Feasibility of Corn Stalk Ash as a Fertilizer Source

Final Report for FNC97-173

Project Type: Farmer/Rancher
Funds awarded in 1997: $4,974.00
Projected End Date: 12/31/2000
Region: North Central
State: Iowa
Project Coordinator:
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Project Information


A local corn stalk processing company collects and processes corn stalks to extract an important chemical used in plastics, called furfural. The ash residue left after processing goes unused and still retains the valuable nutrients important to crop production, mainly phosphorus and potassium.

The plant had been dumping over 11,000 tons of ash per year, mostly to landfills, and was scheduled to expand to 38,000 tons per year. The stalk material contains nutrients such as nitrogen, phosphorus and potassium. If the stalk ash retains much of these nutrients, the ash should be of benefit to crop production. If the ash can be utilized, it would also reduce the dumpage going to landfills.

Dave Reinig Farms covers over 1,000 crop acres in western Iowa, near the town of Harlan. Sustainable agriculture, innovation and research are an integral part of the operation. The farm production is comprised of yellow corn, white corn, soybeans, tofu soybeans, seed soybeans, popcorn, organic food grade products, and includes other research efforts such as chemical comparison trials.

The objective was to determine the feasibility of a biomass fertilizer alternative to traditional synthetic fertilizers. If the biomass material is a feasible source of fertilizer, determine best methods for handling and application. Trials were done over a 2 year duration using different methods of transportation, spreading, and storage. Soil tests were taken to determine responses in soil fertility and yield results were checked to determine production responses.

Transportation Trials:
Trial 1: the first trial for transporting the ash was done using a hopper bottom semi trailer. This method was unsuccessful because the material did not flow out of the hopper bottom trap door. The material had to be shoveled out and a hard lesson was learned.

Trial 2: the next used a 30’ dump trailer (semi version of dump truck) which worked fairly well. The material is light and trucks with large volume cavities are the most efficient. Because the material is so light, the size of dump trucks limits the amount of material that can be hauled. A normal 18’ dump truck body can only haul an ash payload of 5-7 tons. A live bottom trailer could haul more payloads, probably 25 tons, and unload just as effective.

Spreading Trials:
Trial 1: A common dry fertilizer spreader with a small web to move the material back to the spinning spreaders was used. The material was spread the same day as the ash arrived. The sidewalls on this type of spreader are not steep enough and the web is too narrow to move the material. The compartment would bridge up and had to be manually poked down to feed into the web.

Trial 2: Stock piles of biomass ash were made in a field next to stock piles of lime. We used a loader and developed a mixer pile by putting a scoop of each material into the pile and mixing up with the loader bucket. We then used a belt conveyor to load an Ag-Chem lime spreader with a wide web and steep sloping sidewalls.

The method we used to make a 50-50 mixed was not very consistent and when the material seemed to have a good mix it separated out in the spreading procedure. Lime throws further and the ash falls out in a narrower pattern. More importantly, we lost control of the lime rate we needed to achieve for proper pH adjustment.

Trial 3: Stock piles were also used in a field. Using the same large Ag-Chem lime spreader, we had an excellent spread of the pure material with moisture added. Because it is lightweight, the spread pattern was two thirds of the normal spread of lime. To assist in loading the floater spreader, we used a belt conveyor to load, which worked well. We would have loaded directly if our loader could have gotten high enough to dump the material into the floater.

Water was added and we found that the wetter we could get the ash, the better it would spread. At the driest levels of 1% moisture the material was like throwing flour in the wind. A spread pattern was nearly impossible even though it was only a 1-2 mph breeze. We added enough water to reach levels over 30% moisture and the spread pattern was excellent. The spreading gates had to be opened as far as it would open on an Ag-Chem floater with the web going as fast as it would in order to maintain 8 mph spreading speeds.

The water was added as the truck was loaded at the plant, using a water hose into an auger as the material was augured into the truck. At times, I added too much water and it created “chunking” or globs of ash which became difficult to handle. One should only add enough moisture as can e mixed and distributed properly without the material getting “sloppy”. The ash has such high levels of absorbency that the sloppy ash can not be mixed together with dry ash as we thought, to reach an equilibrium of moist ash. Instead, the sloppy ash held on to all water and wouldn’t allow the dry ash in the truck to take on any moisture, so extreme uneven levels of moisture developed. Although the “sloppy” ash froze up during winter stockpiling; ash levels of over 30% moisture and properly mixed, did not experience any freezing in the stockpile.

Stock piles of the material were made in 3 field locations. The material blew around some, but in general stayed within close proximity. The plant could only process and deliver 45 tons of material per day and a good lime spreader can spread over 300 tons per day so stock piling is necessary in order to have enough ash to bring a spreader to the field.

Stock Pile 1: this pile contained 225 tons of ash and was located in an open bottom. It sat less than 1 week and very little was blown away.

Stock Pile 2: this pile contained 300 tons of ash and was located on the south slope of a hill. It was allowed to sit 2 months. Still, only remnants of ash were found more than 20 feet from the pile. The pile did develop different layers of dryness during the exposure. The top 6” became powdery dry and was best mixed with the more moist material deeper in the pile for spreading.

Stock Pile 3: this pile contained 195 tons of ash and was located on top of a hill and very exposed. It was allowed to site all winter, for nearly 3 months. Ash was found up to 200 feet away in road ditches and we estimated the pile lost 5-10% of the ash to the wind. Although the pile lost material, of the ash blown around, it was mostly just dispersed within the field.

The material seems to have an extreme level of absorbency and the ash exposed to rain and snow will quickly absorb the moisture without allowing it to pass through. Due to the snowfall that hit this pile, the material had absorbed moisture and developed a frozen crust over 4” think that became difficult to break up in order to spread. We couldn’t even break the chunks by driving a heavy tractor over them, so we had to smash them individually with sledge hammers and wrecking bars. The material under the crust was well preserved and easy to spread.

Crop Production Trials:
Two fields were chosen for multi year crop production trials. Only the multi year strips are presented here as we found one year’s data on the large areas to be undependable on just one year’s production. We will continue to track those areas for future years.

We were not able to find any soils in our fields that were deficient in nutrients to more easily observe responses in the application of phosphorus, potassium, and other nutrients. The soils had already tested high to very high in all nutrients. Test areas having consistent ground without know variances were used to get more accurate results.

Yields were tabulated using a GPS yield monitor and the average yield was manually recorded on each round in the test strips. The yield was compared with the adjacent rows and maps were printed detailing the findings.

The soybeans trials received accurate results as the strips were not affected by unusual variances. In both trials, the soybean variety is a public variety designed for food grade purposes, Vinton 81, which yields less than many of the new commercial varieties. In the second year of research, 1999, we did larger areas of 1, 2 and 3 ton per acres application rates within a 200 acre field. We also applied heavy applications on hill tops, side hills, and lighter soil areas hoping for larger responses. We could not see any additional yield responses to the heavier applications or advantages on the lighter soils versus heavier soils.

Trial 1 (exhibit 1), Area, Yield, % Increase (Decrease)
No ash, check, 1.2 acres, 38.3 bu/a
.95 ton/a, 2.4 acres, 44.2 bu/a, 15.4%

Trial 2 (exhibit 2), Area, Yield, % Increase (Decrease)
No ash, check, 4.6 acres, 29.0 bu/a
1 ton/a, 4.6 acres, 35.6 bu/a, 22.8%

In both corn trials, the test strips had variances affecting the test, and the data should be considered inconclusive. In 1998, trial 1, the corn test strip is in the lowest lying area of the field and happened to be right where water sat in the rows for extended times during the early summer from an overabundance of rain. In 1999, trial 2, the entire field with corn test strips were seriously down. Probably 25% of the crop could not be harvested and the yield varied on how well the combine head could pick the corn up. We are going another corn trial this coming year to get a more accurate picture of corn responses to that ash. In the second year of research, 1999, we did larger areas of yield checks at 2 ton and 3 ton rates. Because much of the entire 206 acre field went down, yields were more dependent on if the area was exposed to wind instead of ash, and was impossible to get a true reflection on the ash applications.

Trial 1 (exhibit 3), Area, Yield, % Increase (Decrease)
No ash, check, 2.4 acres, 126.4 bu/a
.6 tons/a, 2.8 acres, 118.5 bu/a, 6.3%

Trial 2 (exhibit 4), Area, Yield, % Increase (Decrease)
No ash, check, 1.4 acres, 163.6 bu/a
1 ton/a, 2.4 acres, 151.6 bu/a, 7.3%

Ash Analysis:
The ingredients in the ash important to crop production are the major nutrients nitrogen, phosphorus, potassium, and the trace nutrients sulfur, magnesium, manganese, and zinc. The laboratory analysis of the ash in order of ingredient percentage from highest to lowest is as follows:
Component, % Weight, lb/ton of ash
Silica, SiO2, 72.49%, 1449.8 lb
Potassium Oxide, K2O, 7.42%, 148.4 lb
Carbon, C, 8.39%, 167.8 lb
Calcium Oxide, CaO, 3.09%, 61.8 lb
Phosphorus Pentoxide, P2O5, 2.69%, 53.8 lb
Magnesia, MgO, 2.22%, 44.4 lb
Alumina, Al2O3, 0.90%, 18.0 lb
Sodium Oxide, Na2O, 0.83%, 16.6 lb
Sulfur, S, 0.62%, 12.4 lb
Ferric Oxide, Fe2O3, 0.46%, 9.2 lb
Sulfur Trioxide, SO3, 0.26%, 5.3 lb
Hydrogen, H, 0.21%, 4.2 lb
Nitrogen, N, 0.16%, 3.2 lb
Manganese Oxide, Mn3O4, 0.14%, 2.8 lb
Barium Oxide, BaO, 0.14%, 0.8 lb
Titania, TiO2, 0.02%, 0.4 lb
Strontium Oxide, SrO, 0.01%, 0.2 lb

The ash comes out of the plant very dry, lab analysis shows 1.35% moisture. Even with water added, density is extremely light compared to lime, dry fertilizer, and other common ag materials:

Material, lb/cubic foot
Stalk Biomass Ash, 20% moisture, 36
Lime, 80
Potash Dry Fertilizer, 70
Phosphate Dry Fertilizer, 60

Soil Responses:
Responses in soil nutrients were determined from two year’s applications of biomass ash. In general, pH, P, K and Zn were noticeably higher after the applications. The west test strip had soybeans grown in 1998 and corn in 1999. The east test strip had corn in 1998, followed by soybeans in 1999. My interpretations of the results are:

West test, East Test
pH, same, higher
P, higher, higher
K, higher, higher
CEC, lower, lower
S, higher, same
Zn, same, higher
OM, same, lower

In the attached soil test results, the maps are in the same order as the nutrients are listed in the above chart. The first page of each nutrient was taken in the fall of 1997, before the test began, and the second map of each nutrient was taken in the spring of 1999, after two year’s of biomass applications.

[Editor’s note: There are charts, maps and graphs that could not be posted online. If you would like to see these please email us at [email protected] or call us at 800-529-1342. Thanks]

Environmental Effects:
It appears the stalk biomass ash may be legally classified as “crop residue” which has no limits or restrictions on land applications, or “solid waste” which can be applied up to 2 tons per acre without special permit. I met with Mr. Paul Lundy from the Iowa Department of Natural Resources and received approval for the test as a safeguard. Chapters 120 and 121 of Title IX, Land Applications of Sludge and Solid Waste, Section 567, Environmental Protection of the Iowa Code, details the legal limits of ingredients and waste products. The Solid Waste Section Supervisor has considered the chemical analysis of the biomass and determined no potential hazard or harmful effects from reasonable land applications for agriculture purposes.

The material leaves a black covering which melts through snow fairly soon because of the light absorbency by black colored products. The biomass ash also stays with the soil similar to lime left on the surface without any visible runoff or loss in the wind.

Future Source of Biomass Ash
During the two year trials of this project, the processing plant was owned by the Great Lakes Chemical Corp. of Indiana, which had a major fire at the Harlan collection plant and much of the corn stalk inventory was destroyed. The Omaha processing plant and Harlan collection plant were both sold to Penn Specialties Chemical, of Pennsylvania, which then filed bankruptcy and now production is suspended until a new owner can be found for the Omaha furfural processing plant. The Harlan stalk collection plant is being operated by a group of farmers that have banned together to harvest corn stalk bales and find markets for them. Only one of the potential markets is for furfural.

The Omaha plant, currently sitting idle, has the potential to use oat hulls, rice hulls, cobs and other by product ingredients to extract furfural. The biomass ash from those materials will be similar to that of corn stalk ash. Officials with the plant have commented that having agriculture land applications for the ash instead of landfills will help the economics of the furfural production by saving $7-$8/tom landfill charges. This would also eliminate the company’s concern of having access denied to landfill dumping by the state.

If, and when the Omaha plant resumes operations, it will be back on track to dispose of over 11,000 tons of biomass ash. Plant officials feel new owners would strongly encourage immediate agriculture outlets for the biomass material.

From this 2nd year research effort we conclude:
1) A soybean yield response of over 10% form the application of at least 1 ton/acre of corn stalk biomass ash
2) The best methods for handling corn stalk biomass ash are those used for lime. This includes, dump trucks for hauling, belt conveyors for loading, and wide web lime spreaders for spreading.
3) Levels of phosphorus and postassium can be expected to increase with the applications of at least 1 ton/acre of corn stalk biomass ash.

On a farm visit by Dr. Stan Henning, Iowa State University’s expert on uses of biomass, he commented the nutrients in the broken down ash is in a more available form of phosphorus, potassium, and other nutrients than the synthetic forms such as crushed phosphates or potash.

Because of environmental influences, the corn trials thus far, are inconclusive. The soybean and soil test results are credible. Other plants processing biomass materials similar to stalks, cobs, and oat hulls, can utilize the research and recommendations presented here.

Biomass ash should be spread soon after hauling if possible. If stock piled during frozen temperatures, spreading should until warmer weather. The material must have water added to achieve good spreading patterns. Compared to lime spreading two thirds the width is achieved.

Our test show 1 ton per acre application rates achieve maximum production results. Since the material appears to have no properties to hinder production, it may be most economical to apply at heavier rates so material is available for future year’s production and save the reapplication costs.

Some stockpiling is required because the plant must operate year round and spreading can only take place when the crop is out. Stockpiling in the field on headlands in bottoms or areas not highly exposed to wind would work best for spreading after harvest. An old silage pit would also be an excellent place to put the ash to limit exposure to the wind. Covering ash would prevent frozen crusts to develop in freezing temperatures or a dried outer layer during warmth but not necessary if the ash is spread during above freezing temperatures and is probably not economical.

A fact sheet will be available as a quick reference for farmers to get information on where to acquire biomass ash, how to handle it, and what to expect from the applications of the ash. Fact sheets will be available from the Shelby County Extension Service, Dave Reinig Farms, and the SARE program, scheduled for release in conjunction with the press release.

The research and trials have been documented on video tape. The tape is being professionally edited and will be available to the public July 1, 2000. The tape is also designed to be used by the company, or other companies, at open houses and other public outreach events to demonstrate to farmers how the biomass material can be acquired, handled, applied and at recommended rates. The new buyers of the Omaha plant will have access to the video for these purposes.

Press releases will be sent to selected farm publications July 1. July 1st has been chosen so the media has ample access to the research cooperator, Dave Reinig, who will be done with his busiest time of the crop production cycle. By July, the Omaha plant may have reopened by then giving access to ash so media that would like first hand viewing of the biomass ash spreading process will be able to do on trials with CRP ground.

Media targeted for press releases include the Des Moines Register, Omaha World Herald, Iowa Farmer Today, Successful Farming, Soybean Digest, and Farm Journal. Tapes and fact sheets can be requested from the Shelby County Extension Service, 1105 8th St, Harlan, IA 51537, phone: 712-755-3208; David Reinig Farms, 629 1100th St, Portsmouth, IA 51565, and at the SARE office, North Central Region.


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.