david archer, research agricultural scientist

Agricultural Research Service

Corn Stover Cost, Availability, and

Sustainability

David Archer, Research Agricultural ScientistUSDA Agricultural Research Service

Northern Great Plains Research LaboratoryMandan, ND




Points Favoring Harvest of Crop Residues

• Renewable• Doesn’t require use of additional land• Vast quantities produced• May facilitate adoption of less-intensive

tillage

Source: USDA-NASS Cropland Data Layer

2007 Corn

Midwest (13 States) Totals:73.6 million acres11.4 billion bushels

U.S. Totals:86.5 million acres13.1 billion bushels

~300-350 million tons of stover grown in U.S.


Sustainability Concerns with Harvesting Crop Residues

• Soil quality (tilth), organic matter (carbon) sustainability

• Soil structure, microbial activity• Erosion protection• Plant nutrients• Evaporation• Harvest damage (soil compaction, etc)


Biomass Gasification Demonstration and Research Facility

• University of Minnesota, Morris– Plant-scale project provide

up to 80 percent of campus heating and cooling

– Allow research of alternative feedstocks (e.g. wood chips, grasses, wheat straw, corn cobs, corn stover)

– Require around 10,000 tons of biomass per yearPhoto credit: University of Minnesota

*

http://renewables.morris.umn.edu/pictures/index.php?random=1


Scale-up

* *

UMM plant: ~10,000 tons/yr

Chippewa Valley Ethanol Company,

Benson, MN: ~100,000 tons/yr

(replace natural gas)

100 million gallon/year cellulosic plant would require ~1 million tons/yr

Presenter

Presentation Notes

Goes up by a factor of 10 from UMM to CVEC, and another factor of 10 from CVEC to 100 million gal/yr plant. UMM, WCROC and CVEC will be harvesting corn cobs from 5,000 acres as a test this fall. UMM and CVEC can (and likely will ) use other feedstocks.


1st Step: Corn CobsAdvantages• One-pass harvest,

require little change in current production practices

• Relatively high volumetric energy density

• Low nutrient content



10-mile Radius Around University of Minnesota, Morris


Presenter

Presentation Notes

Need to report acres of each crop (or at least total for the 4 crops).


Analysis

• EPIC simulation model – calibrated to USDA-ARS field research plots

at Morris, MN– Simulation conducted for each SSURGO soil

map unit within a 10-mile radius of UMM• Biomass farm gate cost includes:

– Biomass harvest and in-field transportation– Nutrient replacement (N,P,K)– Short-term crop yield impacts

Presenter

Presentation Notes

Does not include potential long-lasting long-term impacts on crop productivity. Availability estimates do not include timeliness issues, and potential effects of labor/weather constraints.




Average 45,558 tons available within10-mile radius

Note: based on $20/acre cob harvest cost

Presenter

Presentation Notes

Assumed $20/acre cob harvest cost and cob harvest=20% of total stover biomass. Recent research showing 17-20%. Chisel plow tillage is the most common tillage practice in the area, however there is also substantial amount of moldboard plow tillage. Adoption of strip-till and no-till is very low. Corn-soybean rotation is the predominant rotation, however there is an appreciable amount of spring wheat production in the area. Other crops produced in the area include sugar beet, flax, dry beans.


0

10

20

30

40

50

0 10,000 20,000 30,000 40,000 50,000

Biomass Supply (ton)

Farm

gate

Bio

mas

s Pr

ice

($/to

n)

$33.37

Would require harvesting corn cobs from 14,000 acres per year.

Presenter

Presentation Notes

Note: Short-term breakeven, does not include cost of any long-lasting long-term changes in productivity.




Could meet 10,000 ton demand at a price of $26.37/ton harvesting 7,100 ac/year.

Presenter

Presentation Notes

Assumed $5.00/acre added cost for cob harvest. With relatively low per acre harvest rates, changes in harvest cost can have a big effect on net cost/ton.


0

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20

30

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60

0 25,000 50,000 75,000 100,000


Farm

gate

Bio

mas

s Pr

ice

($/to

n)

CP C-S CobCP C-S StoverST C-S Stover

Production Alternatives10,000 ton at: $35.22/ton ST C-S Stover $33.37/ton CP C-S Cob $26.37/ton CP C-S Stover

Presenter

Presentation Notes

The cost difference between ST and CP is due to need to add a stalk chopping operation to ST, while this is a normal operation under CP. I assumed that we would need to provide additional net return benefits beyond any already available in order for ST to be adopted over CP. There are other production alternatives not presented here, including changes in rotation and use of cover crops.


Breakeven Price Components ($/ton)

Breakeven Price = Harvest

Cost + Nutrient Replacement -

Grain Production

ChangeCP C-S Cob 35.66 29.31 7.32 0.97

(31.87-46.13) (27.00-38.12) (5.91-9.42) (-0.51-7.13)

CP C-S Stover 29.39 23.43 7.01 1.06(24.83-37.33) (22.31-27.74) (5.22-8.84) (-1.66-7.95)

ST C-S Stover 37.76 31.32 7.44 1.00(32.24-50.68) (29.60-37.99) (3.05-12.16) (-10.77-4.80)

Presenter

Presentation Notes

Largest factor in determining breakeven price is harvest cost. Nutrient replacement costs are also important, with higher average nutrient replacement costs for ST. This will be discussed in more detail of a later slide. Stover harvest on average has a positive effect on short-term grain productivity, but varies by soil type.


-8,000-7,000-6,000-5,000-4,000-3,000-2,000-1,000

01,0002,000

0 25,000 50,000 75,000 100,000


Soi

l Org

anic

Car

bon

Cha

nge

from

No

Bio

mas

s H

arve

st (t

on/y

ear)


Soil Organic Carbon

Presenter

Presentation Notes

Stover removal results in decrease in SOC relative to baseline. Could be mitigated by change in tillage.


-1,000,000-800,000-600,000-400,000-200,000

0200,000400,000600,000

0 25,000 50,000 75,000 100,000


Soi

l Nitr

ogen

Cha

nge

from

N

o B

iom

ass

Har

vest

(lb

/yea

r)


Soil Nitrogen


-50,000

-40,000

-30,000

-20,000

-10,000

0

10,000

20,000

0 25,000 50,000 75,000 100,000


Wat

er E

rosi

on C

hang

e fro

m

No

Bio

mas

s H

arve

st

(ton/

year

)


Water Erosion

Presenter

Presentation Notes

Even though I included non highly erodible soils, stover removal does increase soil loss. Could be mitigated by change in tillage.


-10,000-8,000-6,000-4,000-2,000

02,0004,0006,0008,000

10,000

0 25,000 50,000 75,000 100,000


P L

oss

with

Sed

imen

t C

hang

e fro

m N

o Bi

omas

s H

arve

st (l

b/ye

ar)


Phosphorus Loss

Presenter

Presentation Notes

Higher erosion rates lead to greater P loss with sediment.


Value of Environmental Impacts relative to CP C-S with no biomass harvest

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

CP C-S Cob CP C-SStover

ST C-SStover

Valu

e of

Env

ironm

enta

l Ben

efits

($/to

n bi

omas

s)

Erosion ReductionC BenefitN Benefit

Sources: N Benefit: replacement cost of soil N depletion ($0.47/lb).C Benefit: 2009 CCX carbon credit value ($6.97/ton C)Erosion Reduction: Hansen and Ribaudo, USDA-ERS 2008 ($5.09/ton)


Summary• In the short-term, production of corn stover could

meet UMM biomass needs at farmgate breakeven prices as low as $26/ton

• Without changes in tillage/cropping practices, corn stover harvest can have negative resource impacts which may threaten long-term sustainability

• Adoption of minimum tillage practices can mitigate many of these resource impacts, allowing sustainable corn stover harvest

Presenter

Presentation Notes

Note: Did not include year-to-year variability and harvest timing issues in this analysis, which can be a very important factor. Stover harvest did not provide a direct incentive for strip-till adoption (beyond any existing advantages).


Acknowledgements

Thank you to collaborators:• Don Reicosky, USDA-ARS Morris, MN• Jane Johnson, USDA-ARS Morris, MN• Mike Reese, University of Minnesota,

West Central Research and Outreach Center

david archer, research agricultural scientist

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