Developing uniformly formatted, densifi ed feedstock from lignocellulosic biomass is of interest to achieve consistent physical properties such as size and shape, bulk and unit density, and durability, which signifi cantly infl uence storage, transportation and handling characteristics, and, by extension, feedstock cost and quality. A variety of densifi cation systems are considered for producing a uniform format feedstock commodity for bioenergy applications, including (i) pellet mill, (ii) cuber, (iii) screw extruder, (iv) briquette press, (v) roller press, (vi) tablet press, and (vii) agglomerator. Each of these systems has varying impacts on feedstock chemical and physical properties, and energy consumption. This review discusses the suitability of these densifi cation systems for biomass feedstocks and the impact these systems have on specifi c energy consumption and end-product quality. For example, a briquette press is more fl exible in terms of feedstock variables where higher moisture content and larger particles are acceptable for making good quality briquettes; or among different densifi cation systems, a screw press consumes the most energy because it not only compresses but also shears and mixes the material. Pre-treatment options like pre-heating, grinding, steam explosion, torrefaction, and ammonia fi ber explosion (AFEX) can also help to reduce specifi c energy consumption during densifi cation and improve binding characteristics. Binding behavior can also be improved by adding natural binders, such as proteins, or commercial binders, such as lignosulfonates. The quality of the densifi ed biomass for both domestic and international markets is evaluated using PFI (United States standard) or A variety of approaches is discussed for understanding the role of densifi cation in development of advanced uniform feedstocks for bioenergy applications, including (i) mechanisms of particle bonding during densifi cation, (ii) diff erent densifi cation systems such as pellet mill, briquette press, cuber, tablet press, roller press, screw extruder and agglomerator, (iii) specifi c energy consumption of diff erent densification systems, (iv) eff ects of densifi cation process variables on quality of the densifi ed products and (v) eff ects of pretreatments, such as grinding, pre-heating, steam explosion, torrefaction, and ammonia fi ber explosion (AFEX process) on densifi cation process. Finally, advantages of particular systems are discussed in relationship to bioenergy applications and recommendations are made for future studies. Mechanisms of bonding of particles during densifi cationTh e quality of densifi ed biomass depends on strength and durability of the particle bonds, which are infl uenced by a number of process variables, like die diameter, die temperature, pressure, binders, and pre-heating of the biomass mix. Tabil 11 and Tabil and Sokhansanj 12,13 suggested that the compaction of biomass during pelletization can be attributed to elastic and plastic deformation of the particles at higher ...

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The economic competitiveness of cellulosic ethanol production is highly dependent on feedstock cost, which constitutes 35-50% of the total ethanol production cost, depending on various geographical factors and the types of systems used for harvesting, collecting, preprocessing, transporting, and handling the material. Consequently, as the deployment of cellulosic ethanol biorefi neries approaches, feedstock cost and availability are the driving factors that infl uence pioneer biorefi nery locations and will largely control the rate at which this industry grows.Initial scenarios were postulated to develop a pioneer dry feedstock supply system design case as a demonstration of the current state of technology. Based on this pioneer design, advanced scenarios were developed to determine key cost barriers, needed supply system improvements, and technology advancements to achieve government and private sector cost targets. Analysis of the pioneer supply system resulted in a delivered feedstock cost to the throat of the pretreatment reactor of $37.00 per dry tonne (2002 $). Pioneer supply systems will start by using current infrastructure and technologies and be individually designed for biorefi neries using specifi c feedstock types and varieties based on local geographic conditions. As the industry develops and cost barriers are addressed, the supply systems will incorporate advanced technologies that will eliminate downstream diversity and provide a uniform, tailored feedstock for multiple biorefi neries located in different regions. given to identify key cost barriers, supply system improvements, and technology advancements necessary to achieve government and private sector cost targets.Th is perspective is largely drawn from a number of recent reports. 1-6Feedstock supply system engineering starts at the biorefi nery Perspective: Cellulosic biomass feedstocks and logistics for ethanol production JR Hess, CT Wright, KL Kenney system technologies, begin supplying large enough quantities to enable them to be cost eff ectively replicated.Supply system costs, which include all expenses associated with harvesting, collecting, storing, preprocessing, handling, and transporting biomass to the biorefi nery ( Fig. 1), face signifi cant logistical and, more importantly, feedstock diversity challenges. Th ese challenges prohibit the near-term establishment of a consistent and uniform biomass supply system. By shift ing preprocessing from inside the biorefi nery gate to the storage location, the complexity of receiving multiple formats (round or square bales) is eliminated at the biorefi nery.Th e costs that make up the minimum price at which cellulosic ethanol is sold, assuming no government incentives, can be roughly divided into feedstock costs and conversion costs.Using the dilute acid biochemical conversion process as the model, it is anticipated that pioneer commercial biorefi neries will be able to devote about 35% of the Minimum Ethanol Selling Price (MESP) to feedstock purchase and supply. Future technology...

Decentralized biomass processing facilities, known as biomass depots, may be necessary to achieve feedstock cost, quantity, and quality required to grow the future U.S. bioeconomy. In this paper, we assess three distinct depot configurations for technical difference and economic performance. The depot designs were chosen to compare and contrast a suite of capabilities that a depot could perform ranging from conventional pelleting to sophisticated pretreatment technologies. Our economic analyses indicate that depot processing costs are likely to range from ∼US$30 to US$63 per dry metric tonne (Mg), depending upon the specific technology implemented and the energy consumption for processing equipment such as grinders and dryers. We conclude that the benefits of integrating depots into the overall biomass feedstock supply chain will outweigh depot processing costs and that incorporation of this technology should be aggressively pursued.

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