Study of sugarcane bagasse/straw combustion and its atmospheric emissions using a pilot-burner.

This work conducted experimental combustion on a closed chamber using two different materials: mixture (1:1) sugarcane bagasse/straw and pre-treated biomass. The sampling method was an Andersen cascade impactor with eight stages. Tests were carried out on untreated biomass varying the velocities observed in the sampling duct (4.18; 5.20, 6.85, and 8.21 m.s-1). Pre-treated biomass tests were performed at 4.19 m.s-1 because in this condition there is a higher speed stability inside the duct. During the combustion tests, the concentration of emitted particles was higher for the lower speed range, with an order of 4.19 > 5.40 > 6.85 > 8.21 m.s-1. The higher speeds observed inside the duct behaved as a dragging agent for particulate material. For the tests at the speed of 8.21 m.s-1 where the flow inside the duct was 0.088 m3s-1, this behavior is more evident. Considering the fine diameter particles (< 2.5 µm), they were emitted in a higher concentration, due to the biomass combustion process, which results in higher emission of ultrafine particles. The emission factors (EFs) obtained for PM10 for untreated biomass were in the range of 0.414 and 0.840. On the other hand, considering the pre-treated biomass, these factors were 0.70 and 1.51. The EFs of PM from the burning of the pre-treated biomass were higher when compared to untreated biomass, which is mainly due to the higher temperature of the process due to the higher HHV (higher heating value) of this material, caused by the removal of hemicellulose (4.71 times) and a proportional increase in lignin (1.52 times). Biomass combustion has the potential to partially replace fossil fuels in heat and energy generation. Nevertheless, more stringent and comprehensive legislation should be established to ensure that air quality is maintained. Furthermore, the emission factors obtained in this study might be useful as input data for air quality modeling in the context of sugarcane's burning biomass, thus, contributing to the generation of inventories that include emissions of this nature.

Evaluation of the efficiency of a Venturi scrubber in particulate matter collection smaller than 2.5 µm emitted by biomass burning.

Energy demand has increased worldwide, and biomass burning is one of the solutions most used by industries, especially in countries that have a great potential in agriculture, such as Brazil. However, these energy sources generate pollutants, consisting of particulate matter (PM) with a complex chemical composition, such as sugarcane bagasse (SB) burning. Controlling these emissions is necessary; therefore, the aim was to evaluate PM collection using a rectangular Venturi scrubber (RVS), and its effects on the composition of the PM emitted. Considering the appropriate use of biomass as an industrial fuel and the emerging need for a technique capable of efficiently removing pollutants from biomass burning, this study shows the control of emissions as an innovation in a situation such as the industrial one with the use of a Venturi scrubber in fine particle collection, in addition to using portable and representative isokinetic sampling equipment of these particles. The pilot-scale simulation of the biomass burning process, the representative sampling of fine particles and obtaining parameters to control pollutant emissions for a Venturi scrubber, meets the current situation of concern about air quality. The average collection efficiency values were 96.6% for PM> 2.5, 85.5% for PM1.0-2.5, and 66.9% for PM< 1.0. The ionic analysis for PM< 1.0 filters showed potassium, chloride, nitrate, and nitrite at concentrations ranging from 20.12 to 36.5 µg/m3. As the ethanol and sugar plants will continue to generate electricity with sugarcane bagasse burning, emission control technologies and cost-effective and efficient portable samplers are needed to monitor particulate materials and improve current gas cleaning equipment projects.

Saccharification of acid-alkali pretreated sugarcane bagasse using immobilized enzymes from Phomopsis stipata.

In this study, a mild-temperature two-step dilute acid and alkaline pretreatment (DA-AL) process was developed to generate highly digestible cellulose pulp from sugarcane bagasse for producing fermentable sugars by novel thermophilic cellulases derived from Phomopsis stipata SC 04. First, DA pretreatment of sugarcane bagasse at 2% (w/v) H2SO4 and 121 °C for 71 min, followed by AL pretreatment at 2.2% (w/v) NaOH and 110 °C for 100 min led to the pulp containing 86% cellulose. The cellulose pulp was hydrolyzed by the immobilized P. stipata cellulase on Ca-alginate beads, following optimization of immobilization conditions. The results showed that mixing the cellulase extract and sodium alginate solutions at a volume ratio of 1:4 led to the highest immobilization efficiencies of 99.83% for ß-glucosidase and 97.52% for endoglucanase while the enzyme leakage was the lowest. The use of the immobilized cellulases led to a cellulose digestibility of 30% in the initial batch and recycling of the immobilized cellulases reduced cellulose digestibility to 18% after s recycling for two times (a total of third rounds). Overall, this study provides useful information in the use of a mild pretreatment process to produce highly digestible cellulose pulp and in the immobilization of thermophilic cellulases to produce fermentable sugars from pretreated biomass. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-03101-2.