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- Microalgae in a global world: New solutions for old problems?Publication . Vieira De Mendonça, Henrique; Assemany, Paula; Abreu, Mariana; De Aguiar Do Couto, Eduardo; Martins Maciel, Alyne; Duarte, Renata Lopes; Santos, Marcela Granato Barbosa dosABSTRACT: The human population blast has brought several problems related with the overconsumption of a wide range of feedstocks and natural resources conducting to their risk of depletion. The consumption of fossil fuels is an example, with increasing levels of exploitation and negative impacts caused by their use. Anthropogenic activities have triggered the over accumulation of many hazardous substances and wastes which are regarded to be detrimental to life in the Earth and to the various planet ecosystems. There is an urgent need to restore natural resources and unwanted residues and wastes to levels prior the demographic explosion. Microalgal biotechnology appears to be pivotal to achieve this goal in a near future to come. This review presents the current resource problems affecting the Earth and how microalgae are expected to be an important part of the solution, discussing how the production of renewable energy from microalgae can help in an integrated way to mitigate different environmental problems. Microalgae are able to convert wastewaters, CO2 and organic residues in marketable biomass for different uses, including biofuels, converting waste in value. An inventory of current microalgal-based biorefineries in operation as well as a directory of companies, products and applications are also presented.
- Hydrothermal liquefaction of biomass produced from domestic sewage treatment in high-rate pondsPublication . De Aguiar Do Couto, Eduardo; Pinto, Filomena; Varela, Francisco; Reis, Alberto; Costa, Paula; Calijuri, Maria LuciaABSTRACT: This study evaluates the application of biomass produced from the treatment of domestic sewage in high-rate ponds (HRPs) as feedstock for the production of bio-oil via hydrothermal liquefaction (HTL). The effects of reaction time, temperature, and biomass/water ratio on the yield of bio-oil were assessed. In addition, a balance of carbon and nitrogen among the products (bio-oil, aqueous phase, solid residue, and gas) was carried out, in order to evaluate the quality of the bio-oil and possibilities for increasing value from the byproducts. In a 15-min operation at 300 degrees C with biomass/water ratio of 1/10 (w.w(-1)), the bio-oil yield was of 44.4% (Dry Ash Free - daf-basis). Under every condition tested, the solid residue was the most abundant byproduct, mostly due to the high ash content in the biomass. The minimum nitrogen recovery in the bio-oil was 57%, obtained in the operation at 275 degrees C, which is considered the main disadvantage of the process. The use of biomass directly after its production may result in an excessive consumption of energy due to the high water content. However, the need for drying is reduced when compared to other microalgal-based bioenergy production processes, potentially achieving a positive energy balance in the HTL.