Biofuels definition

Physical Properties. Physical properties of waste as fuels are defined in accordance with the specific materials under consideration. The greatest degree of definition exists for wood and related biofuels. The least degree of definition exists for MSW, related RDF products, and the broad array of ha2ardous wastes. Table 3 compares the physical property data of some representative combustible wastes with the traditional fossil fuel bituminous coal. The soHd organic wastes typically have specific gravities or bulk densities much lower than those associated with coal and lignite. 

Figure 1. Conceptual product definitions of enzyme-based biofuel cells as they are compared in their specific energy and energy density to the existing primary battery technology. Based on Figure 2 of ref 15. Reproduced with permission. Copyright 1999 The Electrochemical Society, Inc.

Figure 1 Juxtaposes the energy fields of these three potential product definitions with that of conventional primary battery technology. The data on the energy densities for the battery product definitions were adopted from a recent technology review. The expected energy performance figures for biofuel cells...

Because the Evening Primrose is a biannual, the stem shoots up only in the second year of growth. In the first year, a taproot is put down. In the second year a sprout shoots up. Producing a biomass material only every other year is a definite drawback to its use as a biofuel however, the density of its xylem material is significantly greater than that of the other candidate plants, actually giving the evening primrose a competitive output. 

Accessibility to data and accuracy of the data are of particular importance. Even if significant progress is made in data standardization and the development of new databases and search sofiware, relevant issues are still present. The large disagreement in LCA data for biofuel assessment (e.g., the well-known case of ethanol) teaches us the need for more reliable data as well as of procedures in definition of the elements to consider in a LCA analysis. 

The term thermochemical conversion of biomass is generally used within the context of biofuels, so it is important that some definitions are clear before we start the discussion. The reader who is already familiar with the basics of biofuels and technologies for conversion of biomass can skip this sessimi entirely. Otherwise, the definitions presented here will be needed to understand the topics covered later in this chapter. 

According to the World Commission on Environment and Development (the so-called Bmndtland Commission), development can be defined sustainable when it meets the needs of the present without compromising the ability of future generafions to meet their own needs. Reading this definition, we can easily understand why biofuels are not free from sustainability problems. Phenomena such as indirect land use change (BLUC), deforestation, and displacement of agricultural production are only some examples in this regard. 

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