Bioenergy can help mitigate climate change and reduce greenhouse gas emissions by substituting for fossil fuels. The potential emission reductions are considerable. It is estimated that by 2030, biofuels could supply 3% of the energy needs of the transport sector; and this could increase to 5-10% depending on a number of factors, including the development of second-generation biofuels ( IPCC, 2007). In addition there is the spin-off benefit that the rural sectors in developing countries can attract investment by generating tradable emission reduction credits (so-called Certified Emission Reductions), through the Kyoto Protocol and the international market for greenhouse gas (GHG) emission reductions. Finally, through the use of Biogas, also methane emissions are reduced.
It should however be noted that there are a number of uncertainties surrounding the potential climate change related benefits. Realization of the potential is of course subject to the sustainability criteria noted in the previous section. And, the net calculation is often difficult. For instance, the energy balance needs to take into account the full production process and be corrected for any effects of changes in land use and existing carbon content of the land.
Production potential and land requirements
In order to obtain an indication of how much land would have to be devoted to the production of biomass feedstock one could use current data on crop production and conversion efficiency. The next table, from "Testing framework for sustainable biomass" , gives the potential yield of a number of popular crops and the amount of land required to cultivate this crop, if it is to substitute 25% of the current demand for transportation fuels (or 10% of the total energy demand), using first-generation bioenergy technology.
The above data clearly shows that in particular grain crops have too low production potential for this ambitious target to be realized and underline the need to increase the efficiency of the whole production and conversion process. Note further that the assumption of 2.5 billion hectares of available agricultural land is much more than what current statistics give as land used for arable crops. See the next table.
Source: FAO, 2004.
|Global land use (billion ha)||2004|
For country specific data, see FAOStat
With regards to the potential share of bioenergy of the total global energy consumption it is important to note that the latter is increasing steadily. Where in 2003 the world consumed 10 723Mtoe (449EJ/y) of primary energy. By 2030 this is expected to increase to 16 271Mtoe (678EJ/y). (IEA Reference scenario, World Energy Outlook 2005). At the same time, also technological advancements in the conversion of biomass into biofuel may have increased the share of the crop that can be used for conversion, as well as the efficiency of the process, the second generation biofuels. A crop that has the potential to increase dramatically the yield that can be obtained/area cultivated is algae. Where in the past the cost of algae production were considered too high, the higher oil prices may bring it within reach. Production increases of more than 10 fold as compared to palm oil or sugar cane have been mentioned (Fulton 2006). This is however still experimental.