(307b) Techno-Economic Analysis for Upgrading Butanol to Hydrocarbon Fuel

Authors: 
Markham, J., National Renewable Energy Laboratory
Tao, L., National Renewable Energy Laboratory

Under  RFS2, after 2015 all increases to blended renewable fuels for gasoline must be advanced biofuels1. Butanol has received increased attention as an advance biofuel option because it is less miscible with water and has a lower vapor pressure than gasoline 2. Butanol can further be catalytically upgraded to hydrocarbons for blend stocks or direct “drop-in” fuels. The catalytic upgrading process dehydrates butanol and then has the resulting butenes undergo oligomerization to gasoline, diesel, and jet range fuels. For example, if normal-butanol were produced via fermentative pathway from cellulosic sugars, it would make predominantly1-butene during dehydration and followed by oligomerization and hydrotreating to produce a mixture of hydrocarbons. There are several fermentation options to produce butanol from biomass feedstocks. Here we will present a techno-economic analysis on the integrated process design of lignocellulosic biomass to alcohol intermediates and then converting alcohols to hydrocarbons, with consideration of variations of fermentation pathways as well as catalytic upgrading strategies. Both corn grain and corn stover will be considered for this study. We will present conceptual process design concept from biomass to biofuel, economic analysis, and sensitivity analysis of key process variables in order to identify their impacts on both overall process costs and yield of hydrocarbon fuels. For example, the fermentation process can produce co-products that either require additional separation and purification to sell co-product for credit, or use them as additional carbon resources for upgrading to hydrocarbons to achieve maximized yields. The economic analysis will include capital costs, operating cost, and a discounted cash flow analysis that determines the minimum alcohol and hydrocarbon fuel (after alcohol upgrading) selling prices. The integrated process alternatives and sensitivity analysis will have consideration towards fermentation, separation, and catalytic upgrading strategies to maximize cost or maximize hydrocarbon yield with data coming from predominantly from literature. The goal of this work is to provide guidance to R&D using tools in techno-economic analysis and uncertainty analysis.

References:

1.         Schnepf R and Yacobucci BD. Renewable Fuel Standard (RFS): Overview and Issues. 2012.

2.         EthanolToday. Butanol An Energy Alternative. 2007.