Integration of biofuels intermediates production and nutrients recycling in the processing of a marine algae

Abstract

The cost‐effective production of liquid biofuels from microalgae is limited by several factors such as recovery of the lipid fractions as well as nutrients management. Flash hydrolysis, a rapid hydrothermal process, has been successfully applied to fractionate the microalgal biomass into solid biofuels intermediates while recovering a large amount of the nutrients in the aqueous phase (hydrolyzate) in a continuous flow reactor. The aim of the work is to enhance the quality of a high‐ash containing marine algae Nannochloropsis gaditana as biofuel feedstock while recycling nutrients directly for algae cultivation. Characterization of products demonstrated an increase in extractable lipids from 33.5 to 65.5 wt % (dry basis) while retaining the same fatty acid methyl ester profile, in addition to diminution of more than 70 wt % of ash compared to raw microalgae. Moreover, the hydrolyzate was directly used to grow a microalga of the same genus. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1494–1502, 2017

Development of green extraction processes for Nannochloropsis gaditana biomass valorization

“…Multi‐product development has been promoted since the cost‐effective production of biofuels from microalgae is limited by several factors such as the cost of nutrients for large‐scale cultivation. In this sense, complementary approaches to downstream processing such as nutrients recycling are being also investigated . Nannochloropsis gaditana is an interesting strain for biorefinery purposes, since it can be divided in different fractions with potential for biodiesel and industrial production opportunities .…”

Marine Microalgae Contribution to Sustainable Development

“…In fact, several processes of the cultivation system such as harvesting and oil extraction represent bottlenecks and need to be improved in terms of both energy consumption and GHGs emissions. For example, the optimization of crucial steps such as lipid extraction is the key to a successful harvesting process [20]. Most of the LCA studies show how nutrients need an essential issue to face in biofuel production and that without the recycling of nutrients such as nitrogen, phosphorus and potassium, the energy and GHG balances are estimated to be negative [12].…”

“…Marine microalgae have also been described as potential biomass producers [14], and have been targeted as biofuels under different conditions [17][18][19]. Independent studies have highlighted the importance of considering local coastal resources for biofuel production [7] while exploiting other products that can be used with cultivated biomass [20]. Marine microalgae benefit from freshwater microalgae studies, differing only in some key processes and materials used to produce their biomass [9].…”

Conceptual Basis and Techno-Economic Modeling for Integrated Algal Biorefinery Conversion of Microalgae to Fuels and Products (2019 NREL TEA Update: Highlighting Paths to Future Cost Goals via a New Pathway for Combined Algal Processing)

“…However, the reaction requires more severe operating conditions and also necessitates rapid heating and cooling before and after the reaction to avoid degradation products, raising important heat exchange design considerations. Although carbohydrate hydrolysis to sugars is low with this operation, this is acceptable as monomeric sugars are no longer required in this process; additionally, this still is anticipated to enable high lipid extraction yields (which remains a key step for this process) [24,25]. In addition to cell disruption for downstream lipid extraction, the hydrolysis solubilizes a large fraction of protein solids and a smaller portion of carbohydrates.…”

“…In the flash hydrolysis reactor, only 10% of carbohydrates are converted to sugars, but more importantly about two-thirds of the protein content is solubilized [26], and the algae cells are disrupted, making the biomass amenable to downstream lipid extraction. In order to minimize degradation products, the flash hydrolysis reactor residence time is very short, approximately 10 seconds [24,25], therefore the hydrolysate is immediately and rapidly cooled in a flash tank, which reduces the pressure to 560 psig (39.2 atm). The flash vapor (steam) is used to heat the incoming algae in the feed-effluent heat exchanger.…”