How Olive Oil Waste Water Becomes Fuel and Fertilizer

Teresa Madaleno

Most people are familiar with olive oil and while the largest olive growing area on the planet is in Spain, the production of olive oil takes place across the globe, including throughout North America. While in recent years, health experts have been touting the benefits of infusing the oil into our diets, producing the oil creates large amounts of foul wastewater that has the potential to contaminate the environment. Now a study in ACS Sustainable Chemistry and Engineering suggests that there is a more environmentally friendly approach to dealing with olive oil waste.

As it turns out, olive oil waste can be transformed into both a bio-fertilizer and biofuel. According to the study, researchers discovered that they could embed the waste into cypress sawdust, quickly dry the mixture and collect the evaporated water. The water can safely be used to irrigate crops. The research team also subjected the sawdust to pyrolysis, which is a process whereby organic material is exposed to very high temperatures without oxygen. As a result, the material decomposes into combustible gases and charcoal. The team was able to collect the gas, condense it into bio-oil and then use it as a heat source for sawdust drying and the pyrolysis process. They also collected charcoal pellets loaded with potassium, phosphorus, nitrogen, as well as other nutrients taken from the breakdown of the sawdust mixture during the pyrolysis process. The pellets were then used as bio-fertilizers. After five weeks of using the pellets, the researchers recorded significant improvement in plant growth.

While this does sound like quite the waste retrieval process, the research team has offered hope, especially in regions of the world where olive oil waste disposal appears to be out of control. In Mediterranean countries, where olive oil mills generate close to 8 billion gallons of wastewater every year, disposing is a challenge. Dumping the wastewater in rivers and stream puts both aquatic life and the drinking water supply at risk. Disposing of it on farmland can damage the soil and thus reduce crop yields.