Techno-economic analysis of conventional, high moisture pelletization and briquetting process

Developing uniformly formatted, densified feedstock from both forest and agricultural based biomass is of interest to decrease feedstock cost and increase quality through influencing storage, transportation, and handling characteristics. Raw biomass, by nature, is highly variable. Densification eliminates variability by achieving consistent size, shape, bulk and unit density, and durability. A variety of densification systems such as (1) pellet mill, (2) cuber, (3) screw extruder, (4) briquette press, (5) roller press, (6) tablet press, and (7) agglomerator can be used for producing a uniform format feedstock commodity for bioenergy applications. Densified biomass products are widely used as commodity-type products for energy applications and are traded both nationally and internationally. The main objective of this study is to evaluate the techno-economic feasibility of conventional pelleting, high-moisture pelleting and briquetting process. The analysis includes energy consumption and capital, and operational costs for the three processes identified to produce 800, 000 tons of densified corn stover for bioenergy applications. Analysis of conventional pelletization processes indicates drying fuel costs of about 10.70 $/ton to be a substantial financial barrier compared with pellet milling and secondary grinding at 4.9-5.1 $/ton in fuel cost. High-moisture pelletization offers a solution to high drying costs as it could reduce about (10 $/ton) in the total pelletization cost. In this study, high-moisture densification drying costs were estimated to be significantly less by about 9.6 $/ton, due to use of energy efficient dryers like cross flow grain dryers. The total cost to produce 800, 000 tons of pellets/year is about $32.2 million (about 20% lower compared to conventional pelletization process). In contrast, conventional briquetting maintains the high drying cost ($10.70/ton) but reduces the secondary grinder cost ($7.88/ton). This reduction is caused by the briquetting process capability to use bigger particles sizes. The total cost to produce 800, 000 briquettes per year is about $39.3 million.