The concept of growing dedicated energy crops is relatively new to India compared to North America, where there is available land suitable for growing crops but not currently being

used for food, feed or fiber production. In India, energy plantations are being promoted in designated non-farmland areas, where poor soils and lack of water are often limiting factors. Crops suitable for biodiesel production have been given a greater priority in India because high gasoline prices are quickly driving the transportation infrastructure to favor diesel [26], with diesel demand now four times that of gasoline. Diesel has been the standard for agriculture but its use is increasing to fuel urban generators that provide backup to unreliable power utilities and irrigation pumps during seasons of drought [26].

Investment in biodiesel development in India has largely focused on the cultivation and processing of Jatropha seeds, which are very rich (50%) in oil [27] and were reported to grow well on marginal lands. Questions regarding performance of Jatropha plantations have prompted the Indian Union Rural Development Ministry to put a hold on the Jat — ropha plantations, pending further development [27], and to explore other energy crops. Estimated current hectares under Jatropha cultivation are just less than 500 000, which, at mature annual yields of at least 5 MT seeds per hectare, would produce 62.5 million liters biodiesel [28].

In terms of cellulosic energy crops, a few India-native species have been identified as promising but these are in early stages of development. Beema bamboo is a newly developed variety that grows quickly, produces high yields, and has high energy value and low ash content. Beema is suitable for high-density planting, is disease resistant, has good water-use efficiency, and responds well to agricultural practices. Under optimum growing conditions, a mature Beema plantation yields over 50 tonnes per acre. Plantation establishment time ranges from 2-4 years before the first harvest but then has a life span of over 50 years [23].

Marjestica (Paulownia) is a species of tree that will grow up to 28 feet in the first year and can be coppiced annually at least eight times. It has a low water requirement and can yield up to 40 tonnes per acre annually over an eight-year period before replanting [23]. Melia dubia also has promising qualities for plantation production. Traditionally grown as a source of firewood and for the plywood industry, melia dubia can be cultivated in all types of soil and requires a low supply of water on a daily basis. It is fast growing, has high energy value, and can reach a height of 40 feet within two years after planting [23]. It can then be pruned and harvested, often yielding more than 40 tonnes of biomass per acre every 18 months for up to 10 years before needing to be replanted.

Water hyacinth, an invasive floating plant that often jams rivers and lakes with uncounted thousands of tonnes of floating plant matter, is also under consideration as a promising biofuel crop [25]. A healthy acre of water hyacinths can weigh up to 200 tonnes. Water hyacinth in most places is under “maintenance control” and field crews are continuously working to keep the plant numbers at their lowest possible levels in order to keep rivers and lakes usable. Research institutes in India are working on identification of microorganisms that will produce enzymes to degrade the plant’s complex sugars or polysaccharides [25].

A forklift (10-ton capacity) will operate continuously at the plant. This machine will unload full racks from trucks and place them onto a conveyor into the plant for direct processing, or stack these racks in at-plant storage. It will then load empty racks onto the truck for return to the field. Empty racks will be removed from the conveyor and stacked in the storage yard until they are loaded onto trucks.

The operational plan calls for two forklifts at the plant, identified as a “work horse” and a “backup”. The workhorse will operate continuously and the backup will operate during the day when trucks are backed up in the queue. Key point — the system must have a backup forklift because, if a forklift is not available to handle racks, all operations cease.

The handling of the racks emulates the handling of bins at a sugar mill in South Florida. (The Rack System Concept is actually an adaptation of the successful commercial technol­ogy used for sugarcane.) In the bin system, a truck has three bins, two on the first trailer and one on a “pup” trailer. The bins are side-dumped if material is needed directly, or they are off-loaded and stacked two-high on the storage yard for nighttime operation. (A bin system is also used for the sugar industry in Texas. Figure 13.13 shows bins being off-loaded at a sugar mill in Texas, and Figure 13.14 shows bins being stacked on the storage yard at this mill.) When the bins are dumped directly, it takes 3 min to unload a truck. For normal operation, one truck hauls 10 loads (30 bins) a day. At 37 tons/load, each truck hauls 370 ton/d. Sugar cane is 80% moisture content, so 370 ton = 74 dry ton/d/truck. The reader is asked to record this figure for later comparison.

The receiving facility operates 6 d/wk, thus, on average, the daily delivery will be:

For this example, plant size (23 dry ton/h) was chosen to optimize the operation of the two forklifts at the plant. One forklift is expected to unload full racks and load empties

at the rate of one truck every 27 minutes averaged over the 24-h day. The design of the storage yard has to facilitate this operation. A larger at-plant storage will lower the forklift productivity (ton/h) because average cycle time to move an individual rack is greater.

After determining harvest and transportation costs across a landscape, the two can be linked to one another through overlay analysis [21]. Specifically, absolute harvesting costs can be combined with absolute transportation costs based on estimates of woody biomass residues for a given harvest unit and the spatial proximity of that harvest unit to the closest loading area. These combined costs are attributed to the harvest unit and compared in relative fashion across the landscape (cost per acre or weight of material). Furthermore, estimates of available woody biomass residues for the harvesting unit are used to represent potential flow of material from that location. Using these costs and potential flows, questions such as how much woody biomass is available across a landscape, where are the least expensive areas to procure woody biomass, from which locations is it profitable to market woody biomass, and are there timing components related to harvest locations that can reduce logistical costs, can be answered in a relatively quick and easy manner.

When utilizing base data and rules to derive cost and potential woody biomass flows from a landscape, it is important to consider the scale and the level of precision needed to answer these types of questions. Base data and rules that are too coarse may not provide an adequate level of detail to properly estimate woody biomass and flows. On the other hand, too fine a scale may present issues related to finding and developing complete data sets, digital storage space requirements, and total processing time and memory it takes to perform spatial analyses for the landscape of interest. Once defined for harvesting units, these costs and potential flows can be used to plan harvesting schedules across both space and time for a given landscape. Multiple simulations depicting various policies, objectives, and conditions can be compared to evaluate the impacts of decisions made based upon the constraints of those criteria. Moreover, if objectives and constraints can be spatially represented in a relative fashion they, can be optimized across the landscape to minimize logistic costs and maximize woody biomass flows. Such analysis can help reduce biomass supply costs, especially in complex procurement environments.

Civil society organizations (CSOs) are questioning the impact of biomass production for energy on land use changes, greenhouse gas emissions, environmental impacts including soil erosion and water quality, and food prices [22]. In addition, with hunger and food insecurity rising, some have questioned the morality of shifting land use, especially in developing countries, from food production to fuel production for consumers in the global North [23].

Biofuel-specific social sustainability standards were able to build on older movements that used the standards to increase market share for sustainably raised products, particularly those that took an ecosystem-based approach. Forest sustainability schemes often include criteria addressing environmental preservation, labor relations, occupational health and safety, resource use rights, fair employment, extent of forest resources, forest health and vitality, productive functions of forests, biological diversity, protective functions of forests, socioeconomic benefits and needs, and legal, policy and institutional frameworks [18]. Of the three general aspects of sustainability (economic, social, and environmental), the social dimension, such as issues of worker welfare and impacts on local communities, receives the least attention [24,25]. However, since biofuels for biomass require considerable invest­ment in the infrastructure for conversion, social sustainability requirements of government lenders, such as the USDA/Rural Development and the International Finance Corpora­tion of the World Bank, provide additional incentive for adherence to social sustainability standards.

USDA/Rural Development has no social sustainability standards for biofuels. The World Bank does. Its eight standards include labor and working conditions, community health, safety and security, land acquisition and involuntary resettlement, indigenous people, and cultural heritage. Furthermore, the first performance standard, assessment and manage­ment of environmental and social risks and impacts, includes social sustainability issues by requiring effective community engagement through disclosure of project-related informa­tion and consultation with local communities on matters that directly affect them. And even Performance Standard 6, biodiversity conservation and sustainable management of living natural resources, states that where residual impacts remain, to compensate/offset for risks and impacts to workers [26].

In most cases, woody biomass derived from the forest for energy applications today comes from either roundwood timber or forest residues recovered in conjunction with conventional harvesting activities. Certain bioenergy applications, including energy pellets, require or prefer clean fiber feedstock with very low bark content and soil contamination, which results in low ash content of the final product. Also, certain biofuel conversion technologies, specifically certain biochemical platforms, are best adapted to narrowly specified clean fiber feedstocks, often of a single species or species group. When clean fiber is required, conventional harvesting and debarking systems for pulpwood and other small diameter timber are commonly employed. These could include conventional longwood systems for delivering tree-length material to the conversion facility or in-woods chipping operations. In the former case, the timber would typically be debarked and chipped at the conversion facility. In the latter case, debarking would occur in the forest, usually by means of a flail debarking system, close-coupled to the chipper. In this case, clean chips are normally blown directly from the chipper outfeed into a chip van for delivery to the plant.

Logistics associated with utilizing woody biomass from slash, tops, and unmerchantable stem portions produced as a by-product of logging operations depend on the type of harvesting method used. The majority of logging in North America uses ground-based harvesting systems, with a variety of skidder or forwarder types. However, on steep slopes (>40%), cable logging is required. Industrial forest ownerships in the western United States and Canada most commonly require a mix of ground-based and cable logging. The difference in systems has important implications for the cost of extracting woody biomass. In general, cable logging operations are both more expensive and less productive than ground-based logging operations. Landing sizes tend to be smaller due to the steep terrain, and logging roads are more difficult to navigate with conventional chip trailers. In particular, curve radii engineered for conventional log trucks in the western United States may not be suitable for possum-belly chip trailers. A variety of emerging options to productively transport biomass on low volume forest road networks designed for roundwood transport are described in Section 14.7. In this environment, it is rarely cost effective to handle logging residues using cable systems.

14.1.1 Whole Tree Versus Cut-to-Length

As mentioned in the previous section, the distinction between cable and ground-based logging affects the production rate and cost of woody biomass utilization from logging residues. Within ground-based systems, feasibility of biomass extraction, production rates, and costs are further affected by the type of harvest and processing system in use. Whole tree harvesting that involves felling of stems with a feller-buncher, followed by grapple skidding or shovel logging to forward whole trees (including branches and tops) to roadside or a centralized landing, is, by design, paired with a processing method that accumulates loose woody biomass at the roadside. Processing with a grinder or chipper step at a landing or a concentration yard is then required, prior to subsequent transport. By contrast, in cut-to-length harvesting systems, stems are bucked into sawlogs in the woods by a feller — processor that delimbs and tops trees immediately after felling, at the location of the stump. Piled sawlogs are loaded by a log forwarder, which advances them to the landing. This process leaves the majority of logging residue in the woods following the initial harvesting and processing step (Figure 14.2), and thus requires an additional, separate slash bundler, slash forwarder, chipper-forwarder, or other equipment option to collect and move slash to the roadside. If slash is forwarded without processing, or is bundled and compressed for forwarding, it must then be ground or chipped at the roadside, a landing, or a concentration yard before transport. Figure 14.3 shows a small number of the many possible systems and equipment configurations available for moving logging slash from the woods to a conversion facility in whole tree and cut-to-length harvesting operations. From the figure, it is evident that there are various points at which comminution may occur, and the number of pieces of equipment that handle materials along the supply chain can range from very few to very many (Figure 14.4).

When in-woods residues are collected by a self-feeding chipper-forwarder, then, depend­ing on the system, they may be off-loaded directly from the chipper-forwarder to a chip van for subsequent transport. Open top ‘roll-off’ and hook lift containers are another useful option for advancing loose logging residues, either as a forwarder to advance residues to the roadside in cut-to-length operations, or to advance residues from the roadside to cen­tralized concentration depots in whole-tree harvesting. Following a grinding or chipping step at the roadside or concentration depot, chips or hog fuel may be conveyed directly onto a chip trailer for transport to a processing facility (as part of the step, e. g., via equipment outfeed), or it may be piled and loaded at a later time. For example, a large chip trucking contractor in Idaho has developed specialized, large capacity wheel loader buckets for load­ing hog fuel onto chip trucks with higher production rates than could be achieved with a conventional loader.

A simple deterministic profit function was presented in Equation 15.2. The introduction of risk creates a more general expression of the farmer’s decision problem. Instead of all profits, prices and quantities being represented by single values, some are represented as probability distributions. In particular, quantity produced and price of product may be expressed as probability distributions with a known or predicted mean value and, at least, a known or predicted variance. In other words, some of the constraints to Equation 15.2 become stochastic, including the production function and some of the price constraints. The presence of stochastic variables on the right-hand side of the equation means that profit (the left-hand side variable in Equation 15.2) is also stochastic. Rather than maximizing profit, the farmer is now said to maximize expected profit. That is, the farmer chooses inputs to maximize the mean or expected value of profit rather than actual profit.

Consideration of risk caused economists to consider even more general representations of the farmer’s decision problem. Rather than maximizing expected profit, the objective function can include terms for variance of profit or the probability of losses or gains relative to expected profit. Decision makers who are risk averse may prefer to forego some expected profit in exchange for reduced probability of losses below the expected value. A simple objective function that incorporates risk has the left hand side of the equation include expected profit minus some coefficient multiplied by variance of profit. A larger coefficient on the variance of profit term indicates greater risk aversion by the decision maker and a greater willingness to exchange lower expected profit for reduced variance of profit. A zero coefficient on the variance term means the decision maker is risk neutral and will maximize expected profit regardless of variance of profit. In general, this farmer objective function in the presence of risk suggests that two farmers faced with the same yield and price distributions may choose different input quantities solely due to their differing preferences for risk. Risk management comes into focus as an important aspect of farm management.

The choice of which energy crop to grow has a significant impact on production economics, especially establishment costs and how they are treated. Many farmers are accustomed to growing annual crops whose production systems require a more basic annual operating capital scenario, under which establishment costs are financed through a credit line or out of cash reserves. The return comes in the same operating year when the annual crop is harvested. Due to weather, market, and other risks, annual crop production is a high but short-term risk scenario.

Managing establishment costs for perennial crops is somewhat different. With a perennial, the producer must pay establishment costs up front, similar to an annual. However, the producer’s return that will repay those establishment costs may come over a long period of time (e. g., ten years or more in some cases). This high up-front cost without quick recovery can be a barrier to many producers.

Programs such as the United States Department of Agriculture’s (USDA) Biomass Crop Assistance Program (BCAP) and other incentives have sought to overcome this hurdle by providing producers cost-sharing assistance during the establishment year. BCAP repays producers for 75% of the establishment cost (www. fsa. usda. gov/bcap). Some states are evaluating methods by which they can create programs to assist with feedstock estab­lishment and production costs. The challenge is that the long-term viability of incentive programs like BCAP and state incentives has yet to be proven. Furthermore, incentives such as these may become rarer in the current governmental fiscal climate and will likely be subject to political discourse. Nonetheless, to ensure development of a viable bioenergy industry, additional methods of overcoming these costs must be found.

One potential model is to have the biomass consumer, the conversion facility, include costs of establishing perennial biomass crops as part of the overall project financing package. As an incentive to recruit landowners and farmers to produce biomass, the production facility could offer establishment assistance by cost sharing or by providing inputs such as seed at no charge. The biomass consumer would like get a lower feedstock price for a defined period of time in return. However, the assistance from the downstream user mitigates risk to the landowner as well as the facility by making it easier to enroll land into energy crop production.

Harvesting systems can be grouped as coupled systems and uncoupled systems. Ideal coupled systems have a continuous flow of material from the field to the plant. An example is the wood harvest in the Southeast United States; wood is harvested year-round and delivered directly to the processing plant. Uncoupled systems have various storage features in the logistics system.

Sugarcane harvesting is an example of a coupled system for an herbaceous crop. (The sugarcane harvest season in South Florida is 140 days, not year-round as with wood throughout the Southeast.) The harvester cuts the cane into billets about 15-in long and conveys this material into a trailer traveling beside the harvester (Figure 13.5). The harvester has no on-board storage — a trailer has to be in place for it to continue to harvest. The trailer, when full, travels to a transfer point where it empties into a truck for highway hauling (Figure 13.6). Each operation is coupled to the operation upstream and downstream. If the truck is not there for the trailers to dump into, they cannot return to the harvester, and the harvester has to stop. It requires four tractors, trailers, and operators to keep one harvester

operating. The trucks have to cycle on a tight schedule to keep the trailers moving. One breakdown delays the whole operation.

A “silage system” can be used to harvest an herbaceous crop for bioenergy. With this system, a forage harvester chops the biomass into pieces about one inch in length and blows it into a wagon beside the harvester. This wagon delivers directly to a silo, if the field is close to the silo, or it dumps into a truck for a longer haul to the silo. All operations are coupled — a wagon must be in place to keep the harvester moving, and a truck must be in place at the edge of the field to keep the wagons cycling back to the chopper. It is a challenge to keep all these operations coordinated.

A coupled system can work very efficiently when an industry is integrated like the sugarcane industry in South Florida. There, the sugar mill owns the production fields surrounding the mill and the roads through these fields. The mill controls everything: har­vesting, hauling, and processing. Because sugarcane has to be processed within 24 hours after harvest, the need for an integrated industry is obvious.

An example of an uncoupled system is the cotton industry using the new cotton harvester that bales cotton into 7.5-ft diameter by 8-ft long round bales of seed cotton (Figure 13.7). This system was developed to solve a limitation of the current module system. With the module system, in-field hauling trailers, given the rather quaint name “boll buggies”, have to cycle continuously between the harvester and the module builder at the edge of the field. The best organized system can typically keep the harvester on the row harvesting cotton only about 70% of the total field time. Harvesting time is lost when the harvester has to wait for a boll buggy to get into position beside the harvester so the bin on the harvester can be dumped.

The round bale cotton harvester is designed to form a bale, wrap it in plastic, and eject it without stopping the harvester. A new bale is begun while the current bale is being wrapped and ejected. (Current round balers for hay have to stop, wrap the current bale, and eject it before beginning the next bale.) The round bale cotton harvester, because it is uncoupled from the in-field hauling operation, can achieve a 90% field efficiency. This means the harvester is actually harvesting cotton for 90% of the in-field time compared to 70% for the

current harvester in the module system. Repeating a principle stated earlier, more tons/hour through the harvester means the $/ton harvest cost is less.

Techniques have been implemented to improve the in-fleld hauling of round bales of seed cotton. As shown in Figure 13.8, the harvester can carry a completed bale and drop it at the edge of the field to facilitate direct loading onto highway hauling trucks.

There is also a close link between transportation options and material handling capabilities. At the harvest site, large open-topped chip van trailers can be loaded evenly by a conveyor, overhead hopper or front-end bucket loader. Closed trailers and box trucks, as well as trailers that cannot be approached from the side due to terrain or road conditions, must be loaded from the back. Depending on the particle size of the material and ejection range of processing equipment, it may be difficult to fill long compartments uniformly to maximize payload. Similarly, grapple loaders must have sufficient room to maneuver to efficiently load roundwood or compacted bundles onto long trailers. Unloading is discussed in more detail later in this chapter, but similar constraints apply to unloading biomass. Self-unloading configurations, including walking floor (Figure 14.9), side dump, end dump and belly dump trucks and trailers, carry smaller payloads than long, possum belly semi-trailers, but may be required if the end user does not have a hydraulic truck dump system on site. For

roundwood, self-loading log trucks equipped with a hydraulic grapple arm may be required if the log landing does not have a loader or forwarder on site.

Regulations and handling constraints apply broadly to all biomass supply chains but the forest sector is unique in the extent to which transportation logistics are dictated by harvest site characteristics. Plantations and native forests located on flat topography close to end users and accessed over high-speed, wide, paved roads with high GVW are obviously ideal for minimizing transportation costs. However, forested sites are frequently accessed over gravel or native soil low-standard forest roads that are steep, narrow and winding with limited turn-out locations for passing and turning around. In many cases, forest roads were designed for stinger steered log trucks and are inaccessible to the long, low clearance, high-volume tractor-semi-trailer combinations that maximize transportation efficiency for woody biomass. Road improvements can widen curves, flatten rough roads and reduce steep grades, but can rarely be justified by biomass extraction objectives alone and may be limited by regulation or forest management objectives. Recent innovations in stinger steering and rear axle modifications that allow a tighter turn radius than traditional fifth wheel semi­trailers with fixed axles have improved access to difficult sites by large semi-trailers. Such trailers are commercially available but cost more than conventional equipment. Short chip van tractor-semi-trailer configurations are also used to haul woody biomass on low-standard forest roads. Under especially challenging road conditions, shorter, higher clearance, and more maneuverable box trucks, dump trucks, roll-off bins, or tractor-trailers are an option. However, the smaller payloads carried by these vehicles typically translate to higher per unit transportation costs, which are intensified by long on-highway travel distances. In addition, if biomass has received some field drying before processing, smaller truck configurations tend to reach maximum volume before they reach maximum GVW. This is suboptimal from a logistics standpoint because it further reduces payload and increases per unit costs.

Richard Lowrance1 and Adam Davis2

1 Southeast Watershed Research Laboratory, USDA Agricultural Research Service, U. S.A.

2Global Change and Photosynthesis Research Unit, USDA Agricultural Research Service, U. S.A.

16.1 Introduction

All forms of energy extraction/production/use have environmental footprints, most of which have not been thoroughly analyzed. The U. S. Energy Independence and Sustainability Act (EISA) and the European Union Renewable Energy directive establish goals for bioenergy but the EISA is unique in establishing specific sustainability goals with the regulations. The national United States bioenergy system goals, or RFS2 goals, focus on transport fuels and have numerous requirements related to sustainability. Because of the thorough environmental analysis of RFS2 that has been done by the USEPA, there is a clearer understanding of how cellulosic bioenergy crops can meet RFS2 goals. This analysis will also be relevant to other types of energy systems (non-liquid fuels), such as the use of cellulosic biomass for heating pellets. This chapter focuses on the types of systems described in Chapters 1-12 and includes an examination of woody crops and perennial herbaceous crops. Issues related to environmental sustainability of crop residue removal for cellulosic feedstocks have been covered in Chapter 7, Crop Residues. Also not addressed is the environmental sustainability of annual winter cover crops grown for cellulosic feedstocks because the expectation is that those crops would be grown on existing croplands and with only minor inputs of water, nutrients, and pesticides.

Cellulosic Energy Cropping Systems, First Edition. Edited by Douglas L. Karlen. © 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.

Future United States bioenergy production as mandated by the RFS2 provisions of the EISA is an unique enterprise in that regulations have been developed that define the required greenhouse gas (GHG) reductions relative to gasoline and diesel fuel from fossil fuels. In the United States, this is the first national regulation to evaluate direct and indirect GHG for any product — GHG life cycle emissions. This is done through an accounting that has been developed by the USEPA and has undergone rigorous peer review [1]. For the first time, biofuels must meet new GHG reduction thresholds to qualify as “Renewable Fuel” or other EISA specified categories of fuels. In addition, only feedstocks produced from certain types of lands will be considered renewable biomass, and thus eligible to be used in production of a “renewable fuel”. In general, the feedstock/conversion/fuel systems that meet RFS2 standards will be considered environmentally sustainable, largely because of the factors taken into account in the greenhouse gas reduction analysis. To qualify as a “renewable fuel” [1], the fuel must:

“Be produced from ‘renewable biomass’ as defined in the rule and demonstrated by reporting and recordkeeping requirements of the rules and qualify based on fuel type, feedstock, and pro­duction processes specified in Section 80.1426(f) [or qualify byway of an alternative pathway petition]; “Renewable Biomass means:

1) Planted crops and crop residue harvested from existing agricultural land cleared or culti­vated prior to December 19, 2007 and that was nonforested and either actively managed or fallow on December 19, 2007.

2) Planted trees and tree residue from a tree plantation located on non-federal land (including land belonging to an Indian tribe or an Indian individual that is held in trust by the U. S. or subject to a restriction against alienation imposed by the U. S.) that was cleared at any time prior to December 19, 2007 and actively managed on December 19, 2007.

These provisions of the RFS2 rules are generally aimed at environmental sustainability and recognize that if renewable fuels are produced on lands that are cleared of forest or other native vegetation, there are impacts due to both loss of habitat and loss of ecosystem functions as well as the need to account for a large carbon debt (the carbon stored in biomass and soil, [2]).

Environmental sustainability analysis of cellulosic bioenergy necessarily models indus­tries that do not yet exist (e. g., cellulosic ethanol and renewable diesel) [1,3]. The cellulosic feedstocks assumed to meet total EISA goals of 16 Bgal (ethanol equivalent liquid fuel) by 2022 are: dedicated energy crops 7.9 Bgal; agricultural residues 5.7 Bgal; corn (Zea mays) stover 4.9 Bgal; urban waste 2.3 Bgal; sugarcane (Saccharum officinarum) bagasse 0.6 Bgal; and other sources (wheat (Triticum aestivum) residue, sweet sorghum (Sorghum bicolor) pulp, forestry biomass) 0.3 Bgal. Assuming adequate biomass availability, these projections are consistent with the “Billion Ton Study” conducted by the USDA and USDOE [3].

The environmental sustainability of feedstock production systems will depend on sev­eral factors, including their effects on GHG emissions, soil and water resources, wildlife, and whether the feedstock is a potentially invasive species or can harbor them. These direct effects are generally determined based on direct land use change from annual crops, managed perennial vegetation (e. g., perennial pastures, industrial or non-industrial for­est plantations), or other types of perennial vegetation (i. e., natural forest or grassland). Although conversion of natural grasslands or forests to bioenergy crops may occur, both the USDA regulations concerning conversion of natural grasslands and stated policies for biomass sources are meant to avoid conversion of native vegetation. Most of the direct environmental effects of cellulosic biomass production will come from existing agri­cultural land (pasture and row crop), existing forest plantations, or previously harvested forest land.

International land use change is often a large part of the GHG life cycle analysis when food crops such as corn or soybean [Glycine max (L.) Merr.] are used for biofuel. For cellulosic bioenergy crops such as switchgrass (Panicum virgatum) that are not likely to directly displace food crops, it will generally be a smaller component of the GHG life cycle analysis (LCA) because less international land conversion is forecast per unit of bioenergy produced [3]. Although indirect international land use change effects are considered to be an aspect of sustainability for bioenergy feedstocks, it will not be covered in this chapter. Rather, readers are referred to others [4-6] for different perspectives on this issue.

Direct land use effects are based on our understanding of the changes in field, landscape and watershed attributes when dedicated feedstock crops replace other land uses or covers. Direct effects (all of which can be either positive or negative) include GHGs, soil quality (including but not limited to soil carbon), water quantity and quality, invasive species, and wildlife habitat. Some of these factors can lead to direct effects on adjacent ecosystems and some can lead to larger effects at the watershed or landscape scale. The effects will also be dependent on where bioenergy crops are produced. For instance, there may be net environmental benefits (especially GHG and soil/water benefits) from conversion of cropland to warm season grasses (WSG) or to short-rotation woody crops (SRWC) but for conversion from forest, managed for saw timber production, to biomass there may not be any net benefits. The scale of benefits also depends on the land converted with the general idea being that the less productive and more marginal the land, the greater the benefit from conversion to perennial cellulosic biomass crops [7,8].

The global potential to produce bioenergy [9] indicates that as much as 59 million ha of abandoned agricultural land may be available nationwide in the United States alone [3]. There are abandoned and under-used croplands in many parts of the United States and in other agricultural regions. The western United States has areas with the largest amount of available abandoned agricultural land but in many cases these areas are not irrigated [1]. Midwestern states, including typical Corn/Soybean Belt states such as Iowa, Illinois, and Ohio, have approximately 1-2 million ha of abandoned land, all likely to be more productive than more arid areas in the West [1]. In a study of marginal lands in 10 Midwestern states, Gelfand et al. [10] estimated that about 11 million ha of marginal lands would be available for cellulosic biofuel feedstocks.