The UK government and European demand that by 2020 at least ten percent of all car fuel will be derived from biological sources. However, according to research from Australia, water supply in those countries capable of turning over land to fuel crop cultivation could become the limiting factor providing a serious obstacle to that target. Currently, across Europe, just a tiny fraction of total consumption is based on biodiesel.
Patrick Moriarty and Damon Honnery of the Department of Mechanical Engineering at Monash University, Australia, report today in the Inderscience publication the International Journal of Global Energy Issues, an analysis of bio energy that takes into account significant side effects, such as climate change, water consumption, and overall energy costs. They carried out a complete analysis of the energy costs for producing fuels based on plant oils and have found that the energy cost of irrigating crops in arid environments far outweighs the environmental benefits in terms of reduced reliance on fossil fuels.
On average we each use the equivalent of 68 billion joules of energy every year, which adds up to 427 exajoules, or billion billion joules, globally. To meet this demand, we burn fossil fuels with all the manufacturing, pollution, and climate effects associated with their use.
Only about 1% of world electricity is generated using bioenergy, while all other renewable sources, including geothermal, wind, wave, tidal and solar power, provide only an additional 1%.
Efforts to produce sustainable energy supplies based on biological sources, such as agriculture and waste recycling are high on the environmental agenda but their widespread use can only become viable if the energy equation balances in their favour. The team points out that previous studies of energy plantation use in Europe and the USA have not considered the complete life cycle and so do not give policy makers a clear picture of the energy balance, for instance, in growing poplar trees for conversion into biomass for fuel production.
"Widespread use of new bioenergy is probably decades away," say the researchers, "so our evaluation attempts to take into account likely future conditions." Other researchers have failed to balance the energy books in the past, with these earlier analyses showing large variations in the estimates of both energy ratio and technical potential. "We have found that some feedstocks for bioenergy are already attractive from both a monetary and climate change perspective," Moriarty and Honnery add, "However, for energy plantations, water availability, rather than land availability, will drastically limit their scope."
In order to be accepted as an alternative fuel, bioenergy must have lower greenhouse gas emissions (measured in CO2 equivalents) or more broadly, have a lower climate change impact, than the fossil fuels it seeks to replace. The researchers emphasise that bioenergy could offer several advantages if a viable means of production can be found.
For instance, if the production of bioenergy can be made carbon neutral then it would allow us to reduce greenhouse gas emissions, as the crops themselves sequester carbon dioxide from the atmosphere through photosynthesis. Bioenergy could be a cleaner fuel, producing less hydrocarbon air pollutants and particulates than diesel and other fuels.
They also suggest that need to cultivate fuel crops could improve farmland use and boost local economies. Moreover, bioenergy reduces reliance on imported oil.