The potential of algal biomass as a source of liquid and gaseous biofuels is a highly topical theme, but as yet there is no successful economically viable commercial system producing biofuel. However, the majority of the research has focused on producing fuels from microalgae rather than from macroalgae. This article briefly reviews the methods by which useful energy may be extracted from macroalgae biomass including: direct combustion, pyrolysis, gasification, trans-esterification to biodiesel, hydrothermal liquefaction, fermentation to bioethanol, fermentation to biobutanol and anaerobic digestion, and explores technical and engineering difficulties that remain to be resolved.
Digital library
-
-
Macroalgae is an emerging third-generation feedstock and promising biomass within the biorefinery context to produce biofuels and high-added value compounds. Biorefinery involves processes and technologies in the context of sustainable bioeconomy. Throughout the biorefinery process is important not to neglect parameters and conditions that can impact the optimization, such as pretreatment, solid loading in enzymatic hydrolysis and, fermentation. In this case, the techno-economic analysis allows designing a feasible process of macroalgae valorization considering differents important parameters for scaling up the process for biofuels and chemicals to approach all these compounds for a future market and commercial. According to these arguments, this review aims to describe the macroalgae biorefinery, applications, and techno-economic analysis to provide the general panorama of economic feasibility for the valorization of macroalgae biomass in terms of biorefinery and circular bioeconomy.
-
The imminent need for transition to a circular bioeconomy, based on the valorisation of renewable biomass feedstocks, will ameliorate global challenges induced by climate change, environmental pollution and population growth. A reduced reliance on depleting fossil fuel resources and ensured production of eco-friendly and costeffective bioproducts and biofuels, requires the development of sustainable biorefinery processes, with many utilising macroalgae as feedstock, showing promising and viable prospects. Nonetheless, macroalgal biorefinery research is still in its infancy compared to lignocellulosic biorefineries that utilise terrestrial plants. This article presents a review on the latest scientific literature associated with the development and status of macroalgal biorefineries, and how bioproducts generated from these bioprocesses have contributed towards the bioeconomy. The fundamental need to understand how the unique biochemical composition of macroalgae fit within a biorefinery concept are explained, alongside discussion of the novel biotechnologies that have been applied. In order to comprehend the increasing significance of this exciting field, the review will also provide insight, for the first time, on the current global funding and intellectual property landscape related to macroalgae and their implementation across the entire biorefinery concept. Imperative areas for further research and development, to bridge the gap between fundamental bioscience in the laboratory and the successful application of compatible biotechnologies at a commercial scale, to boost the macroalgae industry are also covered.
-
This review focuses on the diversity of French tropical overseas macroalgae and their biotechnological applications. After listing the specific diversity, i.e. 641 species in French Antilles in the Atlantic Ocean, 560 species in the Indian Ocean, and 1015 species in the South Pacific Ocean, we present the potential of their metabolites and their main uses. Among the great diversity of metabolites, we focus on carbohydrates, proteins, lipids, pigments and secondary metabolites, in particular terpenes and phenolic compounds. The main applications of reef macroalgae are described in human and animal consumptions, phycocolloids extraction, production of active ingredients for health, cosmetics, agriculture, and bioremediation. For each application, we list what has been done, or will be done in French tropical overseas territories and point out the challenges faced when using this chemo-diversity, and problems linked to their exploitation. Finally, we discuss challenges to develop seaweed farming, their uses in carbon sequestration and resilience to global change, their uses for alternative proteins together with the production of bioenergy and biomaterials. As a conclusion, we encourage the research on the chemo-diversity of French reef macroalgae for industrial applications as these organisms represent a reservoir of active ingredients that is still insufficiently explored.
-
Ex situ seed banking was first conceptualized and implemented in the early 20th century to maintain and protect crop lines. Today, ex situ seed banking is important for the preservation of heirloom strains, biodiversity conservation and ecosystem restoration, and diverse research applications. However, these efforts primarily target microalgae and terrestrial plants. Although some collections include macroalgae (i.e., seaweeds), they are relatively few and have yet to be connected via any international, coordinated initiative. In this piece, we provide a brief introduction to macroalgal germplasm banking and its application to conservation, industry, and mariculture. We argue that concerted effort should be made globally in germline preservation of marine algal species via germplasm banking with an overview of the technical advances for feasibility and ensured success.
-
Primary production and respiration rates were studied for six seaweed species (Cystoseira abies-marina,Lobophora variegata, Pterocladiella capillacea, Canistrocarpus cervicornis, Padina pavonica and Corallina caespitosa)from Subtropical North-East Atlantic, to estimate the combined effects of different pH and temperature levels.Macroalgal samples were cultured at temperature and pH combinations ranging from current levels to thosepredicted for the next century (19, 21, 23, 25 °C, pH: 8.1, 7.7 and 7.4). Decreased pH had a positive effect onshort-term production of the studied species. Raised temperatures had a more varied and species dependenteffect on short term primary production. Thermophilic algae increased their production at higher temperatures,while temperate species were more productive at lower or present temperature conditions. Temperature alsoaffected algal respiration rates, which were higher at low temperature levels. The results suggest that biomassand productivity of the more tropical species in coastal ecosystems would be enhanced by future ocean con-ditions.
-
The number of hungry mouths to feed keeps growing faster than predicted. A 2009 projection by the United Nations Food and Agriculture Organization (FAO) that by 2050 there would be 9 billion people on the planet may be off by a billion or so. Recently, some estimates have revised that figure closer to 10 billion. A 2018 report by the World Resources Institute (WRI), Creating a Sustainable Food Future, noted that by 2050, the world will need 56 percent more crop calories (7400 trillion) compared with those needed in 2010, and a land mass nearly twice the size of India to grow additional crops, even after accounting for increased yields. Already, agriculture and related land use contribute close to a quarter of all greenhouse gas emissions. But teams of plant geneticists, biosystems engineers, animal scientists, and fish nutritionists, among others, are making headway in finding ways to increase food production while potentially keeping a lid on greenhouse gas emissions. From sophisticated technologies at work in the fields to seaweed diets for cattle and agroforestry practices used by small farmers in Kenya, scientists are developing tools to make agriculture part of the climate solution.
-
Increasingly, consumers are being urged to imagine a future when their vehicles and commercial machinery are powered not just by gasoline or traditional diesel but also by liquid biofuels; electricity generated by wind and solar; and, perhaps, even hydrogen. Ethanol, a gasoline replacement usually made with corn in the United States, already replaces nearly 10 percent of U.S. gasoline. But researchers have made a strong case that multiple types of biomass feedstock are needed to create adequate supplies of biofuel.
The report “Biomass Feedstock For a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply,” published in 2005 by U.S. Department of Energy and Department of Agriculture researchers, has just been revised. Widely known as the “billion-ton study,” the update indicates that as much as 1.6 billion tons of terrestrial biomass from agricultural wastes, forestry waste, municipal solid wastes and energy crops such as miscanthus and switchgrass could be harvested sustainably in the United States annually for biofuels, bioenergy and bio-based products. Considering the theoretical fermentation yields on biomass sugars and the energy content of ethanol, this projection also establishes the theoretical maximum production of bio-based gasoline equivalents at close to 96 billion gallons. Since the United States uses approximately 140 billion gallons of gasoline, 40 billion gallons of road diesel and 20 billion gallons of jet fuel (all derived from crude oil) per year, it is clear that biofuels based on terrestrial feedstocks can never meet that demand. At the National Renewable Energy Laboratory (NREL), where we conduct our research, we concluded the same thing when the original billion-ton study was released. That prompted us to rebuild the Aquatic Species Program, previously funded from 1978 to 1996 by the U.S. Department of Energy, to evaluate the potential of algae-based biofuels.
-
With recent technological developments and the increasingly intensive interest in tropical sea cucumber farming, it is an opportune time to review the existing strategies of the first successful commercial hatchery in the Republic of Maldives (the Maldives). This may help to understand the success of the hatchery and grow-out operations. This paper analyses the strategies used in the production and grow-out of the commercially important sea cucumber Holothuria scabra, and their effects on the local communities and the environment in the Maldives. Holothuria scabra has been cultured in the Maldives since 1996. Hatchery production techniques consistently produce high-quality juveniles. When the juveniles reach 2–3 cm in size, they are transferred to nearby company-owned atoll lagoons for further growth. The sea cucumber grow-out period varies between 12 and 18 months in these waters. In addition to the company’s own sea cucumber grow-out operation, considerable quantities of juveniles are grown, with similar grow-out periods, by contract growers and villagers from the nearby islands. When the sea cucumbers are fully grown (350–425 g), the local growers sell them back to the company and are paid a management fee according to the duration of care and quantity of the product. The participation of the local community and village groups is one of the reasons for the ongoing success of sea cucumber culture in the Maldives. Sea cucumber hatchery production is a profitable operation in the Maldives, even though the cost of production per juvenile is higher due to the remote location and associated higher energy and transportation costs.
-
This paper describes a model for assessment of coastal and offshore shellfish aquaculture at the farm-scale. The Farm Aquaculture Resource Management (FARM) model is directed both at the farmer and the regulator, and has three main uses:
(i)prospective analyses of culture location and species selection; (ii) ecological and economic optimisation of culture practice, such as timing and sizes for seeding and harvesting, densities and spatial distributions (iii) environmental assessment of farm-related eutrophication effects (including mitigation).
The modelling framework applies a combination of physical and biogeochemical models, bivalve growth models and screening models for determining shellfish production and for eutrophication assessment. FARM currently simulates the above interrelations for five bivalve species: the Pacific oyster Crassostrea gigas, the blue mussel Mytilus edulis, the Manila clam Tapes phillipinarum, the cockle Cerastoderma edule and the Chinese scallop Chlamys farreri. Shellfish species combinations (i.e. polyculture) may also be modelled. We present results of several case studies showing how farm location and practice may result in significant (up to 100%) differences in output (production).
Changes in seed density clearly affect output, but (i) the average physical production decreases at higher densities and reduces profitability; and (ii) gains may additionally be offset by environmental costs, e.g. unacceptable reductions in dissolved oxygen. FARM was used for application of a Cobb–Douglas function in order to screen for economically optimal production: we show how marginal analysis can be used to determine stocking density.
Our final case studies examine interactions between shellfish aquaculture and eutrophication, by applying a subset of the ASSETS methodology. We provide a tool for screening various water quality impacts, and examine the mass balance of nutrients within a 6000 m2 oyster farm. An integrated analysis of revenue sources indicates that about 100% extra income could be obtained by emissions trading, since shellfish farms are nutrient sinks. FARM thus provides a valuation methodology useful for integrated nutrient management in coastal regions.
Pages
Marine Agronomy Group, CAFNRM, UH-Hilo
200 W. Kawili st., HI 96720, USA
Contact: Marine.Agronomy.Group@gmail.com
Funding for this web portal is provided by the World Wildlife Fund and the University of Hawaii-Hilo.