Vegetable oil fuel
Vegetable oil fuel
Summary: Vegetable oil is used as an energy carrier for transportation, heat, and electricity generation.
Pure vegetable oil (also pure plant oil or straight vegetable oil) is an alternative fuel for diesel engines in transportation and also stationary applications, namely for heating purposes and electricity generation. Pure vegetable oil is produced from oil plants through pressing, extraction, and comparable procedures.
The major components of vegetable oil are triglycerides (also called triacylglycerols), which chemically are esters of fatty acids attached to one glycerol backbone.
Vegetable Oil Production
Different cultivation methods (soil management and inputs) are used for oil crops, depending on the crop, climate region, and soil type. Following harvesting, oilseeds are cleaned and dried. Large-scale oil extraction is usually preceded by grinding and cooking of the seeds to facilitate the oil extraction process. Vegetable oil may be extracted from the seeds by physical or chemical extraction. After mechanical pressing, protein-rich cake is also produced and can be used in animal feed. The cake has a high oil content, and an additional (chemical) extraction step is usually conducted to extract the remaining oil, using a petroleum-derived solvent (usually hexane). At the end, oil goes through a distillation process to recover the hexane, which is recycled. The life cycle of vegetable oils includes several steps, from the very first step of biomass cultivation up to the final step of biofuel combustion. Life-cycle assessments (LCAs) offer a comprehensive picture of the input (energy and materials) and output (emissions) flows and enable the quantification of environmental impacts.
CountryPalm OilSoybean OilRapeseed OilSunflower Oil Malaysia 17,564.9 Indonesia 16,900.0aUSA8,795.7 China 7,828.65,211.4 Brazil 5,896.0 Argentina 5,771.81,418.8 Germany 3,345.3 Russia 2,804.9 Ukraine 2,796.7 India 1,179.32,284.0 Canada 1,810.8 France 1,742.6588.7 Nigeria 1,380.0 Thailand 1,310.0 Colombia 802.4 Turkey 598.8Top 5 share (%)91.881.667.862.9World production41,340.236,124.621,222.913,056.0Source: Food and Agriculture Organization, http://faostat.fao.org.Notes: Figures are in kilotons as of 2009, except for Indonesia, which shows palm oil data for 2008.Production of Vegetable Oils Worldwide
More than 20 types of vegetable oils have been investigated for potential use as fuels, from castor, grapeseed, maize, camelina, pumpkin seed, beechnut, rapeseed, lupin, pea, poppy seed, groundnut, hemp, linseed, chestnut, sunflower seed, palm, olive, soybean, cottonseed, and shea butter. Research is being conducted to investigate the potential of other materials, such as algae, jatropha, and thistle.
The main feedstocks are soybean, used mainly in the United States and South America; grapeseed, used in Europe; and palm, used in tropical countries. In 2023, approximately 222 million metric tons of vegetable oils were produced worldwide (four species accounting for around 70 percent), both as cooking oil and as diesel fuel.
Vegetable Oil as an Energy Carrier
Vegetable oil can be used for energy purposes in a variety of ways: as straight vegetable oil, blended with fossil diesel, and after conversion into biodiesel. Common applications include motor vehicles and agricultural machinery (compression ignition engines) and stationary applications for power generation (diesel engines or gas turbines) and heating systems (boilers). Germany has been a leading country in using pure vegetable oils in motor vehicles: approximately 1 megaton in 2006, for example. Regarding stationary applications, several manufacturers offer heating systems and small-scale combined heat and power (CHP) units fueled by vegetable oil.
Energy, Environmental, and Economic Issues
Main drivers for the use of vegetable oil as an energy carrier are the security of energy supply, global warming concerns, and support for rural development. Following debates on the sustainability of biofuels, the European Union now requires that biofuels fulfill minimum greenhouse gas (GHG) emission savings in comparison to fossil fuels, based on LCA calculations. GHG emissions from biofuel production arise from land use (fertilizers), carbon stock changes due to (direct and indirect) land-use change, and fossil fuel combustion.
One study (Alabi, 2024) found that combining vegetable oil with diesel reduced nitrogen oxides and particulate matter emissions However, the blend did not significantly affect CO and CO2 emissions.
Soil carbon stock change, in particular, can contribute significantly to the GHG footprint, but there is high uncertainty and variability, and this is a controversial topic; for example, João Malça and Fausto Freire concluded that rapeseed oil savings range between 26 and 72 grams of carbon dioxide equivalent per megajoule. Another controversial aspect is the food-versus-fuel competition issue, since increased vegetable oil fuel production may occur at the expenses of food production.
Vegetable oil fuel, particularly from nonfood sources, seems very promising in developing countries, where self-energy production at minimal cost is of greatest importance and low-cost production technologies (mechanical oilseed presses, either hand- or fuel-driven) may greatly contribute to the socioeconomic welfare of the populations in these nations.
Bibliography
Alabi, Oluwaseyi O., et al. "Exploring the Impact of Diesel-Vegetable Oil Blends as an Alternative Fuel in Combustion Chambers." Biofuels, 2024, doi.org/10.1080/17597269.2024.2386482. Accessed 7 Aug. 2024.
"Biodiesel Production and Distribution." Alternative Fuels Data Center, afdc.energy.gov/fuels/biodiesel-production. Accessed 7 Aug. 2024.
Knothe, G. “Historical Perspectives on Vegetable Oil-Based Diesel Fuels.” Industrial Oils 12 (2001).
Luque, R., L. Davila, J. M. Campelo, J. H. Clark, J. M. Hidalgo, D. Luna, et al. “Biofuels: A Technological Perspective.” Energy and Environmental Science 1, no. 5 (2008).
Malça J., and F. Freire. “Uncertainty Analysis in Biofuel Systems: An Application to the Life Cycle of Rapeseed Oil.” Journal of Industrial Ecology 14, no. 2 (2010).
Walton, J. “The Fuel Possibilities of Vegetable Oils.” Gas Oil Power 33 (1938).