Biorefinery of Agricultural Residues (Corn Stover)

Biorefinery of Agricultural Residues (Corn Stover)

Biorefinery of Agricultural Residues (Corn Stover)


Biorefining is an efficient and innovative approach to sustainable biomass processing into a wide variety of bio-based marketable products/biofuels together with chemicals, pharmaceuticals, and many more. To date, there are more than 100 commercial, pilot and demonstration biorefinery facilities globally (IEA, 2019).

The biorefinery industry converts bio-based materials like agricultural residues into high-value products such as chemicals, fuel, feed, food and energy. The conversion process in the biorefinery industry includes pyrolysis, gasification and liquefaction. In pyrolysis, bio-oil/ pyrolysis oil is produced by heating biomass without oxygen, which is further processed to produce chemicals and fuels. The gasification process converts carbon-rich feedstock into syngas into high pressure, high heat and oxygen-depleted conditions. Direct liquefaction produces liquid fuel without the formation of syngas. 


Corn Stover as a Feedstock for Biorefinery Industry

Agricultural wastes, also known as lignocellulosic residues, such as stalks, straw residues, roots, leaves, corn stover, are produced by Agri-food industries. These residues have high application potential in biorefinery since they are primarily available and do not interfere with the food supply (Taherzadeh and Karimi, 2007).

Some of the potential agriculture residual biomass feedstock with their composition and yields based on the dry mass is presented in Table 1 (Schon, 2012). Using these residues as feedstock provides an additional economic benefit as these do not require an extra piece of land to grow and come as a byproduct with some valued products.

Table 1: Composition and Biofuel Yield of feedstock


Residue/crop ratio

Corp Dry Matter (%)

Lignin (%)

Carbohy-drates (%)

Biofuel yield (L/Kg of dry biomass)

Yield (Kg/ha)

Biofuel yield (lt/ha)

Barley Straw








Corn Stover








Rice Straw








Sorghum Straw








Wheat Straw








Sugarcane bagasse









In this article, we will discuss corn stover as a feedstock for biofuel production. The residue left over after harvesting the corn grain is known as corn stover. It is estimated that around 50 percent by weight of the whole corn plant is its residue, consisting of stalk, cob, leaf and husk (Gould, 2007). It has been identified as a valuable feedstock for bioenergy and bio-product production due to its abundance and low price (Lazarus, 2008). Although the nutrients and the theoretical ethanol yield potential of the corn stover differ concerning climate and location, the above-ear part of the corn-stover is the most suitable biomass for ethanol production despite its growing area. Moreover, compared to overall harvesting of stover biomass, harvesting only above ear stover fractions would reduce nutrient removal by 21 to 61 percent (Mourtzinis et al., 2016).


Global scenario of Corn Stover generation and its utilization for biofuel production

The United States was the largest corn producer worldwide in 2019/2020, with approximately 345.89 million metric tons, followed by China (260.77 million metric tons) and Brazil (101 million metric tons). The other countries in the list in descending order include European Union (66,665 metric tons), Argentina (50,000 metric tons), Ukraine (35,887 metric tons), India (28,900 metric tons), Mexico (25,000 metric tons), South Africa (16,250 metric tons) and Russia (14275 metric tons) (Statista, 2021).

With this increasing corn production, the corn residue has increased. Corn stover is the largest biomass source in the United States for biofuel production, with approximately 75 percent of the total agricultural residue in the country (Xiong et al., 2010). Therefore, the first commercial-scale cellulosic biofuel plants, i.e., DuPont in Nevada and POET plant in Emmetsburg, has targeted corn stover as their feedstock (Edwards et al., 2012).


Challenges to use Corn Stover as a feedstock

Converting the lignocellulosic feedstock to the biofuels is not an easy task. During the process, several challenges occur in capital investment, feedstock properties, and harvesting, implementing efficient technologies for biofuel production, coproducts generation and biofuel distribution. Some of the challenges of using corn stover for biofuel production are described as below:


High Capital Cost:

Considering the energy equivalence, the energy production from second-generation biofuels such as corn stover is up to three times costly than that of petroleum fuels. Utilizing corn stover incurs high costs during the process of harvesting, transporting and storing. 



The technical status of integral biorefineries for pretreatment, conversion, extraction and separation technologies is still non-commercial (IEA, 2019).


Biomass harvesting:

Agri-residues are generally harvested by baling using large machinery, and this process of residues harvesting is very energy-intensive. Corn stover with moisture content higher than 30 percent decreases bales' baling efficiency and storability because of the increased risk of rotting and moulding. Unlike other biomass such as grass hay, the corn stover material can cause more significant wear and tear on harvesting equipment (Gould, 2007). Additionally, biomass-harvesting process such as bailing is also associated with soil contamination, as the baler would pick up more soil during the harvesting process. Thus, the harvesting methods should be accustomed to mitigating soil contamination before scaling up the stover harvest for commercial-scale biofuel production (Schon, 2012).


Feedstock Properties:

Moisture content, ash, and material composition are some of the properties that define feedstock quality. The moisture content of the corn stover should not be more than 30 percent for ideal harvesting (Gould, 2007). It is estimated that corn stover has 8.1 percent ash content on a dry basis (Wang et al., 2011). Higher ash content causes fouling, slagging, and corrosion problems during the conversion process, thereby increasing economic and processing complications due to the high pretreatment cost. 


Coproducts generation:

Corn stover conversion to ethanol does not produce valuable coproducts, unlike cornstarch ethanol, bringing additional economic benefit.


Environmental Issues:

Unsustainable harvesting of corn stover can lead to soil erosion as well as soil organic matter and carbon depletion. Depending on several factors, the return rate of the corn stover into the field to maintain the soil quality varies. Nevertheless, it has been recommended to return 3.5 tons per acre of stover in a soybean corn system and 2.3 tons per acre in a continuous corn system without tillage (Roth, 2019).


A study conducted by Edwards et al. (2012) has outlined the top ten potential challenges of corn stover producers for its marketing, presented in Table 2. These challenges are given a score on a scale of 1 to 7. Score 1 indicates "Not concerned", and score seven means "very concerned".


Table 2: Top 10 Potential Challenges of Corn Stover Producers for its marketing


Average Rating

Nutrient loss


Distance to markets


Long-term biomass market viability


Biomass price volatility


Soil erosion issues


Percent of biomass removed


In-field transport and compaction


Contract opt-out clauses


Contract terms of storage


Residue management



Impact of stover use on productivity and soil quality

Agricultural residues have numerous advantages on productivity and soil quality when returned to the soil. Despite having many benefits when used as a second-generation energy fuel, corn stover harvest might have a detrimental to slightly positive impact depending on the microclimate of the area, soil, and the other agri-residue management practices followed.  A low return of corn stover in the agricultural field may increase soil erosion, decrease soil quality, reduce productivity, and trigger short-term yield responses. Johnson et al. (2013) conducted a study to measure the initial impacts of three corn stover return rates, i.e. total (~ 7.8Mg/ha/yr), medium (~3.8 Mg/ha/yr) and low (~1.5 Mg/ha/yr) on a chisel-tilled field and no-tilled newly (NT 2005) and well (NT 1995) established area. The result shows that the corn and soybean yields were affected under well-established no-tilled (NT 1995) filled. In this case, the low return reduced the yields (2.88 Mg/ha) compared to the medium and total return (3.13 Mg/ha). Additionally, the return rates also had impacts on soil organic matter and acid phosphatase activity. The study concludes that the short-term effect of Stover harvest on the crop yield might be shallow but observed delicate changes on soil, which indicates the possibility of substantial negative consequences over time with repeated harvest (Johnson et al., 2013).



Lignocellulosic biomass produced by Agri-food industries is a good source for the biorefinery process. Corn stover is one of the potential sources for biofuel production. To fully utilize the corn stover as feedstock for biofuel production, different issues such as high cost, pretreatment and conversion process, harvesting etc., need to be addressed. Unsustainable harvesting of corn stover can lead to soil erosion and soil organic matter, and carbon depletion.

  • Memory Quiz


Edwards, W., Hart, C., & Leibold, K. (2012). Economics of corn stover. Integrated crop management conference - Iowa State University

Gould, 2007. Corn Stover Harvesting. Michigan State University. 12(2):1-2.

IEA, 2019. Bioenergy Annual Report.

Johnson, J. M., Acosta-Martinez, V., Cambardella, C. A., & Barbour, N. W. (2013). Crop and soil responses to using corn stover as a bioenergy feedstock: Observations from the northern US Corn Belt. Agriculture3(1), 72-89.

Lazarus, W. F. (2008). Energy crop production costs and breakeven prices under Minnesota conditions (No. 1701-2016-139034).

Mourtzinis, S., Cantrell, K. B., Arriaga, F. J., Balkcom, K. S., Novak, J. M., Frederick, J. R., & Karlen, D. L. (2016). Carbohydrate and nutrient composition of corn stover from three southeastern USA locations. Biomass and Bioenergy85, 153-

Roth, G. (2019). Corn Stover for Biofuel Production.

Schon, Brittany Nicole, (2012) "Characterization and Measurement of Corn Stover Material Properties". Graduate Theses and Dissertations. 15860.

Statista, 2021. Global corn production in 2019/2020, by country.

Wang, L., Shahbazi, A., & Hanna, M. A. (2011). Characterization of Corn Stover, Distiller Grains and Cattle Manure for Thermochemical Conversion. Biomass and Bioenergy, 35.1, 171-78.

Xiong, S., Ohman, M., Zhang, Y., & Lestander, T. (2010). Corn Stalk Ash Composition and Its Melting (Slagging) Behavior during Combustion. Energy & Fuels, 24, 4866-871.