Techno-economic evaluation of microalgae high-density liquid fuel production at 12 international locations.

BACKGROUND: Microalgae-based high-density fuels offer an efficient and environmental pathway towards decarbonization of the transport sector and could be produced as part of a globally distributed network without competing with food systems for arable land. Variations in climatic and economic conditions significantly impact the economic feasibility and productivity of such fuel systems, requiring harmonized technoeconomic assessments to identify important conditions required for commercial scale up. METHODS: Here, our previously validated Techno-economic and Lifecycle Analysis (TELCA) platform was extended to provide a direct performance comparison of microalgae diesel production at 12 international locations with variable climatic and economic settings. For each location, historical weather data, and jurisdiction-specific policy and economic inputs were used to simulate algal productivity, evaporation rates, harvest regime, CapEx and OpEx, interest and tax under location-specific operational parameters optimized for Minimum Diesel Selling Price (MDSP, US$ L-1). The economic feasibility, production capacity and CO2-eq emissions of a defined 500 ha algae-based diesel production facility is reported for each. RESULTS: Under a for-profit business model, 10 of the 12 locations achieved a minimum diesel selling price (MDSP) under US$ 1.85 L-1 / US$ 6.99 gal-1. At a fixed theoretical MDSP of US$ 2 L-1 (US$ 7.57 gal-1) these locations could achieve a profitable Internal Rate of Return (IRR) of 9.5-22.1%. Under a public utility model (0% profit, 0% tax) eight locations delivered cost-competitive renewable diesel at an MDSP of < US$ 1.24 L-1 (US$ 4.69 gal-1). The CO2-eq emissions of microalgae diesel were about one-third of fossil-based diesel. CONCLUSIONS: The public utility approach could reduce the fuel price toward cost-competitiveness, providing a key step on the path to a profitable fully commercial renewable fuel industry by attracting the investment needed to advance technology and commercial biorefinery co-production options. Governments' adoption of such an approach could accelerate decarbonization, improve fuel security, and help support a local COVID-19 economic recovery. This study highlights the benefits and limitations of different factors at each location (e.g., climate, labour costs, policy, C-credits) in terms of the development of the technology-providing insights on how governments, investors and industry can drive the technology forward.

Microalgal Aquafeeds As Part of a Circular Bioeconomy.

Photosynthetic microalgae are unicellular plants, many of which are rich in protein, lipids, and bioactives and form an important part of the base of the natural aquatic food chain. Population growth, demand for high-quality protein, and depletion of wild fishstocks are forecast to increase aquacultural fish demand by 37% between 2016 and 2030. This review highlights the role of microalgae and recent advances that can support a sustainable 'circular' aquaculture industry. Microalgae-based feed supplements and recombinant therapeutic production offer significant opportunities to improve animal health, disease resistance, and yields. Critically, microalgae in biofloc, 'green water', nutrient remediation, and integrated multitrophic aquaculture technologies offer innovative solutions for economic and environmentally sustainable development in line with key UN Sustainability Goals.

High-throughput optimisation of light-driven microalgae biotechnologies.

Microalgae biotechnologies are rapidly developing into new commercial settings. Several high value products already exist on the market, and systems development is focused on cost reduction to open up future economic opportunities for food, fuel and freshwater production. Light is a key environmental driver for photosynthesis and optimising light capture is therefore critical for low cost, high efficiency systems. Here a novel high-throughput screen that simulates fluctuating light regimes in mass cultures is presented. The data was used to model photosynthetic efficiency (PEµ, mol photon-1 m2) and chlorophyll fluorescence of two green algae, Chlamydomonas reinhardtii and Chlorella sp. Response surface methodology defined the effect of three key variables: density factor (Df, 'culture density'), cycle time (tc, 'mixing rate'), and maximum incident irradiance (Imax). Both species exhibited a large rise in PEµ with decreasing Imax and a minimal effect of tc (between 3-20 s). However, the optimal Df of 0.4 for Chlamydomonas and 0.8 for Chlorella suggested strong preferences for dilute and dense cultures respectively. Chlorella had a two-fold higher optimised PEµ than Chlamydomonas, despite its higher light sensitivity. These results demonstrate species-specific light preferences within the green algae clade. Our high-throughput screen enables rapid strain selection and process optimisation.

High resolution spatial mapping of brominated pyrrole-2-aminoimidazole alkaloids distributions in the marine sponge Stylissa flabellata via MALDI-mass spectrometry imaging.

A number of pharmacologically active brominated pyrrole-2-aminoimidazole (B-P-2-AI) alkaloids have been isolated from several families of marine sponges, including those belonging to the genus Stylissa. In the present study, MALDI mass spectrometry imaging (MALDI-imaging) was applied to determine the spatial distribution of B-P-2-AIs within 20 µm cross sections of S. flabellata. A number of previously characterised B-P-2-AIs were readily identified by MALDI-imaging and confirmed by MS-MS and NMR profiling. Unknown B-P-2-AIs were also observed. Discrete microchemical environments were revealed for several B-P-2-AIs including dibromophakellin which was localised within the external pinacoderm and internal network of choanoderm chambers. Additionally, dibromopalau'amine and konbu'acidin B were also found to be confined to the choanoderm, while sceptrin was found to be highly abundant within the mesohyl. Further brominated compounds of unknown structure were also observed to have distinct localisation in both choanoderm chambers and the pinacoderm. These findings provide insights into the chemical ecology of S. flabellata, as most B-P-2-AIs were found on highly exposed surfaces, where they may act to prevent pathogens, predation and/or biofouling. Moreover this study demonstrates the power of MALDI-imaging to visualise the location of a range of metabolites in situ and to characterise compounds by MS-MS directly from intact specimens without the need for extraction. These methodologies facilitate selective targeting of micro-regions of sponge to screen for symbiotic microbial candidates or genes that may be involved in the production of the correlated compounds, and may represent a change in paradigm for natural product drug development.