Fermented Food Waste for Fertilizing Citrus

Len WilcoxCalifornia Corner, Nutrition, Research

food waste
Beneficial bacteria flourished in citrus growing systems treated with fermented waste by-products. (Image by Deborah Pagliaccia/UCR)

Fermented food waste converted to liquid fertilizer and fed through drip irrigation can boost bacteria that increase crop growth, according to a new University of California Riverside (UCR) study. The treatment may also make plants more resistant to pathogens.

“Beneficial microbes increased dramatically when we added fermented food waste to plant growing systems,” said UCR microbiologist Deborah Pagliaccia, who led the research. “When there are enough of these good bacteria, they produce antimicrobial compounds and metabolites that help plants grow better and faster.”

Up to 50 percent of all food is thrown away. Most of this waste isn’t recycled, but instead, takes up more than 20 percent of America’s landfill volume.

This waste represents not only an economic loss, but a significant waste of freshwater resources used to produce food. These losses led the UCR research team to look for alternative uses for food waste. They examined the byproducts from two kinds of readily available waste: beer mash — a byproduct of beer production — and mixed food waste discarded by grocery stores.

Both types of waste were fermented by River Road Research, a New York company with a research operation in California. River Road’s specialty is developing food waste into commercial products such as liquid fertilizer. The researchers added the liquid to the irrigation system used to water citrus plants in a greenhouse. Within 24 hours, the average population of beneficial bacteria was two to three orders of magnitude greater than in plants that did not receive the treatments. This trend continued each time the researchers added treatments.

UCR environmental scientist Samantha Ying and her team then studied the carbon dynamics and nutrients, including nitrogen, in the soil of the treated crops. The analysis showed a spike in the amount of carbon in irrigation water after being treated with waste products, followed by a sharp decrease, suggesting the beneficial bacteria used the available carbon to replicate.

Pagliaccia explained that this finding has an impact on the growth of the bacteria and on the crops themselves. “If waste byproducts can improve the carbon-to-nitrogen ratio in crops, we can leverage this information to optimize production systems,” she said.

Another finding of note is that neither the beer mash nor the mixed food waste products tested positive for salmonella or other pathogenic bacteria, suggesting they would not introduce any harmful element to food crops.

The paper’s results indicate that using these two types of food waste byproducts in agriculture is beneficial, financially viable and complement the use of synthetic chemical additives.

“There is a pressing need to develop novel agricultural practices,” said UCR plant pathologist and study co-author Georgios Vidalakis. “California’s citrus, in particular, is facing historical challenges such as huanglongbing bacterial disease and limited water availability.”

Source: UC Riverside