Profit and policy implications of producing biodiesel–ethanol–diesel fuel blends to specification

Abstract

A nonlinear optimization model is developed in this work to analyze biodiesel–ethanol–diesel (BED) ternary blending processes. The model establishes optimal blends to improve the system profitability given production costs, market demand, and fuel prices while meeting multiple property criteria such as kinematic viscosity, density, lower heating value, cloud point, cetane number, fuel stability and sulfur content. Pertinent fuel mixing rules for predicting the fuel properties of BED blends were extrapolated from previous works and applied as constraints to the present model. Several dynamic and/or uncertainty factors were explored in further depth to quantify their impacts on the fuel composition of BED blends including petro-diesel supply reduction, diesel production cost, diesel blends market retail price, and policy changes on bio-fuel subsidies. By examining key optimization sensitivity analysis such as shadow prices and opportunity costs, the crucial limits or constraints on fuel specifications can be identified and used to proactively identify and promote the development of potential additives. The model also suggests the government policy of simultaneously implementing bio-fuel tax credits and mandates may not have a higher contribution to promoting bio-fuel production than the case only with tax credits for the firms with the goal of profit maximization. The firms enable 5–8% increase of the optimal profit from BED blends by utilizing ethanol derived from food waste feedstocks instead of edible biomass.