In the oven’s mouth

Burning eucalyptus to produce charcoal releases irritating and cancerous substances

In the state of Mato Grosso do Sul, 10,000 people are working under precarious conditions to produce charcoal, which in the main is made from logs of eucalyptus (Eucalyptus sp), to be used in metal working companies and barbecue houses. Generally, they do not have any labor contract, nor do they use protective equipment. In the first survey of compounds released by the combustion of eucalyptus, chemist Nilva Ré-Poppi, from the Federal University of Mato Grosso do Sul (UFMS), came across another problem: the charcoal makers spend the major part of their time exposed to 146 different chemical substances, launched into the air by the wood burning. Among the 80 from the class of polycyclic aromatic hydrocarbons (PAHs), six are found in a great quantity, and there are some that cause cancer or genetic mutations.

The carcinogenic compounds, which include benzoanthracene, benzofluoranthene and dibenzoanthracene, show in their structure four or five rings of benzene, and are the result of the wood not being burned completely, which is a characteristic of the production of charcoal. The process also releases irritant components like phenol and antioxidants like methoxyphenols, derived from the breaking down of lignin, a molecule that gives plant cells their rigidity.

Then there is the breaking down of cellulose, which brings about a high concentration of simple sugars like levoglucosan, lesser quantities of aliphatic (without benzene), and oxygenated compounds, as well as substances derived from waxes, resins and gums. Together, these are the main components of the particulate material – the solid particles of pollutants suspended in the smoke – according to Nilva’s study, published in April in Chromatographia, and also signed by Mary Rosa Santiago da Silva, from the São Paulo State University (Unesp), in Araraquara.

The researchers concentrated on the charcoal production in the municipalities of Água Clara, Ribas do Rio Pardo and Três Lagoas, in the east of Mato Grosso do Sul, where pyrolysis (decomposition by heat) is carried out on eucalyptus on clay ovens, at relatively low temperatures. The next step is to assess the components emitted in the combustion of other woods from the Cerrado (wooded savanna). “The concentrations of pollutants varies according to the species of wood that is burnt, the temperature of combustion and how long the fire lasts”, Nilva explains.

The research identified the components of the gases and the smoke collected 1,5 meters from the oven in production, on the basis of two techniques of chemical analysis, gas chromatography and mass spectrometry. To delimit precisely the risk of the workers developing cancer, the researcher warns, it would be necessary to investigate the concentrations of the substances inhaled, which affect the respiratory system.