Climate Effects of Biomass Derived Fuels

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Fossil fuels can be substituted by biogenic fuels, which may be derived from agriculture and forestry as biomass directly, or via the waste route from wasted material of biogenic origin. For principal routes see figure 13.4.

Bad Effects Off Biomass
Figure 13.4 Principal pathways from biogenic material into the energy system (after Öko-Institut, 2005)

The combustion of biomass, biomass-derived fuels, or biogenic wastes which are used directly or as bioethanol, biodiesel, and biogas results in greenhouse gas emissions. But these are not addressed to climate change. As emissions are from biogenic material (and if the materials are grown on a sustainable basis), those emissions are considered to close the loop of the natural carbon cycle: They originate from atmospheric carbon dioxide from which they were taken by photosynthesis. CO2 from biogenic sources will under natural conditions return to the atmosphere in the same quantity. Only if there are metabolites other than CO2, such as methane, N2O, NOx, etc. then these substances are considered climate relevant and their greenhouse gas effects must be balanced.

Though positive effects of biofuels are of primary importance due to the reduction of greenhouse gas emissions, at the same time the reduction of the demands of fossil material sources is meaningful, and hence, the enhancement of the lifetime of this scarce and expensive resource. Moreover, biofuels support the development of agriculture in rural region, broaden the activity field of farmers, and opens new markets for products such as sugar. In many cases, residues from agriculture as well as from industry can be used as raw material sources of biofuels thus also contributing to reduce negative environmental effects of poor waste management.

However the intended positive effects will not fully occur in every case, and negative effects also have to be considered: Some biofuels are not grown environmental-friendly because they need pesticides and fertilizers which besides production efforts may cause water and air pollution. Impacts on biodiversity are of concern in the case of monocultures for renewable crops. In the international context, the main environmental risks are likely to be those concerning any large expansion in biofuel feedstock production, particularly in Brazil for sugar cane and in South East Asia for palm oil plantations. Growing demand for palm oil may be effectively contributing to clearance of rainforest in countries like Malaysia and Indonesia (Bauen, 2005). Moreover, energy is needed to grow the plants and to produce the biofuels from the crop. CO2 is emitted out of the soil (see chapter 10.4); after the use of nitrogen fertilizers considerable emissions of N2O occur.

Facing the world's rising food prices and recent shortages in nutritional crops, as another factor of concern the competition of energy and nutritional crops must be considered and balanced in such a way that primary needs are covered first. From a sustainability aspect these facts speak for a detailed complex analysis of all environmental, social and economical consequences of biofuels to prevent negative total effects.

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