Volume 5 biomass and biofuel production 5 01 – biomass and biofuels – introduction

Volume 5 biomass and biofuel production 5 01 – biomass and biofuels – introduction Volume 5 biomass and biofuel production 5 01 – biomass and biofuels – introduction Volume 5 biomass and biofuel production 5 01 – biomass and biofuels – introduction Volume 5 biomass and biofuel production 5 01 – biomass and biofuels – introduction Volume 5 biomass and biofuel production 5 01 – biomass and biofuels – introduction Volume 5 biomass and biofuel production 5 01 – biomass and biofuels – introduction Volume 5 biomass and biofuel production 5 01 – biomass and biofuels – introduction

5.01 Biomass and Biofuels – Introduction DJ Roddy, Newcastle University, Newcastle upon Tyne, UK © 2012 Elsevier Ltd All rights reserved 5.01.1 5.01.2 5.01.3 5.01.3.1 5.01.3.2 5.01.4 5.01.5 5.01.5.1 5.01.5.2 5.01.6 5.01.6.1 5.01.6.2 5.01.7 5.01.8 5.01.9 References Background Basic Technology Widespread Deployment of Biomass and Biofuels Biodiesel Other Biofuels Issues, Constraints, and Limitations Technology Solutions – New Processes Anaerobic Digestion Advanced Biofuel Processes Technology Solutions – New Feedstocks Algae Other Options for Increasing Feedstock Availability Expanding the Envelope Recent Developments The Way Forward for Biomass and Biofuels 3 4 5 6 7 9 5.01.1 Background The largest source of renewable energy in use in the world today is biomass [1] This assertion surprises people who expect the crown to be worn by wind, solar photovoltaic, or one of the other high-profile technologies However, when you consider that large parts of the world’s population are still dependent on firewood for cooking and heating, perhaps it is not so surprising Recent estimates place the number of people relying on traditional biomass for their energy needs at 2.5 billion [2] In many countries, there is the unfortunate associated problem of household air pollution, leading to 1.3 million premature deaths per year [2] Biomass is also the most versatile of the renewable resources This is due in part to the sheer breadth of materials that can be classified as biomass Basically, anything that grows and is available in non-fossilized form can be classified as biomass (Today’s fossil fuels used to be biomass several tens of millions of years ago, but they are obviously not ‘renewable’ on any relevant timescale, so it is not helpful to include them.) However, arable crops, trees, bushes, animals, human and animal waste, waste food, and any other waste stream that rots quickly are all biomass materials The United Kingdom alone produces around 25 million tonnes of segregated organic waste per year, equivalent to around 7.5 TWh of energy [3] The volume and variety of biomass materials available are truly remarkable The other reason for biomass’ ubiquity is that it can be used to displace all forms of energy: electricity, heating, and transport fuels Biomass has been used for heating and cooking since mankind first discovered fire, and technology has evolved ever since through various high-efficiency combustion technologies on to the gasification and pyrolysis technologies described by Roddy to offer very high-efficiency heating processes Using a wood-fired boiler to raise steam for power generation is a very basic idea which has been refined and scaled up over time to the 800 MWe scale described by Malmgren (Chapter 5.04) The history of converting biomass into liquid transport fuels is charted in a fascinating fashion by Knothe (Chapter 5.02), going all the way back to Nikolaus August Otto’s work on spark-ignition engines running on ethanol from fermented biomass and early compression-ignition engines running on vegetable oils, especially in parts of Africa where oil-bearing crops were abundant and used as a wartime fuel It is interesting to note that in the early days of the petroleum industry, ethanol was heavily taxed in the United States while the new gasoline fuel was untaxed The very versatility of biomass is arguably also the ‘Achilles heel’ of the technology, because biomass (in some forms) also supplies mankind’s food needs – both directly via food crops and indirectly via animal feed One could argue that other forms of biomass provide shelter in the form of wooden construction materials, various types of roofing material, and so on Inevitably, as populations expand and renewable resources whose annual availability is ultimately finite start to come under pressure, questions are asked about what the priorities ought to be for biomass utilization That very debate is currently slowing the pace of biomass development activity The prime drivers for biomass development vary from country to country In very, very broad terms, the drivers tend to be climate change in Europe, national energy security in the United States, and economic development in Asia Pacific While this assertion is doubtless an oversimplification, it highlights a number of important features of biomass In a climate change context, there is particular interest in growing biomass feedstocks with minimum reliance on chemical fertilizers (whose manufacture can be energy-intensive), with short distances between feedstock production and use (so that fossil fuels are not consumed in transporting materials), and processing them in a manner that minimizes fossil energy use In this way, one can aspire to reach the ideal position Comprehensive Renewable Energy, Volume doi:10.1016/B978-0-08-087872-0.00501-1 Biomass and Biofuels in which every tonne of CO2 emitted when a biomass crop is combusted is canceled out by the tonnes of CO2 that are extracted from the atmosphere during photosynthesis in growing the next season’s biomass crop The subtleties of the argument are explored in detail by Mortimer (Chapter 5.09) In a national energy security context, countries whose energy ‘needs’ exceed their forecast ability to supply from indigenous coal, oil, and gas are interested in exploring the limits of their ability to cultivate biomass on a large scale Developing countries whose agriculture has not yet been developed to the limit of its potential are interested in new biomass and biofuel markets (which they hope will be predictable, steadily growing, high-value markets) to provide the stimulus for economic development Of course, in practice, there is often an interplay between these various drivers As Altieri (Chapter 5.03) explains, the story of bioethanol development in Brazil grew out of necessity at the time of the 1970s’ oil price shock when crude oil imports became unaffordable; then it became a huge engine for development of the agricultural economy; and now it is being taken forward in a way that enables all products and by-products of the sugarcane crop to be used productively without impinging on the rain forest areas that are so critical to maintaining the world’s CO2 balance Before going any further, it is appropriate to say something about terminology In a field that is as wide as the one outlined above, it is inevitable that people around the world will use terminology in slightly different ways Insofar as it has been possible in a volume that draws upon expertise from all over the world, an attempt has been made to standardize terminology such that the term ‘biomass’ refers to solid material while the term ‘biofuel’ refers to liquid fuels (refined or unrefined) used primarily for transport The biomass/biofuels opportunity impinges on the activities of a great many existing interests People often speculate as to whether those parties are supportive or unsupportive Take farming for example In some countries, the clear priority of small farmers is first to grow subsistence crops to meet their food needs, and then to grow a crop that they can sell – ideally for a reliable price For them, the opportunity to supply into growing biofuels markets is potentially attractive provided they can afford to reinvest in improved agricultural techniques which will secure their food production capability That is one of several different perspectives on the so-called ‘food versus fuel’ debate Other aspects are explored by Waller (Chapter 5.08) Larger farmers in the developed world see an opportunity to sell some of their arable crops under long-term contracts while continuing to sell the remainder on the spot market Preferences vary However, there is a noticeable reluctance among landowners to commit to short rotation willow coppicing (for example) where in order to maximize profit (in theory) you need to commit your land to one end use for (say) 30 years The general farmer reaction to biomass and biofuels as a whole is therefore guardedly supportive rather than enthusiastic The oil industry’s reaction to biofuels has been the subject of speculation for a long time In some ways, the early biofuels industry was too small to fit comfortably with oil industry’s aspirations and practices However, in countries like Brazil, the scale of the biofuels industry has reached a point where the oil industry embraces it In other countries, it is interesting to note that when exploring questions about whether there is an impending ‘peak oil’ issue [4] or whether the future will look more like a plateau, future supply-side forecasts are now tending to factor in liquid biofuels and synthetic fuels derived from biomass as part of the industry’s ability to meet forecast demand More controversial for oil companies is any scheme whereby governments incentivize biofuel production over fossil fuels UKPIA (United Kingdom Petroleum Industry Association) offers an interesting petroleum industry perspective on the future of the sector [5] This volume sets out to provide an up-to-date assessment of the current state of development of an energy technology whose complexities are many and diverse, as the broad outline above has begun to suggest In order to provide a structure for those thinking of delving into the detail, the remainder of this chapter provides a general road map of the main topics covered 5.01.2 Basic Technology Fermentation is the basic technology behind bioethanol production It could be argued that even primitive tribes mastered that technology a long time ago, brewing up whatever sugar-rich crops were available locally, adding yeast, and allowing the sugar to then turn to alcohol The basic reaction for converting the simple sugar glucose into alcohol is C6 H12 O6 2C2 H5 OH ỵ 2CO2 To make a strong alcohol, it is then necessary to distill the mixture to separate alcohol from water Whether this is done in a small, rural (often illegal) still or in a large-scale whiskey/gin/vodka distillery, distillation reaches an azeotropic limit of 96% (by mass) – which is not pure enough for a transport fuel (where the water content must be less than 1%) A different process is therefore needed for removing the residual water (Harvey, Chapter 5.12) With more ‘difficult’ feedstocks it may be necessary first to separate the biomass into different fractions – lignin, cellulose, and hemicelluloses – and then process some of those fractions (sometimes via acid hydrolysis) into fermentable sugars before the simple process described above can work Refaat (Chapter 5.13) provides detail on how this can be done for a range of feedstocks including various waste streams There is also a question as to whether everything should be converted into alcohol or whether some streams are better used for some other energy-related purpose Altieri (Chapter 5.03) provides a very practical exposition of this subject based on experience on a large scale in Brazil For biodiesel production, the basic starting technology is transesterification, which involves reaction with an alcohol and an alkaline catalyst A typical vegetable oil differs from conventional petroleum-based diesel by being more viscous, less flammable, Biomass and Biofuels – Introduction and more difficult to atomize reliably [6] At a molecular level, a vegetable oil contains three so-called ‘fatty acids’ linked together on a glycerol ‘backbone’ In transesterification, the three fatty acid chains are stripped off and converted into a fatty acid methyl ester – which is the generic biodiesel The reaction is triglyceride ỵ methanolmethyl ester þ glycerol Harvey (Chapter 5.12) explains the process in more detail before going on to highlight the shortcomings of the process and then develop ideas for addressing them Meanwhile, the basic process has been used around the world to manufacture biodiesel successfully as described in the next section The choice of feedstock varies from country to country In Europe, for example, the principal feedstock is oilseed rape This has moved oilseed rape from being a largely neglected break crop within a crop rotation cycle to a new status as a significant crop in its own right Much work has therefore been done to find ways of improving plant yields from to te yr−1 ha−1 and possibly more – notably in Austria and Germany In other climates, different feedstocks predominate, for example, palm oil and sunflower oil There is increasing interest in Jatropha – an oil-bearing bush that grows in semiarid conditions 5.01.3 Widespread Deployment of Biomass and Biofuels In broad terms, Europe leads the world in deployment of biodiesel technology; the deployment of bioethanol technology is dominated by Brazil and the United States; and a number of countries (particularly those with a large tree cover) are achieving significant levels of biomass use for other purposes such as heating, power generation, and combined heat and power (CHP) Table shows steady growth in liquid biofuels year-on-year, with bioethanol dominating World biofuel production increased by 7.4% in 2009 and by 12.9% in 2010 In 2010, it reached around 114 billion liters, representing about 2% of all road transport fuels consumed Europe’s share of biodiesel production was 49.8% in 2009, followed by the Americas with 32.8% The top five biodiesel producing countries in the world are Germany, the United States, France, Argentina, and Brazil, producing 68.4% of the world's biodiesel Australia is the largest producer of biodiesel in Asia Pacific, followed by China and India [7] On the bioethanol side, the United States and Brazil accounted for 86% of world production in 2009 5.01.3.1 Biodiesel Biodiesel has been produced on an industrial scale in the European Union since 1992, largely in response to positive signals from the EU institutions Today, there are more than 120 plants in the European Union Whereas plant capacities of around 100 000 te yr−1 were once considered to be the state of the art, there are now some plants with capacities of 250 000 te yr−1 (e.g., in Sluiskil in the Netherlands and in North East England) Germany (where for many years the government provided a very generous incentive for biodiesel both as a straight fuel and as a blend) has dominated the European biodiesel picture for many years, but Spain, France, Italy, and the Netherlands are now catching up Of the million tonnes of biodiesel produced in the European Union in 2009, 28% came from Germany and 22% from France (source: European Biodiesel Board, http://www.ebb-eu.org) In terms of installed biodiesel production capacity, the 2010 figures are summarized in Table Table World biofuel production (in billion liters) Biofuel 2005 2006 2007 2008 2009 2010 Ethanol Biodiesel Total biofuels 40 45 49 57 64 12 75 77 16 94 82 18 101 93 21 114 Source: Database – OECD/FAO Agricultural Outlook 2011–2020 Table EU biodiesel production capacity broken down by country Country Capacity (kte yr−1) Capacity (%) Germany Spain France Italy Netherlands Other EU countries Total 933 100 505 375 328 663 21 904 22.5 18.7 11.4 10.9 6.1 30.4 100 Source: UFOP (2010) Biodiesel 2009/1010 – Report on the current situation and prospects http://www.ufop.de (accessed March 2011) [8] 4 Biomass and Biofuels In recent years, the European Union has moved away from incentives for biodiesel production toward targets and mandates for biodiesel inclusion in blended fuels As a result, the European Union has now got an excess of production capacity From the 22 million tonnes of annual production capacity given in Table 2, only about 10 million tonnes of biodiesel was actually produced in 2010 [8] The EU target for biofuels inclusion was raised from 5% to 7% (by volume) in February 2009 Seven percent of EU diesel consumption equates to around 14 million tonnes per year of biodiesel The adoption of the new target across the European Union is proceeding slowly Prospects for raising the target beyond 7% are impacted by societal reactions to debates about biofuel sustainability (Waller, Chapter 5.08), although there remains an EU biofuels target for 2020 of 10% (by energy, which is significantly higher than 10% by volume) There is also an issue with subsidized biodiesel from overseas countries being imported into the European Union, depressing demand for EU-produced biodiesel 5.01.3.2 Other Biofuels Turning to bioethanol, the Brazilian success story is well known Given the country’s capacity for growing sugarcane, the response to the oil price shocks of the 1970s was to promote indigenous production of bioethanol from sugarcane A mandate for blending bioethanol into gasoline was enacted in 1976, with the current target now standing at 25% The ability of the Brazilians to find profitable uses for the various by-product streams led to a very attractive production cost for bioethanol The combination of government policy and targets alongside low production costs has encouraged the manufacturers of so-called ‘flex fuel vehicles’ to focus on the Brazilian market, with more than 12 million such vehicles now on Brazilian roads A flex fuel vehicle can run on bioethanol or conventional gasoline or any blend of the two The Brazilian success story in the area of bioethanol is told in more detail by Altieri (Chapter 5.03) The United States has also seen significant levels of bioethanol promotion and bioethanol investment There the drivers appear to be a combination of reducing dependence on imported oil for gasoline and support for the corn production agricultural sector There is a long-term desire to extend the deployment of so-called ‘first-generation’ biofuel technologies by developing processes that can use more difficult feedstocks such as agricultural straws, fast-growing woody biomass, waste wood, and various refuse-derived fuels Some of these materials are already used for producing heating fuels on a small scale Larger plants have been developed in recent years for the purposes of power generation and also for CHP Initially, the biomass power plants tended to be on a fairly modest scale, for example, 150 000 dry tonnes per year to generate 30 MW Projects are now being developed that are 20 times bigger than that as described by Malmgren (Chapter 5.04) The other route to large-scale use of biomass for power generation is by using it to displace a proportion (say 10%) of the feedstock supplying a large coal-fired power station (known as ‘biomass cofiring’) The development of cofiring technology is covered by Lester (Chapter 5.05) It is presently unclear whether such demands for millions of tonnes per year of biomass will encourage developments in biomass supply to the advantage of ‘next-generation’ transport biofuels, or whether they will compete directly for limited supplies 5.01.4 Issues, Constraints, and Limitations Up until 2006, there was a widespread view that biofuels could provide solutions to many issues associated with climate change Levels of investment activity were high, and many countries offered support mechanisms to encourage further investment and uptake of the products The constraints and limitations at that time tended to be of a technical nature: how to scale up the technology; how to widen the feedstock slate; how to develop engines that could handle larger proportions of biofuel in the fuel blend; how to improve agricultural feedstock yields, and so on Then serious questions were asked about the sustainability of biofuels, with some authors reaching broadly negative conclusions and others broadly positive conclusions [9, 10] The debate has unfortunately tended to continue more in the popular press than in the scientific literature, and has had the effect of causing governments to review their levels of support This, in turn, has had an adverse impact on investor confidence levels Given that a typical biofuels project can take up to 10 years to design, build, start up, and then run for long enough to deliver a return on investment, and given that incentive and regulatory regimes can change very markedly over such a time period, this latter point about investor confidence becomes very important Consequently, any list of biofuels issues and constraints today looks quite different from those of 2006 One of the most serious challenges is to the carbon-saving claims of biofuels Governments that are promoting biofuels as a counter to climate change react strongly to such challenges There is a lot of interest now in calculating the CO2 impact of biofuels, looking at CO2 absorption during crop growth, the CO2 impact of harvesting, transporting, and processing a crop, and the CO2 footprint associated with fertilizer use and with supplying heat and electricity into the fuel production process Processes for calculating the full life-cycle impact of biofuels from a greenhouse gas perspective are described in detail by Mortimer (Chapter 5.09), drawing a distinction between the type of approach that is appropriate in exploring possible new policies and the type of approach that is appropriate for regulation once policy has been decided Beyond greenhouse gas savings there are additional dimensions to the sustainability claim of biofuels People now ask about alternative land uses, water usage rates, impact on biodiversity, and so on There are also ethical questions relating to land rights, workers’ rights, and so on When public money is used to incentivize adoption of a new technology, it is not surprising to find Biomass and Biofuels – Introduction people testing the ethics of that technology The general approach being taken in Europe is to say that only those biofuels that can provide verifiable evidence of their provenance with respect to carbon and sustainability criteria in a very broad sense will be allowed to count toward a county’s (or a company’s) mandated quota The development of practicable processes for enacting such requirements is a complex task, which is explored in detail by Waller (Chapter 5.08) Broad principles concerning carbon and sustainability ultimately translate into hard, physical constraints in a particular country where land availability is finite, water availability is finite, and so on To some extent, limitations in one country can be addressed by importing additional bioresources from countries that have an abundance Hillring (Chapter 5.06) makes the point that while traditionally bioenergy markets have been local or regional, in recent years international as well as intercontinental trade in solid and liquid biofuels has developed At present, the markets for both liquid and solid biofuels are still a long way from being globalized to the same extent as the markets for crude oil, but the implications are potentially far-reaching since they extend into forestry, agriculture, waste management, food, and animal feed markets Hillring (Chapter 5.06) also examines the current status in respect of formal and informal barriers to trade Meanwhile, the more technical constraints that were being addressed before the upsurge in interest in sustainability issues continue to receive attention: improving the efficiency and cost effectiveness of the production processes, and broadening the prospective feedstock slate to facilitate market expansion 5.01.5 Technology Solutions – New Processes 5.01.5.1 Anaerobic Digestion Anaerobic digestion (AD) is arguably not a new process: it has been used for many years for animal manure management Increasingly, however, it is now being used as a means of converting waste materials – usually wet materials with a high organic content – into a biogas that can be used directly as a heating fuel or upgraded to serve as a replacement for natural gas At one end of the technology spectrum, it can be found in the form of a small on-farm unit in (say) China where it is used to convert animal wastes and vegetable wastes into a cooking fuel At the other end of the spectrum, there are people in Germany (where there are more than 6000 sizable plants in operation) working on technology for upgrading the gas to be compatible with the standard of their national gas grids [11], and others working on the efficiency of the AD process itself AD is a microbial process in which complex organic materials are broken down into their simpler chemical components by various enzymes [12] This occurs in the absence of oxygen and results in the production of biogas and a digestate Biogas composition is approximately 60% methane and 40% carbon dioxide Typical feedstocks for AD reactors often consist of animal slurries, energy crops, and other agricultural, retail, and industrial wastes The process can be summarized in four main stages: Hydrolysis The complex organic materials (e.g., proteins, lipids, and carbohydrates) are broken down into low-molecular-weight compounds such as amino acids, fatty acids, and simple sugars Acidogenesis Acid bacteria promote a process of fermentation, producing volatile fatty acids (VFAs), alcohols, hydrogen, and carbon dioxide Acetogenesis Acetic acid, carbon dioxide, and hydrogen are formed from the VFAs by acid-forming bacteria or acetogens Methanogenesis Methanogenic bacteria continue the consumption of the VFAs and produce methane gas [13] The biogas produced can be used as a renewable fuel for various purposes, for instance in the production of heat and/or power by direct combustion The digestate produced can be used as a fertilizer, subject to appropriate storage and application methods to prevent nitrate leaching [14] Feedstocks with a high lipid content tend to produce higher methane yields, while feedstocks with a high carbohydrate content tend to produce more CO2 Three different forms of bacteria are active during the AD process: fermentative bacteria, acetogens, and methanogens The efficiency of these different bacteria, and ultimately therefore the gas yield of the digester, is directly affected by temperature and pH It is therefore important to find the right balance to provide a dynamic equilibrium among the three bacterial groups AD systems usually operate in one of two main temperature ranges: mesophilic (20–40 °C) and thermophilic (>40 °C) Thermophilic temperatures have the benefit of providing sanitation by killing more pathogens The optimum temperature for thermophilic digestion is around 60 °C, although a temperature between 52 and 56 °C may be used in practice to allow for variations in temperature without threatening some of the active microbes [15] Because the microorganisms active during the different phases of AD have different requirements, the process is often carried out in two stages, with thermophilic conditions in the first stage and mesophilic conditions in the second stage [16] Thermophilic processes require a shorter retention time of up to 20 days compared to mesophilic digestion, which may take over a month An increase in process temperature generally increases the metabolic rate of the bacteria However, this also results in a higher concentration of free ammonia, which itself inhibits the AD process Some studies have found that wastes with high ammonia content (e.g., cow manure) were inhibited at higher temperatures [17] Fluctuations in temperature can cause instability in the digestion process, affecting the gas yield This can result from large variations in outdoor temperature, especially in highland and northern climates [15, 18] The United Kingdom is an example of a country where AD technology is currently underexploited but may be about to attract significant interest under new incentive regimes The United Kingdom has substantial biomass resources, which could be processed Biomass and Biofuels via AD: about 150 million wet tonnes of livestock slurry (pig and cattle), 3.4 million wet tonnes of used poultry litter and excreta, together with million tonnes of food production residues (vegetable and dairy processing residues) In addition to this, there is about 90 million tonnes of waste produced in the United Kingdom each year with a high biodegradable fraction of 62% This biodegradable waste will produce about 150 m3 tonne−1 of biogas at 60% methane concentration Using a process efficiency of 70%, a 70% load factor, and the known 37 GJ tonne−1 energy content for methane, after accounting for the 20–40% of energy needed to maintain the temperature of the processor, AD could provide the United Kingdom with about 1.4 GW of electricity, representing about 2% of the UK’s installed capacity UK agriculture contributes 7% of all UK greenhouse gas emissions, including 67% of nitrous oxide and 37% of methane Main sources of greenhouse gas emissions are from animals (32%), manure management (20%), and soil breakdown (48%) During storage of animal manure, significant greenhouse gas emissions occur, particularly of N2O and CH4, as a result of uncontrolled AD processes AD exploits this process so that methane can be used as a fuel resulting in reduced emissions of approximately 90% A well-managed AD scheme aims to maximize methane generation, but not to release any gas to the atmosphere, thereby reducing overall emissions In addition, it provides an energy source with no net release of carbon AD has considerable potential to contribute to the production of renewable energy on farms in addition to reducing the overall contribution of agriculture to global warming In order to upgrade biogas to make it compatible with natural gas (which is mainly methane with small amounts of higher hydrocarbons), there is a requirement to remove CO2, hydrogen sulfide, and siloxanes Hydrogen sulfide levels can be reduced using biological scrubbing (with alkaline water) or chemical desulfurization (using iron oxides and other iron salts) This would usually be followed by fine desulfurization in an adsorptive process using activated carbon or possibly zinc oxide [11] Siloxanes are usually removed using activated carbon [19] There are a number of options for CO2 removal, ranging from mature technologies using chemical solvents (e.g., amine solutions) or physical solvents (e.g., Selexol) to the latest developments in membrane separation technology [20] For further information on the upgrading of biogas to make it compatible with natural gas, the reader is referred to Reference 11 5.01.5.2 Advanced Biofuel Processes Much of the interest in advanced bioethanol production processes centers on ways of enabling a wider range of feedstocks to be used, particularly nonfood feedstocks A biomass feedstock will consist mainly of cellulose, hemicellulose, and lignin Of the three, cellulose is the easiest to convert via fermentation into alcohol The first step in a biochemical route to ethanol production is to separate the cellulose, hemicellulose, and lignin [21] Once these constituents are separated, the cellulose and hemicellulose can be hydrolyzed to sugars, which are subsequently fermented into alcohols and distilled Biochemical processes typically employ a pretreatment process to accelerate the hydrolysis process Common pretreatment processes include dilute acid treatment, steam explosion, and ammonia fiber explosion Following pretreatment, the cellulose and hemicellulose are hydrolyzed into fermentable sugars using acid hydrolysis or enzyme hydrolysis The fermentation and purification processes then follow as in a conventional bioethanol plant There are several companies working on versions of this technology, including Abengoa, BlueFire Ethanol, Iogen, Mascoma, and POET This topic is explored in detail by Refaat (Chapter 5.13), looking in detail at a range of pretreatment options and at the overall energy balance An alternative to the biochemical treatment routes described above is a set of thermochemical routes Here the first step is to gasify the biomass to produce synthesis gas: a mixture of hydrogen and carbon monoxide A range of technologies for achieving the gasification step and the sometimes associated pyrolysis step are presented by Roddy (Chapter 5.10) Starting with synthesis gas (or syngas), there are several different routes to synthesizing fuels One option is the catalytic conversion of syngas into alcohols This represents a major alternative route to the biochemical production of bioethanol as described above Alternatively, it can be used to produce a simpler alcohol, methanol, which is favored by some automotive companies (Pearson, Chapter 5.16) Another option is to use a methanation process to convert the syngas into methane Such a process can be seen as an alternative to the AD route described in the previous section However, perhaps the best known option for converting syngas into fuels is the Fischer–Tropsch process for synthesizing long-chain alkanes, typically used to produce an equivalent fuel to diesel The term ‘advanced biodiesel processes’ usually refers to this route – also often labeled as BtL or biomass-to-liquids Evans (Chapter 5.11) provides a detailed treatment of this subject It is difficult to predict at this stage which advanced biofuels routes will be commercially successful long-term in converting particular types of biomass into particular biofuels Much will depend on how the pilot-scale projects and demonstration projects described in this volume perform in practice However, a design approach that cuts across all of these processes is process intensification This approach can be applied to individual unit operations in a process or it can be applied to the whole process Harvey (Chapter 5.12) explores the process intensification approach for some bioethanol and biodiesel processes 5.01.6 Technology Solutions – New Feedstocks 5.01.6.1 Algae The quest for alternative feedstocks has led many people to algae For those who consider that land availability may at some point in the future become the limiting factor, looking at feedstocks that grow in water holds some attractions – especially since the Earth’s water surface is significantly greater than its land surface There are two broad areas of interest: macroalgae (usually known as seaweed) and microalgae (often found in the form of pond scum) Biomass and Biofuels – Introduction Since they are autotrophs, algae not generally need complex nutritional elements such as proteins, lipids, or carbohydrates They feed on inorganic salts, water, and carbon dioxide, using the sun’s energy to synthesize biomolecules from these simple substrates In fact, their rapid growth rate can sometimes be a problem as has been found on occasions when water has become contaminated with excess phosphorus and nitrogen input from sewerage or farmland runoff Algae synthesize a variety of complex carbon compounds, which are used as food storage materials These compounds include fatty acid esters of glycerol and other lipids and a number of glucose oligomers Many algal strains have more than 50% lipid in their body mass Where this is predominantly triacylglycerides, they provide a good feedstock for transesterification into biodiesel (e.g., Chlorella, Dunaliella salina, and Spirulina) One form of algae (Botryococcus braunii) produces a hydrocarbon oil that is similar to crude oil, so in principle it could serve as a replacement feedstock for the whole petrochemicals chain except that it grows very, very slowly With microalgae there are two broad strands of activity The first is based on open-pond technology, where water is circulated in pond races and the algae skimmed off the surface For rapid algal growth, the water needs to be reasonably warm – so this version is favored in tropical climates and also in locations where there is waste industrial heat available The other is based on photobio­ reactor technology, with the algae growing in glass tubes which trap the sun’s heat Some have likened these two strands of activity to growing crops outdoors in a large field compared with growing crops indoors in a small greenhouse, with both approaches having their place Another possibility is to grow algae as a source of carbohydrate, harvest their carbohydrate reserves, and hydrolyze them to glucose, which when fermented would produce ethanol for use as fuel Algal biomass waste from fermentation could then be processed thermochemically as outlined above Yet another line of research involves those who cultivate whatever algae that grow naturally in a location, and concentrate on finding uses for those algae This contrasts with an alternative line of research that is based on identifying the specific algae that will exhibit the desired properties for a particular application, and then concentrating on finding ways of making such algae grow One of the attractions of algae is that it can grow very fast It is not unusual for a whole crop to grow in a matter of weeks (compared with a summer for land-based materials) Some extrapolations from experimental work suggest that production rates of 60 000 l ha−1 yr−1 should be possible – significantly higher than that from land-based oil-bearing crops One of the drawbacks is that algal research is at a relatively early stage of development, and total annual production of algal biomass stands at only 9000 tonnes While today’s agricultural crops and practices have developed over a period of 3000 years, algal development originated about 50 years ago Much remains to be done in areas such as microalgal chemical ecology, culture, and growth physiology; finding or developing improved strains of algae; maintaining culture stability; effective harvesting of algae; acceptable provision of nutrients for macroalgae in the open sea; developing systems that combine water purification with algal production; developing ways of enabling light to penetrate beyond the surface layer where algae grow; supplying CO2 from industrial processes including bioethanol production; establishing high levels of thermodynamic efficiency; examining the overall water usage from a life-cycle perspective; regulating algal biochemical pathways; and aiming for practical productivity rates of more than 100 tonnes ha−1 yr−1 For further information on the subject of algal biofuels, the reader is referred to a seminal report on the subject by Benemann et al [22] and a more recent report by Darzins et al [23] 5.01.6.2 Other Options for Increasing Feedstock Availability A more conventional place to look for additional feedstocks is on land that can support the growth of woody biomass, especially land that is too uneven to support modern arable crop farming with its combine harvester technology Quite often the upland areas that are otherwise used for sheep farming could be suitable for growing woody biomass One approach is to plant woody crops that can be coppiced – effectively providing a harvest every few years Another approach is to let the trees grow to an optimum age as single-stem trees, and then harvest them sustainably Perlack (Chapter 5.14) provides an in-depth treatment of this subject, providing a rich source of data on achievable yields under various planting strategies and looking in particular at willow, poplar, eucalyptus, and pine He also comments on the extent of feasible planting in the United States, and calculates the contribution that woody biomass could make to reaching renewable fuel targets under various incentive regimes Another obvious option to consider is the use of various types of waste stream as feedstock While there are many possible feedstocks, this volume pays particular attention to bioethanol production from lignocellulosic waste and biodiesel production from waste vegetable oil, looking at the level of pretreatment required in each case (Refaat, Chapter 5.13) The topic of biogas production from agricultural waste streams has been addressed above The other obvious approach is to improve crop yields Spink (Chapter 5.15) provides data to show how the annual yields of oilseed rape across the United Kingdom can be increased from to 6.5 tonnes ha−1, with the potential possibly to reach 9.2 tonnes ha−1 Generalizing his approach, he draws some interesting conclusions about the potential for improving other crop yields in a similar manner via changes to agronomy and husbandry and improving genetics via plant breeding The prospects look particularly promising where the limiting factor is light availability as opposed to water availability 5.01.7 Expanding the Envelope In order to improve the overall commercial viability of biomass and biofuel developments, it is informative to examine them in their broader context, see whether they are overspecified for their intended purpose, whether they can be used for additional Biomass and Biofuels purposes in such a way as to accrue benefits of scale during production, and whether the production processes involved can yield additional high-value products in a way that benefits the overall economics It is interesting to see what players from the auto industry ask for in a fuel, and to consider how planned long-term developments in transport fuels align with planned long-term developments in vehicle technology Pearson (Chapter 5.16) provides an interesting perspective in suggesting that targets for vehicle manufacturers should be specified in terms of fuel energy requirements per kilometer traveled, while targets for fuel suppliers should be specified in terms of grams of fossil-derived CO2 per unit of fuel energy delivered This is quite different from the current practice of setting CO2 emission targets for vehicle manufacturers irrespective of the source of the CO2 His analysis points to methanol as a particularly attractive fuel, especially if used within a multi-flex-fuel vehicle Conventional thinking tends to assign liquid biofuels to transport applications, solid biomass to power generation, and biogas to heating applications It is therefore interesting to note how liquid biofuels (in pure form, in blends, and in emulsions) and even some of their unprocessed feedstocks can be used effectively for CHP applications and for transport (Roskilly, Chapter 5.17) Taken together with options for dual-fueling bioliquids and biogases, this opens up some new avenues for optimizing the process of matching feedstocks to end uses It is sometimes said that biomass is too good to burn The same may soon be said of natural gas (which is an important petrochemicals feedstock) if the world’s population wants a steady supply of fossil fuel-derived plastics and polymers Considering the range of very high-value components that are present in various types of biomass, there is a case to be made for extracting some of them before going through a thermochemical or biochemical biofuels production process that would destroy them Moreover, just as a crude oil refining process linked to a downstream petrochemicals industry leads to a wide variety of carbon-containing products and materials, so too can a biorefining process lead to a wide range of carbon-containing products The difference is that in the latter case the carbon is not of fossil origin (derived as it is from a short carbon cycle) and so the fossil carbon content of the final products is very low Given that the main drivers behind biomass and biofuel developments are usually linked to climate change and dwindling oil and gas supplies, the broader biorefining agenda is highly pertinent This thinking is developed further in a chapter by Askew which looks at small-volume, high-added-value products and in a chapter by Clark (Chapter 5.20) which looks at high-volume opportunities As a specific example of extracting maximum value from biomass and locking in every benefit, a chapter on biochar has been included (Chapter 5.20) Biochar is formed in pyrolysis processes and gasification processes Whether it is labeled as a product, a coproduct, or a by-product, it has some fascinating properties Initial interest stemmed from its benefits as a soil improver, leading to higher yields, displacing fertilizer use, and improving moisture retention in arid areas More recently, it has been found to trap or sequester carbon in soils over a timescale of centuries to millennia If biochar produced in a thermochemical process is used in this way, it opens up the prospect of a carbon-negative energy supply chain Brown (Chapter 5.18) provides a review of the current state of the art in biochar research The volume would not be complete without a chapter that explores the societal impact of biomass and biofuels and the challenge of developing policies to incentivize the intended responses and behaviors The fact that the point of carbon absorption and the point of carbon release lie in different locations – sometimes different countries and even different continents – introduces a level of complication This is compounded by the manner in which biomass pervades so many aspects of life Thornley (Chapter 5.21) reviews the issues involved and suggests some new frameworks that may work better 5.01.8 Recent Developments In the time since work began on this volume, one of the biggest changes in the bioenergy environment is that interest in the alternative of electric vehicles (EVs) has accelerated rapidly The EU target of 10% biofuels (on an energy basis) by 2020 has been translated into a requirement for 10% renewable energy content in transport fuels – specifically to include EVs powered by renewable electricity A number of vehicle manufacturers are bringing EVs to market Unlike the ‘kit cars’ of old, these are designed as production cars for the mass market In order to address the phenomenon of so-called ‘range anxiety’, the vehicles are fitted with sophisticated communication equipment for locating the nearest charging point, and those same technology platforms are offering attractive new features such as remote communication facilities and sophisticated navigation systems Priced at the luxury car end of the spectrum, they will not displace sales of internal combustion engine vehicles overnight, but they have to be seen as serious competition by proponents of biofueled vehicles As for how long it will be until sales of EVs outstrip sales of internal combustion engine vehicles, the year 2050 is often cited – with some saying earlier and others later The prevalent view is that EVs will penetrate the market for city center ‘runabout’ vehicles quite early, with slower progress in the long-distance driving market, and there are serious doubts about whether road freight or air transport will ever switch to electric propulsion There is a related strand of emerging thought which is perhaps best summed up as a move to an all-electric society With an expanding array of low-carbon electricity solutions under active development (including nuclear power and coal-fired generation with carbon capture and storage alongside a maturing set of renewable electricity technologies), and seemingly fewer options for low-carbon heating and low-carbon transport, governments are starting to speculate about the desired future balance between electricity, heat, and transport fuels in the overall energy mix Biomass and Biofuels – Introduction Interestingly, biomass can supply all three However, the technologies required to this cost-effectively are still under development There is a short-term challenge for those working in the biomass sector to influence the funders of research and development activity to continue funding broad-based biomass R&D 5.01.9 The Way Forward for Biomass and Biofuels Specific plans for the various biomass technologies are mapped out in the relevant chapters of this volume Different countries are progressing at different rates This is due in part to different starting points in respect of natural resource availability, with countries tending to play to their strengths However, it is also due in part to some countries waiting for others to go first in the hope of benefiting from their experience As in other parts of the energy sector, there is an increasing reliance on the development of road maps as a process for building consensus, differentiating between short-term, medium-term, and long-term requirements The field of biomass and biofuels has moved in recent years from one of almost unstinting praise through a period of intense (often ill-informed) criticism, emerging now into an environment where developments are viewed with healthy skepticism The chapters of this volume provide some of the science behind the increasingly important sustainability challenge alongside the signposts for future technology development References [1] Knoef HAM (2005) Handbook of Biomass Gasification Enschede, The Netherlands: BTG [2] International Energy Agency (IEA), Paris (2008) World energy outlook, 2008 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World biofuel production (in billion liters) Biofuel 20 05 2006 2007 2008 2009 2010 Ethanol Biodiesel Total biofuels 40 45 49 57 64 12 75 77 16 94 82 18 101 93 21 114 Source: Database – OECD/FAO... agro-wastes and energy crops: Comparison of pilot and full scale experiences Bioresource Technology 101: 54 5 55 0 [16] Deublein D and Steinhauser A (2008) Biogas from Waste and Renewable Resources: An Introduction. .. efficiency and cost effectiveness of the production processes, and broadening the prospective feedstock slate to facilitate market expansion 5. 01 .5 Technology Solutions – New Processes 5. 01 .5. 1 Anaerobic