A solar drying system was designed, constructed and tested for drying of seaweed. Seaweed is a potential source of renewable energy, and it can be converted into energy such as biofuel oil, biodiesel and gas. Red seaweed was dried to the final moisture content of 10% from 90% w.b in 15 h. Drying kinetics of red seaweed were investigated and obtained. The nonlinear regression procedure was used to fit three different drying models. The Page's model clearly showed a better fit to the experimental data between Newton's model and Henderson and Pabis model. The Page's model was resulted in the highest value of R2 and lowest values of MBE and RMSE. At average solar radiation of about 500 W/m2 and air flow rate 0.05 kg/s, the collector, drying system and pick-up efficiencies were found about 35, 27 and 95%, respectively. This study was performed with energy analysis and exergy analyses of the solar drying process of red seaweed. The specific energy consumption (SEC) of 2.62 kWh/kg was obtained. Moreover, the exergy efficiency of solar drying ranged from 1% to 93%, with an average of 30%. The values of improvement potential were found to be in the range of 0.3 and 630 W, with an average of 247 W.
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This chapter provides a brief overview of some of the major steps in the development of microalgae-based processes for renewable energy production. The chapter attempts to highlight the development and evolution of the key concepts and research in the field, preparing the reader for the following chapters, which will deepen the discussion on the subject.
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Macroalgae, commonly known as seaweed, has received significant interest as a potential source of ethanol because of its fast growth, significant sugar content and successful lab-scale conversion to ethanol. Issues such as energy input in seaweed conversion, lifecycle emissions, global production potential and cost have received limited attention. To address this gap, a well-to-tank model of ethanol production from brown seaweed is developed and applied to the case of ethanol production from Saccharina latissima in British Columbia, Canada. Animal feed is proposed as a co-product and co-product credits are estimated. In the case considered, seaweed ethanol is found to have an energy return on invested (EROI) of 1.7 and a carbon intensity (CI) of 10.8 gCO2e MJ 1. Ethanol production from conventionally farmed seaweed could cost less than conventional ethanol and be produced on a scale comparable to 1% of global gasoline production. A drying system is required in regions such as British Columbia that require seasonal seaweed storage due to a limited harvest season. The results are significantly influenced by variations in animal feed processing energy, co-product credit value, seaweed composition, the value of seaweed animal feed and the cost of seaweed farming. We find EROI ranges from 0.64 to 26.7, CI from 33 to 41 gCO2e MJ1 and ethanol production is not financially viable without animal feed production in some scenarios.
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The cultivation of seaweed as a feedstock for third generation biofuels is gathering interest in Europe, however, many questions remain unanswered in practise, notably regarding scales of operation, energy returns on investment (EROI) and greenhouse gas (GHG) emissions, all of which are crucial to determine commercial viability. This study performed an energy and GHG emissions analysis, using EROI and GHG savings potential respectively, as indicators of commercial viability for two systems: the Swedish Seafarm project's seaweed cultivation (0.5 ha), biogas and fer- tilizer biorefinery, and an estimation of the same system scaled up and adjusted to a cultivation of 10 ha. Based on a conservative estimate of biogas yield, neither the 0.5 ha case nor the up-scaled 10 ha estimates met the (commercial viability) target EROI of 3, nor the European Union Renewable Energy Directive GHG savings target of 60% for biofuels, however the potential for commercial viability was substantially improved by scaling up operations: GHG emissions and energy demand, per unit of biogas, was almost halved by scaling operations up by a factor of twenty, thereby approaching the EROI and GHG savings targets set, under beneficial biogas production conditions. Further analysis identified processes whose optimisations would have a large impact on energy use and emissions (such as anaerobic digestion) as well as others embodying potential for further economies of scale (such as harvest- ing), both of which would be of interest for future developments of kelp to biogas and fertilizer biorefineries.
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Global warming has become one of the most serious environmental problems. To cope with the problem, it is necessary to substitute renewable energy for nonrenewable fossil fuel. Biomass, which is one of the renewable energies, is considered to be carbon-neutral, meaning that the net CO{sub 2} concentration in the atmosphere remains unchanged provided the CO{sub 2} emitted by biomass combustion and that fixed by photosynthesis are balanced. Biomass is also unique because it is the only organic matter among renewable energies. In other words, fuels and chemicals can be produced from biomass in addition to electricity and heat. Marine biomass has attracted less attention than terrestrial biomass for energy utilization so far, but is work considering especially for a country like Japan which has long available coastlines. This paper discusses the utilization of marine biomass as an energy resource in Japan. A marine biomass energy system in Japan was proposed consisting of seaweed cultivation (Laminaria japonica) at offshore marine farms, biogas production via methane fermentation of the seaweeds, and fuel cell power generation driven by the generated biogas. The authors estimated energy output, energy supply potential, and CO{sub 2} mitigation in Japan on the basis of the proposed system. As a result, annual energy production was estimated to be 1.02 x 10{sup 9} kWh/yr at nine available sites. Total CO{sub 2} mitigation was estimated to be 1.04 x 10{sup 6} tonnes per annum at the nine sites. However, the CO{sub 2} emission for the construction of relevant facilities is not taken into account in this paper. The estimated CO{sub 2} mitigation is equivalent to about 0.9% of the required CO{sub 2} mitigation for Japan per annum under the Kyoto Protocol framework.
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Biochar, a pyrogenic black carbon is derived by pyrolysis of carbon-rich biomass in an oxygen-limited environ- ment. The physico-chemical characteristics of biochar strongly impact the multifunctional role of biochar e.g., carbon sequestration and enhancement of soil fertility, biosorption or environmental remediation, fuel cells, supercapacitors, and biocatalyst. Owing to the poor performance of pristine biochar, engineered biochars have emerged, that are derived from physical, chemical, and biological modifications of pristine biochar to im- prove its surface properties and thus adsorption capacity. In the past two decades, researchers have been focus- sing more on low-cost biomass. Algal biomass is one such source that has shown significant prospective for biochar fabrication. The present review summarizes various applications of biochar, mechanisms associated with metal removal by biochar, various modification procedures for developing engineered biochars, algal bio- char production methods as well as characterization of algal biochar. The review is intended to evaluate recent advancements and research in engineered algal biochar with a primary focus on contaminant remediation and the development of bioelectrochemical systems using algal biochar. This review opens new vistas and adds inno- vative ideas for future research utilizing engineered algal biochar, towards renewable, sustainable, and low-cost production of biosorbents for remediation of contaminated aqueous environments.
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In the search for renewable fuels, there’s no perfect solution. Biofuels can be readily made from corn starch and sugar cane, but they take land and resources away from food crops. Feedstocks such as switchgrass and wood sidestep that problem—but they are hamstrung by a molecule called lignin, which makes it harder to extract the sugars that ferment into ethanol.
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Processing of biomass for the production of a fuel gas containing methane requires a complex system. The degree of complexity is, in part, a function of the biomass utilized. In general, this system consists of 3 main subsystems;
- Raw material preparation
- Methane fermentation
- Residue processing, utilization and/or disposal
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Whole floc in shrimp diets significantly improved shrimp growth rate and did not affect shrimp survival.
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Intensive algal cultivation usually requires a high flux of dissolved inorganic carbon (Ci) to support productivity, particularly for high density algal cultures. Carbon dioxide (CO2) enrichment can be used to overcome Ci limitation and enhance productivity of algae in intensive culture, however, it is unclear whether algal species with the ability to utilise bicarbonate (HCO32) as a carbon source for photosynthesis will benefit from CO2 enrichment. This study quantified the HCO32 affinity of three green tide algal species, Cladophora coelothrix, Cladophora patentiramea and Chaetomorpha linum, targeted for biomass and bioenergy production. Subsequently, we quantified productivity and carbon, nitrogen and ash content in response to CO2 enrichment. All three species had similar high pH compensation points (9.7–9.9), and grew at similar rates up to pH 9, demonstrating HCO32 utilization. Algal cultures enriched with CO2 as a carbon source had 30% more total Ci available, supplying twenty five times more CO2 than the control. This higher Ci significantly enhanced the productivity of Cladophora coelothrix (26%), Chaetomorpha linum (24%) and to a lesser extent for Cladophora patentiramea (11%), compared to controls. We demonstrated that supplying carbon as CO2 can enhance the productivity of targeted green tide algal species under intensive culture, despite their clear ability to utilise HCO32.
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