[biodiesel] Biodiesel vs Environmental Impact

Readers,

what the environmental impacts of using ethanol?

Environment
All biomass goes through at least some of these steps: it needs to be grown, collected, dried, fermented, and burned. All of these steps require resources and an infrastructure. The total amount of energy input into the process compared to the energy released by burning the resulting ethanol fuel is known as the energy balance.

Figures compiled in a 2007 by National Geographic Magazine[31] point to modest results for corn ethanol produced in the US: one unit of fossil-fuel energy is required to create 1.3 energy units from the resulting ethanol. The energy balance for sugarcane ethanol produced in Brazil is more favorable, 1:8. Energy balance estimates are not easily produced, thus numerous such reports have been generated that are contradictory. For instance, a separate survey reports that production of ethanol from sugarcane, which requires a tropical climate to grow productively, returns from 8 to 9 units of energy for each unit expended, as compared to corn which only returns about 1.34 units of fuel energy for each unit of energy expended.[79]

Carbon dioxide, a greenhouse gas, is emitted during fermentation and combustion. However, this is canceled out by the greater uptake of carbon dioxide by the plants as they grow to produce the biomass.[80] When compared to gasoline, depending on the production method, ethanol releases less greenhouse gases.[81][82]

Air pollution
Compared with conventional unleaded gasoline, ethanol is a particulate-free burning fuel source that combusts cleanly with oxygen to form carbon dioxide and water. Gasoline produces 2.44 CO2 equivalent kg/l and ethanol 1.94 (this is -21% CO2). The Clean Air Act requires the addition of oxygenates to reduce carbon monoxide emissions in the United States. The additive MTBE is currently being phased out due to ground water contamination, hence ethanol becomes an attractive alternative additive. Current production methods includes air pollution from the manufacturer of macronutrient fertilizers such as ammonia.

A study by atmospheric scientists at Stanford University found that E85 fuel would increase the risk of air pollution deaths relative to gasoline.[83] Ozone levels are significantly increased, thereby increasing photochemical smog and aggravating medical problems such as asthma.[84][85]

Manufacture
In 2002, monitoring of ethanol plants revealed that they released VOCs (volatile organic compounds) at a higher rate than had previously been disclosed.[86] The Environmental Protection Agency (EPA) subsequently reached settlement with Archer Daniels Midland and Cargill, two of the largest producers of ethanol, to reduce emission of these VOCs. VOCs are produced when fermented corn mash is dried for sale as a supplement for livestock feed. Devices known as thermal oxidizers or catalytic oxidizers can be attached to the plants to burn off the hazardous gases.

Carbon Dioxide
Calculation of Carbon Intensity of Corn Bioethanol grown in the US and burnt in the UK, using UK government calculation [87]

Graph of UK figures for the Carbon Intensity of bioethanol and fossil fuels. This graph assumes that all bioethanols are burnt in their country of origin and that prevously existing cropland is used to grow the feedstock.[87]

The calculation of exactly how much Carbon Dioxide is produced in the manufacture of bioethanol is a complex and inexact process, and is highly dependent on the method by which the ethanol is produced and the assumptions made in the calculation. A calculation should include:

The cost of growing the feedstock
The cost of transporting the feedstock to the factory
The cost of processing the feedstock into bioethanol
Such a calculation may or may not consider the following effects:
The cost of the change in land use of the area where the fuel feedstock is grown.
The cost of transportation of the bioethanol from the factory to its point of use
The efficiency of the bioethnol compared with standard gasoline
The amount of Carbon Dioxide produced at the tail pipe.
The benefits due to the production of useful bi-products, such as cattle feed or electricity.
The graph on the right shows figures calculated by the UK government for the purposes of the Renewable transport fuel obligation.[87]

The January 2006 Science article from UC Berkeley's ERG, estimated reduction from corn ethanol in GHG to be 13% after reviewing a large number of studies. However, in a correction to that article released shortly after publication, they reduce the estimated value to 7.4%. A National Geographic Magazine overview article (2007)[31] puts the figures at 22% less CO2 emissions in production and use for corn ethanol compared to gasoline and a 56% reduction for cane ethanol. Carmaker Ford reports a 70% reduction in CO2 emissions with bioethanol compared to petrol for one of their flexible-fuel vehicles.[88]

An additional complication is that production requires tilling new soil[89] which produces a one-off release of GHG that it can take decades or centuries of production reductions in GHG emissions to equalize.[90] As an example, converting grass lands to corn production for ethanol takes about a century of annual savings to make up for the GHG released from the initial tilling.[91]

Change in land use
Large-scale farming is necessary to produce agricultural alcohol and this requires substantial amounts of cultivated land. University of Minnesota researchers report that if all corn grown in the U.S. were used to make ethanol it would displace 12% of current U.S. gasoline consumption.[92] There are claims that land for ethanol production is acquired through deforestation, while others have observed that areas currently supporting forests are usually not suitable for growing crops.[93][94] In any case, farming may involve a decline in soil fertility due to reduction of organic matter,[95] a decrease in water availability and quality, an increase in the use of pesticides and fertilizers, and potential dislocation of local communities.[96] However, new technology enables farmers and processors to increasingly produce the same output using less inputs.[92]

There is a concern that as demand for ethanol fuel increases, food crops are replaced by fuel crops, driving food supply down and food prices up. Growing demand for ethanol in the United States has been discussed as a factor in the increased corn prices in Mexico.[97] Average barley prices in the United States rose 17% from January to June 2007 to the highest in 11 years. However, some commentators suggest that recent food price increases mainly reflect high oil prices in recent years, not specific pressures associated with ethanol production.[98]
Cellulosic ethanol production is a new approach which may alleviate land use and related concerns. Cellulosic ethanol can be produced from any plant material, potentially doubling yields, in an effort to minimize conflict between food needs versus fuel needs. Instead of utilizing only the starch by-products from grinding wheat and other crops, cellulosic ethanol production maximizes the use of all plant materials, including gluten. This approach would have a smaller carbon footprint because the amount of energy-intensive fertilisers and fungicides remain the same for higher output of usable material. The technology for producing cellulosic ethanol is currently in the commercialization stage.[99][100]

Many analysts suggest that, whichever ethanol fuel production strategy is used, fuel conservation efforts are also needed to make a large impact on reducing petroleum fuel use