Production of biofuels from raw materials requires energy (for farming, transport and conversion to final product as well as the production of fertilizers, pesticides and herbicides). The level of energy expenditure varies by location: more intensive agricultural regimes such as those found in Western countries are more energy intensive. The more machinery is used for farming, the greater the energy expended in the process; developing countries tend to have less intensive agricultural methods. It is possible to produce biomass without incurring large agricultural energy costs: for example, wild-harvesting excess wood from established forests can be done without much energy input. However the yield of biomass from such resources is not consistent or large enough to support biofuel manufacture on a large scale.
The energy balance of a biofuel is determined by the amount of energy put in to the manufacture of fuel compared to the amount of energy released when it is burned in a vehicle. Biofuels tend to require higher energy inputs per unit energy than fossil fuels: oil can be pumped out of the ground and processed more efficiently than biofuels can be grown and processed. However, this is not necessarily a reason to use oil instead of biofuels, nor does it have an impact on the environmental benefits provided by a given biofuel.
Other factors connected to energy balance are a) cost and b) environmental impact. High energy impacts do not necessarily mean that the resulting fuel will be bad for the environment: energy can be derived from renewable resources to power biofuel manufacture.
Energy balance is not necessarily a measure of a good biofuel. Biofuels should be affordable, sustainable, abundant and provide good GHG emissions savings when compared with fossil fuels.
Energy balance/ efficiency of conversion is relevant when considering how best to use a given amount of biomass resources. For example, given limited resources should biomass be converted into heat and power or liquid transport fuels? Looking at energy balance and the efficiency of energy conversion can help to use biomass resources efficiently and with maximum environmental gain.
Studies have been done that calculate energy balances for biofuel production. Some of these show large differences depending on the biomass feedstock used and location. [19]
The energy balance is more favourable for biofuels made from crops grown in subtropical or tropical areas than those made from crops grown in temperate areas [citation needed]. This is largely due to the increased yield of biomass from crops in areas that receive more sunlight.
Life cycle assessments of biofuel production show that under certain circumstances, biofuels produce only limited savings in energy and greenhouse gas emissions. Fertiliser inputs and transportation of biomass across large distances can reduce the GHG savings achieved. The location of biofuel processing plants can be planned to minimise the need for transport, and agricultural regimes can be developed to limit the amount of fertiliser used for biomass production. A European study on the greenhouse gas emissions found that well-to-wheel (WTW) CO2 emissions of biodiesel from seed crops such as rapeseed could be almost as high as fossil diesel. It showed a similar result for bio-ethanol from starch crops, which could have almost as many WTW CO2 emissions as fossil petrol. This study showed that second generation biofuels have far lower WTW CO2 emissions.[20]
Other independent LCA studies show that biofuels save around 50% of the CO2 emissions of the equivalent fossil fuels. This can be increased to 80-90% GHG emissions savings if second generation processes or reduced fertiliser growing regimes are used (Concawe Well to Wheels LCA for biofuels).
The energy balance of a biofuel is determined by the amount of energy put in to the manufacture of fuel compared to the amount of energy released when it is burned in a vehicle. Biofuels tend to require higher energy inputs per unit energy than fossil fuels: oil can be pumped out of the ground and processed more efficiently than biofuels can be grown and processed. However, this is not necessarily a reason to use oil instead of biofuels, nor does it have an impact on the environmental benefits provided by a given biofuel.
Other factors connected to energy balance are a) cost and b) environmental impact. High energy impacts do not necessarily mean that the resulting fuel will be bad for the environment: energy can be derived from renewable resources to power biofuel manufacture.
Energy balance is not necessarily a measure of a good biofuel. Biofuels should be affordable, sustainable, abundant and provide good GHG emissions savings when compared with fossil fuels.
Energy balance/ efficiency of conversion is relevant when considering how best to use a given amount of biomass resources. For example, given limited resources should biomass be converted into heat and power or liquid transport fuels? Looking at energy balance and the efficiency of energy conversion can help to use biomass resources efficiently and with maximum environmental gain.
Studies have been done that calculate energy balances for biofuel production. Some of these show large differences depending on the biomass feedstock used and location. [19]
The energy balance is more favourable for biofuels made from crops grown in subtropical or tropical areas than those made from crops grown in temperate areas [citation needed]. This is largely due to the increased yield of biomass from crops in areas that receive more sunlight.
Life cycle assessments of biofuel production show that under certain circumstances, biofuels produce only limited savings in energy and greenhouse gas emissions. Fertiliser inputs and transportation of biomass across large distances can reduce the GHG savings achieved. The location of biofuel processing plants can be planned to minimise the need for transport, and agricultural regimes can be developed to limit the amount of fertiliser used for biomass production. A European study on the greenhouse gas emissions found that well-to-wheel (WTW) CO2 emissions of biodiesel from seed crops such as rapeseed could be almost as high as fossil diesel. It showed a similar result for bio-ethanol from starch crops, which could have almost as many WTW CO2 emissions as fossil petrol. This study showed that second generation biofuels have far lower WTW CO2 emissions.[20]
Other independent LCA studies show that biofuels save around 50% of the CO2 emissions of the equivalent fossil fuels. This can be increased to 80-90% GHG emissions savings if second generation processes or reduced fertiliser growing regimes are used (Concawe Well to Wheels LCA for biofuels).
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