# Presentation: 436481

## Crop Residue as Feedstock for the New Bioeconomy:Opportunities and Roadblocks

**W. W. Wilhelm****	****	****USDA-ARS, Lincoln, Nebraska**
**G. E. Varvel****	****	****USDA-ARS, Lincoln, Nebraska**
**D. L. Karlen****	****	****USDA-ARS, Ames, Iowa**
**J. M.-F. Johnson****	****USDA-ARS, Morris, Minnesota**
**J. M. Baker****	****	****USDA-ARS, St. Paul, Minnesota**

**CSSA Symposium – Feedstock Production for the New Bioeconomy: Opportunities and Roadblocks**
**Crop Science Society of American Annual Meeting, Indianapolis, Indiana **
**November 14, 2006**

**Notes:**
Thank you Henry.

I appreciate the invitation to present a few thoughts on the opportunities the bio-economy and biofuels are offering agriculture and the nation.

I will also highlight several reason for caution as we, as crop and agronomic scientists, and a society move toward use of renewable feedstock to power our economy.

First I want to thank my co author, Gary Varvel, Doug Karlen, Jane Johnson, and John Baker. All are members of the ARS REAP effort to develop sustainable practices and guidelines for use of crop residues as  bio-energy and bio-product feedstock.

## Billion Ton Report

- Biomass production – 1366 million ton
- Forestry – 368 million tons
- Agriculture – 998 million tons
- Perennial energy crops – 377 million tons
- Wastes – 87 million tons
- Grain – 87 million tons
- Crop residues – 428 million tons
- Corn stover – 256 million ton

**Notes:**
The Billion Ton Report suggests the US can annually product over one and a third billion tons of biomass.

Agriculture, under the report’s high production scenario, will contribute near ONE BILLION TONS.

Of the 428 million tons from Crop Residues, 256 million tons are expected to come from CORN STOVER

In the high scenario, Agriculture is projected to have the potential to produce nearly ONE BILLION TONS of biomass annually.

CROP RESIDUES represent about half of that amount.

CORN STOVER alone was projected to contribute about one quarter of the BILLION TON need. 

## Billion Ton Report

- Biomass production – 1366 million ton
- Forestry – 368 million tons
- Agriculture – 998 million tons
- Perennial energy crops – 377 million tons
- Wastes – 87 million tons
- Grain – 87 million tons
_**Crop residues – 428 million tons**_
_**Corn stover – 256 million ton**_

**Notes:**
The Billion Ton Report suggests the US can annually product over one and a third billion tons of biomass.

Agriculture, under the report’s high production scenario, will contribute near ONE BILLION TONS.

Of the 428 million tons from Crop Residues, 256 million tons are expected to come from CORN STOVER

In the high scenario, Agriculture is projected to have the potential to produce nearly ONE BILLION TONS of biomass annually.

CROP RESIDUES represent about half of that amount.

CORN STOVER alone was projected to contribute about one quarter of the BILLION TON need. 

## Bold, optimistic projections

***Bold, optimistic projections***
***Basis for discussion***
***Lofty target ***

**Notes:**
I will now take a few minutes to summarize our assessment of projections in the BILLION TON REPORT.

However before I do so, I feel it important to state a few overarching observations.

Though we will be critical of some of the assumptions and projections in the Billion Ton Report, Dr. Perlack and his co-authors MUST be complimented for having the courage to offer a bold and optimistic outlook.

It has been, and will continue to be, the focal point of much of the discussion of bioenergy, biofuels, and bio-products. The discussion, and the thoughts and activity these discussions spawns, will move technology forward. 

Goals in the report are lofty. Great advances are seldom achieved without lofty goals.

## What is a ONE BILLION?

- If one ton = 1 sq in
- 1 billion tons = 145 football fields

**Notes:**
I’ve read and analyzed the Billion Ton Report and discussed the scope of the 30 x ’30, 30% of the 2004 motor fuel from renewable sources by 2030, goal with many individual, but always have an extremely difficult time grasping the magnitude of ONE BILLION TONS.

This visual gives some, admittedly unusual, ways to visualize one billion in comparison to more comprehensible things.

Read slide.

## What is a ONE BILLION?

- If one ton = 1 sq in
- 1 billion tons = 145 football fields
- Agricultural land (cropland plus hay and pasture)
- 5 ton ac-1
- 200 x 106 acres
- 56% of North Central Region agricultural land
- Iowa, Illinois, Nebraska, Minnesota, Indiana, and South Dakota (Total = 195.5 x 106 ac)

**Notes:**
Agricultural land is defined as crop plus hay and pasture land. If 5 ton of biomass is harvested from every one of these acres, a total of 200 million acres of land would be needed to produce one billion tons. Two hundred million acres is 56% of the ag land in the North Central Region or ALL of the agricultural land in six leading corn producing states in the Union. 

State	2000 Ag land (acre x 10^6)
Iowa		32.8
Illinois	27.7		
Nebraska	45.5
Minnesota	30.0
Indiana	15.5
S Dakota	44.0		195.5

Kansas	47.5
Ohio		14.9
Wisconsin	16.2
Missouri	30.0
Michigan	10.4
N Dakota	39.4
North Central total	353.9

## Billion Ton ReportAgriculture Assumptions

**Billion Ton Report****Agriculture Assumptions**

- Yield increase 50% by 2030
- Corn and small grains
- Residue/grain ratio for soybean increase from 1.5:1 to 2.0:1
- Machine to recover 75% stover
- No tillage adopted universally

**Notes:**
Several assumptions were used to develop these projections

50% yield increase by 2030----really 2043, but the report is regularly misquoted
Increase in ratio of residue to grain in soybean
Machines will be developed to EFFICIENTLY harvest 75% of stover
and
100% adoption of No Till crop management practices

Let’s look at these assumptions.

## Corn yield Nebraska contest winners and averages

**Duvick and Cassman. 1999. Crop Sci. 39:1622-1630.**
**Cassman et al. 2003. Ann. Rev. Envir. Res. 28:-315-356.**

**Notes:**
Many of the projections and statements in the Billion Ton Report on crop yield are based on work by Cassman and his coworkers at the University of Nebraska and Pioneer Hi-Bred International.

I present some of the same work, with a somewhat less optimistic tilt.

Data shown here are state annual mean corn yields for Nebraska from 1966 through 2004 as presented by Duvik and Cassman in 1999— data have been updated.

Looking at the lower two lines and circle data pionts, for the past 40 years, mean corn yield has increased LINEARLY at about 1.8 bu/ac/yr for irrigated conditions and 1.4 bu/ac/yr for rainfed.

The shorter lines and square data points at the top of the chart are National Corn Growers Association Yield Contest winners from Nebraska from 1983 through 2005. Rainfed yield contest winning yields have also increased—at an impressive rate of 3.3 bu/ac/yr. HOWEVER, for the past 20 years Irrigated Yield Contest winning yield have been stagnant at near 300 bu/ac.  These fields likely represent near-ideal corn production conditions. The nearly constant yield for the past 20 years suggest that under these near-ideal conditions, yield is NOT changing. That is the “yield potential” under production conditions is not changing. The fact that state-wide average yields are increasing is a result of more growers are becoming able to obtain that level of production nearer the potential. The good news is that a gasp still exists between the average farm yield and that obtainable under nearly ideal conditions.

I took the slopes of these yield trend lines to see if we are on-track to achieve 50% yield increases as suggested by the Billion Ton Report.

Cassman, K.G., A. Dobermann, D.T. Walters, and H. Yang. 2003. Meeting cereal demand while protecting natural resources and improving environmental quality. Annual Review of Environment and Resources 28:315-358.

Duvick, D.N., and K.G. Cassman. 1999. Post-green revolution trends in yield potential of temperate maize in the north-central United States. Crop Science 39:1622-1630.

## Cassman et al. 2006. CAST Report (release Nov. 16, 2006)

**Notes:**

Finally, the technological advances embodied in the yield trend of the period 1966 thought 2005 are tremendous.

Double  Single cross hybrids
Increases in use of irrigation and N fertilizer
Adoption of and improvements in conservation tillage and broader use soil testing to direct of N, P, and K management
Integrated pest management, and
Introduction, and broad use, of transgenic insect resistance

The question of whether comparable advances be achievable in the next 25 years remains to be answered.

Cassman KG., Eidman VR, and Simpson EH. 2006. Convergence of Energy and Agriculture: Implications for Policy and Research. Council on Agriculture, Science and Technology. Ames IA, www.cast-science.org

## Billion Ton ReportAgriculture Assumptions

**Billion Ton Report****Agriculture Assumptions**

- Yield increase 50% by 2030
- Corn and small grains
- Residue/grain ratio for soybean increase from 1.5:1 to 2.0:1
- Machine to recover 75% stover
- No tillage adopted universally

**Notes:**
Now let’s move to the second assumption.

Increased residue:grain ratio in soybean.

This is important for two reasons—according to the Billion Ton Report.
 Increasing soybean residue will allow more biomass to be removed in a corn-soybean rotation because today the low residue from soybean limit erosion and soil carbon management options.
 Under the high yield scenario in the Billion Ton Report, soybean contribute about 48 million tons of biomass annually.

## Residue:grain in soybean

- Low residue production
- Longevity of residue
- Accelerates decay of SOM
- Greater N content of leaves and roots
- Rhizodeposits
- Large biomass soybean (LBS)
- Forage-type soybean
- Grain yield not proven
- Grain harvest efficiency

**Notes:**
In the agronomic and plant science literature, the term Harvest Index is widely used.

It is the ratio of grain yield to aboveground biological yield—simply put ratio of grain yield to sum of grain and stover (residue) yield.

The Billion Ton Report incorrectly states it is the inverse of the residue to grain ratio!

Most soybean breeders I’ve spoken with as I prepared this talk are extremely skeptical of the potential to significantly increase net primary production—which is a requirement if residue yield increases and grain yield is maintained.

Several agronomic characteristic, lodging and standability, of the LBS must also be modified to allow efficient harvest.

Soybean residue, partially because of the greater N content of abscised leaves, composes rapidly.

Donald, C.M. and J. Hamblin. 1976. The biological yield and harvest index of cereals as an agronomic and plant breeding criteria. Adv. Agron. 28:361-405.

## Billion Ton ReportAgriculture Assumptions

**Billion Ton Report****Agriculture Assumptions**

- Yield increase 50% by 2030
- Corn and small grains
- Residue/grain ratio for soybean increase from 1.5:1 to 2.0:1
- Machine to recover 75% stover
- No tillage adopted universally

**Notes:**
The assumption that we can develop machines to effectively harvest 75% of the stover is realistic.

At present, we don’t have definitive data as to what 75% we could collect, but I have great confidence we can get this part of the job done.

## Fractional stover harvestISU proto-type harvester

**Hoskinson et al. 2006. Biomass and Bioenergy (in press).**

| Harvest scenario | Stover collected(Mg ha-1) | Percentharvested* (%) |
| --- | --- | --- |
| High cut (at ear height) | 4.9 | 46 |
| Low cut (header on soil) | 6.7 | 64 |
| Normal cut | 5.1 | 49 |

*** Total residue produced, 10.5 Mg ha****-1**** **

## Billion Ton ReportAgriculture Assumptions

**Billion Ton Report****Agriculture Assumptions**

- Yield increase 50% by 2030
- Corn and small grains
- Residue/grain ratio for soybean increase from 1.5:1 to 2.0:1
- Machine to recover 75% stover
- No tillage adopted universally

**Notes:**
The last assumption—100% adoption of no tillage.

## No tillage adoption(Conservation Tillage Information Center-National Crop Residue Management Survey, 1994-2004, http://lanshark.ctic.purdue.edu/CTIC/CRM.html)

**Notes:**
This will be a tough sell.

The chart on the left shows the total acres of cropland and acres of conservation tillage and no tillage for the passed 10 years.

On the right, numbers for conservation and no tillage are presented as fractions of total cropland.

No tillage adoption has increased steadily, but still only about 22% of total.

Reasons for resistance to adoption vary, but cost and risks associate with changing practices are often listed by farmers. Experiencing, or risk of, reduced yield, especially in cooler, wetter environments are also factors.

Harvest of biomass as a feedstock may actually help no tillage adoption, by reducing surface cover and helping to achieve warmer drier soil earlier in the growing season.

Conservation tillage = No tillage + Ridge tillage + Mulch tillage (>30% cover after planting)
Reduced tillage = 15-30% cover after planting
Conventional tillage = 0-15% cover after planting

## No till with no residue

**No till with no residue**

**Runoff occurred sooner**
**Significant carryover effect of residue removal**
**Runoff initiated 35% sooner in subsequent year**
**Sediment concentrations increasing by > 100%. **

**Wilson et al. 2004. Trans. ASAE 47:119-128.**

**Notes:**
“Residue removal resulted in significantly sooner runoff with the NT system.  There was a significant carryover effect of residue removal with runoff initiated 35% sooner the subsequent year of removal and sediment concentrations increasing by > 100%. ”

Wilson et al. 2004. Tillage and residue effects on runoff and erosion dynamics. Trans. ASAE 47:119-128

## Billion Ton ReportAgriculture Assumptions

**Billion Ton Report****Agriculture Assumptions**

| Assumption | Assessment |
| --- | --- |
| Yield increase 50% by 2030 | Doubtful |
| Residue:grain ratio for soybean increase from 1.5:1 to 2.0:1 | Achievable, but of doubtful use |
| Machine to recover 75% stover | Very achievable |
| No tillage adopted universally | Doubtful |

**Notes:**
To concluded, here is my report card on the feasibility of achieving the goals of the Billion Ton Report, based on the basic assumptions.

## Traditional uses of crop residues

**Traditional uses of crop residues**

**Notes:**
Traditionally crop residues have been used
    To manage soil erosion and runoff
    Feed and bedding for livestock
    Soil amendment
        Replenishing carbon in the soil and returning nutrients to the soil

## Soil C change

**Soil C change**

***Pre-cultivation ***
***steady-state***

***No tillage***
***Cover crops***
***Green manure***

***REAP***

**Notes:**
Going back to the diagram showing the timeline of soil carbon,
    if we remove stover I think if safe to assume SOC will decline further.

    However, if we add other practices to the system
        we should be able to minimize the impact or 

        IF we are creative, even reverse the current trend.

Developing these innovative methods and tools is the objective of the new ARS REAP work

## Residue needed to maintain SOC

| Crop rotation | Tillage | Mg ha-1 | n |
| --- | --- | --- | --- |
| Corn | mbp | 7.5±1.0 | 6 |
| Wheat | mbp | 5.5±1.1 | 5 |
| All | mbp | 6.3±1.0 | 13 |
| All | Chisel/nt | 4.5±0.4 | 5 |

**Johnson et al. 2006. Agron. J. 98:622-636.**

***REAP***

**Notes:**
Jane Johnson presented data yesterday for analyses she published in Agron. J. on the amount of source C or residue needed on the land to maintain SOC under different practices based on data published in the literature. They concluded that from 4.5 to 7.5 Mg/ha of residue would be needed, with greater amounts required with aggressive tillage practices.

She went on to computer the harvestable stover at various corn yield levels with several crop sequences and tillage practices. In the chart on the right, with Conservation Tillage and Continuous Corn (brown line), SOC requires would be minimally met at about 6 Mg/ha grain production. However, in a Moldboard Plow-Corn-Soybean sequence, grain yield of about 14 Mg/ha would be required to met maintian SOC.

Larson et al., 1972; Paustian et al., 1997; Follett et al., 2005 state the minimum amount of source C needed to maintain SOC is a simple linear relationship, y = ax + b where y = SOC, x = organic C input, and a is a ???, and b =????

HI = g / (g + s),

S = (g/hi) - g

Johnson, J.M.F., R.R. Allmaras, and D.C. Reicosky. 2006. Estimating source carbon from crop residues, roots and rhizodeposits using the national grain-yield database. Agronomy Journal 98:622-636.

Johnson, J.M-F., R.R. Allmaras, and D.C. Reicosky. 2006. Minimum C inputs and sustainability of biomass harvest. Abstract No. 26105. In ASA-CSSA-SSSA Abstracts 2006 [CD-ROM]. ASA, CSSA, and SSSA, Madison, WI. 2006.

## Change allocation of biomass

***REAP***

**Notes:**

Changing the question is the GREATEST OPPORTUNITY for crop scientists, agronomist, agriculture in general, and society in the new bioeconomy.

We should be asking a very basic question “How do we increase to production as meet current and future demand for agricultural output, food, feed, and fiber, which continue to increase with world population growth and increased expectations in developing economies. AND address the new needs for biomass to provide renewable fuel feedstock AND sequester C as SOC.

## Change allocation of biomass

***REAP***

**Notes:**
As I near the end of my comments, I want to suggest that we have been debating the wrong question for the past few years. We have been discussing biomass energy and bio-based product feedstocks from the standpoint of how to reallocate the production capacity to meet the need provide ONE BILLION TONS of biomass.

## Change allocation of biomass vs. increase total biomass production

**Increase photosynthetic efficiency 25%, from 4% ******** 5%**

***REAP***

**Long et al. 2006. Plant Cell Envir. 29:315-330.**

**Notes:**
We have known for a long time that the efficiency of conversion of light energy to reduced carbon is very low, about 4%, max. If we would increase efficiency to 5%--we would see a 25% increase in NPP. Our potential of addressing traditional and new demands increase dramatically if the size of the pie increase. Serving more and larger slices of pie is easier from a larger pie.

To achieve this goal, all aspects of crop science need to be involved. Increase light capture through planting in the right row and plant spacing configurations, using upright leaf structure in the upper canopy and more prostrate leaves in the lower canopy. Adding winter cover crops to the cropping sequence with summer crops to capture light year round. Use genetic engineering to change basic crop physiology. Soil scientists to improve nutrient and water management to maximize efficiency and availability to the crop at the time it is needed.

Long et al. (2006) have outlined these and other potential improvements in Ps efficiency.

A man-on-the-moon type coordinated effort is needed to make goal a reality and the 30 x ’30 happen.

Long, S.P., X.-G. Zhu, S.L. Naidu, and D.R. Ort. 2006. Can improvement in photosynthesis increase crop yields? Plant, Cell and Environment 29:315-330.

## Multiple biomass

***Multiple biomass***
***Many technologies***
***Conservation***
***Reduced expectations***
***Asking and answering the right question***

**Notes:**
To close, I want to thank Henry for inviting us to share these thoughts with you.

Crop residues returned to the land are not wasted, but serve an critical role in crop production systems. As crop yields increase, we may be producing more residue than needed to replenish SOC, manage erosion and runoff, and cycle nutrients. However, at this time we have no tools, algorithms, or guidelines to use to determine the residue needed to sustain SOC. These tools need to be developed.

We do not think a reasonable plan to sustainability produce ONE BILLION TONS of feedstock exists. Today we must begin developing a focused plan to bring all facets of agronomy and crop science together to meet the demand of the bioeconomy while still meeting the traditional demands for food, feed, and fiber—which by the way will likely increase as world population increases and world expectations increase. 

Finally, I want to emphasize that our quest for renewable domestic energy is not a search for THE solution!
    It will take all sources of biomass
    Many new technologies
    A fair bit of conservation -- curbing of our appetite for energy
    Reduced expectationss -- smaller, more fuel efficient vehicles,
         greater use of public transportation,
  and
    Asking and answering the right question.

I look forward to the next 25 years with anticipation. If we achieve only half the goals listed in the Billion Ton Report—and do it in a sustainable manner—we will have made great progress.