Feedstock processes from corn field to biorefinery
by Ed van Ouwerkerk, Iowa State University, Ames, Iowa
as of October, 4, 2004

This describes the processes as shown in flowchart (http://i-farmtools.org/USDA-feedstock/feedstock_flowchart5.ppt) in order to design a feedstock module in I-FARM (http://i-farmtools.org/i-farm) as part of task 8 of the project. We need your feed back on this scheme. Is this what we should model? Or is it more or is it less? We need to understand all processes and to describe it in an well accepted way. We need data on input, expected output, and process algorithms. Then we can estimate mass flows. We ask attention from each project member to deliver data in his or her field of expertise. Or send us information of others known to you. Or send us what you expect as an outcome of your current research. All information should be referenced.

We will focus on designing lookup tables for all machinery (combines, tractors, balers, fractionating equipment, etc.) with their properties as capacity, speed, labor requirement, and specific fuel consumption. And make adjustments for those machines newly developed in this project (single pass harvesters).

Multiple pass harvest
This is the traditional way of corn harvest. We should model these processes in detail to be able to compare performance, product quality, labor and costs with the single pass harvest under development.
Required up-to-date information: Fuel consumption of the combine, labor requirement of combine operation, fixed and other variable costs of the combine, specified for various working width/number of rows.

Wet grain
Currently we have no corn growth model in I-FARM. We have county-level and state-level yields from 2002 Census of Agriculture as input. Should we build in a corn growth model, which is soil and weather dependent? We could work on something as available in DSSAT, but that is rather time consuming to re-program that. We could make a large number of calculations under various soil and weather conditions and construct and lookup table from those results.
The grain is first collected in the storage bin on the combine and then blown into a separate cart pulled by a tractor and transferred to the site of destination (drying and/or storage facility). We have a simple calculation equation to estimate the LPG requirement for corn grain drying. It should be adjusted for various levels of grain moisture content across the country.
Required up-to-date information: Lookup table for various tractors to match speed and harvest capacity; fuel consumption of the tractor hauling the grain, labor requirement of hauling operation, fixed and other variable costs of the tractor and cart.

Wet stover
Currently the stover yield is also input. We assume the stover yield is equal to the grain yield in mass units. If we decide to construct a lookup table from various DSSAT calculations this item will be addressed.

Stover drying
The stover is left on the field for drying. How many days (range)? We actually have no module to estimate the on-field stover drying. Is there any model available?

Stover collection
In some cases all the stover is left on the field as a carbon source for the soil (fertility) and as an erosion protective soil cover. In our project we focus on using the stover. Therefore it is collected partially. The stover amount necessary to be left on the field as a soil cover residue can be estimated in the current I-FARM model using soil loss tolerance levels, depending on field hill slope, soil properties, and location defined rain storm intensity. Another criterion should be added: soil carbon sequestration. That part will be dealt with by implementing the Soil Conditioning Index into I-FARM. Part of the stover is collected. Therefore it is windrowed and baled for later transported to the storage.
Required up-to-date information: Windrowing fuel and labor requirements and costs depending on residue levels (percentages) to be left on the field.

Stover baling
There are several ways of baling stover. It can be done in small or large, square of round bales. We focus on large round bales. The bales can be hold together by several types of material, or even packed and sealed in a plastic bag. In all cases the bales are left on the field to be picked up later. Another option is large square bales, that can be stored at a higher storage density.
If the stover is baled and packed in a plastic bag, the pretreatment
Required up-to-date information: Fuel and labor requirements and fixed and other cost of corn stover baling operations.

On-farm stover bale transport
The unitized (baled in any form) corn stover is transported to an on-farm or off-farm storage prior to be shipped to a pretreatment facility.
Required up-to-date information: Fuel and labor requirements and fixed and other cost of corn stover bale hauling operations.

Unitized 'dry' corn stover storage
We should fully understand all processes going on in the unitized stover during the storage. We know that unsealed outdoor stored stover loses lots of quality and quantity. We should develop a module that estimates stover properties over time, depending on weather or indoor climate conditions. If anyone has identified an existing model to start with, please contact us.
Required up-to-date information: Fuel and labor requirements and fixed and other cost of corn stover bale hauling operations and fixed and variable costs of bale storage facilities.

Single pass harvest
Research on single pass harvest in order to process wet corn stover is done at several institutes. Project partner Dr Kevin Shinner conducted research at the University of Wisconsin-Madison http://bse.wisc.edu/Updates_121203_012104/AnnualSum2004/Anul_Summ_Research_04/R_MH/R_MH_1-04.htm . Task 1 focuses on developing new single-pass grain and stover harvest systems, with existing multi-pass systems evaluated for comparative purposes. From that research we will get the basic information to model the stover properties during harvest and compare that with the multi pass harvest method. We focus on two tracks:
a. where grain is harvested separately, the stalks (stem, cubs, leaves) are collected as stover, and a certain amount of residue is left behind on the field; here we have 3 product streams
b. where the whole plant is processed and chopped as a stover and a certain amount of residue is left behind on the field; here we have 2 product streams.

On-farm wet stover stransport
We expect a larger mass to be transported compared to the dry stover transport in the multiple harvest method, because of the high moisture of the stover. In the whole plant chopping method we even expect about 2-3 times the mass flow, because there the grain is included, while the separate grain transport is missing (grain storage bin on combine not used).
Required up-to-date information: Fuel and labor requirement and fixed and variable costs of the transport system for several harvest speeds and distances to the fractionating or packing facilities on the farm.

Stover fractionating
This is done to end up with a fractionated product for unitized (=packed) or bulk storage. Question: where is the fractionation done, on the combine in motion or as a separate stationary process prior to packing and/or storage?
Required up-to-date information: Fuel and labor requirements and fixed and other cost of corn stover fractionating operations.

Packing wet stover
For unitized wet stover storage packing is required. We should consider how to manage the material. Questions: Should we blow the fractionated material in big bags that can be transported on flat trucks? Can the bags be recycled? Or can we use air-tied containers?
Required up-to-date information: Fuel, material, and labor requirement, and fixed and variable costs of a packing facility.

Unitized wet stover storage
The unitized wet stover is transported to a on-farm or off-farm bulk storage prior to be shipped to a pretreatment facility. We should fully understand all processes going on in the unitized stover material. We should develop a module that estimates stover properties over time, depending on storage conditions (type of bags/containers), and having pretreatment in storage as an option. If anyone has identified an existing model to start with, please contact us.
Required up-to-date information: Fuel and labor requirements and fixed and other cost of unitized storage facilities.

Bulk wet stover storage
The bulk wet stover is transported to a on-farm or off-farm bulk storage prior to be shipped to a pretreatment facility. We should fully understand all processes going on in the bulk storage. We should develop a module that estimates stover properties over time, depending on storage conditions (non-covered vs covered bulk silo's), and having pretreatment in the bulk storage as an option. If anyone has identified an existing model to start with, please contact us.
Required up-to-date information: Fuel and labor requirements and fixed and other cost of bulk storage facilities.

Long distance transport
We assume that corn stover is always stored on-farm or close to a cluster of farms prior to long distance transport to the pretreatment facility or biorefinery. Always road truck transport of unitized or bulk is involved. If train or barge transport is available we should consider another couple of handling instances to happen, only if feasible.
We assume that the pretreatment facility will not be at the biorefinery location, because that should require large storage facilities and processing time there. It is more like that the refinery requires a year-around supply of pretreated stover with a constant quality coming from a separate pretreatment facility.