Switchgrass (Panicum virgatum L.)—a perennial, warm-season (C4) species—evolved across North America into multiple, divergent populations. The resulting natural variation within the species presents considerable morphological diversity and a wide range of adaptation. The species was adopted as a crop—initially as a forage—only in the last 50 yr. Its potential uses have recently been expanded to include biofuels. Management of switchgrass for biofuels is informed by an understanding of the plant's biology. Successful establishment requires attention to seed dormancy and weed control as well as proper depth and date of planting. The plant's growth rate is closely tied to temperature, but timing of reproductive development is linked to photoperiod. Accordingly, the period of vegetative growth can be extended by planting lower-latitude cultivars at higher latitudes. This strategy may provide a yield advantage, but cold tolerance can become limiting. Switchgrass is thrifty in its use of applied N; it appears a...

The Biology and Agronomy of Switchgrass for Biofuels

Before the industrial revolution, the global economy was largely based on living carbon from plants. Now the economy is mainly dependent on fossil fuels (dead carbon). Biomass is the only sustainable bioresource that can provide sufficient transportation fuels and renewable materials at the same time. Cellulosic ethanol production from less costly and most abundant lignocellulose is confronted with three main obstacles: (1) high processing costs ($/gallon of ethanol), (2) huge capital investment ($∼4–10/gallon of annual ethanol production capacity), and (3) a narrow margin between feedstock and product prices. Both lignocellulose fractionation technology and effective co-utilization of acetic acid, lignin and hemicellulose will be vital to the realization of profitable lignocellulose biorefineries, since co-product revenues would increase the margin up to 6.2-fold, where all purified lignocellulose co-components have higher selling prices (>∼1.0/kg) than ethanol (∼0.5/kg of ethanol). Isolation of large amounts of lignocellulose components through lignocellulose fractionation would stimulate R&D in lignin and hemicellulose applications, as well as promote new markets for lignin- and hemicellulose-derivative products. Lignocellulose resource would be sufficient to replace significant fractionations (e.g., 30%) of transportation fuels through liquid biofuels, internal combustion engines in the short term, and would provide 100% transportation fuels by sugar–hydrogen–fuel cell systems in the long term.

Reviving the carbohydrate economy via multi-product lignocellulose biorefineries

Biomass-to-bioenergy and biofuel supply chain optimization: Overview, key issues and challenges

Biomass is a renewable energy source with increasing importance. The larger fraction of cost in biomass energy generation originates from the logistics operations. A major issue concerning biomass logistics is its storage, especially when it is characterized by seasonal availability. The biomass energy exploitation literature has rarely investigated the issue of biomass storage. Rather, researchers usually choose arbitrarily the lowest cost storage method available, ignoring the effects this choice may have on the total system efficiency. In this work, the three most frequently used biomass storage methods are analyzed and are applied to a case study to come up with tangible comparative results. Furthermore, the issue of combining multiple biomass supply chains, aiming at reducing the storage space requirements, is introduced. An application of this innovative concept is also performed for the case study examined. The most important results of the case study are that the lowest cost storage method indeed constitutes the system-wide most efficient solution, and that the multi-biomass approach is more advantageous when combined with relatively expensive storage methods. However, low cost biomass storage methods bear increased health, safety and technological risks that should always be taken into account.

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Logistics issues of biomass: The storage problem and the multi-biomass supply chain

Gasification is one of the promising technologies to convert biomass to gaseous fuels for distributed power generation. However, the commercial exploitation of biomass energy suffers from a number of logistics and technological challenges. In this review, the barriers in each of the steps from the collection of biomass to electricity generation are highlighted. The effects of parameters in supply chain management, pretreatment and conversion of biomass to gas, and cleaning and utilization of gas for power generation are discussed. Based on the studies, until recently, the gasification of biomass and gas cleaning are the most challenging part. For electricity generation, either using engine or gas turbine requires a stringent specification of gas composition and tar concentration in the product gas. Different types of updraft and downdraft gasifiers have been developed for gasification and a number of physical and catalytic tar separation methods have been investigated. However, the most efficient and popular one is yet to be developed for commercial purpose. In fact, the efficient gasification and gas cleaning methods can produce highly burnable gas with less tar content, so as to reduce the total consumption of biomass for a desired quantity of electricity generation. According to the recent report, an advanced gasification method with efficient tar cleaning can significantly reduce the biomass consumption, and thus the logistics and biomass pretreatment problems can be ultimately reduced.

Barriers of commercial power generation using biomass gasification gas: A review

A linear programming approach for designing a herbaceous biomass delivery system

To reach the US Department of Energy's goal of replacing 30% of current petroleum consumption by biomass and its products by year 2030, various systems capable of harvesting, storing and transporting biomass efficiently, at a low cost, need to be designed. The transportation system of a cotton gin, which shares several key components with a biomass transportation system, was simulated using a discrete event simulation procedure, to determine the operating parameters under various management practices. The cotton module transportation system, when operating under a FIFO management plan, was found to operate at 77% utilization factor, while the actual ginning process operated at 69%. Two greedy algorithm-based management policies were simulated, which increased the gin operational factor to 100%, but doing so required an increase in gin inventory level. A knapsack model, with travel times, was constructed and solved to obtain the lower bound for the transportation system. The significance of these operating parameters and their links to a biomass transportation system are presented. Using the new management strategies, the utilization factor for the transportation system was increased to 99%. To achieve this improvement, the transportation manager must know where all modules are located and have the ability to dispatch a hauler to any location.

Cotton logistics as a model for a biomass transportation system

Harvest and storage costs for bales of switchgrass in the southeastern United States

Design, modeling, and analysis of a feedstock logistics system

Herbaceous biomass can contribute to the renewable energy supply for electricity, process steam, liquid fuel, and commodity chemicals. Efficient systems to harvest and store round bales of perennial grass in storage locations within 5 km of the production fields are available. The major limitations are loading these bales at the storage locations and hauling to meet a weekly demand schedule at a processing plant operating continuously for 50 weeks yr −1 . Analysis is presented for a 27 Mg h −1 plant. The concept is to pack 32, 1.5-m round bales into a container with the same dimensions as a 12.2-m (40-ft) ISO shipping container. These containers are loaded at a satellite storage location, hauled to a receiving facility at the processing plant, and unloaded. The analysis examines two options. Option 1 uses a forklift to place a loaded container onto a standard transport chassis at the satellite storage location. A similar forklift unloads the containers at the receiving facility. Option 2 uses a Swinglift trailer that loads and unloads the containers onto the trailer using on-board hydraulics. The cost for Option 1 was calculated at $7.80 dry Mg −1 , as compared with $8.37 dry Mg −1 calculated for Option 2. The cost for Option 1 is lower even though the forklift used at the satellite storage location in Option 1 is only operated at 27% of daily capacity, thus operating cost per dry Mg to load is higher than it would be if scheduling could be done such that more containers could be loaded each workday. The forklift spends most of the time waiting for the container to be packed with bales. The limiting factor established in this analysis is the feasibility of packing 32 bales into a container within an allowed 30 min.

John S. Cundiff

Papers

A linear programming approach for designing a herbaceous biomass delivery system

Cotton logistics as a model for a biomass transportation system

Harvest and storage costs for bales of switchgrass in the southeastern United States

Design, modeling, and analysis of a feedstock logistics system

Containerized handling to minimize hauling cost of herbaceous biomass.