By Elton Alisson
Agência FAPESP – Brazil is recognized as the country with the world’s most efficient biofuel production, which is principally based on sugarcane. The success that the country has enjoyed in transforming this plant into a bioenergy source, however, is due more to a pioneering initiative to create an industrial system for ethanol production than the plant itself.
The system began to be developed in the 1930s when an agronomic development program that made the plant highly efficient was established. Despite these efforts, the agronomic performance of sugarcane is still below that of the other raw materials tested for this purpose over the last few years in different parts of world.
These conclusions are from a study conducted by researchers at the Botany Department’s Laboratory of Plant Physiological Ecology (Lafieco) at Universidade de São Paulo’s Biosciences Institute. The project is part of National Institute of Biotechnology for Bioethanol (INCT Bioethanol) and the Center of Biological and Industrial Processes for Biofuels (CeProBio) funded by FAPESP and the National Council of Scientific and Technological Development (CNPq). The results of the study were published in the September edition of BioEnergy Research.
“We concluded that the success of sugarcane in Brazil is related not to the plant itself but to historical contingencies (such as the successive crises in the price of oil) that have led the country to build an industrial ethanol production system from sugarcane. This made the biofuel more efficient than the other varieties found in the world today, which are based on other types of raw materials,” said Marcos Silveira Buckeridge, a faculty member at the Botany Department within USP’s Biosciences Institute and one of the authors of the study.
To reach these conclusions, the researchers compared the harvest cycle duration; yield; and quantities of water, nutrients and pesticides utilized for the crop – including other agronomic pesticides – to those parameters in other plant species currently used for biofuel production. The studied species included sugarcane, switchgrass (Panicum virgatum), miscanthus (Miscanthus spp), sweet sorghum (Sorghum vulgare), sugar beet (Beta vulgaris L.), corn (Zea mays), populus (Populus spp) and willow (Salix spp).
The agronomic comparison revealed that sugarcane has a greater yield in terms of biofuel production per liter per hectare than sweet sorghum, miscanthus and other grasses. The crop, however, requires more water, and, unlike switchgrass, miscanthus and sorghum, has a longer harvest cycle and cannot be produced year-round.
Reasons for success
One of the motives that researchers have cited for Brazil’s success in transforming sugarcane into a source of bioenergy is the fact that the country was the first to use yeast and attempt to produce ethanol based on the plant in the Northeast as early as the 1930s.
Since then, due to successive crises in the price of oil – such as in the 1970s – the country began to develop new fermentation technologies to produce economically feasible bioethanol based on sugarcane and to build an industrial system that is well adapted to certain Brazilian regions.
These developments led the Brazilian fuel sector to be recognized as the most efficient in the world, stressed the researchers.
“The industrial development and agronomic improvements of last few decades made the Brazilian sugarcane-based ethanol production system highly efficient,” said Buckeridge.
Between 1980 and 1998, sugarcane productivity increased from 73 to 90 tons per hectare per year. In this same period, the efficiency of sucrose extraction in the fermentation process rose from 90% to 96%.
The plant yield in terms of biofuel production per liter per hectare increased from 84% to 90%, according to data utilized by the researchers.
“Brazil worked hard on the development of the sugarcane-based bioethanol industry and new varieties of the plant in the last few decades. The country needs to continue to do this if it wants to remain one of the global leaders in ethanol production technology,” stressed Buckeridge.
According to the researcher, in addition to the biofuel production system, another factor that still gives sugarcane an advantage over the other crops tested in different countries is the fact that Brazil began research programs in recent years, such as those at FAPESP’s Bioenergy Research Program (BIOEN) and Bioethanol INCT and CeProBio.
The programs allow for the use of biotechnology to attempt to improve the performance of the plant and make it more efficient than other crops in second-generation biofuel production, related Buckeridge.
“The fact that we study the sugarcane genome and physiology and acquire more knowledge about how it works will allow us to redesign the plant so that it can outperform other crops that are being utilized to produce bioethanol to make it effectively better for second-generation biofuel production,” said the researcher.
“However, this does not mean that sugarcane could become the best plant in the world for biofuel production and be grown in different regions of the planet, as each bioenergy crop is better adapted to certain types of climate,” Buckeridge commented.
Sugarcane, for example, is better adapted to tropical and subtropical climates. For this reason, in addition to Brazil where it became the main source of bioenergy, it has the potential to be utilized as a raw material for biofuel production in regions of Australia, Africa, Asia, South America and the United States, said the researchers.
Switchgrass and miscanthus, on the other hand, are temperate climate plants. Because of this, they can be utilized in the United States, Canada and Europe.
Because they are fast-growing species that prefer temperate climates, populous and willow, in addition to other grasses, such as reed canarygrass, have been gaining more attention from European countries, regions where sugar beets are also widely grown. Corn and sweet sorghum are being used in the United State for bioethanol production.
“Sugarcane, sweet beets, corn and sorghum are the crops that are best established for the use as raw material for bioenergy,” stated Buckeridge, “miscanthus, switchgrass, populous and willow are a bit further behind.”
According to the researcher, miscanthus stands out among these crops as the greatest rival to sugarcane in the race for second-generation biofuel development. Similar to sugarcane, as a first-generation bioethanol, the bioenergy from miscanthus is obtained not only from the sucrose found in the stalk but also from the sugar found in the cell walls of the bagasse, leaves and other crop residues. This is because the plant grows very fast soon after the end of winter in the Northern Hemisphere and produces a structure below the ground – called a rhizome –that stores starch.
Thus, instead of production based on sugarcane sucrose, the fiber accumulated by the plant can be utilized for the direct production of second-generation biofuel, as Brazil has been attempting to do, explained the researcher.
“This is a strategy that many people in the United States are supporting and could be developed in parallel to the Brazilian system,” said Buckeridge.
According to the researcher, the Brazilian industrial biotech company Granbio intends to utilize ancestral sugarcane plants that are very similar to miscanthus to produce cellulosic ethanol using this technological route.
“The initiative is very positive because it will allow Brazil to have two second-generation biofuel development strategies in progress simultaneously,” evaluated Buckeridge.
In addition to increasing its expertise on corn-based ethanol production, the United States is making important advances with sugarcane as both first- and second-generation bioethanol.
For example, a group of researchers from Florida announced this year that they managed to reduce the lignin content of sugarcane in field trials, showing that it is possible to increase the level of plant sucrose to facilitate its utilization for second-generation biofuel production.
“We also have altered crops in Brazil, but we have not yet performed the field studies,” commented Buckeridge.
According to the researcher, due to the recent advances obtained by scientists in the United States, the country is now tied with Brazil for leadership in developing technologies to produce second-generation biofuels.
However, the researcher added that, to stay on top and develop these technologies, Brazil will have to join with other countries.
“This country cannot attempt to do this alone. It needs to form alliances and have solid investments in this area because there are many things to be developed based on plant engineering,” he affirmed.
Although agriculture and the sugarcane industry in Brazil has already achieved a high efficiency, according to researchers, it is possible to increase plant productivity and the country’s bioethanol production system through improvements in some of the biological aspects of crops.
By promoting changes in the way that sugarcane functions through genetic improvement programs, it will be possible to increase both the quantity of bioenergy produced from the plant and reduce the need for agricultural inputs during the growth of the crop, they stressed.
Sugarcane as a bioenergy source: history, performance, and perspectives for second-generation bioethanol can be read in BioEnergy Research at mnras.oxfordjournals.org/content/433/3/2075.abstract?sid=9deb1321-2e70-4bef-a30e-a1a87dd94704.