Galo Rodriguez uses his machete to dig a hole near the small stream on his farm in the north-east of Ecuador, on the cusp of the Amazon rainforest. As he digs there is nothing unusual to be seen – but when he hits 32cm below the surface, the soil releases a distinct and pungent smell of gasoline.

More than half of his 35 hectares of land is primary forest, while the rest is sugar cane or small trees. But where he digs is devoid of trees or crops. It is covered only by grass. This area used to be smothered in oil after a nearby pipeline leaked. The oil filled his stream, killed of all of his fish and contaminated the only fresh water source he used for his cattle.

The oil sat here for 10 years before the company responsible for the pipeline came to clean it up, in 2016. Rodrigo says he watched as they collected some 12-15,000 cubic metres of oil off his property, but they didn’t remediate the soil. Today, in the stream just beside him, blue and green streaks of oil residue can still be seen in the water.

“For 10 or 11 years, this area didn’t produce anything. We abandoned it,” says the farmer. “Now we plan to plant guavas and chaya.”

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Rodriguez is one of dozens of farmers in the north of Ecuador learning how to use plants to try to eliminate the oil contamination from his land. This process, known as bioremediation, uses living organisms like plants, fungi and microbes to break down pollutants, including crude oil.

There are several ways this could happen, but most of the hard work to break down crude oil happens below ground, where microorganisms are concentrated around the roots of plants and mineralise, or decompose, the crude components, making it easier for plants to take up. Some contaminants can be taken in by the plant directly and stored in its shoots and roots, or can be evaporated through the leaves.

The course Rodriguez attends is called “Guardians of the Soil”, which is an introduction to permaculture-based bioremediation for low-income communities, founded by local resident and independent researcher, Lexie Gropper.