The use of agroforestry residues for energy purposes has long been a reality in Brazil. About 84.8% of the produced electricity comes from renewable resources; vegetable biomass contributes 9.1% to this total. This percentage has the potential to increase if Amazon biomass residues are processed to be used as fuel. The major difficulty for this scenario is the lack of available information on energy properties, mainly the HHVs for Amazon agroforestry biomass types. Considering that there are important deviations in the equations for predicting the HHVs of Amazon biomass types in the literature, the main objective of this work was to propose equations to determine the HHVs of these biomass types using the proximate or ultimate analysis results as input. The methodology adopted to develop such equations was simple and multiple linear regression methods, using experimental results for HHVs and proximate and ultimate analyses for biomass types from the north region of Brazil. Four distinct equations were considered based on ranges from the proximate and ultimate analyses of the biomass types to deliver better results. The obtained equations were validated by application to 28 other biomass types from the same region. The proposed HHV equations presented good agreement between predicted and experimental values, with errors below 5% for equations based on proximate analysis and below 3% for equations based on ultimate analysis.

This study investigates the effects of the co-combustion of coal and açai seed in circulating fluidized bed (CFB) boilers, highlighting the increase in thermal efficiency and relevance of a less-polluting source of energy. Using the computer software 1.5D CeSFaMB™^® v4.3.0, simulations of the co-combustion process of coal and biomass were carried out in a CFB boiler, obtaining results such as the temperature profile, boiler efficiency and emissions. The work acquired data regarding the equipment in real operational conditions, consisting of the fundamental geometric and operational parameters used in the simulation campaign. The thermal and chemical properties of the fuels were analyzed by carrying out proximate, ultimate, heating value, particle size and specific mass analyses. The model validation was achieved by simulating the boiler in its real operating conditions and comparing the obtained results with the real data; the obtained error was below 10%. Simulations with different fractions of açai seed for energy replacement (10% and 30%) were carried out. As a result, an increase in the average temperature of the bed was observed, highlighting the region immediately above the dense bed. An increase in boiler efficiency was verified from 56% to 85% with 10% açai and to 83% with 30% açai seed. Decreases in SO₂ and CO emissions with the insertion of açai were obtained, showing that co-combustion is more complete, while CO₂ emissions were increased due to the higher quantity of fuel inserted into the equipment. The fossil CO₂ emissions were reduced.

The residue of the so-called fibrous seed from the açai fruit represents 70% of the mass of the fruit and has potential for useful energy generation. Evaluating and treating the residue as a renewable fuel offers both economic and environmental benefits, whereas today, it is disposed of as organic waste. The co-firing of the fibrous seed and coal in fluidized bed boilers is an attractive option due to the high efficiency of the combustion process and the low bed temperature. However, one of the issues for this application is the low seed ash sintering temperature, which promotes the agglomeration of the bed material. This work aims to present a new procedure for evaluating the sintering temperature of açai seed and coal ash, making it simpler and consistent with traditional techniques. The proposed procedure for determining the starting ash sintering temperature is based on two simple and dynamic methodologies: simultaneous thermal analysis (STA) and sintering by an area reduction in ash samples. The data obtained allow us to determine that the coal ash begins to sinter at around 1000 °C, while the açai seed ash starts at around 700–850 °C, exhibiting a significant area reduction.