With food and biomass competing for land use, and with first generation biofuels receiving widespread criticism for undermining food security, algae is viewed by some as an alternative that will allow the biofuels industry to sidestep some of the more controversial issues that it has encountered.
On the face of it, it is true that algae-based fuels offer a wide range of advantages. Research into the technology has been underway for many years, which means that it is currently at an advanced stage of development. Many species of microalgae have high lipid contents that can readily be extracted and converted to biodiesel. Similarly, their high fermentable sugar content makes them suitable for bioethanol production.1 As a result, microalgae can be used to generate a wide range of bioenergy products with good environmental credentials.
Moreover, algal fuel is carbon neutral – it absorbs carbon dioxide as it grows and both CO2 and waste water can be used as nutrients for its cultivation. The energy yield per acre is higher than for other biofuels, and algae can be produced on land that is unsuitable for other types of agriculture – in tanks in deserts, for example. Algal cells reproduce much faster than crop plants and can be grown using both saline and wastewater, which means they have a minimal impact on fresh water resources. To this impressive array of benefits we can also add the fact the fuels produced from algae are completely biodegradable and relatively harmless to the environment if spilled.
However, as with any emerging technology, there are still some issues to be dealt with. Gerhard Knothe, a research chemist with the US Department of Agriculture's Agricultural Research Service, has identified some problems with the cold flow properties of algal biofuels (their ability to flow well at low temperatures).2 Algal fuels have also been found to degrade more easily than other biofuels, due to the fact that many of the oils from which the biofuels are derived contain relatively high amounts of saturated and polyunsaturated fatty acids. There are also some questions about the cost per litre of the fuel, which is currently too high.
Several EU-funded projects have been set up to address these issues and to advance the technology for energy production from algae. The Biowalk4Biofuels Project aims to develop an innovative system for biowaste energy recovery in order to produce biofuels using macroalgae (seaweed) as a catalyser. In so doing, the project aims to achieve the cost-efficient production of biogas without using cereal crops. Moreover, with a view to further reducing the land impact of the technology, the project aims to optimise the biogas yield from the amount of biowaste and CO2 used and expand the range of biowastes that can be utilised for biogas production.
To achieve these objectives, the project’s research will focus on selecting macroalgae species that provide significant yields of biomass with high carbohydrate content, which it will do by choosing algae species according to growth rate and high-energy content. The researchers will then isolate and regenerate protopoplasts from the selected species in order to optimize cell growth rate and achieve the maximum biomass yield from the selected species.
Another work package will focus on the selection of biowaste and exhaust gases to be used for algae growth and studying and implementing a piping system for recovering and transporting CO2 to the project’s algae ponds. These ponds will also be used to evaluate a closed macroalgae cultivation system and the results of this evaluation will be used to optimize macroalgae cultivation parameters with a view to ultimately increasing biomass yield.
Finally, a two-phase anaerobic digestion biogas production plant and a gas cleaning and upgrading process is required to achieve compressed biomethane, which will be used to fuel motor vehicles. The ultimate goal is to produce a cost-efficient, low energy-intensive, purified biogas, and to reduce biowaste and negative environmental impacts from industry.
Another EU-funded project also believes that the answer to the food-fuel conundrum lies with aquatic organisms. The nine-partner team behind the DirectFuel project ('Direct biological conversion of solar energy to volatile hydrocarbon fuels by engineered cyanobacteria') aims to develop photobiological systems for the production of volatile hydrocarbon fuels such as propane using only CO2, water and sunlight as the principal substrates. Biological energy-conversion processes are well-suited for the production of hydrocarbon fuel molecules. However, as the natural potential for this conversion is limited, DirectFuel’s aims to construct new metabolic pathways with this capability.
The project has chosen propane as a key-target as it is volatile at room temperature, yet easily liquefied at moderate pressure. This allows the fuel product to be harvested without disturbing the biological production process, while at the same time allowing the fuel to be directly and easily used under high energy-density storage conditions. Propane has already been utilized as vehicle fuel for over half a century and many EU countries already have infrastructure for distributing liquefied propane in the form of LPG. This compatibility with existing distribution and end-use infrastructures increases the market uptake potential of the technology.
Cultivation of the essential cyanobacteria can be carried out on land unsuitable for agriculture, and in enclosed containers that require no soil, thus eliminating any competition between land use for food and fuel production. It will take some time before the technology developed within DIRECTFUEL is available on the market, but the research has already attracted interest from petroleum gas associations and the project’s eventual impact on the production of carbon-based fuels and chemicals is likely to be considerable.
A recent report from the Institute for European Environmental Policy3 has concluded that there is limited ‘spare’ land in Europe for the cultivation of energy crops. In light of this, and given the good land-use credentials of algae, we are likely to see growing market demand for systems that allow the production of high quality fuels from algal biomass. With projects like Biowalk4Biofuels and DirectFuel successfully meeting this demand, we can expect algae farming to become a major player in the fuel industry in the coming years.
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