2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Annually, from each hectare of sugar cane crops, an average of 2.26 kilograms of nitrous oxide is emitted into the atmosphere. This is due to the low efficiency of using nitrogen fertilizers - the N2O emission factor of sugar cane is higher than that of almost all other crops. Given this, the impact of biofuel production on anthropogenic climate change may be underestimated, according to an article published in the journal Science of The Total Environment.
Over the past 50 years, global energy consumption has grown by an average of 45 percent per capita. This happened thanks to fossil fuels - a non-renewable resource, the use of which has become a leading factor in anthropogenic climate change. Bioethanol, a type of biofuel obtained from the processing of plant materials, was recognized as one of the most popular options for switching to cleaner energy sources in 2020. A recent study found that ethanol, extracted from Brazilian sugarcane alone, could replace up to 13.7 percent of global oil consumption. However, the cultivation of this crop requires significant application of nitrogen fertilizers - from 60 kilograms per hectare in Brazil to 755 kilograms per hectare in parts of China. This leads to increased emissions of nitrous oxide (N2O), a substance that depletes the ozone layer, as well as a gas whose potential to cause the greenhouse effect is estimated 265 times higher than that of CO2.
Scientists led by Linsheng Yang of Southwestern University in Chongqing have estimated the global nitrous oxide emissions associated with sugarcane cultivation. To do this, they studied 67 publications in the ISI-Web of Science, Google Scholar and China Knowledge Resource Integrated Database systems, collecting data from 141 measurements of N2O emissions from sugarcane fields in various regions of the world, as well as data on irrigation and fertilization of lands on which they are grown. this culture. 80 percent of the measurements were taken in the tropics, the remaining 20 in the subtropics.
Scheme for converting nitrogen fertilizers into nitrous oxide emissions from sugar cane cultivation.
It turned out that every year from each hectare of sugar cane crops, an average of 2.26 kilograms of nitrous oxide is emitted into the atmosphere. The authors of the study calculated the emission factor - an indicator that reflects the loss of nitrogen fertilizers for emissions. In sugar cane, it turned out to be 1.21 percent, which exceeds the values of this indicator for almost all agricultural crops - vegetables (0.69 percent), fruits (1.15 percent), cotton (0.31 percent), rice (0.68 percent), wheat (0.81 percent) and various cereals (1.04 percent). Less efficiently nitrogen fertilizers are consumed only when growing rapeseed (1.27 percent). The authors note that in the reports of the Intergovernmental Panel on Climate Change (IPCC), the nitrous oxide emission factor for cane is taken equal to one percent, which can lead to a significant underestimation of the contribution of biofuels to anthropogenic greenhouse gas emissions.
Editor's note
The authors of the study presented in the article a formula for calculating the EF (emission factor). According to it, the emission factor of 1.21 percent should not be taken as a loss of 1.21 percent of the mass of nitrogen applied with fertilizers with emissions of nitrous oxide. This indicator is relative and only characterizes the efficiency of fertilizer use. In fact, at EF = 1, 21 with emissions, 60 and even 80 percent of the mass of applied nitrogen fertilizers can be lost.
Scientists have previously found that the introduction of bioeconomy in the Nordic countries could pose a threat to forests in their territory: the shift from plastic production to wood-based materials has already led to a 44 percent increase in clearcutting.
