ISTC researchers develop greener biofuels process

tall green grass

Kirtika Kohli and BK Sharma have been busy in the lab creating a greener delignification method for biofuels refinery processes. Many see biofuels as a viable alternative to fossil fuels because they are renewable and can reduce carbon emissions through plant growth. However, biomass needs to be processed before it can be converted to biofuels.

Lignin is a substance found in plants that makes them rigid and woody. Lignin helps plants resist rotting, so biomass harvested for biofuels must undergo a pre-treatment process to break down the lignin. Once lignin is removed, the remaining biomass could be easily converted to monomeric sugars, which can  be converted biochemically into biofuels and other components in a biorefinery. With some additional refinement, the extracted lignin has the potential to be used in other applications in biofuels, biolubricants, polymers, binders, and biochemicals.

Current delignification processes have limited industrial applications because of their high costs, toxicity, and inability to recycle/reuse the chemicals used in the process. The team’s new method is more efficient, economic, and less toxic than current processes. It should ease operation/maintenance requirements and the need for special equipment as well as increase cost-effectiveness and recyclability. Their process is able to extract 85-88% of the lignin from Birchwood and Miscanthus (the two biomasses tested).

The team also developed a new lignin quantification method. The delignification process developed dissolves lignin into a green solvent that can be directly used for the quantification using a UV-Vis spectrophotometer. This new method is easier and more accurate than older lignin quantification methods, which were based on weight of the lignin yields that resulted in rough estimates.

Their paper is in-press and available online in Bioresource Technology: Effective Delignification of Lignocellulosic Biomass by Microwave Assisted Deep Eutectic Solvents.

New publication: Advancing Pilot-Scale Integrated Systems for Algal Carbon Capture and Biofuel Production

In this research study, funded by ISTC’s Sponsored Research Program, Lance Schideman and his team partnered with Abbott Power Plant and the Urbana & Champaign Sanitary District to address critical challenges to practical demonstrations of biological CO2 capture systems and subsequent thermochemical conversion of biomass to biofuels.

The researchers developed the capability to harvest and store actual power plant flue gas samples in pressurized cylinders, then used these samples to study acclimation in algae cultivation systems dosed with flue gas. The project also demonstrated the use of anaerobic digestion to recover residual energy from the aqueous byproduct of hydrothermal liquefaction (HTLaq), which is generated during the conversion of algae or other organic feedstocks to biofuels.

This study showed that mixed culture algae are capable of using CO2 in flue gas, and the impact of the flue gas on algal growth rates was positive. Because higher flue gas injection rates resulted in higher productivity and lower CO2 removal efficiency, higher flue gas injection rates are preferable when the CO2 source is cheap and algae are considered the main product. Low flue gas injection rates would be preferable when the CO2 source is expensive or the CO2 removal efficiency is important. Heavy metal analysis showed that algal biomass will accumulate Zn, Pb, and Cu from flue gas, which can exceed certain animal feed regulatory limits.

This work also demonstrated that anaerobic treatment of HTLaq in combination with sewage sludge is feasible in both lab- and full-scale applications, which highlights the potential for enhancing energy recovery from sewage sludge through integration of hydrothermal liquefaction  (HTL) technology with municipal wastewater treatment. Overall, this study highlights that integrating HTL technology with existing municipal sludge anaerobic digesters could significantly improve the bioenergy production of municipal wastewater treatment systems by 50 to 70% at a cost that is favorable compared to other alternatives.

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Biomass research is heating up

There aren’t many ancient practices that still have a place in the 21st century. One exception is the burning of biomass, which is organic matter that can be used as fuel, like grass or wood. Biomass is made up of plant material that absorbs the sun’s energy through photosynthesis. When it’s burned, the chemical energy is released as heat. Biomass can be burned directly or converted to liquid biofuels or biogas that can also be burned as fuel.

On July 18th, ISTC researchers B.K Sharma and Sriraam Chandrasekaran held an open house to demonstrate a biomass system they’ve developed with funding from the Illinois Department of Transportation. The project’s goal is to create a renewable, carbon-neutral heating system. The demonstration was organized to raise community awareness about biomass, as well as ISTC’s renewable energy research.

The project uses waste grass that has grown along highways in Illinois to power a combustion heating system. Currently, the system is being used to heat greenhouses, but the researchers believe this technology has the potential to become able to heat even larger spaces. The researchers estimate that the project will save $3 million in public funds by harvesting the biomass for energy. Chandrasekaran says that he believes the possibilities of using biomass as an energy source are endless.

Collection, production, storage, transportation, and the environmental impact of the biomass all need to be carefully evaluated before it becomes marketable. Sharma and Chandrasekaran are interested in discovering which species of plants will produce the maximum amount of efficiency per pound. They are also researching the pelletizing ability of the grasses.

There are some downsides to burning biomass. The sustainability of the energy created depends on the carbon emissions produced during the entire lifecycle of the feedstock. Variables include the type of feedstock, the manner in which it is harvested, and the scale and technology used to convert the feedstock to energy.

This project has made great strides in three years. The efficiency of the combustion and boiler is near 80 percent, compared to other systems that average just under 50 percent. Research is heating up. Burning biomass is a technology from the past that will continue to be useful in the future.