Charcoal produced with brewing malt residue, development and characterization

In South America, almost 2 billion litres of beer were produced in 2019 by small and medium-sized breweries, generating approximately 150 thousand tons of malt residue per year. If, on the one hand, large breweries use the waste from the brewing process to generate energy for their own factories, on the other hand, many of small and medium-sized breweries do not have an adequate destination for their waste. The unfeasibility is mainly since each of these breweries individually produces low volumes of waste. At the same time, briquets for energy generation in boilers have relatively low added value, which is only justified when produced in large quantities.

In this context, this research aimed to develop and characterise charcoal for use in barbecue grills produced from malt residue from the brewing process. To produce charcoal from brewing residue, pre-gelatinised corn was initially made by extrusion, in an IMBRA RX50 single screw extruder (INBRAMAQ, Ribeirão Preto, SP). Soon after extrusion, expanded corn ground it in a hammer mill with a smaller than 0.7 mm particle size. The pre-gelatinised was mixed with the brewer's residue in the proportions established in the experimental design and passed through a cold extruder M-10 (Braesi, Curitiba, Brazil) followed by drying in an oven time and temperature according to the experimental design. The briquet obtained subsequently underwent the pyrolysis process at 180°C for 3 hours in a muffle.

Once the charcoal is ready, all treatments established in the experimental planning, as well as conventional charcoal and commercial briquet charcoal (as standard), were analysed using the methods of Universal testing machine (model DL1000, EMIC, São José dos Pinhais, Brazil) in compression mode, Calorific power value by C-200 calorimeter (IKA, Staufen, Germany), density by seed displacement, acceptance by sensorial analysis and Colour by Minolta Chroma Meter CR-400 colourimeter.

The statistical analysis of the results obtained showed that the charcoal produced with brewer's residue and pre-gelatinised corn in the proportion of 95:5 presented adequate results. It enabled both good mechanical strength and a high calorific value when compared to the standard.

It was possible to conclude that charcoal produced with brewer's residue and pre-gelatinised corn had characteristics similar to conventional charcoal. Since the process used is of low installation cost and low energy consumption, the product proved viable to add value to the residue from small and medium breweries.