UC Davis Interdisciplinary Team Using Waste Heat Solutions to Decarbonize Food Processing

By Neelanjana Gautam

Industries and automobiles that rely on fossil fuels, as well as household appliances like air conditioners, refrigerators and electronics give off a significant amount of heat. That heat, known as “waste heat,” exhausts into the environment and contributes to heating the planet.

About a third of greenhouse gas emissions come from industrial emissions resulting from combustion of fossil fuels for process heating and electricity generation. As per estimates, 20-50% of heat from combustion in industries is lost as waste heat from hot exhaust gasses, equipment surfaces, products and cooling water. While additional electrical energy can be extracted from high temperature exhaust gases in the 300 ^oC or higher range, it is not economical to do so for low grade waste heat.

“Low-grade waste heat, at temperatures less than 230 ^oC, is ubiquitous in industrial applications. However, it is difficult to extract this heat efficiently and find good use for it,” said Vinod Narayanan, a professor of Mechanical and Aerospace Engineering, and the director of the Western Cooling Efficiency Center (WCEC) within the Office of Research.

But with a recent $1.98 million in funding from the U.S. Department of Energy, Narayanan and an interdisciplinary team of researchers are now aiming to decarbonize the industrial sector by developing a novel suite of solutions to efficiently extract ultra-low grade waste heat from gas streams and use it for various applications in the food and beverage industry.

Developing technological solutions to utilize waste heat

Engineer Erfan Rasouli and students in Bainer Hall. (Paul Fortunato / UC Davis)

For a long time, Narayanan has been considering a collaboration with the Department of Food Science and Technology at UC Davis, as a partnership could pave a meaningful path to decarbonizing the industrial sector. “We have fairly good solutions for how to decarbonize buildings using heat pumps and other technologies, like efficient lighting and control strategies. We also know how to decarbonize transportation with electric vehicles, but decarbonizing the industry is a hard one,” said Narayanan, an expert on efficient waste heat extraction, “because it’s a diverse arena with processes of varying size, scale, and diverse range of energy needs.”

Narayanan shared that a lot of the industrial heat is just exhausted in the environment. For example, in food processing, more than 56% of the energy used is for heating or thermal processes that use large boilers running on natural gas. Although industries reuse some of the heat to recuperate, such as to preheat the water that goes into the boiler, a lot of low-temperature heat is just exhausted at the boiler stack. “If that heat can be extracted efficiently and used in a process for something valuable like low-temperature pasteurization, you can reduce the total amount of natural gas used by this industry,” said Narayanan.

Narayanan teamed up with Nitin Nitin, a Professor in Food Sciences and Biological and Agricultural Engineering, who works on low-temperature synergistic processing using food-grade compounds, to help enable an elegant low-temperature waste heat utilization solution by combining their respective strengths in energy efficiency and food science technology.

“In the food industry, the ability to process food with lower energy inputs and achieving desired levels of inactivation of pathogens and spoilage microbes is highly desirable as lowering the processing temperature can aid in improving food quality, including the retention of nutrients and reducing the energy footprint of the food industry,” said Nitin. In this project, the synergistic combination of food-grade compounds and extract with low-temperature heat recovered from waste heat sources will be evaluated for sanitation of food contact surfaces, fresh produce, and thermal processing of food products. “The collaborative efforts will enable the development and validation of this novel concept and provide a pathway towards translation. Success in these efforts will be transformative for the food industry in terms of saving energy, reducing carbon footprint, and improving food quality, nutrition and shelf life—a win-win scenario for food systems,” said Nitin.

Using WCEC’s novel microchannel polymer heat exchangers (MPHX) technology, for which a patent has been approved, Narayanan and WCEC engineer Erfan Rasouli, will investigate high-efficiency methods of extracting ultra-low-grade waste heat from gas streams. With Nitin’s team, they plan to utilize that heat synergistically with food-grade compounds for low-temperature pasteurization of beverages (e.g., juice, milk, soft drink) and cleaning and sanitation, including produce sanitation.

Pathway toward market adoption

Sarah Outcault and her team will gather input from industry partners and other stakeholders to ensure the project results in a solution that is easy and cost-effective to adopt. (Paul Fortunato / UC Davis)

The team is partnering with the California Dairy Innovation Center, Pacific Coast Producers, and the California League of Food Producers to help advance and integrate the technology into the existing infrastructure. The market adoption team is led by Sarah Outcault, the market transformation research director for the Energy Efficiency Institute. “Ensuring the method under development is responsive to industry needs and constraints is critical to its market adoption down the road,” said Outcault. Her team will gather input from industry partners and other stakeholders to ensure the project results in a solution that is easy and cost-effective to adopt. “We are also going to work with labor representatives to prioritize applications that improve the health and safety of working conditions in food processing plants by reducing exposure to high ambient temperatures, hot water, and toxic chemicals used for cleaning,” said Outcault. “These secondary benefits of the technology could have significant monetary value.”

About 96 million metric tons of carbon dioxide equivalent is emitted by food and beverage processing every year. “It’s an important issue for us to tackle being in the Central Valley as the area produces about 40% of the fruits and vegetables in the country,” said Narayanan. “If we can remove even one million metric ton of CO₂ out of it using this process, that’s a win for California and the United States.”