The cultivation and processing of microalgal biomass is resource- and energy-intensive, negatively affecting the sustainability and profitability of producing bulk commodities, limiting this platform to the manufacture of relatively small quantities of high-value compounds. A biorefinery approach where all fractions of the biomass are valorized might improve the case for producing lower-value products. However, these systems are still likely to operate very close to thresholds of profitability and energy balance, with wide-ranging environmental and societal impacts. It thus remains critically important to reduce the use of costly and impactful inputs and energy-intensive processes involved in these scenarios. Integration with industrial infrastructure can provide a number of residual streams that can be readily used during microalgal cultivation and downstream processing. This review critically considers some of the main inputs required for microalgal biorefineries\u2014such as nutrients, water, carbon dioxide, and heat\u2014and appraises the benefits and possibilities for industrial integration on a more quantitative basis. Recent literature and demonstration studies will also be considered to best illustrate these benefits to both producers and industrial operators. Additionally, this review will highlight some inconsistencies in the data used in assessments of microalgal production scenarios, allowing more accurate evaluation of potential future biorefineries.<\/p>\n
Introduction
\nOver the past few decades, microalgal biotechnology has seen significant contributions from the fields of biology; engineering and physics relating to cellular physiology and biochemistry; bioreactor design and operation; and biomass downstream processing. High growth rates, no arable land requirement, flexible use of water and nutrient sources, and manipulatable biochemical composition are all reasons to investigate microalgal-derived products. This has resulted in a diverse and attractive array of products, the value of which are increasingly being recognized and pursued by the food, feed, cosmetic, and nutraceutical markets.1 However, expansion into production of bulk products with lower market values, i.e., fuel, animal feed, and biomaterials, is limited.<\/p>\n
Numerous factors limit the potential to fully exploit algae in these market areas\u2014not the least of which is profitability (biomass \u2265$470\/t,2,3 biodiesel \u2265$3\/gal)3,4\u2014but also the energy intensity, resources requirement, and global warming potential (GWP) of production. 5\u20139 Commercial production is consequently limited to a relatively small number of species\u2014including Chlorella, Spirulina, Dunaliella, and Haematococcus\u2014and products, including pigments and whole cell supplements.1,10 Development of multi-product\/service biorefineries, where biomass components are separated to generate several products while using residual nutrient streams and abatement of carbon dioxide (CO2) from flue gases, may aid in reducing costs and improving the sustainability of these approaches. 5,7,11 Although meaningful advances have been made in attaining larger scales of production with high-performing strains,12 and more energy efficient and environmentally viable biorefinery practices are in development,7,13 it is still likely that these production platforms will operate close to profitability and sustainability margins, with high degrees of uncertainty. 4\u20137,9,14,15<\/p>\n
To develop more feasible algal biorefineries, integration or symbiosis with industrial infrastructure could provide many of the resources required for large-scale production of biomass, including nutrients, water, CO2, and heat. A more sustainable supply of these resources can contribute significantly to decreasing the negative energy balance, GWP, and cost of production. It should subsequently be of the utmost importance to match appropriate outputs (quantity and quality) from different industrial or municipal sectors to microalgal biorefineries to realize these benefits.16\u201318<\/p>\n
Life-cycle assessments (LCA) and techno-economic analysis (TEA) will also play a key role in shaping the selection and development of sustainable technologies and biorefinery processes. LCA are critical for determining the life-cycle greenhouse gas (GHG) reductions associated with biofuels. In Europe, the Renewable Energy Directive states that by 2020 at least 10% of energy in transport should be renewable and these fuels need to provide a reduction of GHG emissions of at least 35%. From 2017 the reduction of GHGs should be 50%, and, from 2018, 60% compared to fossil fuels. Production of biofuels should not cause destruction of land with high biodiversity or take place on land with high carbon stock.19 The Renewable Fuel Standard developed by the United States Energy Independence and Security Act of 2007 requires production of renewable fuels to have at least a 50% CO2 reduction compared to petroleum fuels to be classed as an advanced biofuel. Comprehensive LCA that consider the whole production chain cradle-to-grave (and land-use change implications) with a consistent methodological approach are subsequently required.20,21<\/p>\n
Through examination of available literature, a detailed overview of the requirements of these inputs and processes for large-scale microalgal production (nutrients, water, CO2, and heat) is presented with considerations on reducing\/recycling them. Arguments for the use of low-impact resources from industry in terms of cost and sustainability criteria are presented where appropriate. Furthermore, through a broad consultation of the literature, inconsistencies in reported data for different inputs and processes are highlighted, with an intention to improve future analysis of microalgal production scenarios.<\/p>\n
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The cultivation and processing of microalgal biomass is resource- and energy-intensive, negatively affecting the sustainability and profitability of producing bulk commodities, limiting this platform to the manufacture of relatively small quantities of high-value compounds. A biorefinery approach where all fractions of the biomass are valorized might improve the case for producing lower-value products. However, these […]<\/p>\n","protected":false},"author":59,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","nova_meta_subtitle":"","footnotes":""},"categories":[5572],"tags":[5796,10477],"supplier":[8249,12576],"class_list":["post-37127","post","type-post","status-publish","format-standard","hentry","category-bio-based","tag-biotechnology","tag-microalgae","supplier-chalmers-university-of-technology","supplier-sp-technical-research-institute-of-sweden"],"_links":{"self":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/37127","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/users\/59"}],"replies":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/comments?post=37127"}],"version-history":[{"count":0,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/37127\/revisions"}],"wp:attachment":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media?parent=37127"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/categories?post=37127"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/tags?post=37127"},{"taxonomy":"supplier","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/supplier?post=37127"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}