Armando Lucas Cherem da Cunha

Rice husk is a lignocellulosic biomass rich in silica, which, when disposed of inappropriately, represents an environmental hazard. This study investigated the application of deep eutectic solvents (DES) as a green and efficient approach to the rice husk fractionation, combining the selective dissolution of lignin and sugars with the purification of the silica-rich inorganic fraction. Six different DES were produced from choline chloride or betaine with different hydrogen bond donors and characterized for water content and pH. The DES based on carboxylic acids was more acidic, which favored the cleavage of ester and glycosidic bonds in the biomass. The TGA, XRF, SEM, and XRD analyses revealed that the lactic acid-based DES promoted better removal of lignin and mineral impurities, resulting in a purer silica with an amorphous morphology. The 110 °C condition was the most effective in preserving the thermal integrity of the organic (sugars and lignin) and inorganic (silica-rich ash) fractions. The results highlight the potential of DES as selective, sustainable, and tunable solvents for the valorization of agricultural waste, achieving biosilica with SiO₂ purity exceeding 80% and lignin removal above 70%, reinforcing the potential of DES as sustainable solvents for agricultural waste valorization.

Fertilizers are essential inputs for the agribusiness chain—they increase the productivity on available arable land and help to avoid changes in land use. Currently, Brazil is one of the largest consumers of fertilizers in the world but its imports of NPK fertilizers, as a percentage of its total consumption, have risen from 32% in 1988 to 77% in 2018. Biofuels are relevant in the transport sector and the Brazilian government, after the Paris Agreement, created the National Biofuels Policy (Renovabio), which has as one of its goals to raise the participation of biofuels in the transport sector to 28.6% by 2028. Soy, corn, and sugarcane (biofuels raw material) currently account for more than 70% of the consumption of NPK fertilizers in the country. Due to several reasons, in the last 10 years many local projects designed to fill the supply gap for fertilizers in Brazil have not been successful. The recent COVID-19 pandemic has raised questions about the reliability of fertilizer supply in global value chains. In this context, is Brazil’s long-term biofuel market at risk after COVID-19? A total of 38 experts were consulted and four reference scenarios were developed. The article concluded that the Brazilian fertilizer industry must be prepared for a scenario of limited increase in demand on a global scale—strategic alliances may be forged to maintain existing installed capacity. Should the Brazilian government fail to provide any stimulus for the country’s fertilizer industry, it is likely that by 2035, Brazil’s biofuel industry sector would be overexposed to price volatility and availability on the global fertilizer market.

The influence of NaCl salt in the hydration of the Portland cement paste class G was studied using a Non Conventional Differential Thermal Analysis (NCDTA) on the first 24 hours of cement hydration. The mass of salt used corresponds to 0, 5, 10, 15 and 20% of mass of water used in the preparation of the pastes. The water/cement ratio (w/c) remained constant, being 0.46, and the pastes final volume was 99.9mL. Applying a deconvolution method to separate overlapped NCDTA peaks it was possible to estimate the energy released during the different stages of hydration and the effect of salt in cement hydration process. The presence of up to 10% of salt accelerated the hydration process and increased the hydration of C₃S and C₃A, while the 20% of the salt causes a delayed hydration and decreased the hydration of C₃S and C₃A. Futhermore, cement pastes with the same percentages of NaCl and with different hydration times were evaluated by Thermogravimetry (TG), Derivative Thermogravimetry (DTG) and Differential Thermal Analysis (DTA). After 28 days the presence of salt caused a greater increase in the formation of hydrated products.