Clean technology in aquaculture — a production without waste products?

A method has been developed for the determination of H₂S and FeS in sediments. FeS is converted into H₂S which is flushed from the samples directly into an excess of chlorine bleach, NaC1O or KClO with some Zn²⁺ added. Either the excess can be titrated back potentiometrically with As₂O₃, or the sulphate formed can be measured colorimetrically. The precision is primarily controlled by the homogeneity of the sediment suspensions and can be better than 99%.     

The First International Seaweed Symposium held in Edinburgh,UK, 1952: applied seaweed science coming of age

Since the first commercial and systematic use of large brown algae for potash in the eighteenth century, chemists have applied their knowledge to benefit the industrial utilization of seaweeds. Towards the end of the nineteenth century, the focus of seaweed chemistry started to shift from the inorganic to the organic content. Trailing the chemists, seaweed botanists also became directly involved in the industrial efforts by surveying and assessing seaweed populations. In the 1930s, a modern seaweed industry emerged, based on seaweed polysaccharides and seaweed meal. Prior to World War II seaweed botanists, chemists and industrialists had no regular, joint international arena.The First International Seaweed Symposium (ISS) was held in Edinburgh, 14–17 July 1952. It was referred to as the follow-up of the limited: “Conference on utilization of seaweeds” which was held in Halifax, Nova Scotia, 1948. A main driving force was the Canadian war effort to extract substitute gelling materials from local seaweeds for use in the foodstuff industry. The conference in Halifax was rooted both in the annual Canadian “Irish Moss meetings” in Ottawa 1944–1947 and in the post-WWII expansion of regional laboratories of the National Research Council of Canada. The First ISS was attended by approximately 160 scientists from 21 countries. The symposium demonstrated the role and secured the position of this new applied, multi-disciplinary seaweed science.     

Carbohydrate degradation and methane production during fermentation ofLaminaria saccharina (Laminariales,Phaeophyceae)

Anaerobic digestion of the brown algaLaminaria saccharina (L.) Lamour. harvested in spring and autumn was carried out at controlled laboratory conditions in stirred fermentor systems. Due to the normal seasonal variations, the autumn material had a much higher content of carbohydrates such as mannitol and laminaran. Both batch and semi-continuous feeding conditions were investigated for periods up to 800 h, with inoculum provided from previous kelp fermentations. In batch cultures, the methane yield from the autumn material was doubled compared to that of the spring material. Semi-continuous conditions gave more similar methane yields for both raw materials, 0.22 and 0.27 l CH₄ per g VS for spring and autumn material, respectively. In all experiments, mannitol and laminaran were reduced to less than 5 of the initial values within 24–48 hours after inoculation, whereas 30 of the alginate content was detectable even after 30 days. Viscometry revealed that this material was severely depolymerized, and alginate lyase activity was found to develop rapidly in all cultures. Although mannitol and laminaran were fermented much faster than alginate, the total accumulated methane yields seemed to be determined by the total carbohydrate content of the raw material during extended semi-continuous feeding.(*author for correspondence)