How Biofuels Are Made?
Petroleum-based products – such as oil, gasoline, and diesel – that are currently used as fuel contain a complex mix of hydrocarbons. Hydrocarbons can also be produced from biomass sources using various biological and chemical processes.
The Question of Conversion
With the pressing need for new and cost-effective energy sources, we are revisiting the way we produce biofuels. Oil is becoming harder to find and is a dirty fuel. The impending threat of global warming and pollution have encouraged further research to ensure the health of our planet and that of future generations.
Lignocellulosic material, referred to as “biomass”, is the most common material used to convert to biofuel, biodiesel, and biogas. Lignocellulose is the fibrous, woody tissue found in plants that is otherwise inconsumable by humans. Utilizing this dry plant material will eliminate the unnecessary waste that comes from food crop preparation.
Deconstruction of plant cells
The plant cell wall must be broken down as the first part of the conversion process. This can be achieved via high-temperature deconstruction or low-temperature deconstruction.
High-Temperature Deconstruction of biomass
Extreme temperatures and pressure are used to break down biomass into liquid or gas intermediates, primarily taking the form of three routes:
Hydrolysis: Biomass is superheated in an oxygen-free environment, breaking it down into pyrolysis vapor, gas, and char. Once the char is removed, the vapors are cooled and condensed into a liquid bio-crude oil.
Gasification: Biomass is superheated to temperatures above that of hydrolysis (over 700 degrees Celsius) with some oxygen present to produce a synthetic gas, composed mostly of carbon monoxide and hydrogen.
Hydrothermal liquefaction: Used with wet feed stock, such as algae, moderate temperature and high pressure are used to create liquid bio-crude oil.
Low-Temperature Deconstruction
Biomass is pretreated by physically altering its structure to make sugar polymers more accessible. These polymers are then deconstructed chemically or enzymatically into simple blocks.
Upgrading of intermediates
Intermediates formed in deconstruction must be upgraded biologically or chemically to create a final product. Microorganisms such as bacteria and yeast can be used to ferment sugars and gaseous intermediates to make fuel blend stocks and chemicals. Alternatively, a catalyst can be used to remove any unwanted compounds to improve storage and handling. The finished products can be biofuels, bioproducts, or stabilized intermediates that can be finished in a chemical or petroleum processing plant.
Animal Studies
Vegetarian animal studies have been key in making strides toward sustainability, specifically the study of their gastrointestinal tracts. Scientists and zoologists examine the microbiomes of these creatures in order to single out symbiotic bacteria that make enzymes to break apart cellulose. They grind poop samples and sequence the billions of DNA base pairs with the help of computer technology in an effort to better bioengineer plants into the sugars needed to convert to biofuels.
- Pandas: notorious for eating tough bamboo, scientists have discovered 17 bacteria within their GI tract to break down cellulose.
- Cows: ruminant animals that eat grass and grains; study of their rumen – the primary site for microbial fermentation – identifies enzymes that break down switch grass into oligosaccharides.
- Hoatzin: with a digestive tract similar to that of cows, this leaf-eating bird is loaded with cellulose-busting enzymes.
- Tammar Wallaby: despite having a similar GI tract to cows, these animals produce less methane; further study of their microbiomes may reveal how this is possible.
- Asian Long-horned Beetle: this wood-eating beetle has a fungus living within its digestive tract which breaks down lignin.
- Shipworms: known as termites of the sea, these clams use enzymes in their digestive tract to breakdown wood consumed from driftwood
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