# Exploring an Integrated Manure-Sewater System for Sustainable Cyanobacterial Biomass Production
## 1 Introduction  
Cyanobacteria (blue green algae) are a diverse group of prokaryotic oxygen-generating photosynthetic micro-organisms that conduct photosynthesis in a very similar way as higher plants [1]. Cyanobacteria are able to produce useful metabolic products, such as pigment for feed additives, fatty acids, proteins and other nutrients [2]. Because of the continuous increase in the global human population and degradation of natural resources, meeting the demand for obtaining sustainable food and energy without creating environmental problems has become a topic of concern. Therefore, cyanobacteria have recently emerged as a potential candidate that might meet the above mentioned criteria due to its capacity to effectively harvest natural solar energy, utilize water, CO\({}_{2}\) and nutrients, and convert them into biomass [3]. The biomass of cyanobacteria can be used for many purposes, such as food production, biofertilizer for crop production and soil fertility, biofuels (energy), cosmetics, and medical applications [3]. Cyanobacterial and microalgal biomasses have become importantsubstances for feed, biofuel, chemical production, and agricultural crop production that aims to meet the global food demand. In addition, because of their photoautotrophic nature, they are cultivated to generate important products, such as proteins, pigments, fatty acids, vitamins, and polysaccharides [4]. Interest in the production of biomass from cyanobacteria and microalgae for the extraction of bio-fuels, bio-fertilizer, animal feed and other bio-products is increasing. Although microalgae are considered as a potential alternative to meet some of the global demands, a decrease in the cost of biomass production cost is required to actually achieve this potential [5]. _Spirulina_ sp. is a filamentous cyanobacteria with a relatively high cell growth rate, which makes it ideal for biomass production [6]. The role of _Spirulina platensis_ biomass in poultry manure treatment and biogas production was studied by [PERSON] and [PERSON] [7] through an integrated anaerobic digestion (AD) and microalgae cultivation system. Nowadays, the interest in microalgal mass culturing technology is focused on small-scale cultivation, such as for commercial production and production for human food, as well as large-scale production, for example, for renewable energy and environmentally sustainable approaches [5]. A major problem in algal mass cultivation for the production of sustainable biofuels is the need for high phosphate and nitrogen nutrients. To address such nutrient demand problems, studies have been conducted on anaerobic digestion effluent (ADE) as an alternative, cost-effective nutrient supplement [8; 9; 10]. For the production of microalgal biomass, the waste of animals such as poultry litter digester efflux (PLDE) can be used as an alternative culture medium source, because theycontain all the necessary nutrients, and therefore might be an attractive low-cost microalgal growth media [11]. Developing economical and sustainable biomass production technology is likely to make microalgal and cyanobacterial biomasses someof the most useful substances in bioinustries [12]. Experiments on the treatment of anaerobically digested pig waste effluent by immobilized algae [13], suspended micro-algae in large pond systems ([14; 15; 16]) and algal mass-cultures [17] were conducted for biomass production. In some studies [18; 19; 20], the researchers tested agricultural fertilizer as a possible low-cost growth medium alternative to [PERSON]'s medium [21] for algal biomass production. Considering the significantly high microalgal biomass production from anaerobic digestion effluent of cattle manure [22; 23], extracts of poultry manure [11], and pig waste effluent [9; 24], and increased spirulina cell growth rates in hypersaline medium [25], in this study we explored potential cyanobacterial growth media using integrated animal manure and seawater as organic and inorganic nutrient sources, respectively.