Algae-Based Biofuels

Start with the basic idea. Exam options often twist the “generation” labels.

1. What is an algae-based biofuel?

An algae-based biofuel is a fuel made from algal biomass. The algae use sunlight, carbon dioxide and nutrients to grow. They make lipids (oils) and carbohydrates. These are processed into fuels and useful by-products.

A review by Indian researchers lists the fuel family. It names biodiesel, bioethanol, biogas and biohydrogen. The same review notes that algae can also supply animal feed and biofertiliser. They can also help treat wastewater.

• Raw material: algal biomass (microalgae, macroalgae, cyanobacteria).
• What the algae need: light, carbon dioxide, water, nitrogen, phosphorus, potassium.
• What comes out: liquid, gaseous and solid fuels, plus co-products.

2. Which kinds of algae are used?

The US Department of Energy (DOE) says algal biomass includes three groups. They are microalgae, macroalgae and cyanobacteria.

Microalgae are single cells, measured in micrometres. Macroalgae are large algae such as seaweed or kelp. The Indian review says microalgae hold more lipid than macroalgae and grow faster. It adds that giant kelp, a brown alga, can reach 50 m in length.

Authors disagree on how many microalgal species exist. The Indian review says more than 50,000, with about 30,000 studied. A 2022 review says there are over 20,000 kinds. The same 2022 review also quotes a range of 200,000 to 800,000 species. Do not memorise any one count.

3. What are first, second and third generation biofuels?

India’s 2018 policy sorts biofuels into two classes. “Basic Biofuels” are first-generation (1G) bioethanol and biodiesel. “Advanced Biofuels” include second-generation (2G) ethanol, municipal solid waste (MSW) to drop-in fuels, third-generation (3G) biofuels and bio-CNG.

A 2023 review gives the science behind the labels. First-generation fuels come from food crops such as corn, sugar cane and soybean. Second-generation fuel, or cellulosic ethanol, comes from low-value cellulose biomass instead of edible crops. Third-generation biofuel uses microalgae as raw material.

• 1G: food crops (corn, sugar cane, soybean oil).
• 2G: crop residues, wood chips, municipal waste.
• 3G: algae.

The policy summary names 3G biofuels but does not define them as “algae” . The algae link comes from the science literature.

Algae are a flexible raw material. The fuel depends on which part of the cell you use and how you process it.

4. How is biodiesel made from algae?

Biodiesel needs oil. Many microalgae store that oil as triglycerides. A 2022 review says the triglyceride is the starting material for biodiesel. It is converted by a reaction called transesterification.

Biodiesel is a mixture of fatty acid methyl esters (FAME). The Indian review says oil content in microalgae can reach up to 80% of dry weight in some cases. A 2022 review gives a wider range of about 20% to 80%. That difference is a disagreement between sources.

Biodiesel from algae oil has to meet fuel standards. The 2022 review says it can meet both the ASTM and European standards.

5. How is bioethanol made from algae?

Ethanol can also come from algae. The Indian review names Chlorococcum, Gelidium, Gracilaria, Laminaria, Sargassum and Spirogyra as tried examples.

The steps are simple. The polysaccharides are broken into fermentable sugars by hydrolysis. Yeast ferments the sugars. Distillation then separates the ethanol.

Algae hold little lignin and hemicellulose. The same review notes that bioethanol from algae follows a process similar to corn-based first-generation ethanol.

6. Can algae give biogas and biohydrogen too?

Yes, in research studies. Biogas comes from anaerobic digestion, where microbes break down biomass without oxygen. The Indian review says seaweeds are an excellent feedstock for this. Algae carry polysaccharides such as agar, alginate and carrageenan, with zero lignin.

Biohydrogen comes by two routes named in the review. They are biophotolysis and photofermentation. In one cited test, red alga Gelidium amansii gave 53.5 mL of hydrogen from 1 g of dry algae.

The review’s tables compare algae with land plants. In one test, Chlamydomonas reinhardtii gave 587 mL of biogas per gram of volatile solids. Banana stem gave 357.9 mL per gram in another study.

7. Can algae make jet fuel, and has it flown?

The US DOE says an algal fuel industry could one day make renewable diesel, gasoline and jet fuel. It says its work aims to help realise that potential.

A real flight did happen. In November 2011, a United (Continental) Boeing 737-800 flew from Houston to Chicago. The fuel was a blend of algae-derived fuel and ordinary jet fuel. The company announced it on 8 November 2011.

That fuel was made to the HEFA standard, which ASTM approved in July 2011. Honeywell UOP refined the algal oil. One catch matters for exams. The oil came from algae grown in fermenters on plant sugars, not from sunlit ponds.

The chain has four stages. Grow the algae, harvest them, extract the oil or sugars, then convert to fuel.

8. What is an open raceway pond?

A raceway pond is a shallow channel. A paddlewheel keeps the water moving. The 2023 review says one paddlewheel is enough to mix a 5-hectare raceway.

Open ponds are cheap. A 2016 comparison paper cites minimal capital and operating costs and low mixing energy. The same paper lists the drawbacks. Ponds need large areas and can be contaminated, for example by birds. Ponds are exposed to bad weather, and evaporation and temperature are hard to control.

The DOE shows raceway ponds at Sapphire Energy’s research site in Las Cruces, New Mexico. The ponds sit on land, not at sea.

9. What is a photobioreactor?

A photobioreactor (PBR) is a closed container. Algae grow inside it. The DOE lists flat-panel photobioreactors at Arizona State University as one design.

The 2016 comparison paper says a PBR can be run under highly controlled conditions. It greatly reduces contamination. The price is very high capital cost. Bio-fouling, overheating and cleaning are also problems.

The same paper describes a hybrid system. Algae grow in a PBR first, then oil is induced in a pond. The paper says this reduces the problem of organisms that graze on the algae.

10. How are algae harvested and dewatered?

Algae grow in very dilute water. The DOE says harvesting, dewatering and concentrating come before any fuel step. Centrifuges or membranes are typically used for concentrating the solids.

This stage costs a lot of energy. The Indian review says harvesting needs high energy input, about 20% to 30% of production cost. Techniques include centrifugation, flocculation, flotation, sedimentation and filtration.

Recycling the leftover water back to the ponds lowers total water use. The DOE names this as part of good harvesting.

11. How is the oil taken out of the algae?

The DOE calls this “preprocessing”. One route extracts lipids from the algal cells. Another route heats whole cells under high pressure. That route is hydrothermal liquefaction.

A 2022 review says solvent extraction and supercritical CO2 extraction are the most commonly used methods. Solvents such as n-hexane or a chloroform-methanol mixture appear in the Indian review’s tables.

Hydrothermal routes help because drying algae is problematic. An EU project in Ireland and Turkey used hydrothermal gasification on “wet biomass” for this reason.

12. What is transesterification, and what is left over?

Transesterification turns algal oil into biodiesel. The Indian review lists test rows with NaOH and with H2SO4 as the catalyst. The main product is FAME, which is biodiesel.

The Indian review lists test conditions. One used NaOH at 70 degrees C. Another used an acid catalyst, H2SO4, at the same temperature.

Not all the algae become fuel. The DOE says the parts not converted can be 40% to 75% of the biomass. These parts can return nutrients and power to the system. They can also be sold as animal feed or commodity chemicals.

Algae look strong on paper. The hard part is turning that into cheap fuel at scale.

13. How much oil can algae give per unit of land?

Estimates are high but they vary a lot. A CORDIS success-story article on the EU’s Mabfuel project says algal oil yield is estimated at 19,000 to 75,000 litres per acre per year. It says this is 7 to 31 times that of palm oil.

The Indian review gives a different range. It says 5,000 to 15,000 US gallons of biodiesel per acre per year. Converted, that is about 19,000 to 57,000 litres. The two lower figures agree. The upper figures do not.

Both sources use acres, not hectares. A 2022 review gives only a theoretical ceiling. It says algae could make 280 tonnes of dry biomass per hectare per year at 9% solar conversion. Treat that as a limit, not a farm result.

14. Do algae really avoid farmland and fresh water?

Partly. The US National Research Council says algae can grow in ponds or photobioreactors on non-arable land. They can use saline water or wastewater. Algae are studied as a way to avoid the “food versus fuel” clash of first-generation crops.

The DOE lists what a farm needs: non-arable land, non-potable water, waste nutrient streams, waste carbon dioxide and enough sunlight. The Indian review adds that algae need no herbicide or pesticide.

Fresh-water use is not always small. Item 18 shows how much water some systems consume.

15. How do algae capture carbon dioxide?

Algae take in CO2 as they photosynthesise. The DOE counts waste CO2 as a useful input. A 2022 review puts a theoretical figure of 513 tonnes of CO2 used for 280 tonnes of dry biomass.

Algenol’s design is a practical example. The company says its process turns 1 tonne of CO2 into 144 gallons of fuel. It says 85% of the CO2 used becomes ethanol, gasoline, diesel and jet fuels. These are company design claims, not independent results.

16. Is algae fuel cheap, and does it give more energy than it uses?

Not yet. In 2014 the DOE’s Bioenergy Technologies Office said its modelled 2019 cost was about $7 per gallon gasoline equivalent. That was without co-products. It hoped new work could cut costs by 30% to 50%.

The Indian review lists the same problem. Cultivation costs more than for conventional crops, and harvesting uses heavy energy.

The National Research Council found energy trouble too. For some system designs, the energy output was less than the energy input. It gave an energy return on investment range of 0.13 to 3.33. The NRC defines EROI as total energy outputs, including co-products, divided by energy inputs. A value below 1 means the fuel and its co-products hold less energy than it took to make.

17. What about contamination, nutrients and mosquitoes?

Open ponds can be invaded by other organisms. The 2016 comparison paper names contamination as one open-pond weakness. Closed photobioreactors reduce it but cost much more.

Fertiliser is another limit. The National Research Council estimated that making 39 billion litres of algal biofuel needs 6 to 15 million tonnes of nitrogen a year. It also needs 1 to 2 million tonnes of phosphorus. This assumes no recycling. That equals 44% to 107% of total US nitrogen use.

Open ponds also raise local risks. The council lists leaks into groundwater if liners fail. It also lists mosquitoes and mosquito-borne disease around badly managed ponds.

18. How much water do algal biofuels use?

The National Research Council says the water use depends on the design. Its summary gives 3.15 to 3,650 litres of fresh water per litre of gasoline-equivalent algal fuel. Its Natural Resource Use chapter gives a range of 32 to 3,650 litres for three open-pond studies. The lower end differs between the two parts of the same report.

For comparison, the council says making 1 litre of petrol from crude oil or oil sands uses 1.9 to 6.6 litres of water. At least 123 billion litres of water would be needed for 39 billion litres of algal fuel. That fuel volume equals 5% of US transport fuel demand.

Choice of water matters. Fresh, saline, marine and waste water give very different footprints. Recycling harvest water also lowers use.

India’s main biofuel programme is ethanol from crops. Algae work is research and pilot scale. Keep the two apart.

19. Does the National Policy on Biofuels, 2018 mention algae?

The Cabinet approved the policy on 16 May 2018. PIB’s summary names “Third Generation (3G) biofuels” among Advanced Biofuels. It does not name algae in that summary. The full policy text was not checked, so the exact algae wording is unconfirmed.

An earlier policy is clearer. A PIB release of 24 December 2009 on the first National Policy on Bio-fuels mentions an Indo-US MoU. Its focus was joint research on second-generation biofuels such as cellulosic ethanol and algal biodiesel.

The 2022 Cabinet amendment moved the 20% ethanol blending target to ethanol supply year 2025-26 from 2030. PIB’s release says it allows more feedstocks. The release text checked does not name algae.

20. Does any current Indian scheme list algae?

Yes. On 9 August 2024 the Cabinet approved a modified Pradhan Mantri JI-VAN Yojana. The scheme backs advanced biofuel projects. PIB says its scope now includes advanced biofuels from lignocellulosic feedstocks, industrial waste, syngas, algae and others.

The modified scheme runs until 2028-29. It also lets “bolt on” plants and brownfield projects apply. Preference goes to proposals with new technologies.

21. What did Indian Oil and DBT build at Faridabad?

The IOC-DBT Centre for Advanced Bio-Energy Research sits at Indian Oil’s R&D Centre in Faridabad. In August 2018 Indian Oil unveiled a pilot plant there with LanzaTech. It makes lipids (“algal oil”) from CO2 in two steps.

First, LanzaTech’s gas fermentation turns CO2 into acetic acid. Then Indian Oil’s aerobic fermentation turns acetic acid into lipids. The lipids are trans-esterified. Omega-3 DHA esters are separated as a high-value product.

The pilot reactor is 100 litres and takes in about 10 kg of CO2 a day. The release calls it a 3G technology. The release describes fermentation steps, not ponds.

22. What was the Reliance and Algenol project?

Algenol and Reliance Industries announced a demonstration module in India on 3 February 2015. It sits near Reliance’s Jamnagar refinery, described as the world’s largest. Construction ended in November 2014.

The module completed several batches of Algenol’s wildtype host algae. Reliance runs it day to day, after training from Algenol. Reliance has been a strategic investor in Algenol since June 2011.

The release says the process needs saltwater, not fresh water, which it calls a key advantage for drought-prone India. The announced results are company statements, not a commercial plant.

23. Which Indian agencies fund and do algae research?

The ISTI portal lists an Energy Biosciences-Biofuel programme. It says it supports R&D on next-generation biofuels. It names algal biodiesel, cellulosic ethanol, biobutanol and biohydrogen.

University work fits in here. In August 2020 PIB reported on Dr T. Mathimani of NIT Tiruchirappalli. His project was funded by a DST INSPIRE faculty fellowship. His team isolated marine microalgae from Tamil Nadu’s coast. The strains were Picochlorum, Scenedesmus and Chlorella, chosen for carbon and TAG (lipid) content.

The Indian review quoted in this lesson comes from the Sardar Swaran Singh National Institute of Renewable Energy, Kapurthala.

24. How big is India's blending programme compared with algae?

India’s real biofuel numbers are about ethanol. A PIB backgrounder of 10 July 2026 gives the blending achieved in each ethanol supply year (ESY).

• ESY 2020-21: about 8.1%.
• ESY 2021-22: 10.0%.
• ESY 2022-23: 12.1%.
• ESY 2023-24: 14.6%.
• ESY 2024-25: 19.2%.
• ESY 2025-26 (November to June): 20%.

An older PIB release gives 12.06% for ESY 2022-23, which rounds to the same 12.1%. The same release shows ethanol blending rising from 38 crore litres in ESY 2013-14 to more than 500 crore litres in ESY 2022-23. None of the releases checked reports an algae share in these figures.

The global story is large public research and slow commercial progress.

25. What are the main global algae biofuel programmes?

In the United States, the DOE’s Advanced Algal Systems area funds research to lower the cost of algal biofuels. It was formerly under the Bioenergy Technologies Office. The DOE says it works with public and private partners.

In Europe, the EU’s FP7 research programme funded the Mabfuel project. It tested seaweeds and microalgae in Ireland and Turkey. Its team picked Nannochloropsis oculata and N. salina for high oil content. It found outdoor cultures had better oil content than indoor ones and were cheaper.

The private sector led the commercial push. ExxonMobil and Synthetic Genomics announced a programme in 2009. MIT Technology Review reported a new agreement between the companies on 20 May 2013. Exxon sent the firm back to basic science after a greenhouse-scale effort. MIT Technology Review says the partners do not seem to have cracked the code for cheap algae fuels.

26. Which exam claims about algae biofuels are wrong?

Reported Exxon dollar figures measure different things. Do not memorise one for the exam.

Now the traps. These come from the UPSC 2017 question on algae biofuels and its options.

• “Algae biofuel can be made only at sea.” This is false. The DOE shows raceway ponds on land, and Algenol’s module sits near a refinery in Jamnagar.
• “Developing countries lack expertise and need large facilities.” The official UPSC key marks statements 2 and 3 as correct (“2 and 3 only”).
• “All algal fuel needs sunlight.” This is false. The 2011 United flight fuel came from algae fed on plant sugars. Indian Oil’s Faridabad pilot also ferments CO2-derived acetic acid.
• “Algal biofuel is already cheaper than fossil fuel.” False. MIT Technology Review reported in 2013 that algae-based fuels were, so far, too expensive. A DOE model puts the cost at about $7 per gallon gasoline equivalent for 2019.
• “The 2018 policy sets an algae blending target.” Not supported. The PIB summary names 3G biofuels but gives no algae target.