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This study is the first report in the literature of exergetic, economic, and environmental (3E) analysis for low cost solar heaters (LCSH). In this context, 3E analyses were performed for two LCSH configurations, tubes of the absorber plate connected in series and parallel. The mean exergy efficiency of the LCSH in parallel was 2.56% while for the LCSH in series it was 2.01%. The parallel collector presented lower rates of exergetic destruction and entropy generation, besides a higher overall efficiency. The use of alternative materials in the construction of the LCSH made it possible to achieve low values of embodied energy and embodied carbon emission and consequently excellent environmental indicators. It was found that the simple payback period (SPP) and the leveled heating cost (LCOH) found were 0.38 years and 0.014 US$ kWh−1 for the collector in parallel and 0.42 years and 0.016 US$ kWh−1 for the collector in series. Based on the analyses performed, the LCSH in parallel proved to be the most attractive alternative among the evaluated ones and is indicated for operations where high efficiencies and high temperatures are not required and the cost factor is important.

The whole process of algae farming and biomass biorefining was evaluated on a pilot scale for the production of protein concentrate for poultry feeding and crude lipids. Scenedesmus obliquus was produced in open raceway ponds, and the cells were disrupted under low-pressure homogenization operating at 150 bar. Lipids were efficiently extracted using a hybrid multistage process based on a wet extraction using hexane and ethyl acetate, followed by dry extractions using hexane. The protein concentrate containing 43.1% of total proteins was recovered at low centrifugation of 400g and submitted to a desolventization process to remove residual hexane. The protein concentrate showed a similar composition of essential amino acids in comparison to soybean which is the main protein source used in feed formulation. Aspartic acid and glutamic acid were the main amino acids observed in the microalgal protein concentrate. As a feed supplement for broilers, the protein concentrate-based feed showed equal ingestion of the control, but the latter showed lower energy efficiency. The processing of 168 kg of wet biomass (14.8 kg on a dry weight basis) resulted in a production of 1.3 kg of crude lipids and 12.6 kg of protein concentrate, which corresponded to 93.7% of the total dry biomass.

Ten green microalgae (Chlorophyta) were screened in different culture media based on sugarcane ethanol vinasse (SEV) and ethanol biorefinery wastewater (EBW) under neutral and acidic pH. The strain Scenedesmus bajacalifornicus BR024 showed an intermediate growth performance in the different media in comparison to other microalgae species. Hence, the strain BR024 was chosen for further evaluation of the ozone pretreatment on SEV and EBW. Ozone gas was used to improve the nutrient uptake and biodegradability of these wastewaters by S. bajacalifornicus BR024. The algae farming combined with the ozone pretreatment resulted in a biomass production of 20.5% higher in comparison to the non-ozonized wastewaters, and the biochemical (BOD5) and chemical oxygen (COD) demands showed reductions up to 60.3% and 51.9%, respectively. Nitrate ( NO 3 − ) and ammonium ( NH 4 + ) were also reduced after the ozonation followed by microalga cultivation. This strategy resulted in reductions of the organic and inorganic compounds in the wastewaters of sugarcane ethanol biorefinery in comparison to algae farming and ozone pretreatment alone.