Biofuels
Author: Professor P.J Harvey, Head of Bioenergy Research University of Greenwich.
( Article Type: Explanation )
What are biofuels?
Biofuels are liquids, solids or gases derived from sustainable renewable sources, whose use instead of fossil-based fuel is an important route by which to achieve major gains in the reduction of carbon emissions.
This is particularly so when they are used to fuel Combined Heat and Power (CHP) systems. The biofuels portfolio includes:
- ethanol
- biodiesel
- biomethane
- lignocellulosic biomass and
- more recent introductions such as biobutanol and glycerol. Amongst renewable energy sources, only biofuels can be used to efficiently produce both heat and power in CHP systems.
Biofuel Resources
Approaches to establish biofuel resources have been developed on the back of long-established farming practices aimed at providing food, but new technologies based on the exploitation of industrial by-products such as glycerol, as well as food and agricultural wastes, are paving a way forward to ensure food production is not compromised and renewable resources are not wasted.
One of the most efficient ways to sustainably process heterogeneous food waste and plant by-product streams is by anaerobic digestion (AD)* to produce biomethane. The technology has been in existence for treating waste water for more than a century, but take-up at an industrial scale has only recently been stimulated by rising oil prices; the need to divert organic wastes from landfill; and political incentives such as the availability of Carbon Credits and of Feed-in Tariffs, the latter of which are paving the way for gas supply to grid systems in Europe and parts of Africa such as Kenya.
Biofuel in South Africa
In South Africa, lack of enabling legislation in the past has slowed the development of CHP programmes and in turn, industrial-scale take-up of biogas production. However, the Renewable Energy Feed In Tariff (REFIT) in South Africa should stimulate further development of this technology.
In the biodiesel industry sector, technologies to make biodiesel esters and glycerol from plant oil have been in existence since the 1920’s and are now widespread because biodiesel can be used in place of fossil fuel in standard diesel engines without engine modification.
It has the safest handling properties of all known fuels - it is water soluble, bio-degradable, non-odorous, non-volatile, non toxic and has low flammability. Moreover since it has a high boiling point and relatively high density and heat capacity and extremely low volatility, glycerol fuel tanks can be safely used as thermal batteries, storing heat for CHP applications.
Co-development of a glycerol biofuel market is predicted to completely overhaul the biodiesel industry sector, providing the necessary timelines to establish alternative new sources of glycerol, ultimately a better fuel than biodiesel. In this regard, significant attention is being paid to halophytic microalgae that generate up to 80% of their mass as glycerol in highly saline environments. Even so, industrial-scale production of glycerol from algae still needs fundamental research to find economical ways to deliver micro-algal glycerol from saline waters to CHP systems.
