, cornstovers, and rice straws into a stable form of carbon—biochar, which could be used as a soil amendment to improve soil fertility and at the same time, to serve as a carbon sequestration agent, since biochar can be stable in soil for thousands of years and can help retain nutrients in soil to reduce the runoff of fer­tilizers from agriculture lands that would otherwise pollute the rivers and water bodies. This “carbon negative” approach, which was co-initiated by Danny Day of Eprida Inc. and James Weifu Lee (the Editor) through their joint 2002 U. S. provi­sional patent application followed by a PCT application [2, 3], is now receiving increased attention worldwide [4, 5], especially since certain related studies have also indicated the possibility of using biochar as a soil amendment for carbon sequestration [6-9].

Chapter 3 provides an overview of this smokeless biomass-pyrolysis approach for producing biofuels and biochar as a possible arsenal to control climate change. For the immediate future, application of this biochar producing biomass-pyrolysis approach to turn waste biomass into valuable products could likely provide the best economic and environmental benefits. Globally, each year, there are about 6.6 Gt dry matter of biomass (3.3 GtC) such as crop stovers that are appropriated but not used. Development and deployment of the smokeless biomass pyrolysis technol­ogy could turn this type of waste biomass into valuable biochar and biofuel prod­ucts. Even if assuming that only half amount of this waste biomass is utilized by this approach, it would produce 0.825 GtC y-1 of biochar and large amounts of biofuel (with a heating value equivalent to that of 3,250 million barrels of crude oil). By storing 0.825 GtC y-1 of biochar (equivalent to 3 Gt of CO2 per year) into soil and/or underground reservoirs alone, it could offset the world’s 8.67 GtC y-1 of fossil fuel CO2 emissions by 9.5%, which is still very significant. So far, there are no other technologies that could have such a big (GtC) capacity in effectively cap­turing and sequestering CO2 from the atmosphere. Therefore, this is a unique “carbon-negative” bioenergy technology system approach, which in the perspec­tive of carbon management is likely going to be more effective (and better) than the nuclear energy option, since the nuclear-power energy system is merely a carbon — neutral energy technology that could not capture CO2 from the atmosphere. This is true also in comparing the “carbon-negative” smokeless biomass-pyrolysis approach with any other carbon-neutral energy technologies, including solar pho­tovoltaic electricity, geothermal, wind, and hydropower, and all carbon-neutral biofuel technologies such as cellulosic biofuels, photobiological biofuels from car­bon dioxide and water, lipid-based biodiesels, and electrofuels, which are also cov­ered in this book. Consequently, nuclear energy and any other carbon-neutral energy technologies all cannot reverse the trend of climate change; on the other hand, the smokeless biochar-producing biomass-pyrolysis energy system approach, in principle, could not only reduce but also could possibly reverse the climate change. Therefore, this “carbon-negative” smokeless biomass-pyrolysis approach clearly merits serious research and development worldwide to help provide clean energy and control climate change for a sustainable future of human civilization on Earth [10].

Chapter 4 reports an invention on partial oxygenation of biochar for enhanced cation exchange capacity, which is one of the key properties that enable biochar to help retain soil nutrients to reduce fertilizers runoff from agriculture lands and to keep water environment clean. Chapter 5 describes chemical structural character­ization of biochars using advanced solid-state 13C nuclear magnetic resonance spec­troscopy, which is scientifically important in understanding the chemistry and application of biochar materials. As reported in Chap. 6, one of the ideas is to use biochar particles incorporated with certain fertilizer species such as ammonium bicarbonate and/or urea, hopefully to make a type of slow-releasing fertilizer.

Use of this type of biochar fertilizer would place the biochar carbon into soil to improve soil fertility and, at the same time, store (sequester) carbon into the soil and subsoil earth layers to achieve carbon sequestration. Chapter 7 discusses selection and use of designer biochars to improve characteristics of Southeastern USA Coastal Plain degraded soils while Chap. 8 describes biochar as a co-product to bioenergy from slow-pyrolysis technology.

There are significant progresses and scientific understanding in the arts of biomass pyrolysis. Chapter 9 reports the arts of catalytic pyrolysis of biomass for the produc­tion of both biofuels and biochar while Chap. 10 describes the selective fast pyrolysis of biomass to produce fuels and chemicals. As reported in Chap. 11, it is also possi­ble to produce advanced biofuels and biochar through hydrothermo processing of biomass.

To avoid negative impact on air quality with such a large (GtC)-scale operation required to achieve the envisioned global biochar carbon sequestration, the bio­mass-pyrolysis process technology must be smokeless (emission-free, clean, and efficient). Therefore, it is essential to fully develop a smokeless biomass-pyrolysis process to achieve the mission. One of the possible productive ways to achieve the smokeless (emission-free, clean, and efficient) feature is by converting the pyrolysis syngas “smoke” into clean energy such as liquid transportation fuel. Currently, there are a number of Fischer-Tropsch processing technologies [11, 12] that could be helpful for conversion of biomass-derived syngas into advanced (drop-in-ready) liquid biofuels, such as biodiesel, to replace petroleum-based transportation fuels. Chapter 12 describes the fundamentals of the biomass-to-liquid fuel process tech­nologies via Fischer-Tropsch and related syntheses. Chapter 13 reports Fischer — Tropsch hydrocarbons synthesis from a simulated biosyngas while Chap. 14 describes Fischer-Tropsch synthesis of liquid fuel with Fe catalyst using CO2 — containing syngas that can be produced from biomass pyrolysis.

Jose Goldemberg

Abstract 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.

1 Introduction

Sugarcane has been cultivated in Brazil since the sixteenth century and more recently the country became the largest producers of sugar accounting for approximately 25% of the world’s production. The production of ethanol has been small but starting in 1931 the Government decided that all the gasoline used in the country (mostly imported) should contain 5% of ethanol from sugarcane. This was done to benefit sugar producing units when faced by declining prices of sugar in the international market which notoriously fluctuate over the years (Fig. 1).

Around 1970 the sugar industry in Brazil was stagnated, processing only 70-80 million tonnes of sugarcane per year mainly due to Government policies of guaranteed prices to producers: when the international price of sugar was low the

J. Goldemberg (*)

University of Sao Paulo, Institute of Eletrotechnics and Energy, Sao Paulo, Brazil e-mail: goldemb@iee. usp. br

J. W. Lee (ed.), Advanced Biofuels and Bioproducts, DOI 10.1007/978-1-4614-3348-4_2, © Springer Science+Business Media New York 2013

government purchased the sugar at prices that satisfied the producers. Competition and modernization were thus discouraged; each producer had a quota and therefore few concerns about losing money. Sugar producers did not plan in the long run and usually produced strictly what they considered attractive in a given year. Since the price of sugar in the international markets varies significantly over time, as seen in Fig. 1, such lack of planning frequently left them out of the market when prices suffered strong fluctuations [1].

The solution proposed at that time by Ministry of Industry and Commerce [2] was to expand production regardless of the prices of sugar and use the excess pro­duction (when prices were low) to produce ethanol which was more expensive to produce than gasoline. One of the drivers for that was the need to eliminate lead components from gasoline (lead tetraethyl) which was imported saving thus foreign currency. Such ideas did not prosper until the oil crisis of 1973: the cost of oil went suddenly from US$ 2.90 per barrel to US$ 11.65 per barrel. The import bill with oil (80% of which was imported) skyrocketed from 600 million dollars in 1973 to 2.5 billion in 1974, approximately 32% of all Brazilian imports and 50% of all the hard currency that the country received from exports.

James Weifu Lee, A. C. Buchanan III, Barbara R. Evans, and Michelle Kidder

Abstract 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.

1 Introduction

Photosynthesis captures more carbon dioxide (CO2) from the atmosphere than any other process on Earth. Each year, land-based green plants capture about 403 giga — tons (Gt) of CO2 (equivalent to 110 Gt C y-1) from the atmosphere into biomass [1]. However, only about й of the primary photosynthesis product (110 Gt C y_1) becomes plant tissue (biomass), the other half is respired directly from photosyn­thetic sugars; furthermore, since biomass is not a stable form of carbon material,

J. W. Lee (*)

Formerly, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, TN 37831, USA

Department of Chemistry and Biochemistry, Old Dominion University,

Physical Sciences Building 3100B, Norfolk, VA 23529, USA

Whiting School of Engineering, Johns Hopkins University,

118 Latrobe Hall, Baltimore, MD 21218, USA e-mail: JWLee@odu. edu; JLee349@jhu. edu

A. C. Buchanan III • B. R. Evans • M. Kidder

Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, TN 37831, USA

J. W. Lee (ed.), Advanced Biofuels and Bioproducts, DOI 10.1007/978-1-4614-3348-4_4, 35

© Springer Science+Business Media New York 2013

a substantial portion of the biomass decomposes in a relatively short time to CO2. As a result, increased biomass production (i. e., by increased tree growth) is of limited utility for carbon sequestration since the resulting biomass soon returns the absorbed CO2.

Unlike untreated biomass, carbonized biomass (i. e., charcoal or “biochar”) contains carbon in a highly stabilized state, i. e., as elemental carbon. The inertness of elemental carbon results in its very slow decomposition to CO2 . Typically, at least several 100 years are necessary for the complete decomposition of biochar to CO2. Through a 14C labeling study, the mean residence time of pyrogenic carbon in soils has now been estimated in the range of millennia [2]. As a result, there is great interest in producing biochar as a means for mitigating atmospheric CO2 production. There is particular interest in incorporating produced biochar into soil (i. e., as a soil amendment) where the biochar functions both as a CO2 sequestrant and as a soil amendment [3].

Biochar production and incorporation into soil has been practiced since ancient times. Of particular relevance is the recent discovery of biochar particles in soils formed by pre-Columbian indigenous agriculturalists in Amazonia, i. e., the so-called Terra Preta soil [4].

The capacity of carbon sequestration by the application of biochar fertilizer is estimated to be quite significant. The amount of biochar materials that could be placed into soil could be as high as 10% by weight of the soil [5]. Accordingly, in the first 30-cm layer of US cropland soil alone, 40 Gt of carbon could be sequestered in the form of biochar particles. The worldwide capacity for storing biochar carbon in agricultural soils could exceed 400 Gt of carbon. A conversion as low as 8% of the annual terrestrial photosynthetic products (110 Gt C y_1) into stable biochar material would be sufficient to offset the entire amount (over 8 Gt C y-1) of CO. emitted into the atmosphere annually from the use of fossil fuels.

Significant amounts of biochar are currently being produced as a byproduct in biomass-to-biofuel production processes. The most common biomass-to-biofuel production processes include low temperature and high temperature pyrolysis (i. e., gasification) processes [6, 7). Pyrolysis operations generally entail combusting biomass in the substantial absence of oxygen. Biofuels commonly produced in low temperature pyrolysis operations include hydrogen, methane, and ethanol. Gasification processes are generally useful for producing syngas (i. e., H2 and CO).

An important property of biochar is its cation-exchanging ability. The cation­exchanging ability or lack thereof of a biochar is evident by the magnitude of its cation exchange capacity (CEC). It is known that biochar which has an increased CEC generally possesses a greater nutrient retention capability. These biochars with greater CEC generally possess a significant amount of hydrophilic oxygen-containing groups, such as phenolic and carboxylic groups, which impart the greater cation exchange ability [7] .

The CEC is defined as the amount of exchangeable cations (e. g., K+, Na+, NH4+, Mg2+, Ca2+, Fe3+, Al3+, Ni2+, and Zn2+) bound to a sample of soil. CEC is often expressed as centimoles (cmol) or millimoles (mmol) of total or specific cations per kilogram (kg) of soil. A substantial lack of a cation-exchanging property is generally considered to be reflected in a CEC of less than 50 mmol kg-1 . A moderate CEC is typically considered to be within the range of above 50 and at or less than 250 mmol kg-1. An atypical or exceptionally high CEC would be at least 250 mmol kg-1.

Though biochar is generally considered useful for CO2 sequestration, the types of biochar found in ancient soils or produced as an industrial byproduct are highly variable in their physical and property characteristics, e. g., chemical composition, porosity, charge density, and CEC. One of the most common production processes of biochar is the practice since ancient times of burning biomass in open pits. Such uncontrolled processes generally produce significant quantities of oxide gases of combustion, such as CO2 and CO, generally in amounts significantly greater than 20% by weight of the carbon content of the biochar source. In addition, the resulting biochar is highly nonuniform in composition, e. g., substantially nonoxygenated portions particularly in the interior portions of the biochar pit and moderately oxygenated portions at the outer peripheral portions of the biochar pit. Furthermore, the uncontrolled process generally results in significant batch-to-batch variability. Moreover, by the uncontrolled process, the characteristics of the resulting biochar are generally unpredictable and not capable of being adjusted or optimized.

Though biochar materials possessing moderate cation exchange capacities are known, such biochar compositions are not typical, and moreover, are found sporadi­cally and in unpredictable locations of the world. Therefore, there is a need for a method that produces oxygenated biochar compositions which have at least a moderate CEC, and more preferably, a CEC significantly higher than found in known soil deposits. Such biochar materials would have the advantage of more effectively retaining soil nutrients, and thus, functioning as superior fertilizing/soil amending materials as well as sequestering carbon.

In order to make such superior biochar materials readily available for widespread soil application, the biochar must be reproducibly manufactured with low batch-to — batch variation in one or more characteristics of the biochar (e. g., CEC, particle size, porosity, C:O ratio, and the like) and should be substantially uniform in its characteristics, such as oxygen-to-carbon ratio, CEC, and chemical composition. Further, the production method needs to able to be appropriately modified in order to obtain adjustment or optimization in one or more properties dependent on desired application and source feed stock. In the remainder of this chapter, we discuss several technology concepts to achieve these goals.

Chapter 15 reports cellulosic butanol production from agricultural biomass and residues: recent advances in technology while Chap. 16 describes the technology concept of consolidated bioprocessing of lignocellulosic biomass for biofuels pro­duction. The research opportunity here is the possibility of converting vast amount of lignocellulosic plant biomass materials such as cornstover, wheat straw, switch — grass, and woody plant materials into usable biofuels such as ethanol and/or butanol. Recently, bisabolane has also been identified as a terpene-based advanced biofuel that may be used as an alternative to D2 diesel [13]. This field of cellulosic biofuels has been active for more than 25 years and it still remains a hot topic because of its significant potential. One of the major challenges is known as the “lignocellulosic recalcitrance” which represents a quite formidable technical barrier to the cost — effective conversion of plant biomass to fermentable sugars. That is, because of the recalcitrance problem, lignocellulosic biomasses (such as cornstover, switchgrass, and woody plant materials) could not be readily converted to fermentable sugars to make ethanol or butanol without certain pretreatment, which is often associated with high processing cost. Despite more than 25 years of R&D efforts in lignocel — lulosic biomass pretreatment and fermentative processing, the problem of recalci­trant lignocellulosics still remains as a formidable technical barrier that has not yet been fully eliminated so far. This problem is probably rooted from the long history of natural plant evolution; plant biomass has evolved effective mechanisms for resisting assault on its cell-wall structural sugars from the microbial and animal kingdoms. This property underlies a natural recalcitrance, creating roadblocks to the cost-effective transformation of lignocellulosic biomass to fermentable sugars. Therefore, one of the R&D approaches is to unlock the sugars by re-engineering the cell wall structure through molecular genetics. Chapter 17 describes the synthesis, regulation, and modification of plant cell wall carbohydrates (lignocellulosic bio­mass) as a resource for biofuels and bioproducts while Chap. 18 reports genetic modifications of plant cell walls to increase biomass and bioethanol production. Other approaches include but are not limited to developing more effective pretreat­ment, enzymes, and microorganisms that could help convert the biomass materials into biofuels. Chapter 19 reviews the structural features of cellulose and cellulose degrading enzymes and describes the technology concept of designer enzymes/cel — lulosomes for cellulose-based biofuels production.

Under these conditions the Government decided to accelerate ethanol production thorough decree 76,593 of November 14, 1975 which is really the birth certificate of the Brazilian “Alcohol Program.” The idea was to reduce gasoline consumption

and therefore decrease oil imports. Production goals were set at three billion liters of ethanol in 1980 and 10.7 billion liters in 1985.

This decree determined that very generous financing terms were to be offered to entrepreneurs through Government banks[1] and that the price of ethanol should be on a parity with sugar 35% higher than the price of 1 kg of sugar.[2]

The decree made the production of ethanol and the production of sugar equally attractive to the entrepreneurs. This opened the way for the increase in the produc­tion of ethanol which happened indeed as seen in Fig. 2.

Production increased from 600 million liters/year in 1975/1976 to 3.4 billion liters per year in 1979/1980. This corresponded to 14% of the gasoline used in 1979.