Ethanol production, environmental sustainability and soil biodiversity in Brazil

André Franco, PhD student

Carlos Cerri, PhD

University of São Paulo - Center for Nuclear Energy in Agriculture

(Left: Preparing the mololith to extract soil macrofauna according TSBF methods in a sugarcane crop in Goiás state.)

Brazil has become a reference in the production and marketing of renewable energy through the strengthening of the ethanol productive chain from sugarcane, recognized as the most efficient in the agroenergy industry. 

A number of advantages qualify Brazil to take the lead of energy agriculture and the bioenergy market on a global scale. The possibility to allocate new lands for sugarcane cultivation, without reducing the area used for food agriculture or causing deforestation of native forests are some of the advantages. An additional 5,720,000 ha in planted area with sugarcane would be required to achieve the objectives of ethanol production for 2020, and approximately 88% of this expansion will come from areas previously used as pasture, specially degraded pastures.

However, what about the environmental sustainability of this expected expansion of sugarcane cropped area in Brazil? How will these changes in land use affect the biogeochemical cycles of carbon, nitrogen and phosphorus, greenhouse gases (GHG) emissions, and above and belowground biodiversity? Still what are the effective indicators for environmental sustainability? These are some of the issues that impose non-tariff trade barriers to Brazilian ethanol from sugarcane.

To answer these questions, we are developing a research project to evaluate the main land-use sequence for ethanol production in Brazil, i.e., the conversion of native vegetation to pasture and them to sugarcane production without straw burning. This conversion model will be analyzed in three different locations in the Cerrado biome. The following sustainability indicators were selected by the research team: i) GHG emissions in the life cycle; ii) soil quality, especially the changes in soil C/N/P stocks due the land use change; and iii) above and belowground biodiversity. The challenge is to propose a way of integrating the different indicators of environmental sustainability, usually treated individually.

(Right: The main land use change for sugarcane production in the center-south part of Brazil.)

The importance of soil biodiversity for the terrestrial ecosystem through its ecosystem services such as regulation of carbon sequestration in the soil, reducing GHG emissions, maintenance of the physical structure and water-holding capacity of the soil, providing nutrients for plants and control of phytopathogens, makes the evaluation of soil biodiversity a key indicator of the long-term environmental sustainability.

The land use changes greatly affect the soil fauna since the structure and abundance of soil organisms are very sensitive to changes in vegetation cover. In our study we are applying different sampling methods suited to the biology and ecology of the organisms from soil micro, meso, and macrofauna. The identification of biological communities whose presence/absence, abundance, and conditions under which individuals are present show correlation with the anthropic factor will allow the grouping of bioindicators of the degree of change and environmental balance in the sugarcane agroecosystem. To bind the soil organisms to its ecosystem services, the biota will be ordered by key functional groups, i.e., sets of species that have similar effects on ecosystem biogeochemical or biophysical processes in a specific level.

(Left: An integrated view of the environmental sustainability indicators.)

The evaluation of cost-effectiveness will identify the indicators of high-performance to represent the environmental changes due to land use sequence evaluated in this research and the indicators that are also economically and logistically feasible for application in such studies. Our proposal will still classify the indicators hierarchically in order to suggest a protocol with minimal analysis to evaluate the environmental sustainability of sugarcane production.

The information obtained from this project may be used by decision makers of federal government programs such as the Agriculture Program of Low Carbon, Forest Investment Plan, Action Plan for Prevention and Control of Deforestation and Fires in Cerrado and Program to Stimulate Sustainable Agricultural Program.


(Bottom, clockwise from top left: Sampling in a pature in Goiás state, Preparing the mololith to extract soil macrofauna according TSBF methods in a pasture in Goiás state, After a working morning, Manual sorting of macrofauna in the Lab)