## 1 Introduction  
With the development of industry and agriculture, a large number of industrial sewage and domestic wastewater carrying nitrogen and phosphorus nutrients are continuously imported into the surrounding rivers, contributing to serious eutrophication [1, 2]. The accumulation effect of eutrophication would stimulate rapid growth of phytoplankton--cyanobacteria [3, 4]. The massive growth of cyanobacteria not only inhibits the growth and reproduction of other beneficial algae, but also causes poisoning or diseases of cultured animals. The traditional disposal methods for cyanobacteria include mechanical salvage, adding flocculant or algal removal agent, etc. [5]. Although mechanical salvage or adding flocculant is simple to operate, the investment is large and the problem of precipitated cyanobacteria and recovered flocculant is highlighted. Aquatic plants controlling is another method with a small impact on the ecosystem, while the treatment period is time consuming and the effect on algal bloom is limited [6]. [PERSON] et al. [7] passivated the nutrients in American Green Lake by adding alum and sodium aluminate, which significantly inhibited algal growth and increased algal migration. [PERSON] et al. [8] found that phytoplankton could be reduced by 28.8% by the shading controlling method. In fact, cyanobacteria are a kind of renewable bioenergy, which has high photosynthetic efficiency and strong CO\({}_{2}\) sequestration capacity [9, 10, 11]. Under the background of carbon neutral, cyanobacteria as a carbon neutral energy could be utilized in the combustion process, which would not increase the total amount of greenhouse gases [12]. At present, although the carbon conversion efficiency and reaction rate of cyanobacteria are rather high through the conventional combustion treatment, the drying and dehydration of cyanobacteria before thermal treatment as well as the CO\({}_{2}\) capture from the exit will greatly increase the application cost. The disadvantage of low energy density is enlarged for these conventional cyanobacteria treatments [13]. Biomass densification technology is one of the key options to increase energy density. The biomass raw material could be processed into an energy carrier with a specific shape by extrusion [14; 15]. In addition, through the biomass densification technology, the cost of handling and conveyance is decreased and particle size distribution could also be controlled and more uniform. However, another problem, a large amount of tar produced in the combustion process, is also particularly tricky. In the conventional biomass combustion process, tar decomposition is a cumbersome task, which would pass through the reactor and block the system tail pipe [16]. In addition, there is a high content of nitrogen and phosphorus in cyanobacteria. A large amount of thermal NO\({}_{\text{x}}\) and fuel NO\({}_{\text{x}}\) will be released in the conventional combustion process [17]. Therefore, it is necessary to find a promising combustion technology solving cyanobacteria tar generation and NO\({}_{\text{x}}\) emission. Besides, phosphorus is one of the essential nutrients for human beings. The phosphorus resource in cyanobacteria would be lost massively during the conventional combustion process [18]. It would be better if the selected technology includes a phosphorus recycling system from cyanobacteria to compensate for the global phosphorus depletion. Chemical looping combustion (CLC) is an innovative combustion technology. Compared with the conventional combustion process, CLC has great differences in heat and mass conversion and energy utilization. CO\({}_{2}\) capture, tar catalytic cracking, low NO\({}_{\text{x}}\) emission and phosphorus recovery are the obvious technical advantages of CLC. Fuel conversion in CLC no longer uses pure oxygen directly but relies on the lattice oxygen contained in the circulating metal oxide, i.e., oxygen carrier (OC) particles.