Timothy C. Lindsey

Abstract

Basic corn-to-ethanol manufacturing processes have provided important first steps for bio­refining operations but have barely scratched the surface with respect to overall biorefining opportunities. Multiple options exist to modify or supplement existing processes to make these plants more productive and increase the types and quantities of valuable materials that they produce. Some low — value byproducts and wastes generated from these facilities can be converted into higher value products. Additionally, byproducts and wastes from other industries, such as food processing, landscaping, paper, and municipal solid waste facilities, could be substituted for crops as feedstocks and processed into ethanol. This chapter focuses on two incremental modifications that dry-mill ethanol plants could imple­ment that would enlarge their feedstock options and also expand the products and associated value of their output. The proposed modifications include (1) incorporation of cellulosic feedstocks into existing operations and (2) recovery of oil for sale as a value-added product. Modification of existing processes to accommodate cellulosic feedstocks could greatly improve the diversity and flexibility of feedstock options. Recovery of oil from by products such as germ, thin stillage syrup, or dried distillers ’ grains and solubles (DDGS) could expand greatly the quantities and value of products produced from dry-mill plants and also provide valuable feedstock options for biodiesel producers. Multiple other opportunities exist for expanding and diversifying dry-mill ethanol plant feedstocks, processes, and prod­ucts but are beyond the scope of this chapter. For instance, DDGS could be further frac­tionated to separate and pelletize high-protein/high-value components from lower value materials. Cogeneration systems could be implemented to burn lignin and other coproducts to simultaneously produce steam and electricity, thereby reducing electricity requirements from external sources and providing electrical power for additional biorefining operations. Ethanol is an important industrial ingredient and has widespread use as a base chemical for other organic compounds. These include ethyl halides, ethyl esters, diethyl ether, acetic acid, butadiene, and ethyl amines.

Biofuels from Agricultural Wastes and Byproducts Edited by Hans P. Blaschek, Thaddeus C. Ezeji and Ju rgen Scheffran 161 © 2010 Blackwell Publishing. ISBN: 978-0-813-80252-7

Introduction

Today ’s ethanol industry is frequently criticized for being resource intensive in terms of energy, water, grain, fertilizer, and other inputs required for production. While the ethanol produced at these facilities is a very valuable fuel, numerous opportunities exist to reduce waste and expand the diversity of both the inputs and the outputs associated with their opera­tions. Multiple options exist to modify or supplement existing processes to make these plants more productive and increase the types and quantities of valuable materials that they produce. Some low-value byproducts and wastes generated from these facilities can be converted into higher value products. Additionally, byproducts and wastes from other industries, such as food processing, landscaping, paper, and municipal solid waste facilities, could be substituted for crops as feedstocks and processed into ethanol. This would reduce the strain on food resources commonly associated with biofuels production.

Basic corn-to-ethanol manufacturing processes have provided important first steps for biorefining operations but have barely scratched the surface with respect to overall biorefining opportunities. This chapter focuses on two incremental modifications that dry-mill ethanol plants could implement that would enlarge their feedstock options and also expand the prod­ucts and associated value of their outputs. The proposed modifications include (1) incorpora­tion of cellulosic feedstocks into existing operations and (2) recovery of oil for sale as a value — added product.

The United States currently converts approximately 15 million tons of agricultural products into ethanol and biodiesel and discards approximately 270 million tons of agriculturally derived residues in the form of harvestable crop residues, animal manure forest residues, and the organic fraction of municipal solid wastes (Baker 2006). As of February 2006, the annual capacity of the U. S. ethanol sector stood at 4.4 billion gallons, and plants under construction or expansion are likely to add another 2.1 billion gallons to this number (Clements and Van Dyne 2006). According to the U. S. Department of Agriculture Agricultural Baseline Projections (released in February 2006), the share of ethanol in total corn use will rise from 12% in 2004-2005 to 23% in 2014-2015. A comparison of the 2006 Baseline with the 2005 Baseline suggests that much of the increased use by ethanol producers will be diverted from potential exports because the 2006 Baseline projects higher use for ethanol and lower exports than the 2005 Baseline.

With a corn-to-ethanol conversion rate of 2.7 gallons per bushel (a rate that many state-of — the-art facilities are already surpassing), the U. S. ethanol sector will need 2.6 billion bushels per year by 2010, which is 1.2 billion bushels more than it consumed in 2005 (U. S. Department of Agriculture, Economic Research Service 2006) Adaptation of the market to this increased demand is likely to be one of the major developments of the early 21st century in U. S. agriculture.