Algae biofuel is a renewable fuel made from fast-growing microscopic plants that use sunlight, water, and carbon dioxide to build energy-rich molecules. Instead of drilling fossil fuels from underground, an algae biofuel system grows new biomass in ponds or transparent photobioreactors. This matters because algae can produce oils that can be refined into biodiesel, jet fuel, or other liquid fuels.
The main idea is to turn solar energy and carbon from the air or waste gases into useful chemical energy.
Key Facts
- Photosynthesis stores energy: 6CO2 + 6H2O + light energy = C6H12O6 + 6O2.
- Algae biomass growth depends on light, CO2, water, nutrients, and temperature.
- Oil yield = mass of extracted oil / mass of dry algae.
- Biodiesel production often uses transesterification: triglyceride + alcohol = biodiesel + glycerol.
- Energy efficiency = useful fuel energy output / total energy input.
- Algae can be grown in open ponds or closed photobioreactors, each with different cost and control tradeoffs.
Vocabulary
- Algae
- Algae are simple photosynthetic organisms that can grow quickly in water and produce oils, proteins, and carbohydrates.
- Photobioreactor
- A photobioreactor is a controlled transparent growing system that exposes algae to light, carbon dioxide, and nutrients.
- Biomass
- Biomass is the total organic material produced by living organisms, such as harvested algae cells.
- Lipid
- A lipid is a fat or oil molecule that stores chemical energy and can be converted into liquid fuel.
- Biodiesel
- Biodiesel is a renewable liquid fuel made by chemically converting oils or fats into fuel molecules that can power diesel engines.
Common Mistakes to Avoid
- Assuming algae fuel is automatically carbon neutral is wrong because pumps, drying, harvesting, and refining can use energy that may come from fossil fuels.
- Ignoring water and nutrient needs is wrong because algae growth requires nitrogen, phosphorus, and controlled water conditions, not just sunlight.
- Confusing biomass with fuel is wrong because harvested algae must be separated, dried or processed, and converted before it becomes usable fuel.
- Treating open ponds and photobioreactors as the same machine is wrong because open ponds are cheaper but less controlled, while photobioreactors are more controlled but usually more expensive.
Practice Questions
- 1 A photobioreactor produces 80 kg of dry algae in one day. If the algae are 30 percent oil by mass and extraction captures 85 percent of the oil, how many kilograms of oil are collected?
- 2 A processing system uses 500 MJ of energy to grow, harvest, and refine algae. The biodiesel produced contains 650 MJ of chemical energy. What is the energy efficiency, expressed as a decimal and as a percent?
- 3 A company can choose an open algae pond or a closed photobioreactor for a new biofuel site. Explain which system would be better if the main goal is low cost, and which would be better if the main goal is tight control of contamination, temperature, and CO2.