Biofuels are an inevitable part of the energy fuel mix. In the future, as biofuel percentage increases as part of worldwide consumption, we need to be smart about what plant material we convert to biofuels. The conservation of native ecosystems depends on the world making wise choices. Biofuel production is going to require more land than the land need for oil and coal extraction. The production of biofuels is already having a devastating impact on ecosystems like the Amazon forest, and on orchid habitat like oil palm production in Sumatra.
Ethanol and Biodiesel Yields per Acre from Selected Crops
|Fuel||Crop||Fuel Yield (L/hec)
|Sugar beet (France)||1,221.34||714||29,312.24||26,250.71|
|Sweet Sorghum (India)||639.75||374||15,354.03||13,750.37|
|Oil Palm (Indonesia)||868.97||508||28,675.91||25,680.84|
Fuel Yield (gallons/acre) figures are from Joshua Tickell, "From the Fryer to the Fuel Tank: The Complete Guide to Using Vegetable Oil as an Alternative Fuel." 3rd Ed. 2000. Crop yields vary widely. The main objective of the chart is comparing different biofuels by energy density yields. Efficiency of production and use also need to be considered.
Often not talked about in the biofuel discussion is the burning of wood as a biofuel. If you count the chopping down of forests to make charcoal in third world countries, the devastation to native ecosystems and orchid habitat is great. Madagascar and Haiti are examples of charcoal production destroying the native ecosystems to an extreme. Land denuded of trees causes landslides, floods, and may lead to desertification. The landslides often wipe out the villages below where the trees had been used as a biofuel. Forests are natural water storages that retain water which is slowly released overtime. With forests gone, water becomes scarce.
The challenges of biofuels are:
1. Whether there is a net energy gain or loss in turning plant material into biofuel is hard to determine. There are many factors to take into consideration. One thing is certain: If it takes more or an equal amount of energy to make a biofuel than the combustion the biofuel produces, then it is not worth producing.
“Brazil supports this population of ethanol-burning automobiles with large national infrastructure that produces ethanol from domestically grown sugar cane. Sugar cane not only has a greater concentration of sucrose than corn (by about 30%), but is also much easier to extract. The bagasse generated by the process is not wasted, but is utilized in power plants as a surprisingly efficient fuel to produce electricity.” https://biogas.ifas.ufl.edu/biogasdefs.htm
“For net energy yield, ethanol from sugarcane in Brazil is in a class all by itself, yielding over 8 units of energy for each unit invested in cane production and ethanol distillation. Once the sugary syrup is removed from the cane, the fibrous remainder, bagasse, is burned to provide the heat needed for distillation, eliminating the need for an additional external energy source. This helps explain why Brazil can produce cane-based ethanol for 60¢ per gallon.
Ethanol from sugar beets in France comes in at 1.9 energy units for each unit of invested energy. Among the three principal feedstocks now used for ethanol production, U.S. corn-based ethanol, which relies largely on natural gas for distillation energy, comes in a distant third in net energy efficiency, yielding only 1.5 units of energy for each energy unit used.” Earth Policy Institute- https://www.earth-policy.org/Books/PB2/Contents.htm
“The energy economics get worse at the processing plants, where the grain is crushed and fermented. As many as three distillation steps are needed to separate the 8 percent ethanol from the 92 percent water. Additional treatment and energy are required to produce the 99.8 percent pure ethanol for mixing with gasoline. Adding up the energy costs of corn production and its conversion to ethanol, 131,000 BTUs are needed to make 1 gallon of ethanol. One gallon of ethanol has an energy value of only 77,000 BTU. "Put another way," Pimentel says, "about 70 percent more energy is required to produce ethanol than the energy that actually is in ethanol. Every time you make 1 gallon of ethanol, there is a net energy loss of 54,000 BTU." Cornell University Professor Dr. David Pimentel. https://www.news.cornell.edu/releases/Aug01/corn-basedethanol.hrs.html
2. They require land on which to grow. This land comes from using agricultural land by displacing other crops used for food and textiles. The land also comes from destroying native ecosystems.
3. The biofuel crops are often themselves food and are often grown in countries where many people are food insecure or are starving. As food is turned into a biofuel the price of that food crop goes up. This results in fewer people being able to afford the cost of that food item. We are basically feeding our cars with food instead of people.
It takes 26.1 pounds (11.84 kg) of corn to yield a single gallon (3.78 L) of ethanol fuel. https://en.wikipedia.org/wiki/Ethanol
4. Some of the biofuel crops require a lot of water. Fresh water is becoming a scarce resource in much of the world.
“Research at the International Water Management Institute (IWMI) in Sri Lanka has shown that at a global average, the biomass needed to produce one litre of biofuel evaporates between 1000 and 4000 litres of water, depending on the type of feedstock and conversion techniques used.
Sugarcane in Brazil evaporates around 2200 litres for every litre of ethanol. But in this water-rich region, the demand is easily met by abundant rainfall. In more arid countries, irrigation must make up the shortfall. In India, for example, a litre of sugarcane ethanol requires 3500 litres of irrigation water.”
5. Crops like corn require a lot of fertilizer. Fertilizer used in large scale farming operation is derived from petroleum. The amount of energy and petroleum required to produce, transport, spread the fertilizer on a crop and then transport the crop to a biofuel processing plant and then to your automobile can make the net benefit negligible to no energy gain. It would be better if you had just used the petroleum used in the process to fill your car. This is especially true with low energy yield per acre crops like wheat, corn, sweet sorghum, and cassava. The uses of these crops for biofuels are more a result of lobbying and politics within a country. There are better energy yield per acre crops available.
6. Crops like corn also require a large amount of pesticides which are detrimental to the environment. Pesticides require energy, petroleum, and transportation costs to get to the crops.
7. The use of biofuels does not reduce the amount of carbon released into the atmosphere. It is at best an equal exchange and often it actually increases carbon in the atmosphere.
“The carbon lost by converting rainforests, peatlands, savannas, or grasslands outweighs the carbon savings from biofuels. Such conversions for corn or sugarcane (ethanol), or palms or soybeans (biodiesel) release 17 to 420 times more carbon than the annual savings from replacing fossil fuels, the researchers said.
The conversion of peatlands for palm oil plantations in Indonesia ran up the greatest carbon debt, one that would require 423 years to pay off. The next worst case was the production of soybeans in the Amazon, which would not "pay for itself" in renewable soy biodiesel for 319 years.”
Fixing a Critical Climate Accounting Error https://www.sciencemag.org/cgi/content/short/326/5952/527
The development of biofuels by nations has more to do with energy independence than carbon emission reduction.
While there is often talk about switchgrass as a future biofuel, there is very little research being done. More research is being done by big agricultural companies to increase crop yield and energy density in a crop like corn. A possible future biofuel which is being researched is algae. Some algae species/hybrids actually produce small quantities of petroleum. While the joke is that crude oil comes from dead dinosaurs, the truth is that it mostly comes from algae at the time of the dinosaurs. Algae is easy to grow and can be grown in brackish or salt water. Making a biofuel from algae outside of a lab is still off in the future.