Optimal blending management of biomass resources used for biochemical conversion

Abstract

This research develops an optimization model to describe the tradeoff among blend components in the least‐cost biomass blend, based on resource availability, quality requirements, and logistics cost for a biochemical conversion. A mixed‐integer linear programming model is developed to determine the least‐cost blend from a set of candidate feedstocks. A case study – based on a biorefinery located in western Kansas that uses three‐pass corn stover, two‐pass corn stover, switchgrass, miscanthus, and municipal solid waste fractions to meet biochemical conversion specifications and feedstock demand – shows that the delivered cost of an optimal blend that meets carbohydrate and ash specifications is 12.12% higher than the delivered cost of optimal blend that meets a carbohydrate specification only. The results indicate that a least‐cost blend that meets both carbohydrate and ash specifications consists of miscanthus (48.2%) and switchgrass (29.4%) whereas the least‐cost blend meeting carbohydrate specification only comprises three‐pass corn stover (55.4%) and two‐pass corn stover (20.4%). An optimal blend uses a low‐cost municipal solid waste fraction in all cases, implying that blending could be a potential strategy to reduce delivered feedstock cost. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

Supply and value chain analysis of mixed biomass feedstock supply system for lignocellulosic sugar production

“…The major differences are due to differing assumptions regarding grower payment, feedstock supply radius, and operating hours and efficiencies of field machinery. For instance, miscanthus feedstock supply logistics cost estimated in this study is 1.8 times higher than a previous study and as much as 1.2 times lower than a more recent work . The more recent study assumes a grower payment of 57.57 $ t −1 for miscanthus; however, this study only considered the nutrient replacement cost for all the feedstock.…”

“…For instance, miscanthus feedstock supply logistics cost estimated in this study is 1.8 times higher than a previous study and as much as 1.2 times lower than a more recent work . The more recent study assumes a grower payment of 57.57 $ t −1 for miscanthus; however, this study only considered the nutrient replacement cost for all the feedstock. The grower payment may comprise biomass production cost (including costs for nutrients, seeds, herbicides/pesticides, and cost associated with farming resources such as machinery, fuel, and labor), incentives, and opportunity cost (depends on the market demands of biomass).…”

“…For comparison, the grower payment is unsurprisingly higher than the nutrient replacement cost for miscanthus of 10.6 $ t −1 (increases with decreasing biomass yield or harvest rate) estimated in this study, whereas costs for other components of this study are similar to those cited above. Nutrient replacement cost of switchgrass estimated in this study of 15.3 $ t −1 is also 2.6 times less than the growers’ payment considered in the study cited previously . Once these energy crops are established at a commercial scale the growers’ payment may reduce as these are perennial crops.…”

“…The pellet‐production process considered in this study includes feedstock preparation, such as primary milling, drying, and secondary milling, conditioning (i.e., mixing of steam), pellet production, and storage . A detailed process model of pelletization is provided in the supplementary material (SI‐S2 in File S1).…”

“…They used two groups of feedstocks: (i) pulpwood, wood residues, switchgrass, and construction and demolition waste, and (ii) corn stover (single pass and multi‐pass), switchgrass, and municipal solid waste. A recent study also demonstrates the importance of mixed feedstock to achieve compositional quality targets determined by total carbohydrate content of at least 59% and ash content of <5% considering blends of corn stover, miscanthus, switchgrass, and grass clippings.…”