Conflict of interest

reaction conversion, and conversions of over 99% were observed. Some reactions of synthesis of biodiesel require a huge quantity of álcool for a high yield. An experiment performed with an excess of 200% of álcool in a reaction using a zeolite 3A like adsorbent showed higher yield than the reaction with 800% of excess álcool in a reaction without water adsorption, proving to

About the use of wastes for biodiesel production, there are still some different reports in the literature; for example, there is one paper that investigated the potential that the yeast Candida lipolytica UCP0988, in an anamorphous state, has to produce simultaneously a bioemulsifier and to accumulate lipids using inexpensive and alternative substrates such as waste soybean oil, and one of the biomass obtained was able to accumulate lipids of 0.425 g/g biomass (corresponding to 42.5%), which consisted of palmitic acid (28.4%), stearic acid (7.7%), oleic acid (42.8%), linoleic acid (19.0%), and linolenic acid (2.1%) [62]. In another interesting study, Jesus et al. [63] showed the use of vegetable waste as a potential source of raw material for biofuel production. In the work, the microalga Chlorella vulgaris was used to maximize the production of lipids and carbohydrates, and the culture medium was prepared with vegetable waste (pumpkin, zucchini, potato, eggplant, broccoli, carrot, cabbage, tomato, and green bean.) The positive results of this work motivate us to replace traditional culture media with

At last, Gomes & Pasquini [64] described the purification of sunflower-oil-derived biodiesel by dry cold washing using chicken's eggshells (Gallus Gallus domesticus), as well as a subsequent comparison with conventional wet washing with hot water and the reuse of eggshells. Both purification methods were efficient in the removal of free glycerin, free fatty acid molecules, and the catalyst. Thus, they provide the advantage of reducing effluent emission as well as offering an application for eggshells of which large amounts are generated due to excessive

In this chapter, it was possible to understand the importance of waste valorization for the future of biodiesel production, either by using waste cooking oils and beef tallow or by investigating new techniques for analysis and catalysts and methods of synthesis or by the development of pilot plants and economic studies. If these materials cannot replace totally edible oils or diesel, it is clear that their use could be very higher in the energy matrix. For this reason, all researches have great importance, since those that could help to improve the social inclusion and minimize poverty, even those in which there is an improvement of the biodiesel production, by their properties, yields, process, as well as the production of catalysts more efficient, environmental friendly, among others technical aspects. Considering the highlighted position of Brazil in the world scenario of biofuels (despite the scarcity of research funds in this country), it is also possible to affirm that these researches gave/give a fundamental contribution to this reality, improving methodologies, investigating new types of wastes, upgrading their chain of collect and valorization by sensitizing and including more and more people. At

egg consumption and for which an appropriate use has not yet been found.

be a good candidate to be used in the biodiesel industry.

media prepared with vegetable waste.

22 Biofuels - Challenges and opportunities

3. Conclusions

The authors declare no conflict of interest.
