Building a Long Term, Sustainable Supply Chain for Cellulosic Biofuels Industry

by Olatomiwa Bifarin* (Advanced Biofuel USA) On Tuesday, July 15 2014, Biofuels Digest hosted a webinar discussing creating sustainable supply chains for cellulosic biofuels – a germane issue that will ultimately determine the commercial viability of cellulosic biofuels.
One of the biggest challenges that we face in the world today is energy – amongst food and security. By 2035, it has been heralded that the global energy need will rise by 40% necessitating the need for cleaner and sustainable energy in order to abate dependence on fossil fuels.
During the webinar, John Pieper, corn stover work stream lead at DuPont, stated that this prescient dearth of energy – among other reasons – galvanized biofuels investments at DuPont.

DuPont cellulosic biofuel production at Nevada

DuPont is uniquely positioned with critical capabilities in the biofuel value chain from the biomass production stage to the production of advanced bio-based materials and fuels, with projects in the area of ethanol, bioethanol, bio-PDO, and bio-Isoprene.
Making Cellulosic Ethanol a Reality: By the Numbers
Pieper admitted that, in general, the cost conversion of biomass to liquid fuels is still much higher than is crude oil; however, these are rife vicissitudes in the span of any technology. Using the conversion of sugar cane’s sucrose to ethanol as an example, he said, over a period of 20 years, conversion of sucrose to ethanol decreased by a factor of four. “In the long run, as technology advances, biomass could be the lowest cost source of fuels.”
The DuPont Nevada cellulosic ethanol facility is expected to be completed in the second half of 2014. Situated in a prime agricultural location – north central Iowa – the over-$200 million facility will be among the first commercial scale cellulosic biorefineries in the world, with ethanol production of about 30 million gallons/year from corn stover.
Annually, 375,000 tons of corn stover would be harvested and stored. Crop residues from about 190,000 acres of farmlands would be partially harvested; which is about 25% of the corn acres within a 30 miles radius of the facility.
Building the Supply Chain

The imperative step for DuPont is the building of the supply chain, which they started about four years ago. In this vein, a survey, carried out to study growers’ satisfaction and value, divulged that residue management and improved corn production are key areas of satisfaction for growers.
John Maxwell, a grower at Nevada, Iowa, who has been working with DuPont to study the sustainable harvest of corn stover as a cellulosic ethanol feedstock, was also featured on the webinar. He stated the advantages of the removal of corn stover which includes: the soil temperature warming up quickly in the spring, lower inoculum levels of corn pathogens, and reduction in tillage – which would not only save cost on labor but also on diesel.
This is particularly important in many highly fecund farming systems, particularly under continuous corn production, where production of corn stover exceeds the minimum amounts needed to maintain soil health and productivity – this will make sustainable stover harvest viable.
Andy Heggenstaller, the agronomy research manager at DuPont Pioneer stated that, beyond approximately 4 tons per acre, stover becomes a management challenge; and since tillage is the primary means of residue management, partial stover harvest can help manage increasing residue levels. Corn stover – when more than the minimum amount needed – interferes with crop establishment and early growth, immobilizes nitrogen, and harbors crop pathogens.
Given the aforementioned alluring benefits, Dr. Heggenstaller said, the benefits do not in any way conceal the possible detrimental effects of the removal of corn stover from certain farmlands.This is because, corn stover is equally critical in the recycle of organic nutrients and protection of soils from erosion.
How Much Stover Can Be Harvested Sustainably?
As expected, the answer to the question would not be exact, given the distinct farming and harvesting practices of growers.Using a study that was developed by USDA as a guideline, Dr. Heggenstaller pointed out that tillage practices and crop rotation models have colossal influence on how much stover can be harvested sustainably. A two-ton per acre stover harvest would be sustainable for continuous corn production when yields are moderately high and tillage is minimal; on the other hand, in a corn-soybean rotation or with increased level of tillage, the frequency of stover harvest should be reduced.
The DuPont stover sustainability program through collaboration with the Natural Resources Conservation Service (NRCS) provides participating growers with field scale maps and metrics to show how stover harvest are expected to affect the soil health, given the idiosyncratic farming and harvesting practices of growers.
Marty Adkins, assistant state conservationist for special projects at NRCS during his presentation reiterated that – by removing residues from the farmlands, it can have a negative effect on soil health but by making wise management decisions it may be done sustainably. He spoke at length on stover harvest and soil health.

*Olatomiwa Bifarin is studying for his Masters degree in Biotechnology at The Catholic University of America. As an intern at Advanced Biofuels USA, he represents the organization and reports on events in Washington, DC, and nearby areas.