New process for using beer bagasse (spent brewers grain) to obtain raw materials for the production of biofuels
Currently, considerable quantities of lingo-cellulosic residues are generated continuously in many sectors of the agro-food industry. If these can be suitably processed, they are of great commercial interest to industry as potential raw materials for the production of biofuels and a variety of other high value-added products. The residual biomass of the agro-food industry typically has a high content in lipids, carbohydrates, proteins and other compounds of industrial interest. The only limitations to its use as a precursor of biofuel are the economic viability of the process for obtaining these precursors and their quality. One of the byproducts of special interest for this application is spent beer grain, also known as bagasse; given the existing lack of commercial value, this bagasse is widely available as a low-cost raw material. Currently, the principal application of bagasse is as feedstuff for livestock. In general, bagasse does not represent a source of income for breweries, and the reason why it is sold is to minimize the associated problems of waste management and disposal. The UCA research group on "Allelopathy in Higher Plants and Microorganisms" (FQM- 286) has developed an acid hydrolysis procedure whereby precursor materials for biofuels and other high -value-added products are obtained from beer bagasse. Its content in lipids and food fibre (equal to or more than 5% and 20%, dry weight, respectively), make it an ideal material for this application. This would represent a more attractive commercial outlet for many of the residues resulting from operations of the agro-food industry, and in particular, for beer bagasse. The object of the process is to obtain two different products. The first is an oil consisting mainly of the fats contained in the bagasse; the second is a substance rich in sugars or molasses. The oil is of interest as raw material for the production of biodiesel by the process of transesterification; the molasses can be employed as raw material for the production of bio-ethanol by means of fermentation. Molasses can also be formulated as sugar, after a crystallization process. The oil would be particularly useful for correcting the viscosity of biodiesel, thus achieving the optimum parameters for its use as biofuel. In outline, the process developed by the research group consists of a principal line, in which a series of operations take place for the conditioning of the bagasse, such as milling, extraction of lipids and the separation of the resulting solids. Downstream, this line divides into two secondary lines: in one line, for production of oils, the solvents from the prior extraction stage are separated out; in the other secondary line, for the production of molasses, an acid hydrolysis of the sugars is carried out. Another significant feature is that the optimum operating mode of the process is continuous operation, although batch loading is also accepted.