How preprocessing methods affect the conversion efficiency of biomass energy production

October 11, 2019

URBANA, Ill. ¬- Research on energy production from biomass usually focuses on the amount of energy generated. But it is also important to consider how much energy goes into the process, a component that is often neglected, says Tony Grift, professor of Agricultural and Biological Engineering in the College of Agricultural, Consumer and Environmental Sciences and the Grainger College of Engineering at the University of Illinois.

Grift is co-author on a new study, published in Bioresource Technology Reports, that takes a look at the bioconversion efficiency of two products often used as biomass for energy production, miscanthus giganteus and sugarcane bagasse.

"Our goal was to determine how much energy it takes to prepare these materials. It's a comprehensive look at various preprocessing methods and their relationship to conversion efficiency," he explains.

The two materials were chosen because of their importance for energy production. Miscanthus is typically grown as an ornamental crop, but it has a high amount of biomass and grows easily with very little nitrogen use. Sugarcane bagasse is the byproduct left over after sugarcane is crushed to extract the juice for sugar.

The study was done in collaboration with chemists from University of California at Berkeley. Grift says the interdisciplinary approach makes the research unique, because it considers the whole energy balance. The U of I researchers studied the energy expenditure of harvesting and preprocessing materials, while the Berkeley chemists focused on converting the biomass to glucose, which is used to make ethanol.

The researchers defined the percentage of inherent heating value (PIHV), which measures the amount of energy going into and out of the production process. "It tells you that you have a certain amount of biomass, which contains a certain amount of energy. How much energy do you spend on processing? You don't want to spend more than 5% of the total energy value," Grift says.

The researchers subjected the two materials to nine different preprocessing methods, either separately or as a blend. Preprocessing is done for various reasons, Grift explains. After the crop is harvested, it needs to be transported to a processing plant, and to make transportation efficient, the material first undergoes a process called comminution, in which is it chopped or cut into smaller pieces, and then it is compressed.

Grift explains that harvesting and compression do not add much to the energy equation. The main source of energy expenditure is comminution, or size reduction. That brings the energy expenditure to 5%. "Smaller particle sizes make compression easier," he says. "It's also better for energy production, because it provides a larger surface area for enzymes to attach to in the conversion process. But comminution takes a certain amount of energy, so there is a tradeoff."

The preprocessing methods included chopped and cut stems, pelletization, comminution, and various levels of compression. Of the nine treatment groups, five included miscanthus, three included sugarcane bagasse, and one included a blend of the two products. The processed materials were all subjected to the same chemical processes to release the glucose.

The researchers also evaluated the effects of particle size, compression level, and blending on biomass conversion efficiency. The results showed that comminution had a positive effect on the efficiency of miscanthus but not sugarcane bagasse, while the opposite was the case for pelletization. The researchers also found that a 50/50 blend of the two materials had higher conversion efficiency than sugarcane bagasse, but there was no significant difference compared to miscanthus alone.

The results can be used to help make biomass energy production more efficient, Grift says.

"The differences are not huge. But if you want to do something on a larger scale it's actually quite important to figure these things out," he explains.

Grift emphasizes that the results are preliminary and should be examined in further studies.

Continued research is needed to substantiate the findings and to broaden the knowledge base to other products and other preprocessing methods.
-end-
The article, "Measuring the influence of biomass preprocessing methods on the bioconversion efficiency of miscanthus giganteus and sugarcane bagasse," is published in Bioresource Technology Reports. Funding was provided by the Energy Biosciences Institute.

Authors include Zewei Miao, formerly a postdoc research associate at the U of I, now at Bayer Company, Stefan Bauer and Ana B. Ibáñez, University of California at Berkeley, and Tony Grift, Department of Agricultural and Biological Engineering and Grainger College of Engineering, U of I.

University of Illinois College of Agricultural, Consumer and Environmental Sciences

Related Biomass Articles from Brightsurf:

Bound for the EU, American-made biomass checks the right boxes
A first-of-its-kind study published in the journal Scientific Reports finds that wood produced in the southeastern United States for the EU's renewable energy needs has a net positive effect on US forests--but that future industry expansion could warrant more research.

The highest heat-resistant plastic ever is developed from biomass
The use of biomass-derived plastics is one of the prime concerns to establish a sustainable society, which is incorporated as one of the Sustainable Development Goals.

Laser technology measures biomass in world's largest trees
Laser technology has been used to measure the volume and biomass of giant Californian redwood trees for the first time, records a new study by UCL researchers.

Inducing plasma in biomass could make biogas easier to produce
Producing biogas from the bacterial breakdown of biomass presents options for a greener energy future, but the complex composition of biomass comes with challenges.

Microbes working together multiply biomass conversion possibilities
Non-edible plants are a promising alternative to crude oil, but their heterogenous composition can be a challenge to producing high yields of useful products.

Evergreen idea turns biomass DNA into degradable materials
A Cornell-led collaboration is turning DNA from organic matter -- such as onions, fish and algae -- into biodegradable gels and plastics.

Upgrading biomass with selective surface-modified catalysts
Loading single platinum atoms on titanium dioxide promotes the conversion of a plant derivative into a potential biofuel.

A novel biofuel system for hydrogen production from biomass
A recent study, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST) has presented a new biofuel system that uses lignin found in biomass for the production of hydrogen.

Biomass fuels can significantly mitigate global warming
'Every crop we tested had a very significant mitigation capacity despite being grown on very different soils and under natural climate variability,' says Dr.

Traditional biomass stoves shown to cause lung inflammation
Traditional stoves that burn biomass materials and are not properly ventilated, which are widely used in developing nations where cooking is done indoors, have been shown to significantly increase indoor levels of harmful PM2.5 (miniscule atmospheric particulates) and carbon monoxide (CO) and to stimulate biological processes that cause lung inflammation and may lead to chronic obstructive pulmonary disease (COPD), according to new research published online in the Annals of the American Thoracic Society.

Read More: Biomass News and Biomass Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.