With ever-increasing indications that resource use is exceeding the planet’s biocapacity [33] — largely driven by non-renewable fossil fuel consumption — it is clear that humankind must shift to sustainable practices in order for a peaceful, equitable, and thriving future to be possible. Furthermore, given mounting evidence of climate change — to the point that some say we are now living in a new geologic epoch, the Anthropocene [34] — this transformation must begin now and be completed within decades, not centuries. Indeed, it is fair to characterize this transition, moving from finite resource capital to renewable resource income, as the defining challenge of our time.

Most sustainable paths from primary resources to human needs pass through either plant biomass or renewable electricity, with biomass being the only foreseeable source of organic fuels, chemicals, and materials, as well as food. In comparison, other large-scale sustainable energy sources are most readily converted to electricity and heat. Because liquid organic fuels have a greater energy density than batteries, both today and with anticipated improvements in battery technology, it is reasonable to expect that organic fuels will meet a significant fraction of transportation energy demand for the indefinite future. This is particularly true for long-distance travel via personal vehicles and for heavy-duty applications, such as aviation and long-haul trucking, which account for more than half of global transportation energy [35]. Biofuels would, therefore, appear to be an essential component of tomorrow’s sustainable world rather than a discretionary option.

Cellulosic biomass energy potentially offers many environmental benefits that contribute to its sustainability, some of which are:

• Fossil fuel displacement.

• Lower emissions of greenhouse gases and other air pollutants.

• Enhanced soil quality.

• Reduced soil erosion.

• Reduced nutrient run-off.

• Enhanced biodiversity.

Demirbas [36], Rowe et al. [37], Arjum [38], and Skinner et al. [39] provide more detailed reviews and discussion of these and other potential benefits.

In addition to the environment, cellulosic biomass energy also has the potential to enhance energy security and rural economic development. Nations dependent upon petroleum face increasing security costs to ensure the steady supply of oil. The United States, for example, according to the RAND Corporation [40], spends about $75.5-93 billion per year — repre­senting between 12 and 15% of its current defense budget — to secure the supply and transit of oil. Furthermore, major oil supplying countries hold leverage over nations relying upon imports, as the oil producers control price stability. This directly affects foreign policy, forcing import nations to prioritize stability over values such as democracy, transparency, and human rights. Even if a country could produce 100% of the oil it uses, its consumers would still be vulnerable to global price fluctuations based on supply disruptions in unstable regions. Beyond consumerism, modern militaries invest for the long term — new airplanes, ships, and vehicles are expected to last decades. This requires alternative energy sources to be able to accommodate infrastructure that is likely to be in place for years.

In recognition of this, the United States Department of Defense has developed an alter­native fuels policy to “ensure operational military readiness, improve battle space effec­tiveness,” and increase “the ability to use multiple, reliable fuel sources [41].” Consistent with this, the US Navy has plans to deploy a “Great Green Fleet” strike group of ships and aircraft running entirely on alternative fuel blends — including cellulosic fuels — by 2016 [42]. It also has a goal of meeting 50% of its total energy consumption from alternative sources by 2020. To help enable these goals, the Navy — together with the Departments of Energy and Agriculture — signed a Memorandum of Understanding (MOU) to “assist the development and support of a sustainable commercial biofuels industry [43].” The MOU calls for $510 million in funding over three years to develop advanced biofuels that meet military specifications, are price competitively with petroleum, are at geographically diverse locations with ready market access, and have no significant impact on the food supply.

A cellulosic biofuels industry, by generating demand for agricultural products, has the potential to significantly increase employment in rural areas in sectors ranging from farming to feedstock transportation to plant construction and operation. Workers would be required in a variety of occupations, including: scientists and engineers conducting research and development; construction workers building plants and maintaining infrastructure; agricul­tural workers growing and harvesting energy crops; plant workers processing feedstocks into fuel; and sales workers selling the biofuels. Brazil’s sugar/ethanol industry directly employs about 489 000 workers, with an additional 511 000 workers engaged in supporting agricultural activities [44]; the United States corn ethanol industry directly employs about 400 000 [45]. A study forecasting the impact of advanced biofuels on the US economy estimates that the industry could create over 800 000 jobs by 2022 [46].

Cellulosic biofuels also have the potential to promote rural economic activity within developing nations and improve the lives of the world’s poor. Farmers would have increased demand for their products, including crop residues from existing crops, and employ addi­tional workers to produce the energy feedstocks. They would also be able to make use of degraded or marginal land not suitable for food production. Care must be taken, how­ever, to include small landholders in the sector’s development and to adequately invest in local workforce training for feedstock production, production facilities construction, and process operation. In addition, to the extent possible, the sector should be developed around existing industries, such as sugarcane processing, to lower investment barriers [47]. Also, selection of feedstock supply chains that do not compromise food security is critical. Signif­icant potential exists to actually enhance food security through bioenergy production — by using inedible crops grown on marginal land, for example, or integrating production of food, animal feed, and bioenergy. One can envision many benefits that might be realized: employ­ment and development of marketable skills; introduction of agricultural infrastructure and knowledge; energy democratization, self-sufficiency, and availability for agricultural pro­cessing; and an economically rewarding way to restore degraded land. Bioenergy could potentially improve both food security and economic security for the rural poor [48].

Such benefits, however, are by no means guaranteed. The environmental impact of biomass energy very much depends upon how the given system is designed and imple­mented. Detractors of bioenergy have called into question its sustainability, citing a number of concerns, including:

• Food versus fuel.

• Land use change (direct and indirect).

• Water use.

• Invasive species.

• Biodiversity.

This productive debate has prompted an expanding literature analyzing and discussing the keys to “getting biofuels right,” so that the promise of sustainable bioenergy can be realized [49-51]. To minimize both competition with food production and land use change effects, multiple classes of feedstocks are available, including energy crops grown on abandoned agricultural lands; food crop residues such as corn stover and wheat straw; sustainably harvested forest residues; double crops grown between the summer growing seasons of conventional row crops; mixed cropping systems in which food and energy crops are grown simultaneously; municipal and industrial wastes; and harvesting invasive species for bioenergy [49,50,52-54]. Water use can be minimized by selecting crops having low irrigation requirements, by using non-potable sources such as wastewater or high-saline water for any necessary irrigation [55,56], and using subsurface drip irrigation to minimize evaporative losses [57]. The potential for non-native energy crops becoming invasive can be limited by proper preliminary risk assessment, including test plots [58], regular monitoring and stewardship programs [59], and by using sterile plant varieties [60]. The impact of a given energy crop upon biodiversity depends strongly on specific regional circumstances, the type of land and land use shifts involved, and the associated management practices [61]. Herbaceous perennial crops, in particular, appear to be capable of providing suitable habitats for a variety of species, especially with careful attention to crop placement and when mixed cultures are used [62-65]. By incorporating many of the above strategies, Dale et al. [51] calculated that, using the 114 million hectares of cropland currently allocated in the United States for animal feed, corn ethanol, and exports, 400 billion liters of cellulosic ethanol (80% of current gasoline demand) could be made — all while producing the same amount of food. In summarizing their findings, the authors write:

Our analysis shows that the U. S. can produce very large amounts of biofuels, maintain domestic

food supplies, continue our contribution to international food supplies, increase soil fertility,

and significantly reduce GHGs. If so, then integrating biofuel production with animal feed

production may also be a pathway available to many other countries. Resolving the apparent “food versus fuel” conflict seems to be more a matter of making the right choices rather than hard resource and technical constraints. If we so choose, we can quite readily adapt our agricultural system to produce food, animal feed, and sustainable biofuels.

Any human activity involving new technology can potentially be harmful if not thoughtfully planned and appropriately conducted. The early-generation Altamont Pass wind farm in California, for example, unwittingly located on a major bird migratory route, results in thousands of bird deaths every year [66]. To remedy the problem, the farm’s owners are installing new, less destructive turbines and shutting down a significant fraction of the turbines during the migration season [67]. In the case of cellulosic biomass, if care is taken to address the key concerns noted above, the resource could very likely contribute substantially — indeed, uniquely and essentially, by accommodating energy services not easily met by other means — towards achieving a sustainable global energy future. Kline et al. [50] succinctly capture the promise of this vision:

When biofuel crops are grown in appropriate places and under sustainable conditions, they offer a host of benefits: reduced fossil fuel use; diversified fuel supplies; increased employment; decreased greenhouse gas emissions; enhanced habitat for wildlife; improved soil and water quality; and more stable global land use, thereby reducing pressure to clear new land.

This book — through detailed consideration of cellulosic energy crop production; the logis­tics of feedstock harvest, storage, and transport; and commercial deployment that is mindful of economic, environmental, and social concerns — seeks to disseminate knowledge that can help make large-scale, sustainable bioenergy a reality.