How Balsa Trees Could Eliminate Mercury Use in Gold Mining

Brazil research shows that bio-extraction from Amazon trees could save lives.

Tue 27 Jun 23


New research has shown that bio-extraction from the selective harvesting of leaves from balsa trees native to the Amazon could replace toxic mercury metal in gold recovery.

The study, a collaboration between Embrapa Forests in Paraná and other research institutions, is centred on the Ochroma pyramidale, a large, fast-growing ‘soft’ hardwood and the sole member of the genus Ochroma.

The researchers will evaluate various bio-extraction formulations for their efficiency in recovering gold from alluvial ore. 

The best bio-extractor will be adjusted to improve further extraction, followed by toxicity and cytotoxicity trials.

The research supports a 2020 project which determined that mercury emissions can be reduced using “woody biomass.”

Mercury is a toxic metal that can harm the nervous, digestive and immune systems, the lungs, kidneys, skin and eyes.

The Ochroma pyramidale tree is native from southern Mexico to southern Brazil.

It can also be found in many other countries, including Papua New Guinea, Indonesia, Thailand and the Solomon Islands.

The tree contributes to the improved development of secondary forests and can be used in forest restorations.

In the case of adopting balsa leaves for gold recovery, the idea is that it will be associated with using the species to recover land affected by mining.

The potential use of balsa trees in gold mining is not the only industry where trees have a significant role to play. The new research provides a secondary market for a product fuelling the drive to renewable energy.

The booming renewable energy sector, particularly wind power, has seen increased demand for balsa wood.

Wind turbine technology is the major driver of balsa wood exports 

As reported by the Economist in 2021, Balsa wood is a significant component of wind turbine blades, with turbine construction driving a skyrocketing export market.

Wind-based technology has emerged as a leading renewable energy source, especially in China and the European Union.

Wind turbines are being embraced globally as a renewable energy source to meet climate commitments.

In 2019, the Financial Times reported that a global slowdown in balsa wood led to a slowdown in wind-power projects.

According to General Electric, a major manufacturer of wind turbines, workers make the blades from fibreglass fabric and balsa wood. 

General Electric has invested more than USD 35 billion into its wind turbine programme – with balsa wood used in the turbine’s blade construction. Footage courtesy of @adin

The blade is then covered with an airtight foil, and the team installs a network of tubes that pumps in and distributes the resin that will hold it together.

In the past decade, the Chinese government eliminated taxes for the alternative energy industry, prompting a boom in wind turbine production, so most of Ecuador’s balsa exports go to China.

Transporting balsa wood blades – with the boom in wind turbine manufacture, particularly in China, blades are now made from balsa wood and fibreglass fabric.
Ecuador supplies 95% of the world’s commercial balsa wood.

The wood is so fast-growing that it can grow between 1.8 and 2.7 metres a year and reach 30.5 metres in 10-15 years.

The trees are short-lived, lasting only 30-40 years.

Inside the wood, the cells are large, thin-walled and full of water, so the tree stands upright.

When cut and kiln-dried, the wood is lightweight and sturdy.

In recent years, about 60% of balsa has been plantation-grown in densely packed patches of around 1000 trees a hectare, compared to about two to three per hectare in the wild.

Once classified as a weed, 95% of commercially available balsa wood originates from Ecuador; however, large plantations of balsa tree can also be found in Papua New Guinea, Indonesia, Thailand and the Solomon Islands. Ecuador reportedly has 20,000 hectares of industrial balsa plantations in Los Rios, Manabi, and Esmeraldas provinces.

The trees are harvested after a 6-to-10-year growth cycle.

Demand for balsa wood has skyrocketed

According to a report commissioned by Forest Trends, the estimated demand for balsa sawn wood (to July 2022) was between 400,000 and 465,000 cubic metres per year.

In addition to China, the European Union is a growing market for export owing to the emergence of wind power as a mechanism to meet climate targets.

Denmark, Poland, Netherlands, Germany, and Italy are the leading European markets for the product.

According to The Asociación Ecuatoriana de Industriales de la Madera (AIMA), Ecuador exported 86 percent more wood in 2019 than in 2012.

However, there have been reported concerns about the production and trade of balsa.

According to Forest Trends, Ecuador lacks commercial and environmental regulation mechanisms to prevent negative social, ecological, and economic impacts from the country’s balsa boom.

The high demand has been linked to illegal logging in indigenous communities’ territories in the Ecuadorian Amazon region, with the issue reportedly crossing borders into Peru.

To satisfy the skyrocketing global demand over the COVID-19 pandemic from 2020 to 2021, Ecuador supplemented its domestic production using balsa harvested in Peru and trucked across land borders.

According to SUNAT – the central tax authority for the Peru Government, in 2021, 100 percent of Peru’s balsa destined for export went first to Ecuador, mixed with locally harvested wood and shipped globally.

  • Learn more about this and its potential implications in the full Forest Trends report, available here.


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