(54c) Sustainable Biomass Supply Systems
AIChE Spring Meeting and Global Congress on Process Safety
Establishing and Ensuring Sustainable Biofuels Development: A Department of Energy/Industry Perspective
Tuesday, April 28, 2009 - 9:20am to 9:45am
The terms ?sustainable? and ?sustainability? embody efforts to balance today's resource requirements with future demands. For example, agriculture is considered ?sustainable? when agricultural inputs ? natural resources, energy, chemicals, labor and so on ? meet current demand for food, fuel, and fiber without environmental consequences that impair future production. In terms of meeting the DOE 30x30 goals, the sustainability concern is whether or not the U.S. agricultural system can produce sufficient feedstocks for biofuel production while continuing to meet the food price expectations of American consumers without causing environmental degradation that would threaten to curtail the production of both food and fuel. From a feedstock supply system design perspective, the concern is to develop a means of assessing the sustainability of a national commoditized feedstock supply system. This paper will demonstrate the tools being developed at the Idaho National Laboratory (INL) in collaboration with Oak Ridge National Laboratory, Kansas State University and the University of California, Davis that help design and analyze biomass supply system logistics and biorefinery siting at a very detailed level. The goal is to determine a ?best? feedstock supply system and to establish performance criteria that need to be met to make the system functional and aid in siting biorefineries to ensure adequate feedstock supply.
INL believes that there are two main barriers for meeting the amount of biomass: first, providing a sustainable diverse biomass supply that doesn't significantly impact food supply, and second, developing a feedstock supply system that is able to access the supply in a cost effective manner. The supply system includes more that just transportation issues but densification, stability, and timing are also areas of consideration. This report will outline current status, developing trends, and future vision for biofuel production.
A common perspective on dealing with feedstock supply system challenges is to reduce the radius necessary around a biorefinery to provide sufficient quantities of material for operation. This radius reduction perspective leads down two primary pathways: (1) build smaller, more distributed biorefineries and (2) increase the per acre energy density of the lignocellulosic feedstock. As with most processing facilities, biorefineries find significant operational benefit in the economics of scale. Scaling down conversion facilities to deal with feedstock supply system constraints puts added economic pressure on an already challenged system. Increasing the energy provided per acre of feedstock is a highly desirable outcome from multiple perspectives. For example, if a feedstock genome is developed that results in a two-fold increase in per acre tonnage, the radius necessary to provide material to the biorefinery could drop by 30% or more. Supply system economics and revenue for growers are positively impacted by this dynamic. The basic idea is that a high-yielding bioenergy feedstock will provide a profitable crop for growers and a consistent resource base within a tight logistical radius for conversion facilities. Unfortunately, this dynamic also has the potentially crippling effect of creating unsustainable monoculture cropping systems.
As demonstrated by recent increases in the value of corn grain, profit margins will quickly drive agricultural decisions on land use. The acreage committed to growing corn for grain has increased by approximately 29% over the last 20 years (USDA-NASS 2008). The upper Midwest of the United States is generally a corn grain monoculture. It is well understood and accepted within the agronomy community that monoculture cropping systems create wide-ranging problems and are generally not sustainable over the long-term (Wilhelm et al. 2007; Hoskinson et al. 2006). This includes the suite of perennial crops (Tilman 2006) along with standard annual cropping systems.
The key to developing sustainable cropping systems, and ultimately maintaining the long-term health of the agricultural landscape, is providing growers access to a diverse set of markets. An emerging cellulosic bioenergy industry has the potential to provide these new markets capable of fueling a move toward agronomic sustainable integrated cropping systems. The essential hurdle in providing market access to growers is the design and implementation of a uniform-format, commodity-scale lignocellulosic biomass supply system.
While perhaps not immediately clear, the issue of sustainable cropping systems is crucially important to biorefinery siting. Conversion facilities built based on access to unsustainable resources will quickly become unsustainable themselves. It is proposed here that through the development of a commodity-scale lignocellulosic biomass supply system, diverse markets will become available to the agricultural community. These markets will facilitate, and even encourage, a shift toward sustainable integrated cropping systems producing a multitude of bioenergy feedstocks which will be processed and blended to a market-driven specification. Through this commodity distribution system the material will be delivered within tight quality specifications to conversion facilities that are sited based more on utility and transportation access and upstream distribution constraints, rather than downstream resource access constraints.
The feedstock supply system consists of five basic operations, harvest and collection, storage, handling and queuing and preprocessing. The INL research is focused on three feedstock system designs (Figure 1). The Conventional-Bale and Pioneer-Uniform designs represent systems that use current technologies and can be implemented today. A third design, Advanced-Uniform, represents a supply system that can achieve the 2017 and 2030 feedstock cost and quantity targets established by Department of Energy Office of Biomass Program (DOE-OBP) (MYPP, 2007). The pioneer-bale system is what is the current design being used to collect feedstock supplies. While the pioneer-bale works for the current demand there are cost and performance restrictions that will come into play as the demand grows. The INL believes a transformation of the supply system must to occur in order to support the increased demand for cost effective biomass supply.
Figure 1. Three feedstock supply systems are currently being analyzed. The first two systems are assumed to use current technology and equipment. The third supply system concept requires new equipment yet to be developed.
For any supply system design to be truly functional, the design must flexible enough to demonstrate its ability to physically and logistically couple to the resource, which can be quite site-specific. This is a fundamental design feature of the Advanced-Uniform design, envisioned under the premise that the upstream modular nature of the supply system is much better suited to effectively conform to feedstock supply diversity than downstream, larger capital supply and conversion systems.
Additionally, harvesting systems will have variable rate harvesters that can selectively collect biomass based on localized conditions. Access to USGS and USDA soil, slope and climate data will provide real-time analysis of removable biomass.
When connecting supply systems to the biorefinery, the vision is clear; that is, develop a supply system infrastructure that can connect to a uniform format biorefinery receiving and conversion system. However, at the resource end of the supply system, the objective is to accommodate the diversity of biomass resources without unique equipment for each respective resource. The design concept is to invest in a minimum number of technologies that, with adjustments or attachments, are able to adapt to handle diverse feedstock resources and production systems.
The overall objective of this work to identify adequate sustainable resources on a regional basis and cost effectively couple those resources to biorefineries. Identify bottlenecks and restrictions for different supply system designs. Identify potential biorefinery sites that will ensure adequate, sustainable biomass supply. The presentation will demonstrate the capabilities of these tools and present some of the results that are being generated by these analyses.
This paper has an Extended Abstract file available; you must purchase the conference proceedings to access it.
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