Bioeconomy Institute

Technical Relevance and Merit

We propose a new system for maintaining soil fertility that employs cornstover or corn fiber for production of a nitrogen-rich, biologically active char that both enriches the soil and sequesters carbon from the atmosphere. In this system, cornstover or corn hulls are collected and preprocessed locally to yield fine, porous char and energy-rich bio-oil. The bio-oil, which can be thought of as densified biomass, is transported by tanker truck to a central facility for steam reforming to hydrogen followed by some part of it being converted to anhydrous ammonia (the process yields excess hydrogen for other applications). Using existing infrastructure of the agricultural fertilizer industry, anhydrous ammonia is transported back to the distributed preprocessing facilities where it is reacted with carbon dioxide, water, and char, which are byproducts from pyrolysis of biomass, to yield ammonia bicarbonate (NH4HCO3) precipitated within the pores of the char. The nitrogen-rich char is injected into the soil where it serves three purposes: nitrogen fertilizer, biologically-active soil amendment, and a means for sequestering carbon from the atmosphere.

Technical Approach/Work Plan

The goals of this project include controlling pyrolysis conditions to achieve optimum mass fractions of bio-oil, char, and gas for production of fertilizer; improving steam reforming of bio-oil to obtain hydrogen for synthesis of anhydrous ammonia; synthesizing ammonium bicarbonate-impregnated char with desirable agronomic properties; establishing the carbon sequestration potential of the proposed N-rich char fertilizer; evaluating the corn yield response to the application of different amounts of nitrogen-char fertilizer to soils; and evaluating the economic performance of the proposed fertilizer system. These goals will be achieved with a workplan consisting of seven technical tasks and two project management tasks.

Energy Efficiency/Displacement, Rural Economic Development, and Environmental Benefits

This analysis is based on the benefits resulting from the application of this new fiber-to-fertilizer system on a 250 ha (620 acre) farm that produces about 7 Mg/ha (110 bu/acre) of corn. Net fossil energy use is reduced by 1,000 GJ (990 MMBtu) by substituting stover for natural gas in the production of N-fertilizer. The net reduction in CO2 emissions is in excess of 1900 Mg/yr compared to conventional fertilizer application. This is equivalent to the annual CO2 emissions from 330 automobiles (driving 12,000 miles per year and averaging 20 mpg).

Rural economic development is advanced in three ways. First, producers will participate in supplying the energy requirements of fertilizer manufacture, which reduces their net operating cost. We estimate that the producers’ credit for providing energy to the fertilizer manufacturer could reduce their net cost for fertilizer to $327/Mg N ($245/ton) compared to prevailing prices of $600/Mg N ($450/ton NH3). Second, producers participate in sequestering carbon from the atmosphere, which has the potential of generating additional farm income if carbon trading is implemented in the United States. Based on carbon trading in Europe under the Kyoto Accord in late 2005 ($20/ton of sequestered CO2), this could represent additional income of $30,000 for a producer with a 250 ha farm. Third, long term soil quality will improve as a result of application of char.

Technical, Management, and Facility Capabilities

The team assembled for this investigation includes Iowa State University, Cargill Corporation, Eprida, Inc., Demonstratives, Inc., National Renewable Energy Laboratory, Oak Ridge National Laboratory, and the USDA ARS North Central Soil Conservation Research Laboratory. We will employ iPrismGlobal’s online Web Portal as a collaboration platform to manage information and people involved in this project. An advisory committee has been formed that includes representatives from the National Corn Board, Green Valley Chemical (an anhydrous ammonia manufacturer), Broin, Tall Corn Ethanol, the Iowa Energy Center, the ISU Sustainable Agriculture Program, and the USDA sponsored Biorefinery Supply Chain Research and Demonstration project.

Investigators:

Robert C. Brown, Iowa State University

Randy Killorn, Iowa State University

Associated Contracts or Grants:

Environmental Enhancement Through Corn Stover Utilization (USDA) 

Participating and/or Sponsoring Organizations:

Cargill, Inc.
Eprida, Inc.
iPRISMGlobal, Inc.
National Renewable Energy Laboratory
Oak Ridge National Laboratory
USDA-ARS North Central Soil Conservation Research Laboratory