Developing Corn Stover as the Next Agricultural Commodity

DuPont creates a new feedstock supply chain for cellulosic ethanol through a project in Iowa
By Andy Heggenstaller | May 10, 2012

“The process for converting biomass to ethanol is far from trivial. At DuPont, we’ve solved the technology issues,” explains Jim Collins, president of DuPont Industrial Biosciences. DuPont has been investing for over a decade to develop cellulosic technologies that will bring about the next-generation of biofuels, and it’s our intention to demonstrate our commitment to these technologies, he says, by breaking ground on a first-of-its-kind cellulosic ethanol biorefinery, near Nevada, Iowa, later this year.

DuPont’s initial plant will have a capacity of 28 MMgy, requiring 350,000 tons of biomass feedstock. The real challenge then, as the cellulosic ethanol industry scales up for commercial production, isn’t so much conversion technology, but rather securing a reliable, cost-efficient and sustainable supply of biomass. Because it’s plentiful, doesn’t displace food crops and isn’t widely used for other commercial purposes, DuPont and other companies have selected corn stover as the logical feedstock of choice for the first cellulosic biorefineries.

Despite its obvious advantages, corn stover, like any other cellulosic feedstock, lacks one very important characteristic—it’s not yet a commodity. Processors can’t simply order it through a conventional supply chain. At present, feedstocks must be sourced directly by the processor using equipment and systems that, for the most part, have been developed for other purposes. Moreover, in the case of corn stover, the vast majority of annual feedstock supply has to be sourced during a narrow window each year at the time of or immediately following grain harvest.

Recognizing the challenges and risks associated with feedstock supply, DuPont initiated a comprehensive development and scale-up Corn Stover Harvest and Collection Project in 2010 around the site of its planned Iowa biorefinery. This project, which is providing key knowledge on the sustainable harvest, collection, transport and storage of corn stover, is now entering its third year. According to Kyle Althoff, DuPont Cellulosic Ethanol LLC supply chain manager, “The goal of our Iowa project, from the outset, has been to develop corn stover into a local commodity, and this necessarily involves identifying and creating value for all supply chain participants.”   

Building a Sustainable Value Chain
In 2010, DuPont began its corn stover project by partnering with six leading Iowa corn growers and conducting a pilot-scale stover harvest on 2,500 acres. The 2010 pilot program helped the company establish a presence with local growers and to begin assessing equipment options and configurations for stover harvest, collection and transportation. Following the pilot program, DuPont initiated a custom, third-party harvest model, which it is further developing for commercialization and is one of several harvest options currently being considered for corn stover supply. Different approaches are currently being tested by the industry, but custom stover harvest offers several important advantages, including the ability for the processor to better control moisture and ash content through the use of standardized equipment and harvest techniques. Equally important is that custom harvest allows corn growers to keep their attention focused on grain harvest and fall field operations. “For corn stover to work as a feedstock there needs to be a value proposition for corn growers, but it is equally important that stover harvest itself not interfere with growers’ primary business of producing grain,” explains Denny Penland, DuPont Cellulosic Ethanol business development manager.

The most important outcome of DuPont’s 2010 pilot harvest was that it demonstrated that Iowa corn growers see value in participating in a commodity chain around stover. Because of strong grower interest, we were able to expand our project in 2011 to include 50 growers and harvest 7,500 acres, with all six growers who partnered with us in 2010 choosing to continue their involvement with the program. The 2011 harvest represented an increase in scale over the previous year, but also provided an opportunity to conduct critical research and development to advance equipment productivity, improve feedstock quality and evaluate cost-effective approaches for minimizing feedstock losses during storage.

Iowa State University has been, and continues to be, an indispensable partner with DuPont on supply chain research and development efforts. In 2011, DuPont also engaged research talent from its Pioneer Hi-Bred business to better define the agronomic dimension of corn stover harvest by establishing a network of long-term field trials with partnering growers. These field trials, which represent the first commercial-scale investigation of the impacts of corn stover harvest on crop performance and soil quality, will guide DuPont and Iowa’s corn growers as stover is developed as a sustainable feedstock. Although the agronomy field trials were established just last year, a significant finding from the overall project in 2011 was that most participating corn growers see agronomic value in having a portion of the stover removed from their fields.

As corn grain yields continue to increase, so too does the amount of residue left in the field after grain harvest. Therefore, many corn growers, especially those achieving high yields, indicate that residue management is one of the greatest challenges they face when producing corn following corn or when implementing minimum or no-till practices. Corn stover from the previous years’ crop interferes with planting and delays stand establishment. Corn residue also ties-up nitrogen as it breaks down in the soil and often harbors damaging insect pests and pathogens. All of these factors can reduce crop growth and ultimately grain yield.

According to John Pieper, Pioneer Hi-Bred director of cellulosic ethanol, “Last year, following stover harvest, we conducted a survey with the growers who participated in our program. In the survey, we asked growers what they felt was the greatest value of stover harvest in their farming operation. Many growers responded that agronomic advantages of stover harvest, most importantly residue management, were more valuable to them than the direct income they received as payment for stover.”             

It’s important that the corn stover supply chain provide added value for corn growers and that stover harvest be implemented in a sustainable manner that doesn’t jeopardize long-term productivity. In this regard, DuPont has worked closely with USDA, Iowa State University and other organizations to identify and implement the critical components of a sustainable stover harvest system.

Mitigation of soil erosion, maintenance of soil organic matter and replacement of nutrients removed from the field with stover are three key sustainability factors that are taken into consideration in the harvest program. In practice, DuPont achieves sustainable stover harvest by targeting high-yielding fields where excess stover is available and leaving a portion of stover behind in the field, and by altering harvest frequency based on field and management conditions. “On certain fields, stover should not be removed at all. On fields that are suited for removal, we don’t harvest every year and we don’t remove all of the stover when we do harvest,” explains Steven Mirshak, DuPont business director for cellulosic ethanol. “Environmental stewardship is one of DuPont’s core values, and this project offers us an immense opportunity to demonstrate how we act on this core value in creating a sustainable business around corn stover.”

Commercialization through Collaboration
DuPont is continuing to expand the Iowa Corn Stover Harvest and Collection Project in 2012. This year, more than 100 corn growers and approximately 25,000 acres of stover will be contracted, representing about one-seventh of DuPont’s first biorefinery’s annual commercial feedstock requirement. While the 2011 corn stover program had a focus on research and development, the primary objectives of the 2012 program are to conduct a commercially representative harvest operation and to prove out the business model developed for corn stover supply. DuPont plans to begin construction of the Nevada biorefinery in the second half of 2012, with plant start-up expected to follow in late 2013 or early 2014.

DuPont’s first cellulosic ethanol biorefinery site will be strategically located next to Lincolnway Energy, a corn grain ethanol processor in Nevada, Iowa. “The stover value chain doesn’t end at the biorefinery gate,” explains DuPont plant manager, Keith Gibson. “Coproducts will be important for cellulosic ethanol, just as they are for starch-based ethanol. Lignin will be our primary coproduct and this material is targeted to be recycled onsite to provide low-cost, sustainable process energy for our biorefinery as well as for the neighboring corn grain ethanol plant. The two plants will also look to leverage synergies such as utilities and logistics.”

Collaborations have proved critically important for DuPont’s efforts so far in developing the corn stover commodity supply chain. At DuPont, we believe that partnering in this way is how we will arrive at more sustainable energy solutions for a world that increasingly demands them. “Corn stover is clearly not the only cellulosic feedstock out there,” explains Althoff, “just the first one.” As DuPont looks ahead at commercializing cellulosic ethanol in other parts of the country, it will also be exploring other feedstocks and working with new partners to create sustainable supply chains that capture value for fuel processors as well as feedstock producers. 

Author: Andy Heggenstaller, PhD
Agronomy Research Manager, Pioneer Hi-Bred
(800) 247-6803
[email protected]


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