Biomassa residual cafeeira como alternativa para produção de biocombustíveis

Abstract

The environmental problems caused by greenhouse gas emissions, mainly due to the use of non-renewable sources, as well as the final destination of agroindustrial waste, have instigated the search for new technologies and alternatives that may contribute to the mitigation of the environmental impacts caused by these factors. Thus, the objective of the study was to evaluate the quality and energy potential of the coffee husk, as well as to transform coffee agroindustrial residues into higher added value products (biofuels) through two technologies: briquetting and slow pyrolysis. Firstly, characterization of the coffee husk was carried out: composition analysis (lignin, holocellulose and extractives), proximate analysis (fixed carbon, volatile materials and ashes), ultimate analysis (C, H, N, S and O), physics bulk), energy (gross calorific value) and thermal (thermogravimetric analysis).These chemical characteristics provided the parameters of coffee biomass quality in the conversion of biofuels. A model of briquette production was developed using three particle sizes (particles> 1.8 mm, 1.8 mm> particles> 1.2 mm and particles <1.2 mm) of coffee agroindustrial residues. The physical-mechanical and energetic characteristics such as: mechanical strength, durability, volumetric expansion and apparent density, energy density and combustion characteristics were evaluated. The effect of the reduction of the coffee bark particles was pronounced for the characteristics of apparent density, mechanical resistance to compression and energy density, being better for the briquettes made with the particles <1,2 mm.In a second step, the briquettes were pyrolyzed / charred to evaluate the energy potential of these residues in the generation of liquid biofuels (bio-oil) and solids (biochar). Approximately 1.5 kg of briquettes produced with particles smaller than 1.2 mm were used for each pyrolysis process. The briquettes were charred at the following final temperatures: 350 ° C, 400 ° C and 450 ° C at the heating rate 0.5° C/min. Then, the products obtained at the end of the process were quantified and solid fractions were characterized by chemical analyzes (proximate analysis and ultimate analysis), energetic (gross calorific value) and morphological (scanning electron microscopy). The composition of the bio-oil was identified in gas chromatography-mass spectrometer (GC / MS). The results found in the research evidenced the effect of the final pyrolysis temperature on the distribution and properties of the pyrolysis final products. Pyrolysis at higher final temperatures (450 ° C) considerably increased the fixed carbon content of the biochar and reduced the amount of acetic acid in the bio-oil, ie high temperatures are more favorable for the production of more energetic biofuels and less corrosive. The results can contribute to the final destination of agroindustrial waste, as well as to the energy and chemical industry, due to the extraction of valuable compounds, such as phenolic compounds, aromatics and caffeine, which are the end products of carbonization and are of interest for this sector.