A biofuel is a solid, liquid or gas fuel derived from relatively recently dead biological material and is distinguished from fossil fuels, which are derived from long dead biological material. Theoretically, biofuels can be produced from any biological carbon source, although the most common sources are photosynthetic plants.
There are two common strategies of producing biofuels.
One is to grow crops high in sugar (sugar cane, sugar beet, sweet sorghum) or starch (corn, maize), and then use yeast fermentation to produce ethyl alcohol (ethanol).
The second is to grow plants that contain high amounts of vegetable oil, such as oil palm, soybean, algae or jatropha. When these oils are heated, their viscosity is reduced and they can be burned directly in a diesel engine, or they can be chemically processed to produce fuels such as biodiesel.
Concerns over biofuels
In September 2007, the Organization for Economic Co-operation and Development warned that biofuels could cause more problems than they solve (Doornbosch & Steenblik, 2007) and the primatologist, Jane Goodall, warned that the demand for biofuels was causing rainforests to be cut down to grow more sugar cane and oil palms. The August report to the UN General Assembly also noted that:
“Rushing to turn food crops… into fuel for cars, without first examining the impact on global hunger, is a recipe for disaster…..To fill one car tank with biofuel requires an amount of maize that would feed one person for one year.”
In November 2007, Jean Ziegler, the UN special rapporteur on the right to food, called biofuels a “crime against humanity” and asked for a five-year moratorium on the practice of using food crops for fuel (Ziegler, 2007)
The growing criticism of biofuels is based on a variety of concerns, including:
- The conflict with land for growing food. Biofuels use up resources that would otherwise feed people.
- The threat to human rights. Indigenous people are forced from their land to make way for biofuel plantations.
- The threat to natural ecosystems and their native species. For example, the World Wildlife Fund warned that biodiesel from palm oil will only have a positive environmental impact if the new plantations are planted on fallow land. If forests are cleared to create new plantations, the resulting biofuel will actually have a negative effect (Reinhardt et al., 2007).
- The return on expended energy. Do biofuels provide enough energy to be worth the effort? Fossil fuels are relatively energy-dense because their pre-processing has been accomplished by geological forces over millions of years. In contrast, corn and sugar cane are much less energy-efficient. It takes about 2.7 kilograms of corn, or 12 kilograms of sugar cane, to produce a litre of ethanol (Kleiner, 2007).
- Increased CO2 emissions. According to Righelato & Spracklen (2007), the required land clearance for biofuel crops would result in “the rapid oxidation of carbon stores in the vegetation and soil, creating a large up-front emissions cost that would, in all cases examined, out-weigh the avoided emissions.”
- Decreased CO2 sequestration due to deforestation. The increased demand for biofuels will cause farmers to cut down forests in order to plant more corn, sugar cane, oil palm trees or soybeans. According to an analysis by Renton Righelato of the World Land Trust in Suffolk and Dominick V. Spracklen of the University of Leeds, leaving the land forested would sequester two to nine times as much carbon over a 30-year period as would be saved by using biofuels (Righelato & Spracklen, 2007).
- Increased nitrous oxide emissions. Crutzen et al. (2007) conclude that many studies underestimate the amount of the greenhouse gas nitrogen oxide produced by agricultural use of nitrogen fertilizer. If their new number is right, they say, ethanol made from corn could actually produce more greenhouse gasses than the use of gasoline.
The Gallagher Review
On 21 February 2008, the UK’s Secretary of State for Transport, Ruth Kelly, invited the Renewable Fuels Agency to undertake a ‘Review of the Indirect Effects of Biofuels’.
Many of the conclusions listed in the resulting Gallagher Review Executive Summary support the use of azolla as a potential biofuel source for the following reasons (the Gallagher Report’s conclusions are quoted below in italics):
 The biofuel source should not displace agricultural land
“It is essential that future biofuel crops should not displace existing agricultural production: “feedstock production must avoid agricultural land…..
“The introduction of biofuels should be significantly slowed until adequate controls to address displacement effects are implemented and are demonstrated to be effective.”
Azolla does not displace agricultural land because it grows in freshwater as shallow as 2.5 cm. A process developed by Azolla BioSystems Ltd uses stacked growing trays of azolla and strongly reduces the ‘footprint’ needed for azolla’s growth
Azolla therefore does not displace land used for existing agricultural production. In fact it does not use any land because it grows in freshwater as shallow as 2.5 cm.
In addition, the water that is used for azolla’s growth provides a source of organic fertilizer for growing crops that can be used for both food and for livestock feed (fodder).
Azolla therefore increases global food and fodder production.
 The biofuel source should reduce greenhouse gas emissions
“Advanced technologies have the potential to produce biofuels with higher greenhouse gas savings…..
“We recommend the replacement of volume or energy based targets with comparable greenhouse gas saving targets as soon as practicable to incentivise the supply of fuels with a lower carbon intensity.”
Azolla actually reduces greenhouse gas emissions because biofuel produced by azolla is a by-product of its sequestration of atmospheric CO2.
 Incentives will be required to develop the new advanced technologies
“Advanced technologies are currently immature, expensive and will require specific incentives to accelerate their market penetration.”
Azolla uses a natural biological system that has evolved for tens of millions of years and it is ready to use now.
Data from the 2004 Arctic Coring Expedition (ACEX) also indicate that fossilized azolla is a source for both biogas and bio-oil, indicating the suitability of modern azolla as a biofuel source (Knies et al., 2008). This is substantiated by Azolla BioSystems Ltd’s research.
Azolla can therefore provide a constantly renewable biofuel source that meets all of the criteria listed in the Gallagher report.
Several other studies have also indicated azolla’s potential as a biogas and hydrogen fuel source. These are briefly outlined below.
Anaerobic fermentation of azolla, or a mixture of azolla and rice straw, produces methane gas which can be utilized as fuel. The remaining effluent can be used as a fertilizer as it contains all of the nutrients originally incorporated in the plant tissues except for a small amount of nitrogen lost as ammonia (Van Hove, 1989).
However, there has been little systematic research into azolla’s potential as a biogas source. Das et al. (1994) mixed cowdung and Azolla pinnata residues and found that the best ratio was 1:0.4, which gave a gas production 1.4 times that of cowdung alone.
This indicates azolla’s potential to produce biogas on an industrial scale.
There has been some research undertaken into azolla to produce hydrogen, a nonpolluting, high-energy fuel. When azolla-anabaena is grown in a nitrogen-free atmosphere or a water medium containing nitrate, the nitrogenase in the symbiont, instead of fixing nitrogen, evolves hydrogen, using water as the source (Peters, 1976). Newton (1976) recorded hydrogen production at rates of 760 nmol of H2 per gram fresh weight of azolla per hour.
Hall et al. (1995) also demonstrated that the rate of hydrogen production can be increased by:
- Exposing azolla to a microaerobic environment
- Exposing azolla to a partial vacuum
- Exposing an argon-enriched or carbon dioxide-enriched atmosphere
- The immobilization of Anabaena cells isolated from the azolla
Cells may be immobilized by entrapment in transparent or translucent gels or polymers in order to increase the functional life time of the cells. Using a “trickling-medium” column bioreactor, Park et al. (1991) obtained a production rate of 83 ml H2 per gram per day.
Azolla as a source of bio-oil
Azolla Biosystems Ltd has developed a process for converting a significant proportion of azolla to bio-oil. This is confidential at present.
The LPP Foundation, University of Utrecht