In many industrial processes there is often a source of effluent as well as flue gases. Wastewater treatment plants, farms with AD plants, breweries, distilleries and oil refineries all have the potential to offer both materials. The basic requirements of a system to cultivate algae are an area for in­frastructure, a source of nutrients (most importantly N and P), a source of concentrated carbon dioxide, freshwater and a consumer for the products obtained. Table 10 displays a number of areas where algal cultivation may be appropriate and the advantages and disadvantages of such a system. Table 10 shows a variety of potential industries where cultivation of algae could be possible. The majority of these industries provide a wastewater stream with sufficient nutrient loading for the growth of algae. Oil refinery wastewater may have a nutrient concentration too low for optimal growth nevertheless if necessary additional fertiliser could be supplemented. The flue gases found in each of the industries are likely to contain a CO2 con­centration of up to 15% and this value is considered to be near the maxi­mum level that will allow algal growth before it becomes toxic [49]. Each of the flue gases mentioned is likely to boost algal growth whilst seques­tering carbon simultaneously.

Depending upon the industry, there are likely to be many problems to overcome. High nutrient loadings (farm effluent, distillery effluent)

would lead to poor treatment or toxicity and therefore require dilution with freshwater. To dilute such high concentrations would require significant sources of freshwater possibly needing expensive transportation costs and environmental issues if located in a water stressed area. Wastewaters, par­ticularly those from chemical industries such as oil refining and bioethanol production, could potentially contain toxic contaminants. Similarly flue gases may contain toxins that could affect the growth of the algal biomass. It is evident that there are many different opportunities for the implemen­tation of algal cultivation in industry. Nevertheless it is not possible to have one fixed solution. Every scenario will have different wastewater characteristics, available water and land, varying flue gas characteristics, energy needs and problems related to implementation. Every approach to implementation may be different but the concept allows flexibility.