For the last few decades there has been a global agreement that use of renewable biofuels, instead of finite fossil fuels, is vital for energy security as well as providing a range of other economic and environmental benefits. However despite the best of intentions, many argue that the global increase in the use of food crop based biofuel has caused more harm than good, causing increased deforestation, greenhouse gas emissions and potentially increasing food prices.
This argument has been heard by the US and EU who recently introduced legislation limiting the use of food crop based biofuels and encouraging the use of ‘advanced’ non-food based biofuels to meet their biofuels usage targets. The EU Renewable Energy Directive states that by 2020 10% of transport fuel must come from biofuel, of this 10%, only 5.5% can come from food crops, with the other 4.5% coming from advanced biofuels. There is also legislation from the EU Fuel Quality Directive aiming for a 6% reduction is greenhouse gas emissions by 2020, which could be achieved by increased use of advanced biofuels.
There are a number of established technologies that come under the heading of advanced biofuels, including the use of food waste or lignocellulose crops, but the use of these crops is still plagued by environmental issues. A novel and exciting future source of biofuel could come from algae which could have an advantage over other biofuel crops because it does not take up land used for growing food and has the potential to be carbon neutral.
The term Algae refers to a diverse group of photosynthesising marine plants, the smallest of which can be microscopic single celled organisms referred to as microalgae. Some algae are complex multicellular organisms such as seaweed these are referred to as macroalgae.
The prospect of using microalgae to produce biofuel has been around since the 1970s when an energy crisis prompted the start of the US Department of Energy’s Aquatic Species Program, which aimed to exploit the high lipid content of microalgae to produce biodiesel.
Since the 1970s huge progress has been made in the identification and cultivation of microalgae as well as progress in the extraction of useful chemicals from the algae to produce biofuels and other products. However, microalgae has yet to be used to produce biodiesel at an economically viable scale, mainly due to the costs involved in growing the huge quantities required to produce useful amounts biodiesel at a competitive price.
Many believe that using microalgae to produce biodiesel will never be economically viable in the UK, although it is already established in non-biofuel industries, such as the production of Omega oils, which are more profitable. Microalgae can be grown in enclosed bioreactors or open pond systems both of which have their benefits and limitations, the development of low cost large scale production methods for growing microalgae is the main factor preventing the establishment of a market for Algal biodiesel in the UK.
Seaweed or macroalgae such as Kelp have been farmed, or harvested from the wild, for centuries particularly in Asia. Macroalgae is used in million dollar industries such as fertiliser production and animal feed. In the UK on shore and off shore farming of macroalgae is only done for research purposes, on a small scale. The technology for large scale farming is well established in China and similar methods could be adopted by the UK, although further research needs to be done to find suitable production sites and to minimise the environmental impact.
Macroalgae has a much lower lipid content than microalgae, this means it is less suited for biodiesel production, however macroalgae can be used to produce biogas via a process called anaerobic digestion. Much of the infrastructure for anaerobic digestion already exists in the UK, for the production of biogas from waste crops, so commercial scale biogas production from macroalgae could be easy to achieve.
A recently published document (2012) from the Algae Bioenergy Special Interest Group (AB-SIG) outlines the research needs that need to be met for the commercialisation of Algae biofuels. There is debate as to whether the commercial production of algal based biodiesel will ever become viable in the UK, but AB-SIG predict that use of Algal biomass, particularly from on-shore Macroalgae, could be used to produce bioenergy through anaerobic digestion in the next 5-10 years.