Tracking air pollution from Brazilian sugar-cane ethanol
March 15th, 2012 by Rachel Perlman,Article: Tsao, C-C. et al. (2012). Increased estimates of air-pollution emissions from Brazilian sugar-cane ethanol. Nature Climate Change 2: 53-57.
Background: Burning sugar cane fields prior to harvest is a common practice employed to remove dried leaves, considered “trash.” The burning decreases labor and equipment needs for harvest, but emits quantities of air pollutants that may be of concern.
Summary: Tsao’s research group used a life-cycle approach to quantify the air-pollutant emissions associated with producing sugar-cane ethanol in Brazil. To inventory emissions in Brazil, they used agriculture survey data, emissions factors and life-cycle assessment tools. Based on changes seen between 2000-2008, they found that regional emissions of pollutants are continuing to increase as sugar-cane cropland expands. This group’s estimates are (up to four-times) higher than pre-existing estimates obtained using satellite-based approaches, which tend to underestimate burned area. Satellites can underestimate burned area, since the burning occurs at a small spatial scale of individual fires.
Roughly half of sugar-cane croplands are still burned, and most of the burning in Brazil occurs in the north-central region of the Sao Paulo state. Their comparison of life-cycle emissions per unit energy produced from sugar-cane ethanol versus from conventional gasoline and diesel showed that: (1) greenhouse gas (CO2 equivalent) emissions for sugar-cane ethanol were lower (2) the emissions of volatile organic compounds, CO, NOx, SOx, and particulates were all significantly higher for sugar-cane ethanol. In the life-cycle of sugar-cane ethanol, the field burning phase is the primary source of all of these species except SOx.
CATF take-away message: The life-cycle emissions of a biofuel crop can vary greatly depending on the methods used in harvesting. The LCA of sugar-cane ethanol may show that it “beats” fossil fuels in terms of greenhouse gases, but could be worse for air pollutants that directly affect human health if the fields are burned. Pre-harvest burning of residue from sugar-cane grown for ethanol production is a practice that must be questioned, given its release of air pollutants (VOC, CO, CO2, NOx, SOx, and particulates).
RESEARCH: Bioethanol may be more water intensive than initial estimates due to a shift toward more intensive irrigation infrastructure
March 10th, 2009 by CATF,Article: Y.Chiu et al (2009). Water Embodied in Bioethanol in the United States. Environ Sci Techno., 3 (8), pp 2688–2692
Previous studies have estimated that the production of one liter of bioethanol in the United States requires 263-784 liters of water, but this figure ignores the varying irrigation practices from region to region. Taking these practices into account, the range of water consumption is actually 5 to 2138 liters depending on the actual area where the corn is produced. However, in recent years bioethanol production has shifted towards areas with more intensive irrigation infrastructure, so the industry has increased its total water consumption 246% from 1.9 trillion liters to 6.1 trillion liters between 2005 and 2008, while production only increased 133% from 15 to 34 billion liters during this period.
The full article can be downloaded here.
RESEARCH: Transportation costs from the Midwest may negate positive economic effects for ethanol
February 25th, 2009 by CATF,Article: H.L.Wakeley et al (2009). Economic and Environmental Transportation Effects of Large-Scale Ethanol Production and Distribution in the United States. Environ Sci Technol, 43 (7), pp 2228–2233.
The United States currently produced 50 billion liters of ethanol per year, with a stated goal of 136 billion liters by 2022. This ethanol must be transported long distances from its production area in the Midwest, and the estimated transportation cost from the 2022 production goal ranges from $1.3 to $2.8 per gallon. This additional cost plus the additional emissions from such large amounts of transport may negate any positive environmental and economic effects ethanol may have.
The full article can be downloaded here.
