A Stochastic Biomass Blending Problem in Decentralized Supply Chains

TL;DR

This paper develops a stochastic programming model for biomass blending in supply chains, optimizing quality and cost under uncertainty, and compares centralized versus decentralized decision-making.

Contribution

It introduces a chance-constraint programming model for biomass blending that accounts for stochastic quality, with solution algorithms for both centralized and decentralized supply chains.

Findings

Centralized supply chain costs are 2-6% lower than decentralized.

Blends mainly consist of pine and softwood residues.

The model effectively manages biomass quality variability.

Abstract

Blending biomass materials of different physical or chemical properties provides an opportunity to adjust the quality of the feedstock to meet the specifications of the conversion platform. We propose a model which identifies the right mix of biomass to optimize the performance of the thermochemical conversion process at the minimum cost. This is a chance-constraint programming (CCP) model which takes into account the stochastic nature of biomass quality. The proposed CCP model ensures that process requirements, which are impacted by physical and chemical properties of biomass, are met most of the time. We consider two problem settings, a centralized and a decentralized supply chain. We propose a mixed-integer linear program to model the blending problem in the centralized setting and a bilevel program to model the blending problem in the decentralized setting. We use the sample average approximation (SAA) method to approximate the chance constraints, and propose solution algorithms to solve this approximation. We develop a case study for South Carolina using data provided by the Billion Ton Study. Based on our results, the blends identified consist mainly of pine and softwood residues. The cost of the centralized supply chain is 2 to 6% lower, which shows that the assumption of centralized decision making leads to underestimating costs in the supply chain.