Alternative energy biomass in all these processes is necessary to analyze some characteristics that you judge whether the fuel obtained can be considered a renewable source of energy: Emissions of CO2 (carbon dioxide). In general, the use of biomass or their derivatives can be considered neutral in terms of net emissions if only used in amounts at most equal to the net production of biomass is exploited ecosystem. Such is the case for traditional uses (use of yard trimmings such as firewood, dung stoves, etc.). If not exceeded the capacity of the territory. In industrial processes, as it is inevitable the use of alternative energy sources (in construction machinery, transportation of materials and in some of the essential processes, such as the use of agricultural machinery during cultivation of raw material) , the emissions from these sources are reported as net emissions.In some energy-intensive processes can be realized net fuel with significantly lower emissions than comparable fossil fuel. However, the use of inadequate processes (as would be the traditional pot still distillation residue to produce) can lead to higher emissions fuels. We must also consider whether there are other emissions of greenhouse gases. For example, in the production of biogas, an accidental release may ruin the balance zero emissions, because methane has a potential 21 times greater than carbon dioxide as the IPCC. Both the balance of emissions and the balance of useful energy must not forget the accounting of indirect energy inputs, such is the case of the embodied energy used in fresh water.The importance of these inputs depends on the process, in the case of biodiesel, for example, the estimated consumption of 20 kilograms of water per kilogram of fuel: depending on the industrial context embodied energy in water can be higher than the fuel obtained (Estevan, 2008: Table 1). If the raw material used comes from waste, these help fuel recycling. But one must always consider whether the production of fuels is the best use for a particular residue. If the raw material comes from crops, consider if this is the best use of land compared to other alternatives (food crops, reforestation, etc.). This consideration depends on how the specific circumstances of each territory. Some of these fuels (bioethanol, for example) do not emit pollutants sulfur or nitrogen, or just solid particles but others (eg direct combustion of wood).