From the beginning of its operation, this large steel industrial complex in the Santa Cruz Industrial District, Rio de Janeiro, Brazil, with an annual capacity of 5 million tons, has been at the center of controversy related to its atmospheric emissions. Since the air filter used for its routine air particulate monitoring network is not appropriate for a source apportionment study, biomonitoring was tested as an alternative way to carry out this evaluation. Thus, the bromeliad species Tillandsia usneoides was used as a bioindicator in the Santa Cruz Industrial District, Rio de Janeiro, Brazil. Six samplings were performed over a period of approximately one year. The results showed that the sampling point located inside the industrial complex presented higher elemental concentration values for all samples. Among the quantifiable elements found in the biomonitor samples, iron seems to be the element that best represents the emissions from the steelwork complex, which was corroborated based on the analysis of dust jar samples collected inside the complex area.

The reduced size of the cells (< 30 µm in diameter) and the low cell concentration of microalgae and cyanobacteria cultures (0.5 g/L on average) greatly hinder the densification of the biomass, a crucial step to becoming biofuel production from algal biomass economically viable. To identify the best densification method, about 90 studies applied to 60 different microalgae and cyanobacteria were compiled through an extensive literature survey, classified into eight methods of algal biomass densification, and analyzed regarding the harvesting efficiency, energy consumption, and costs. Low-cost methods (spontaneous settling, autoflocculation, and bioflocculation) can achieve high densification only with specific species and conditions. On the contrary, many species only achieve high densification using high-cost methods (centrifugation, membrane filtration, electrocoagulation). Based on the analyzed data, researchers should focus on selecting species that combine the desired characteristics for the downstream processes with their potential for biofuel production.

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