Local and global changes associated with anthropogenic activities are impacting marine and terrestrial ecosystems. Macroalgae, especially habitat-forming species like kelp, play critical roles in ...temperate coastal ecosystems. However, their abundance and distribution patterns have been negatively affected by warming in many regions around the globe. Along with global change, coastal ecosystems are also impacted by local drivers such as eutrophication. The interaction between global and local drivers might modulate kelp responses to environmental change. This study examines the regulatory effect of NO
on the thermal plasticity of the giant kelp Macrocystis pyrifera. To do this, thermal performance curves (TPCs) of key temperature-dependant traits-growth, photosynthesis, NO
assimilation and chlorophyll a fluorescence-were examined under nitrate replete and deplete conditions in a short-term incubation. We found that thermal plasticity was modulated by NO
but different thermal responses were observed among traits. Our study reveals that nitrogen, a local driver, modulates kelp responses to high seawater temperatures, ameliorating the negative impacts on physiological performance (i.e. growth and photosynthesis). However, this effect might be species-specific and vary among biogeographic regions - thus, further work is needed to determine the generality of our findings to other key temperate macroalgae that are experiencing temperatures close to their thermal tolerance due to climate change.
The increasing demands placed on natural resources for fuel and food production require that we explore the use of efficient, sustainable feedstocks such as brown macroalgae. The full potential of ...brown macroalgae as feedstocks for commercial-scale fuel ethanol production, however, requires extensive re-engineering of the alginate and mannitol catabolic pathways in the standard industrial microbe Saccharomyces cerevisiae. Here we present the discovery of an alginate monomer (4-deoxy-L-erythro-5-hexoseulose uronate, or DEHU) transporter from the alginolytic eukaryote Asteromyces cruciatus. The genomic integration and overexpression of the gene encoding this transporter, together with the necessary bacterial alginate and deregulated native mannitol catabolism genes, conferred the ability of an S. cerevisiae strain to efficiently metabolize DEHU and mannitol. When this platform was further adapted to grow on mannitol and DEHU under anaerobic conditions, it was capable of ethanol fermentation from mannitol and DEHU, achieving titres of 4.6% (v/v) (36.2 g l(-1)) and yields up to 83% of the maximum theoretical yield from consumed sugars. These results show that all major sugars in brown macroalgae can be used as feedstocks for biofuels and value-added renewable chemicals in a manner that is comparable to traditional arable-land-based feedstocks.
•A cogeneration system is proposed to convert algae into H2 and power production.•The system consists of drying, gasification, chemical looping, and power generation.•The system is modeled and ...evaluated using Aspen Plus software package.•The relations between the parameters and the performance of the system are obtained.
A cogeneration system is proposed in this study to produce H2 and generate power from brown macroalgae with a high moisture content. The processes used in the cogeneration system consisted of drying, steam gasification, syngas chemical looping (SCL), and power generation. Enhanced process integration technology was utilized to maximize heat recovery in the system by minimizing the destruction of exergy. The SCL system used in this study consisted of a fuel reactor, a steam reactor, and an air reactor. Iron oxide was utilized as the circulating oxygen carrier in the SCL system and was reduced and oxidized during its passage through the SCL reactors. The performance of the cogeneration system was evaluated at different target moisture contents during drying, steam-to-biomass ratios during gasification, and operating pressures in the SCL system by means of process simulation using the Aspen Plus software package. The results of the simulation show that the proposed system had a relatively high total efficiency (about 72%), which consisted of H2 production and power generation efficiencies of about 57% and 15%, respectively.
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•H2O2 induced microwave treatment in acidic condition (AHMW) enhance disintegration.•Higher organic release was attained at 0.024 g/g TS H2O2 and at pH 5.•A liquefaction of 38.5% was ...obtained at the specific energy of 10800 kJ/kg TS.•Biohydrogen production of 92.5 mL H2/g COD was achieved in AHMW pretreatment.
The objective of the present study is to improve the biohydrogen production from marine macroalgae (Ulva reticulate) by acidic - hydrogen peroxide (H2O2) induced microwave (AHMW) pretreatment. Higher soluble chemical oxygen demand (SCOD) release of 1450 mg/L and its liquefaction rate of 30.2% was achieved in microwave (MW) pretreatment with treatment time period of 15 mins. Varying concentration of H2O2 from 0.003 to 0.03 g/g TS were used in the optimal microwave power (40%) to enhance the organic release in H2O2 induced microwave pretreatment (HMW). Maximum liquefaction of 33.9% was obtained at the H2O2 concentration of 0.024 g /g TS. The combined HMW pretreatment under acidic (pH 4–6.5) show synergistic effect on organic release. At optimal pH 5, AHMW pretreatment shows the SCOD release of 1850 mg/L with its liquefaction of 38.5% at time of 10 min. Therefore, AHMW pretreatment significantly reduce the treatment time and increase liquefaction when compared to MW and HMW. The maximum biohydrogen production was observed as 92.5 mL H2/g COD in AHMW pretreatment.
In this work, Cladophora glomerata, a harmful seaweed, is converted into an olive-shaped magnetic biochar by a slow pyrolysis process catalyzed by iron. The resultant magnetic biochar has a high ...surface area of 296.4 m2 g−1 with a carbon-rich structure that makes it suitable to be used as an electrode in Li-ion batteries. The catalytic pyrolysis process showed significant effect on steam reforming, ketonization and deoxygenation and/or denitrogenation reactions. The overall quality of the pyrolysis products increases: the gas contains a higher percentage of hydrogen (up to 22%), while the oil is enriched in furans (with a selectivity of about 14%). The electrochemistry behavior of magnetic biochar has been also evaluated, using galvanostatic charge–discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) analyses. The electrochemical results indicated a higher initial specific discharge capacity (740 mAh g−1) and great cyclic stability for magnetic electrode as compared to the biochar electrode.
•Magnetic material in renewable energy production and storage systems.•The effect of magnetic catalyst on bio-products derived from cladophora glomerata.•The effect of magnetic electrode on the electrochemical performance of Li-ion batteries.•High thermal stability and easy recyclability of magnetic electrode.•Hydrogen-rich gas and furan compounds in the presence of magnetic catalyst.
Biomethane Potential (BMP) of green macroalga Ulva lactuca post extraction of sap, ulvan and protein was analysed in batch studies. Extraction was performed in two different ways (individual and ...sequential) to understand the effect of removal of these components on methane yields. Both the treatments resulted in enhanced biomethane production in most of the treated residues, however, the highest methane yield of 408 ± 20.02 ml CH4 g−1 VS (70.93% of theoretical) was observed in sap and ulvan removed residue (batch VI). The methane production rates improved after both the treatments (0.15–0.28 day−1 for untreated and treated batches). This corroborates well with the fact that high protein and sulphate content are major inhibitors in anaerobic digestion (AD) of U. lactuca and their removal leads to improved methane yields. Sequential extraction of value-added products prior to the AD process not only improves biomass amenability and respective methane yields but also makes the overall process more efficient and viable.
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•Enhanced amenability of Ulva lactuca biomass post sequential treatment.•Rapid anaerobic digestion with increased substrate utilization (upto 46%).•Improved biomethane yields (∼2 folds) from treated residues.•Sequential extraction of bio-products for biorefining of Ulva lactuca.
Herein, we report on a combined process that incorporates hydrothermal liquefaction (HTL) and supercritical water gasification (SCWG) to improve energy recovered from algal biomass. Eight algal ...biomasses, including four microalgae and four macroalgae with a large difference in biochemical compositions, were screened for this dual process. The algal biomass feedstocks significantly affected the carbon and energy distribution in the product fractions (crude bio-oil, solid, gas, and water-soluble products). 62.50–71.34% energy of microalgae and 6.03–41.06% energy of macroalgae could be recovered as crude bio-oil. 11.86–21.55% carbon of the microalgae and 8.01–15.82% carbon of the macroalgae was distributed in the HTL process water in form of water soluble products after the HTL process. 14.3–33.7% energy of microalgae and 30.18–36.34% energy of macroalgae was retained in the HTL process water. SCWG could convert the organics in the HTL process water into fuel gases consisting mainly of H2 and CH4. 54–91% carbon of the HTL process water was transformed into the fuel gases, which correspond 5.53–18.30% energy of the algal biomass. Thus, this work shows that the integration of HTL and SCWG could improve energy recovery from algal biomass relative to the HTL process alone.
•Integration of HTL and SCWG can improve energy recovery from algal biomass.•Algal biomass significantly affected carbon and energy distribution in the products.•14.3–36.34% energy of algal biomass distributed in the HTL process water.•57–94% TOC of the HTL process water after SCWG was substantially reduced.•5.53–18.30% energy of the algal biomass was recovered from the HTL process water.
•A new feedstock (Gelidium floridanum – GF) for bioenergy production.•First attempt on pyrolysis study of the Gelidium floridanum.•Thermochemical characteristics indicated that GF is suitable for ...pyrolysis.•Thermodynamic and kinetics analysis suggested a favorable potential for bioenergy.
The aim of this study was to investigate the bioenergy potential of red macroalgae GF by evaluating its biofuel physicochemical characteristics, and conducting a kinetic study and thermodynamic analysis of pyrolysis for the first time. The thermal decomposition study was performed at low heating rates (5, 10, 20 and 30 °C min−1) under N2 atmosphere. The thermal behavior of GF pyrolysis indicated the presence of three different decomposition stages, which are associated with different components in its structure and consequently influence the kinetic and thermodynamic parameters. The kinetic triplet obtained for GF provided a suitable description of experimental thermal behavior. The thermodynamic parameters demonstrated that GF is as a new promising feedstock for bioenergy and presented a similar potential to well-known bioenergy feedstock.
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•Hydrothermal gasification of Cladophoraglomerata for hydrogen production.•Porous and alkaline solid product as hydrochar, favorable for using as a catalyst.•H2 and CO2 promotion in ...the presence of hydrochar as a catalyst.•Phenols enhancement and acids decrement in aqueous products.
A tubular batch micro-reactor system was used for hydrothermal gasification (HTG) of Cladophora glomerata (C. glomerata) as green macroalgae found in the southern coast of the Caspian Sea, Iran. Non-catalytic tests were performed to determine the optimum condition for hydrogen production. Hydrochar, as a solid residue of non-catalytic HTG was characterized by BET, FESEM, and ICP-OES methods to determine its physiochemical properties. Surface area and pore volume of C. glomerata increased drastically after HTG. Also, the aqueous products were identified and quantified by GC–MS and GC-FID methods. Hydrochar was loaded to the reactor to determine its catalytic effect on HTG. HTG was promoted by inorganic compounds in the hydrochar and its porosity. The maximum hydrogen yield of 9.63mmol/g was observed in the presence of algal hydrochar with the weight ratio of 0.4 to feedstock. Also, acids production was inhibited while phenol production was promoted in the presence of hydrochar.
Brown macroalgae are an attractive, untapped resource and a favourable alternative for conventional fossil fuels, given their low lignin and high polysaccharide content. However, the restricted ...bioavailability of structurally complex carbohydrates for digestion, results in a low biomethane potential. This paper reviews the various pretreatment technologies explored to optimise saccharification prior to fermentation, categorised as: physical, biological, chemical, thermal and a combination of methods. A techno-economic assessment was conducted to evaluate the commercial viability of each process. Hydrothermal pretreatment proves the most promising technique for brown algae application, since it improves methane productivity, carries a net positive energy balance and generates a bio-fertilizer, while mitigating greenhouse gas emissions. Pilot scale research is necessary to evaluate the feasibility of full-scale implementation for brown algae bioconversion. A case study of the Cambi™ process concludes the paper as it exemplifies the successful utilisation of hydrothermal pretreatment for sewage sludge biogas production.
•Pretreatment methods have been applied to brown macroalgae with varying success.•These processes improve algal bioconversion and biogas recovery.•Full-scale implementation is impaired by high capital costs and energy inputs.•Thermal hydrolysis is most commercially viable for brown algae application.•Pilot scale research is necessary to evaluate the scalability.
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