Digital library

Mesocosm experiments conducted for ecological purposes have become increasingly popular because they can provide a holistic understanding of the biological complexities associated with natural systems. This paper describes a new outdoor mesocosm designed for CO₂ perturbation experiments of benthos. Manipulated the carbonate chemistry in a continuous flow-through system can be parallelized with diurnal changes, while irradiance, temperature, and nutrients can vary according to the local environment. A target hydrogen ion activity (pH) of seawater was sufficiently stabilized and maintained within 4 h after dilution, which was initiated by the ratio of CO₂-saturated seawater to ambient seawater. Specifically, pH and CO₂ partial pressure (pCO₂) levels gradually varied from 8.05–7.28 and 375–2,691 μatm, respectively, over a range of dilution ratios. This mesocosm can successfully manipulate the pH and pCO₂ of seawater, and it demonstrates suitability for ocean acidification experiments on benthic communities.

Algae are one of the most viable feedstock options that can be converted into different bioenergies viz., bioethanol, biobutanol, biodiesel, biomethane, biohydrogen, etc. owing to their renewable, sustainable and economic credibility features. Algal biomass to fuel biorefining process is generally classified into three categories as chemical, biochemical and thermochemical methods. The present article aims to provide a state-of-the-art review on the factors affecting the thermochemical conversion process of algal biomass to bioenergy. Further, reaction conditions of each techniques (torrefaction, pyrolysis, gasification and hydrothermal process) influence biochar, bio-oil and syngas yield were discussed. Reaction parameters or factors such as reactor temperature, residence time, pressure, biomass load/feedstock composition, catalyst addition and carrier gas flow affecting process efficiency in terms of product yield and quality were spotlighted and extensively discussed with copious literature. It also presents the novel insights on production of solid (char), liquid (bio-oil) and gaseous (syngas) biofuel through torrefaction, pyrolysis and gasification, respectively. It is found that the energy intensive drying was more efficient mode involved in thermochemical process for wet algal biomass. However other modes of thermochemical process were having unique feature on improving the product yield and quality. Among the various factors, reaction temperature and residence time were relatively more important factors which affected the process efficiency. The other factors signposted in this review will lay a roadmap to researchers to choose an optimal thermochemical conditions for high quality end product. Lastly, the perspectives and challenges in thermochemical conversion algae biomass to biofuels were also discussed.

A Bayesian inference method was employed to quantify uncertainty in an Integrated Multi-Trophic Aquaculture (IMTA) model. A deterministic model was reformulated as a Bayesian Hierarchical Model (BHM) with uncertainty in the parameters accounted for using “prior” distributions and unresolved time varying processes modelled using auto-regressive processes. Observations of kelp grown in 3 seeding densities around salmon pens were assimilated using a Sequential Monte Carlo method implemented within the LibBi package. This resulted in a considerable reduction in the variability in model output for both the observed and unobserved state variables. A reduction in variance between the prior and posterior was observed for a subset of model parameters which varied with seeding density. Kullback–Liebler (KL) divergence method showed the reduction in variability of the state and parameters was approximately 90%. A low to medium seeding density results in the most efficient removal of excess nutrients in this simple system.

Modern methods of macroalgal cultivation of the large brown seaweeds commonly and collectively referred to as ‘kelp’ began in the early 1950’s in China, with research spearheaded by ‘the father of mariculture’, Prof. CK Tseng and his team. Since this time, kelp aquaculture has steadily grown in China and other Asian countries such as Japan, and the Republic of Korea. Now, almost all of the seaweed produced for human consumption, alginates and other purposes comes from aquaculture, with the extent of cultivation clearly visible on satellite images in some regions. Research in these countries has focused on brown algal species including Saccharina japonica and Undaria pinnatifida, concentrating primarily on developing a number of commercial strains that demonstrate temperature-tolerance of warmer seawater, and latterly, on improved productivity. In China, it is common practice to have centralised seaweed hatchery facilities that produce plantlets for further on-growing at a number of local sea sites.The development of centralised facilities using controlled seaweed strains most likely lends itself to a higher degree of standardised operations during the production cycle.

In direct contrast to the mass culture of seaweed in China and other Asian countries, commercial cultivation production in Europe remains on a small scale. While European research on kelp has existed at least as long as for that conducted in China, seaweed cultivation techniques have been known (generally only within research facilities) for approximately thirty years. For most of this time, cultivation has existed at a demonstration/pilot-scale only, although this is now changing in a number of countries, primarily across NW Europe. It was recognised early on that the Chinese method of growing seaweed by inserting small plantlets into ropes for on-growing at sea would not be economically efficient in Europe, given the cost of labour. Alternative cheaper seeding techniques, as described in this document, have been developed instead. Longline design is also different in Europe, where sea conditions are generally more challenging than the more sheltered areas that typically support Chinese aquaculture. This influences design and of course the cost of equipment that is used. The concurrent European research on wild strains of kelp species, partnered with a strong requirement for developing site specific cultivation systems has naturally led to some variance in production protocols and systems.

The EnAlgae project has allowed its research partners in NW Europe the opportunity to use hindsight of the expansion of global seaweed cultivation to full advantage. A theme of the project(WP1, Action 5) has been ‘the development and exchange of best practice for mass production of macroalgae’. For this action to be completed satisfactorily, demonstration/pilot sites (WP1, Action 2)were constructed at the macroalgal partner facilities. The subsequent development of a close working relationship enabled production of comparable data for identified species (Saccharina latissima and Alaria esculenta) on cultivation methodology, data collection (WP1, Action 3) and macroalgal growth results. The standardisation of all of these elements was designed to produce reliable data and share common experiences between macroalgal cultivation stakeholders in NW Europe, culminating in the production of this manual, and the accompanying Macroalgal Best Practice document.

This document is a manual of collated Standard Operating Protocols (SOPs) that were developed in the three EnAlgae macroalgal hatcheries in the National University of Ireland, Galway(NUIG), Queen’s University, Belfast (QUB) and the Centre d’Etude et de Valorisation des Algues (CEVA). It describes the set-up/requirements of each seaweed hatchery, the hatchery cultivation process, thesea on-growing process, as well as biomass and environmental parameter measurements and sampling. While some SOPs were subject to some inherent differences within each hatchery (e.g. pre-existing seawater pumping and distribution systems), an effort was made to ensure that as many elements of the SOPs were standardised across the partners. For example, the biomass sampling SOP was particularly important to enable the collection of comparable data in Ireland, Northern Ireland and France.

The SOP manual has been designed for reading with the EnAlgae Macroalgal Best Practice document. This sister document offers further advice and observations of the methods used, including elements of the processes that worked, and equally importantly, where system failures occurred, and revisions were made. It is hoped that both documents will become a valuable resource for those interested in developing European kelp cultivation in NW Europe and beyond, providing information on techniques that can further refined, leading to ever-increasingly efficient seaweed production at sea.