Jorge del Real Olvera and Alberto Lopez-Lopez

Environmental Technology Unit, Centre of Research and Assistance in Technology and Design of the State of Jalisco, (CIATEJ),

Mexico

1. Introduction

Today, globally most energy is provided by burning oil and only a very small percentage is generated by nuclear power plants. The contribution of energy from renewable resources is almost negligible. But this will change in the future with increasing in environmental pollution and fossil fuel depletion, in addition to environmental problems generated by the Fukushima nuclear power plant.

One of the most attractive ways to obtain sources of alternative energy and the pollution control is the recover resource and energy from waste streams through bioconversion processes (Cantrell et al., 2008). In this respect, intensive studies have been conducted in the past few decades and various "green technologies" have been extensively reviewed (Kleerebezemand and Loosdrecht, 2007; Hallenbeck and Ghosh, 2009). For many years, anaerobic digestion has been a prevailing technology for biogas production, in which substrates are converted to methane and other products under a joint effort of several microbial groups in a reaction system (Sterling et al., 2001).

In this context biogas generated by agro-industrial wastewater will play a vital role in future. Biogas is a versatile renewable energy source, which can be used for replacement of fossil fuels in power and heat production, and it can be used also as gaseous vehicle fuel. Methane-rich biogas can replace also natural gas, as a feedstock in the production of chemicals and materials (Shin et al., 2010).

Sustainable development must be the foundation for economic growth in the twenty-first century. It is necessary redirect the efforts toward bioenergy production from renewable material, low-cost and locally available feedstock such as waste and wastewater agro­industrial. This effort will not only alleviate environmental pollution, but also reduce energy insecurity and demand for declining natural resources. The most cost-effective and sustainable approach is to employ a biotechnology option. Anaerobic treatment is a technology that generates renewable bioenergy necessary to replace the energy requirements around the world through the production of methane and hydrogen. However, it has also been employed for production of polyhydroxyalkanoates (PHA), these are linear polyesters generated by bacterial fermentation of sugar or lipids. They are produced by the bacteria to store carbon and energy. More than 150 different monomers can be combined within this family to give

materials with extremely different properties. These plastics are biodegradeable and are used in the production of bioplastics (Mu et al., 2006) and other biochemicals.

This chapter intends to bring together the knowledge obtained from different applications of anaerobic technology in the treatment of various kinds of agro-industrial wastewaters to generate biogas. The first part covers essential information on the fundamentals of anaerobic technology, to demonstrate how the anaerobic treatment is able to generate significant volumes of methane-rich biogas. The wastewaters used in this chapter to generate biogas, contribute significantly in the pollution of the water bodies. In this opportunity the wastewater from Tequila vinasses were treated by different microbial consortia with energy purpose. This chapter illustrates the basics concepts of microbiology and biochemistry involved in the wastewater anaerobic treatment. The remainder focuses on various anaerobic reactor configurations and operating conditions used for the treatment of agro­industrial wastewaters different, show some examples with technical viability and the potential benefits that would be obtained by the utilization of the biogas as source of energy to full scale.