Slow pyrolysis of different Brazilian waste biomasses as sources of soil conditioners and energy, and for environmental protection

Abstract

This paper explores the viability of producing energy and agricultural soil conditioners with biochars and bio-oils from the pyrolysis of biomasses that in some cases are potential environmental pollutants. This approach addresses the need to develop sustainable production systems that minimize pollution and soil degradation, and meet the demand for renewable fuels. Large volumes of biomass from different sources are available in Brazil, including Eucalyptus crop residues (CE), castor meal (CM), coconut pericarp (CP), sugarcane bagasse (SB), and water hyacinth (WH). CM char and SB bio-oil are good prospects for energy generation. Characterization using DRIFT, 13C NMR, and van Krevelen diagrams indicated that after carbonization, aromatic structures were predominant in the biochars produced from the CP, CE, and SB biomasses, while aliphatic groups were abundant in the biochars from CM and WH. Analysis using EPR showed that unpaired electrons were preferentially located on carbon atoms in the case of the CP, CE, and SB biochars, with EPR g values around 2.0030, while the CM and WH biochars presented g values around 2.0035, indicating that the unpaired electrons were closer to oxygen atoms. In terms of bio-oil chemical composition, the most abundant compounds were 3-pyridinol and furans (WH), phenols (CP), and hexadecanoic, octadecanoic, 9,12-octadecenoic (z,z), 3-docosenoic, and 5-docosenoic acids (present only in the CM bio-oil). The bio-oils from SB and CE were quite similar and the main compound was 1,2,6-hexanetriol. The biomass sources studied produced reasonable amounts of bio-oil, and could compete as suitable raw materials for biofuel production.