Biofuels
What are biofuels?
The term 'biofuels' covers all transportation or liquid fuels which are made from biomass.
Biomass itself is organic plant material which has stored energy from the sun in the form of chemical energy. We can convert this stored chemical energy into liquid fuels by a number of relatively simple steps. For example we can ferment the starch or sugars in crops like corn, wheat or sugarcane into ethanol. We can convert vegetable oils from oil bearing crops such as rape-seed or soy beans, or even oil derived from algae into biodiesel by processes such as esterificiation or hydrogenation.
Biofuels are increasingly being used as a component in gasoline and diesel as they can help to diversify energy supplies – and so reduce reliance on imported oil. They also have a significant role to play in reducing greenhouse gas emissions.
In the USA, the Energy Independence and Security Act of 2007, mandates that there should be 36 billion gallons of biofuels blended into fuels by 2022, of which 21 billion gallons must be advanced biofuels. Europe also has targets for increased use of biofuels under the Renewable Energy Directive. 10% of road transport fuels, by energy, must be from renewable sources by 2020.
How are biofuels used?
Ethanol and biodiesel can be blended with gasoline or diesel respectively to produce a finished fuel. However, they are not ideal fuel components due to reduced energy content and reduced compatibility with vehicles and distribution infrastructure.
In Europe and the USA, for example, ethanol can be used in conventional gasoline in blend of up to 10% volume.
Higher percentage blends can be used in specially designed or modified vehicles (e.g. flex-fuel vehicles).
Are biofuels better for the environment than conventional fuels?
Biofuels reduce overall greenhouse gas emissions when looked at across the entire lifecycle (known as "well-to-wheel" emissions). The carbon dioxide (CO2) emitted when the biofuel is burnt in the vehicle is offset by the CO2 absorbed from the atmosphere during the growing of the crop that is used to make the biofuel. Calculations of the well-to-wheel emissions include considerations about the energy that has been produced to make the biofuel (in farming, harvesting, converting the crop to fuel and transporting the fuel). Actual emissions from biofuels vary widely depending on how they are produced.
Today's biofuels produced from conventional crops (such as bioethanol from corn or sugar cane, or biodiesel from vegetable oils) deliver around a 20-60% GHG emission reduction on a well-to-wheels or crop-to-car basis, versus conventional fossil fuels such as gasoline and diesel. Ethanol produced from Brazilian sugarcane is the most efficient current generation biofuel and can provide emissions reductions of up to 90%.
Biobutanol's chemical properties allow it to be blended at 16vol% in gasoline, thereby displacing more gasoline per gallon of fuel consumed than the standard 10vol% ethanol blend. On a mile driven basis, the 16vol% butanol blend also has the potential to reduce GHG emissions further than the 10vol% ethanol blend, given similar biorefinery site and process specific conditions. LCA is used alongside process development and economic evaluation to guide the research and development team to the most sustainable biobutanol design.