Eco-Friendly Pesticide Made With Beer Brewing Waste And Cow Manure

Conventional pesticides are harmful to the environment, but farmers still use them because they need to keep weeds and crop-damaging organisms away. Some growers are turning to robotics and AI to kill weeds while avoiding pesticides. However, not all farmers can afford these expensive types of machinery.

With this in mind, scientists at Spain’s Neiker Basque Institute for Agricultural Research and Development have created an eco-friendly mixture of agricultural and beer brewing waste that could serve as an alternative.

When the sugar is extracted from barley in the commercial beer brewing process, a by-product called bagasse is created. Likewise, after the oil is extracted from harvested rapeseed plants (also known as canola), a solid by-product known as rapeseed cake is left over.

The scientists, led by Ph.D. student Maite Gandariasbeitia, combined beer bagasse with rapeseed cake and fresh cow manure. They then applied this mixture to the soil in a commercial greenhouse where lettuce is grown.

That greenhouse had previously experienced significant yield losses of 45% due to crop-damaging organisms in the soil called Meloidogyne incognita nematodes. These plant-parasitic roundworms lay their eggs in the roots of plants, forming galls that diminish the roots’ ability to draw nutrients. Even after the greenhouse carried out conventional chemical fumigation, the persistent parasites were still present.

At the beginning of a growing season, the Spanish scientists added their eco-friendly mixture to the soil of some of the greenhouse’s lettuce crops. The results showed that the plants with the treated soil had significantly fewer galls on their roots than untreated. In addition, the crops in the treated soil had a 15% higher yield.

Gandariasbeitia points out that this effect was primarily due to the high nitrogen content of the bagasse and rapeseed cake. That nitrogen enhances beneficial microbes’ activity in the soil while eradicating nematodes. It additionally breaks down organic matter – like the manure – allowing it to serve as fertilizer more effectively.

In the meantime, the scientists will be exploring the properties of other types of organic waste to determine if they could also be used as alternatives to conventional pesticides. The study was published on May 31 in Frontiers in Sustainable Food Systems.

This year, beer waste has proven to hold great potential. For example, Heineken began converting beer waste into sustainable energy, and scientists from State University (Virginia Tech) and Virginia Polytechnic developed a method of turning beer waste into valuable protein and fiber. In 2019, a researcher from Ireland’s Queen’s University discovered a way to convert leftover barley from beer into activated carbon.