Research Update The power of culls

UBCO teamaims to develop process for turning waste fruit into electrical energy.

By Judie Steeves R

esearch is underway at the University of B.C. Okanagan on turning cull fruit into energy using a microbial fuel cell. Debbie Roberts is a professor in Environmental Engineering and Applied Microbiology at the university, and describes the process as “like sticking electrodes in both sides of a spud,” an experiment many youngsters have tried over the years.

The fuel cells use bacteria to break down and oxidize organic material and during that process, electrons are released that can be captured in the fuel cell and become a source of electricity.

“It’s not going to generate a ton of electricity,” she admits, but it could fuel a pump or supply power for lighting.

The benefits include the re-use of waste fruit and production of power in the process.

Roberts and her students are currently working with Tantalus Winery of Kelowna to develop a process to convert a winery wastewater treatment plant to a microbial fuel cell. It’s a very ‘green’ winery and this is good technology to use as part of the promotion of the winery as an environmentally-friendly operation, she explains.

As well, they’re working with David Geen’s Coral Beach Farms and Jealous Fruits in Lake Country to turn cull cherries into power.

She is working with the Geens to find out how much inoculant is needed to turn the waste product into energy and to get some idea of the time that would be needed for the process. In this case, the electrodes will be inserted in to the lined container of cull cherries where they come off the conveyor belt in the packing plant. Once they have degraded the available organics from the cherries and power

20 British Columbia FRUIT GROWER • Spring 2018

production slows down, the lid with the electrode inserts could be transferred to the next container of reject cherries, she explains. In the meantime, Geen has retained them to go ahead and design the insert for the containers of culls with the electrodes to go into the waste fruit, through a senior design project. Four fourth-year undergraduate students will tackle the problem to experience working with clients and solving real- world problems, says Roberts. The research project would not only help the Geens deal with cull fruit, but would also help the environment, by providing a process to re-use that waste product, and there’s a possibility the technology could be used to produce a product to help other farmers with waste produce — to use it more efficiently and provide a beneficial end product: power. One of the problems in using cherries is the pits in the middle of each, but Roberts believes that as part of the anaerobic process, the enzymes will soften the pits to the point they could be composted easily.

Part of the research will involve testing to see how long that might take. “We usually start with wastewater biosolids as the source of bacteria, then acclimate these to the cull fruit,” she explains. “This allows the organisms that grow best on the fruit to thrive and become better at degrading the compounds in the fruits. Once the process is finished the remainder could be composted.” It can be more efficient than a turbine or solar power for generating electricity,

Prof. Debbie Roberts

she says. As well, no heavy metals are needed and there’s no combustible substrate and no toxic end-products, she adds.

“Cherries have inherent energy, so it’s a shame to just bury them.” Another issue would be the seasonality of fruit availability, but if different fruits with different ripening times are used, it would become more efficient, she notes.

She envisions the process being used for fruit such as grapes and apples as well, and wonders if the industry is interested in working with she and her students to take the experiment a step further.

At present, they have frozen some cull cherries to experiment with this year in the off-season.

If you’re interested, contact her at:

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