Experimental processing of seaweeds for biofuels

Abstract

The following paper provides an overview of the potential uses of seaweeds derived both from artificial cultivation as well as from eutrophic reservoirs as the feedstock for biofuels production. This review presents biochemical (anaerobic digestion [AD] and fermentation), chemical (extraction and transesterification) and thermochemical conversions (combustion, liquefaction, gasification and pyrolysis) of seaweeds for biofuels with special attention being paid to seaweeds processing such as pretreatment techniques, production methods and experimental conditions, and so forth. Seaweeds are considered as a suitable source for biogas and bioethanol production due to their high carbohydrate content. This review explores also the possibility of the application of oil extracted from seaweeds for biodiesel production. Since the chemical composition of seaweeds significantly differs from land biomass, a new comprehensive approach is required. Many macroalgal components are recalcitrant to bioconversion and pose microbiological challenges. The text deals with advantages and disadvantages of seaweeds as a feedstock for biofuels. Since macroalgae exploitation only for energy production is too expensive, seaweed integrated biorefineries were proposed as a solution which enables a development of high‐value algal bioproducts. Algae appear to be a promising source of biofuels. Utilization of waste algal biomass constitutes a link between the pollution abatement and energy production. This article is categorized under: Bioenergy > Science and Materials

A Comprehensive Review of the Nutraceutical and Therapeutic Applications of Red Seaweeds (Rhodophyta)

“…Currently, none of the mentioned processes proved to be feasible at an industrial scale nowadays, but they are gaining new interest due to the depletion of fossil fuels, which has given rise to a demand for alternatives, of which seaweeds are a possibility. The actual techniques of fatty acid extraction have disruptive pros and cons when compared with microalgae (mainly because of the lack of fatty acids in great quantity), but they can be used to produce bioethanol and bio-oil from wet macroalgae with a viable condition [25,26].…”

Recent trends on seaweed fractionation for liquid biofuels production

“…Seaweeds can be separated into three different groups depending on their pigmentation: green, red and brown seaweeds and, in each specific group, the variation of carbohydrates is distinctive (Jung et al, 2013;Michalak, 2018). Table 1 shows the chemical composition of the three types of seaweed.…”

“…Their photosynthetic pigments are essentially chlorophyll A and B, and carotenoids (Jung et al, 2013;Sudhakar et al, 2018). Moreover, green algae carbohydrate content varies between 40 and 60% dry matter, and it mainly consists of polysaccharides as ulvan, starch and cellulose (Michalak, 2018;Praveen et al, 2019). Ulvan is mainly composed by α-and β-(1,4)-linked units of rhamnose, xylose, galactose, glucuronic acid and iduronic acid and several repeating disaccharides (such as β-D-glucuronic acid (1,4)-linked to α-L-rhamnose 3-sulfate) (Kidgell et al, 2019), while both starch and cellulose are composed by glucose units, but with different spatial configurations.…”

“…Prior to pretreatment, some steps are proposed to prepare the seaweeds (Dave et al, 2019;Maneein et al, 2018;Michalak, 2018;Rigdon et al, 2013), namely:…”

“…In this way, algae are the third generation feedstock and currently stand out as a potential biomass to obtain biofuels (Michalak, 2018) due to some advantages such as: i) ubiquity, ii) low rate of biomass fluctuation owing to overpopulation, iii) production of the majority of oxygen in the planet with a high absorption of annual CO 2 , iv) higher photosynthetic efficiency (6-8%) than terrestrial biomass (1.8-2.2%), v) low consumption of water, vi) no alteration of human food supply, vii) no competition for arable land, viii) capacity of growing in a wide range of territories like saline water or wastewater, ix) absence or low lignin content; x) potential to obtain high-added value products (cosmetics, drugs, pigments, biofertilizers, food additives…) and xi) ability to achieve larger production rates of biomass than land-based feedstock (in terms of land surface employed) (Rodríguez-Jasso et al, 2013;Ruiz et al, 2013;Sirajunnisa and Surendhiran, 2016). In a recent study, the US Energy Department has estimated (under specific conditions) that the biofuel productivity from seaweed is two and five-fold higher than ethanol productivity obtained from sugarcane and corn, respectively (Soliman et al, 2018).…”