A study by CONICET and the University of Groningen turns yerba mate waste and applied pyrolysis to used yerba, generating a renewable alternative to petroleum derivatives for the chemical and pharmaceutical industries.
An international scientific team has developed an efficient and economical method to transform yerba mate waste into high-value bio-oil. The research, led by an expert from CONICET in Mendoza and colleagues from the Netherlands, uses already consumed yerba (from infusions) to generate key inputs for the energy transition.
Facing the challenge of more than 220,000 tons annually of this waste in Argentina, the team designed and assembled a low-cost experimental reactor.
This device was custom-built to process the specific biomass of used yerba, first validating its performance with pine sawdust.
The method used is pyrolysis, a thermal degradation technique applied at 550 °C in the absence of oxygen.
This process breaks down the raw material into three distinct fractions: a solid residue known as biochar (with agricultural potential), a mixture of combustible gases (CO2, H2, and CH4), and a liquid product called bio-oil or pyrolysis oil.
The researchers focused their efforts on the bio-oil, considered a crucial renewable source of aromatic compounds capable of replacing petroleum derivatives.
To maximize its yield, the study optimized key variables, such as temperature, and incorporated copper oxide as a catalyst. This step promotes the formation of small aromatic compounds. Subsequently, a renewable solvent was used to extract and concentrate the molecules of interest.
The analysis of the final product revealed that it is a liquid rich in methoxyphenols, compounds derived from the lignin present in yerba mate. These components are in high demand in the chemical, pharmaceutical, and food industries. Their potential application is vast, being usable for making plastics, aromas, fragrances, resins, and renewable nature fuels.
The project, detailed in the journal Waste Management, exemplifies a comprehensive circular economy model. Not only is the bio-oil valorized, but the biochar and gases are also usable.
Even the pre-treatment of used yerba mate allowed for the separation of caffeine and minerals with commercial potential. Researcher Martín Palazzolo concluded that the strategy is “scientifically viable, logistically possible, and environmentally makes perfect sense” to reduce waste and generate valuable products.
