Biofuels

Oil

  • Oil reserves are formed from photosynthetic organisms that lived in the Carboniferous era, 300 million years ago
    • Over time they became oil and coal
  • The era of cheap oil was made possible due to solar energy, photosynthesis, geological processes, and time
  • Under ideal conditions, the energy required to extract crude oil is minimal compared to its energy potential
    • This means there is a good Energy Return On Energy Invested (EROEI)
    • outputs/inputs
  • But, easily exploited oil reserves are steadily declining, so EROEI is decreasing as well

Goal

  • The goal should now be to “densify” organic biomass quickly (not over millions of years)
  • We must use modern technology in cooperation with natural processes
  • We want to optimize the sustainable densification of plant-derived energy into biofuels

Ethanol (C2H5OH)

Glycolysis

  • Glycolysis breaks down sugars to produce ethanol
  • One molecule of glucose yields two pyruvate
  • Under anaerobic conditions (fermentation) pyruvate is made into ethanol

In the Lab

  • In the production of ethanol, scientists use microorganisms (yeast) to provide the necessary enzymes
    • When provided with a source of sugars and the correct growing conditions the microorganisms will produce ethanol
    • The same reaction is used to make beer and wine
  • Currently, the US is the number 1 producer of Ethanol, followed by Brazil
    • These countries produce 85% of the world’s ethanol fuel

Ways of making ethanol

  • The nature of starting material will determine how cost-efficient the production of ethanol is
  • The ethanol is the same no matter how it is produced
  • The only difference is how much it costs to produce it (EROEI), and how much pollution is generated in the process
Conventional (Grain-based) Ethanol
  • The starting material of conventional ethanol is corn, wheat, soybean, and sugar cane (Brazil)
    • These are major food crops
    • Known as “Feed to Fuel” ethanol
  • Ethanol production from corn yielded ~10% more energy than was used in the production
  • Ethanol made from sugarcane is the only sustainable form
    • Sugar cane varieties are high yield with low amounts of inputs (herbicide, insecticide) and are drought tolerant
    • Sugar cane waste (Bagasse) left after sucrose extraction is burned to provide electricity to run the ethanol processing facility
    • However, it may indirectly threaten the Amazonian Rain Forests and Savannas
  • Starch from corn is easily broken down into sugars which are then fermented using yeast, to produce ethanol
  • In addition to solar energy (FREE), there’s still all of the energy needed to grow, harvest, and transport crop to the fermentation site, etc.
  • The fermentors need to be powered by electricity
  • Even though corn growing is much more energy efficient than it used to be it is still going to be more costly than using biowaste material
  • However, even if all the corn grown in the US was used for fuel ethanol, it would only reduce our gas consumption by 7-12%.
  • The production of grain-based ethanol uses fossil fuels (production of fertilizers, use of tractors, trucks, etc.) and leads to greenhouse gas emissions
    • It also uses food crops
    • An ethical issue of using food crops when people are starving
    • Ethanol production will cause the price of corn to increase due to higher demand
Cellulose Ethanol
  • A more energy-efficient process and will reduce greenhouse gas emissions
  • Cellulose ethanol is made using corn stover (stem, leaves after the cobs have been harvested), sawdust, paper pulp, and plants that are grown specifically for ethanol production like switch grass and Miscanthus.
    • Switchgrass is hardy even in poor soils and climatic conditions and requires few inputs.
    • However, the presence of lignin in the cells with secondary walls is a drawback to the breakdown of cellulose
    • Miscanthus Species have high rates of photosynthesis and can tolerate poor soils
    • However, varieties are limited by frost and drought
    • Miscanthus outperformed other bioethanol sources producing 3x more biomass than some switchgrass
  • Starting material is cellulose, lignin, and hemicellulose
    • These are untapped resources, especially when coming from waste materials
  • Uses Acid Hydrolysis and Enzymatic Hydrolysis to convert compounds into fermentable sugars
    • The energy to do this can be obtained from biomass, not fossil fuels
    • However, acid and enzyme hydrolysis is still costly, but research will eventually lead to lower costs
    • Some facilities are also using Fungal hydrolysis
  • But can enough agricultural waste and other biomass be produced without using land grown for food?
  • The goal will be to build biorefineries in diverse locations reducing the energy needed to transport the waste materials
  • Crop residues, food wastes, wood wastes, and municipal solid waste could be refined into ethanol and used all within a relatively limited area

The Cars

  • The motor industry produces cars that will run on blended fuels or ethanol
  • More than 22 million cars in the US can run on a mix of 85% ethanol, 15% gasoline (E85)
  • Some cars can use anything from E10 to E85
    • E10 is 10% ethanol, 90% gasoline
E10
  • AKA Gasohol
  • E10 is sold in existing gas stations and can be used in conventional cars
  • Widely accepted
  • Been in use for years
  • Advantages: less expensive and adds 1-3 octane points
    • The price of E10 is up to $0.10 less per gallon, so the consumer benefits
E85
  • E85 cannot be used in conventional cars
  • Slightly modified “flex-fuel vehicles” (FFVs) can burn gasoline containing anywhere from 0-85% ethanol
  • Gas stations selling E85 fuel are scarce in some parts of the country, but with FFVs, you can always revert to E10 or pure gasoline if E85 is not available
    • “Technology is proven and the knowledge base about them is strong”
    • A sensor automatically detects the ethanol percentage in the fuel and sends a signal to adjust fuel injection and spark timing
    • The only problem appears to be in very cold weather
    • Cars probably need to have less ethanol in the mix in very cold climates
  • EPA data for 2006 says that the city highway average fuel economy for FFVs using E85 is 25% lower than ethanol-free gasoline
  • E85 has a 27% lower energy content than gasoline
    • But you use as much as 2/3 less gasoline to go the same mileage
  • Today, technology exists whereby vehicles can be optimized for E85, narrowing the fuel economy gap
Hybrid Cars
  • Fueled by gasoline and uses a battery to improve efficiency
  • The electric motor is great for city driving, gasoline engine superior for highway
  • The goal would be to have a gasoline engine an E85 engine
Electric Cars (EVs)
  • Electric cars are powered exclusively by electricity, which is stored in its rechargeable batteries, which are recharged by common household electricity
  • EVs produce no tailpipe emissions, reduce our dependence on oil, and are cheaper to operate than conventional vehicles
  • The limited driving range before needing to be recharged (~300 miles)
    • but batteries are improving and there are more and more charging stations

Diesel

Petroleum Refinery

  • Gasoline: This is a hydrocarbon octane (C8H18), or in automobiles use iso-octane which is 2,2,4, methyl-pentane
    • If we wanted to use a non-fossil fuel instead of gasoline we would use ethanol
  • At higher temperatures what distills off is “diesel”
    • This is a mix of hydrocarbons (C9H20-C12H26)
    • If you want to replace this you would use biodiesel

Biodiesel

  • Biodiesel produces little soot and other pollutants
  • Biodiesel is a vegetable oil product
    • In the US this is mostly soybean oil
    • In Europe, use canola or sunflower oil
    • Malaysia, Indonesia, and Nigeria are producers of palm oil for biodiesel
    • Palm Oil (from the flesh of palm fruits)
    • Palm Kernal Oil (extracted from the seeds)
    • Major environmental concerns: loss of rainforest habitats and biodiversity
    • You can also use waste cooking oil and tallow (animal fat)
    • Algae is also being used to create biodiesel
    • The focus has been on microalgae and cyanobacteria
    • The biomass production is much greater than that of the land plants, often doubling in 24 hours
    • Many microalgae produce high levels of triglycerides that can be readily converted into biodiesel
      • Oil content can be up to 80% of the dried biomass, but 20-50% yield is more common
    • The only sustainable substitute for petroleum-based diesel
      • Does not compete for food production since they can be grown in various water sources
    • However, the production cost needs to be decreased dramatically to be economically viable
      • Harvesting is more expensive than growing land crops
    • The algae are either grown in open ponds or photobioreactors
      • Open pond cultivation is cheaper but photobioreactor cultivation has higher yields
  • The diesel engine (designed by Rudolf Diesel in 1900) can use either diesel or biodiesel
    • You can even blend them
    • B20 is 80% diesel, 20% biodiesel
    • Can’t use gasoline and ethanol in a diesel engine and can’t use diesel fuel or biodiesel in a conventional car engine
    • Biodiesel use in the US started in the late 1990s with the US Postal Service in Florida
  • Biodiesel is also available for use as home heating oil and is also being developed as jet fuel

Ethanol vs. Biodiesel

  • Growing corn calls for more fertilizers and pesticides than soybean production
  • Corn ethanol produces 10% more energy than is required to convert the corn to fuel
  • Soybean Biodiesel with its lower energy costs produces an energy gain of 93%
  • Greenhouse gas emissions are reduced by 12% when switching from gasoline to ethanol
  • Greenhouse gas emissions are reduced by 41% by burning biodiesel instead of diesel