Green technology uses corn stover to produce high-value bioderivatives and generate savings

In a study published in the Biofuel Research Journal, researchers affiliated with the State University of Campinas (UNICAMP) and the Federal Technological University of Paraná (UTFPR) in Brazil evaluated the efficiency and environmental impact of using corn stover with a technique that uses pure water as the only solvent for extracting bioderivatives.

Corn stover, an abundant agricultural by-product often discarded, is rich in lignocellulosic compounds, such as hemicellulose, cellulose, and lignin.

In the work, which is the result of the doctoral research of Rafael Gabriel da Rosa, the group of scientists extracted sugars, organic acids, and phenolic compounds with antioxidant, anti-inflammatory, and antimicrobial properties from this waste, optimizing the process parameters by using hydrolysis (the breakdown of large molecules into smaller ones) with “subcritical water” (at a high temperature and under high pressure to prevent boiling) instead of acid hydrolysis. This breakthrough is useful for applications in the food, pharmaceutical, and biofuel industries.

The production of each by-product depends on variations in temperature and pH, following a decomposition sequence that starts with phenolic compounds, passes through sugars, and ends with organic acids.

The results showed a significant recovery: subcritical hydrolysis was able to obtain phenolic compounds ranging from 16.06 milligrams to 76.82 milligrams of gallic acid equivalent per gram (the standard for quantifying phenolic compounds). In contrast, acid hydrolysis obtained 12.76 milligrams of gallic acid equivalent per gram.

In the case of sugars (glucose, xylose, and cellobiose), 448.54 milligrams were obtained per gram of corn stover hydrolyzed at 170 °C for a maximum of 30 minutes at a pH of 1. Traditional hydrolysis methods do not exceed 74.5 milligrams per gram of hydrolyzed stover. Thus, the yield increases six-fold while reducing time and energy costs.

Finally, in the case of organic acids (acetic and formic), 1,157.19 milligrams were obtained per gram of hydrolyzed corn stover at 226 °C and a pH of 4.5. “This extraction of organic acids represents a concrete opportunity for producing renewable chemical precursors for use in biodegradable plastics, solvents, and natural preservatives,” says Tânia Forster-Carneiro, Rosa’s advisor, co-author of the article, and professor at UNICAMP’s School of Food Engineering (FEA).

Sustainable method

The researchers also carried out a sustainability analysis of the technology, called EcoScale. This is a semi-quantitative metric for assessing chemical reaction conditions on a laboratory scale. The tool can assess the environmental, economic, and social impacts of a process or technology.

It uses a scale from 0 to 100, with 0 representing a totally failed reaction (0% yield) and 100 representing the ideal reaction: compound A (the substrate) reacts with (or in the presence of) cheap compound B to produce the desired compound C with a yield of 100%, at room temperature, with minimal risk to the operator and minimal environmental impact.

“Our result was surprising: the method scored 93 points,” celebrates Forster-Carneiro. Other processes that use aggressive chemicals, such as sulfuric acid and sodium hydroxide, scored between 54.63 and 85.13 points.

According to the scientist, another novel aspect of the study was the preliminary technical-economic analysis (or payback rate), which integrated experimental data with estimates of investments, operations, and economic returns. This analysis took into account factors such as the cost of equipment, inputs, and energy.

“The analysis provides a strategic vision for decision-making, simulates different scenarios, and identifies the most promising ones for industrial application, strengthening the link between science, innovation, and practical application,” explains Forster-Carneiro.

The work focused on sugar as the end product with the greatest economic value for biofuels. The results showed a payback period of between four and five years.