At the 2026 GEAPS Exchange, I was honored to speak on a panel focused on what’s next in grain processing. Are we facing a wave of new coproducts from both the corn and soybean industries as new soy crush facilities come online and E15 and SAF requirements grow? Perhaps. We need to prepare now. We’ve actually been here before, and we know what to do. In this article, I will discuss various aspects of corn coproducts — specifically from the corn ethanol industry.
1. Introduction
Corn-based ethanol production generates valuable feed coproducts that directly link renewable fuel manufacturing with animal agriculture. Distillers dried grains with solubles (DDGS) and emerging varieties of high-protein distillers grains (HP-DDG) represent concentrated sources of protein, energy, fiber, phosphorus and other nutrients. These ingredients play a major economic role for ethanol plants and serve as cost-effective feed components for ruminant and nonruminant livestock.
It is important to consider current knowledge regarding nutrient composition, digestibility, variability, feeding value, economics, sustainability and logistics. We must also consider remaining technical challenges and market questions that must be addressed to improve alignment between ethanol producers and livestock end users — especially as the supply of coproducts grows. While the ethanol industry produces more than just DDGS and HP-DDG, this article focuses only on these two product types.
Over the past few decades, the dry-grind ethanol industry has transformed corn from a traditional feed grain into a multioutput industrial commodity. While ethanol is the primary product, coproduct streams represent a significant portion of plant revenue and overall system sustainability. DDGS emerged as the dominant coproduct during the rapid ethanol expansion in the 2000s. More recently, technological innovations in fractionation have produced a variety of high-protein distillers grains with altered nutrient profiles and potentially improved suitability for monogastric species.
For ethanol producers, coproduct optimization improves plant margins, reduces financial risk and diversifies revenue streams. For livestock producers, DDGS and HP-DDG can provide economically competitive sources of digestible nutrients — depending on the cost of competing ingredients, primarily soybean meal. The interdependence of these industries creates both opportunities and challenges in standardization, quality control and market development.
2. Production Pathways and Product Types
Traditional DDGS is produced through dry-grind processing. Corn is ground, liquefied, enzymatically hydrolyzed and fermented to convert starch into ethanol. Following distillation, the remaining solids and solubles are centrifuged, recombined and dried to produce DDGS. During fermentation, nonstarch nutrients are concentrated approximately threefold relative to the original grain.
High-protein DDG products, however, arise from fractionation technologies that separate fiber or protein either before or after fermentation. Front-end fractionation removes fiber prior to fermentation, while back-end fractionation concentrates protein from post-fermentation streams. These technologies create differentiated coproducts with protein concentrations typically ranging from 40% to 50% crude protein (dry basis), compared with 26% to 32% for conventional DDGS.
3. Nutrient Composition and Variability
Traditional DDGS typically contains 26% to 32% crude protein, 6% to 12% fat (depending on oil extraction), 28% to 35% neutral detergent fiber and 0.6% to 0.9% phosphorus. Sulfur levels can range from 0.3% to 0.8%, reflecting sulfuric acid use during processing. High-protein DDG generally contains 40% to 50% crude protein, lower fiber (15% to 25%) and reduced fat content. Fractionation typically leads ethanol plants to sell high-fiber streams as a new coproduct used in ruminant diets.
Despite improved processing controls, interplant variability remains a significant challenge. Variability may stem from differences in corn quality, enzyme systems, fermentation efficiency, oil extraction rates, drying temperatures and blending ratios of solubles. Coefficients of variation for fat content are often higher than for crude protein, reflecting differential oil removal practices.
From a livestock producer standpoint, nutrient variability complicates ration formulation. Accurate and timely nutrient analysis — preferably plant-specific — is increasingly important for precision feeding systems. New coproduct streams, such as various HP-DDG and fiber streams, can also create confusion for livestock producers, making clear guidance imperative.
4. Digestibility and Feeding Values
Ruminant Systems
For beef and dairy cattle, DDGS provides rumen undegradable protein (RUP), digestible fiber and energy. Inclusion rates commonly range from 10% to 40% of diet dry matter in feedlot systems. Phosphorus bioavailability is high, reducing supplemental mineral needs. Dairy responses vary with fat concentration and inclusion rate but generally support milk yield when diets are properly balanced. Oil separation over the past decade has also allowed greater inclusion levels.
Swine and Poultry Systems
For monogastric species, fiber content can limit inclusion levels of traditional DDGS. Standardized ileal digestibility (SID) of lysine may range from 55% to 70% in conventional DDGS, depending on heat damage during drying. High-protein DDG products often demonstrate improved lysine digestibility (70% to 85%), potentially making them more attractive for swine and poultry diets. However, more research is needed to fully understand whether HP-DDG consistently achieves these benefits.
Enzyme supplementation and advanced formulation strategies have increased feasible inclusion rates. Nevertheless, amino acid variability and potential heat damage during ethanol processing remain areas requiring attention. Limited research suggests HP-DDG can be used at higher levels than traditional DDGS, but further feeding trial research is required to understand how to optimize use of these ingredients and whether cost savings can be achieved.
5. Economic Considerations
Ethanol Producer Perspective
Coproduct revenue often accounts for 25% to 40% of total ethanol plant income. Upgrading coproducts through fractionation can enable access to higher-value feed markets and export channels. Market premiums for high-protein products can justify capital investment in fractionation systems.
However, differentiation requires consistent quality assurance, marketing infrastructure and customer trust. Ethanol plants must balance capital investments in new technologies and energy costs associated with drying against shelf stability requirements and transportation efficiency. More feeding trials are also necessary to fully understand the value of these products to livestock producers.
Livestock Producer Perspective
Livestock producers evaluate DDGS relative to corn and soybean meal prices — the two most common competing ingredients. Value depends on digestible amino acids, metabolizable energy and phosphorus contribution, even though coproducts are often priced on protein-fat (e.g., pro-fat) levels. Transportation distance from ethanol plants can substantially influence delivered cost.
Producers seek predictable nutrient supplies, low mycotoxin risk, manageable sulfur levels and consistent physical handling characteristics. Flowability and bulk density affect storage and mixing behavior in feed mills and on-farm systems. New HP-DDG products remain largely unstudied in terms of flowability characteristics.
6. Sustainability and Environmental Considerations
Life cycle assessment studies consistently show DDGS can displace conventional feed ingredients — primarily corn or soybean meal — reducing the net greenhouse gas intensity of ethanol production. Allocation methods vary, but coproduct credits can substantially improve carbon intensity scores, as can carbon capture and sequestration.
From the livestock perspective, nutrient recycling can enhance resource efficiency. However, phosphorus and nitrogen excretion must be managed to avoid environmental impacts in farm fields. Integrated crop-fuel-livestock systems offer potential synergies when manure nutrients are returned to corn production fields.
7. Logistics and Handling
DDGS is hygroscopic and prone to caking under high-humidity conditions. Flowability challenges can arise during rail or truck transport. Variability in particle size and fat content influences handling characteristics. This is true for both traditional DDGS and HP-DDG products.
Ethanol plants must optimize drying temperatures to ensure shelf stability while avoiding excessive heat damage. Livestock producers require proper storage conditions to maintain feed quality.
8. Remaining Research Questions
Although many feeding trials and other research studies have been conducted over the past few decades, relatively little work has been pursued on HP-DDG products. Several research priorities include:
- Feeding recommendations and long-term animal performance data for emerging fractionated coproduct streams.
- Standardization of high-protein DDG definitions and labeling conventions.
- Improved real-time nutrient analysis technologies at the plant and feed mill levels.
- Expanded digestibility datasets across species and processing technologies.
- Enhanced understanding of sulfur metabolism and mitigation strategies in ruminants.
- Improved predictive models for mycotoxin concentration during fermentation.
- Refined life cycle accounting methods for coproduct allocation.
9. Strategic Alignment Opportunities
Closer collaboration among ethanol plants, animal nutritionists and academic researchers can reduce uncertainty and increase value capture for both HP-DDG and traditional DDGS. Shared data platforms, precision feeding integration and standardized reporting systems could improve market transparency.
Emerging carbon markets and sustainability verification programs may further reward integrated systems if coproduct nutrient recycling and emission reductions are accurately quantified.
10. Conclusions
DDGS and high-protein DDG represent critical linkages between renewable fuel production and animal agriculture. Considerable knowledge already exists regarding nutrient composition, feeding value and economic importance for traditional DDGS. However, the story is not yet complete.
Variability, digestibility precision, sustainability accounting and market standardization remain areas requiring continued research and industry coordination to better utilize DDGS and other ethanol coproduct streams — particularly if supply increases.
The long-term success of corn coproducts will depend on transparency, technological innovation and sustained collaboration between ethanol producers and livestock end users. Evolving HP-DDG products require considerably more research for livestock producers to fully understand their characteristics and optimal use. They must also provide economic benefits, including gains in feed efficiency. Achieving similar performance alone is not enough to justify purchasing more expensive ingredients or making capital investments at ethanol plants.
Hopefully, this discussion has been thought-provoking. In my next article, I will discuss coproducts from the soy industry.
Kurt A. Rosentrater, Ph.D., is a professor in the Department of Agricultural and Biosystems Engineering at Iowa State University, Ames. He can be contacted at karosent@iastate.edu or 515-294-4019.