How to Use Algae As a Sustainable Biofuel Source
Introduction to Algae Biofuels
Algae are one of the most promising and sustainable sources of biofuel. Unlike other crops used for biofuels like corn and sugarcane, algae can be grown quickly and efficiently without disrupting the food supply. Algae also have a higher yield per acre than other biofuel sources. For these reasons, algae are an ideal candidate to produce biodiesel, ethanol, biogas, and other biofuels sustainably.
Why Algae Make Good Biofuel Feedstocks
There are several key advantages that make algae well-suited for biofuel production:
High yields – Algae can produce over 2,000 gallons of biofuel per acre per year. In comparison, soybeans only produce 50 gallons per acre per year. The high oil and biomass yields of algae result in more biofuel output.
Rapid growth – Under ideal conditions, algae can double their volume within 24 hours. Their quick growth allows algae biofuel production to be scalable and responsive to demand.
Less resource intensive – Algae require less water and fertilizer than conventional crops. Many types of algae grow in brackish water unsuitable for agriculture. Algae can utilize waste resources like CO2 and nitrogen run-off as nutrients.
Utilize marginal land – Algae farms can be built on land unsuitable for food production, like deserts and coastal areas. This avoids competition with agriculture.
High oil content – The oil in algae can reach up to 50% of their overall biomass. Many species have naturally high oil levels ideal for biodiesel.
How Algae Can Be Grown For Biofuels
There are two main approaches to cultivating algae for biofuel production:
Open Pond Systems
- Open ponds are shallow basins filled with an algae and water solution.
- These are the simplest and cheapest systems to build and operate.
- Open ponds provide a natural source of CO2 and sunlight to feed algae growth.
- However, they are less productive than closed systems due to contamination.
- Photobioreactors are closed loop systems made of transparent tubes or panels.
- They provide more controlled conditions than open ponds.
- Photobioreactors have higher algae density and productivity potential.
- But they are also more expensive to build and operate than ponds.
The best cultivation system depends on the algae species, climate, and economic factors. Both open and closed systems are used in algae biofuel production today.
How Biofuel Is Made From Algae
There are several methods to produce biofuel from algae:
Extracting Oil for Biodiesel
- The algae are dried and the oil is chemically extracted or mechanically pressed.
- This algae oil then goes through a process called transesterification to create biodiesel.
Fermenting Sugar for Ethanol
- The algae are processed to extract their sugar content.
- This algae sugar is fermented using yeast to produce ethanol, just like corn or sugarcane ethanol.
Anaerobic Digestion for Biogas
- Whole algae are put into an oxygen-free digester, where bacteria break down the biomass.
- This process releases biogas containing methane that can be combusted to generate energy.
- Dried algae biomass can be burned directly for its energy content, releasing heat that can be used to generate electricity.
Challenges With Algae Biofuels
While algae biofuels show a lot of promise, there are still some technological and economic obstacles:
- The process to extract and convert the oils into usable fuel remains energy-intensive and expensive. More R&D is needed.
- Open pond contamination and inconsistent yields make large-scale production difficult.
- Sensitive photobioreactors are prone to system crashes from temperature swings and fouling.
- Economies of scale have not yet pushed algae fuel to cost parity with fossil fuels.
However, with sufficient investment and research, algae could become a major sustainable transport fuel within the next decade. Algae biofuel offers great potential to provide renewable energy while minimizing pressure on food crops and scarce resources.
With their high yields, fast growth, and sustainability benefits, algae are one of the most promising feedstocks for biofuel. Both open pond and photobioreactor systems offer scalable cultivation methods. Extraction and processing can produce biodiesel, ethanol, biogas, and other renewable fuels. While technical hurdles remain, algae present an opportunity for high-output biofuel production with minimal impact on freshwater supplies and agriculture. With further commercialization and economies of scale, algae-derived fuels could play a major role in sustainably powering transportation and energy needs.