Two-Stage anaerobic digestion in agroindustrial waste treatment: A review.

The anaerobic digestion is a process widely recognized as an interesting alternative for the treatment and stabilization of residual organic substrates. However, several technical limitations were observed based on the characteristics of the organic matter submitted to the process, such as the presence of high concentrations of soluble sugars or fats. The technology of anaerobic digestion in multiple stages is described as a viable option in the control of variables, optimizing the environmental conditions of the main microorganisms involved in the process, assuring high solid removal and methane production, besides allowing a higher energy yield through the generation of molecular fuel hydrogen.

Use of rice husk in waste cooking oil pretreatment.

Since industrial wastes are increasing, the development of studies to find ways for their use is urgent. Waste cooking oil is an important source for the production of biodiesel, one of the main biofuels in Brazil. However, during cooking, the oil undergoes conditions that change its properties and decrease its quality, such as its acidity value.