Brazilian farmers use a carbon calculator to grow yerba mate


Technology and sustainability are closely linked in the growth of yerba mate in Brazil. To estimate carbon stocks and greenhouse gas emissions during the plant’s growth, Embrapa Florestas and the Solidariedad Foundation have developed the Carbon Matte calculator. The technology will provide a better understanding of the relationship between yerba mate production and the mitigation of GHG emissions through carbon storage.
The calculator can be used as a management tool for farms and companies to account for GHG emissions and carbon stocks based on managing practices deployed and help with decision-making. In addition, it can support certification or labeling processes for environmentally sustainable products, as well as measure environmental assets and help to achieve the targets of the United Nations Sustainable Development Goal (SDG) 13, related to global climate change.
The first results obtained with the calculator point to a negative carbon balance, which means that CO2 is removed from the atmosphere and stored in production systems. “The calculation tool will make it possible to quantify the role of yerba mate production systems in mitigating GHG emissions and will also test combinations of management practices that result in more promising scenarios for environmental quality,” explains Embrapa researcher Josileia Zanatta.

How Carbon Matte works
Carbon Matte consists of a spreadsheet in which data from yerba mate production systems (dense, wooded, and full-sun) is added. Among the variables collected and entered into the spreadsheet are biomass production and the silvicultural practices used. The spreadsheet calculates the total carbon emissions and removals from the system (plant biomass and soil) and the emission sources of some of the main GHGs, such as carbon dioxide (CO2) and methane (CH4). This tool is aimed at farmers, herb growers, rural extension agents, and the scientific community.
According to Gabriel Dedini, an agricultural engineer at the Solidaridad Foundation, the technical parameters were developed for the growing of yerba mate on partner farms in Paraná, a state in the Brazilian south. The production conditions in these towns represent cultivation systems in the state, serving as a testing and calibration environment for using the calculator. “The calculator can be implemented in other regions, with specific adjustments that consider the particulars of the climate and soil, expressed by the indicators and emission factors,” says Dedini.

How yerba mate stores carbon
Within the herb production system, carbon is stored by plant biomass via photosynthesis, and by the soil through plant residues that form organic matter. “This provides not only GHG mitigation but also other positive factors related to soil fertility and nutrient cycling,” says Zanatta. Yerba mate stores carbon in its biomass (tree trunks, branches, leaves, and roots), as well as in the soil. The crop also emits a small amount of GHG since it requires low amounts of inputs for the biomass produced.
Another aspect that turns yerba mate into a mitigator is the absorption of methane by forest soils. “The rates are quite significant and vary from 5 to 10 kilos per hectare per year. This amount, transformed into CO2 equivalent, corresponds to the removal of around 250 kilos of CO2e per hectare each year,” says Zanatta. This is due to methane having a global warming potential 25 to 30 times greater than carbon dioxide.