# Analysis of Seaweeds from South West England as a Biorefinery Feedstock
## 3 Results and Discussion
### Minerals  
The ash content of the seaweeds ranged between an 18.2 and 85.3% dry biomass weight (Table 4). High ash content is indicative of high levels of minerals and trace elements [32] which are beneficial in fertilisers as a sustainable source of essential nutrients required for plant/crop growth/development. However, high levels of metal can be an issue when used as a food source or as fertilisers if they are found at unacceptably high levels. Indeed, some species of seaweed can perform a bioremediation service within metal-polluted waters, and seaweed harvested from such environments may be unsuitable for use in food or fertilizer without costly processing to remove heavy metals [33]. However, conversely, the bioremediation opportunities for seaweeds within aquatic systems may offer a significant and valuable upstream \"service product\" within a biorefinery process, subsidising the production of lower value downstream products. X-ray fluorescence spectroscopy was used to assess whole dry biomass for the presence of a range of minerals (Table 5). Demand for phosphorus is expected to outstrip supply as soon as 2035 [34]. An estimated 80-90% of phosphorus use is in the form of fertiliser production with much of this then being lost through leaching from the soils [35]. Seaweeds can make an excellent alternative to current commercial fertilisers because of trace nutrients such as phosphorus and nitrogen, as well as the presence of hormones that can encourage plant growth. Seaweeds can, however, also rapidly accumulate pollutants, such as dissolved metals from their environment [36], or become loosely or transiently associated with metal particulates. As such, composition analysis of this nature must be taken with a pinch of (metallic) salt, as even the smallest metallic fragment derived from, for example, litter, fishing or structural material could give a potentially misleading result. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & & & & & & & & & & & \\ \hline \multicolumn{1}{c}{**Mineral (ppm)**} & & & & & & & & & & \\ \multicolumn{1}{c}{**Fe**} & **Sn** & **Mn** & **Al** & **Si** & **K** & **P** & **S** & **Ca** & **Cu** & **Zn** \\ \hline \multicolumn{1}{c}{_S. aeruginosa_} & 620 & 0 & 0 & 1120 & 2530 & 35,020 & 910 & 1070 & 7370 & 0 & 10 \\ \multicolumn{1}{c}{_L. articulata_} & 4040 & 0 & 260 & 9090 & 74,010 & 16,320 & 3010 & 1290 & 46,780 & 0 & 80 \\ \multicolumn{1}{c}{_A. deconiensis_} & 180 & 20 & 70 & 230 & 1980 & 30,480 & 1430 & 390 & 12,720 & 0 & 20 \\ \multicolumn{1}{c}{_P. palmata_} & 0 & 0 & 30 & 0 & 0 & 105,740 & 2390 & 0 & 2550 & 0 & 10 \\ \multicolumn{1}{c}{_R. confervoides_} & 900 & 1420 & 1740 & 6450 & 77,280 & 1970 & 260 & 11,960 & 0 & 200 \\ \multicolumn{1}{c}{_D. carrosa_} & 0 & 70 & 0 & 0 & 0 & 41,130 & 1650 & 0 & 9930 & 0 & 10 \\ \multicolumn{1}{c}{C. spp.} & 1320 & 0 & 160 & 2290 & 12,400 & 25,130 & 1620 & 1400 & 16,250 & 0 & 20 \\ \multicolumn{1}{c}{_S. muticum_} & 80 & 60 & 10 & 280 & 1990 & 75,760 & 1340 & 0 & 11,200 & 0 & 10 \\ \multicolumn{1}{c}{_H. elongata_} & 0 & 0 & 20 & 200 & 1350 & 72,290 & 1140 & 0 & 7530 & 10 & 20 \\ \multicolumn{1}{c}{_F. serratus_} & 440 & 0 & 10 & 730 & 3950 & 34,320 & 890 & 730 & 5110 & 0 & 10 \\ \multicolumn{1}{c}{_L. digitalta_} & 210 & 30 & 10 & 120 & 2800 & 34,560 & 2850 & 0 & 3160 & 0 & 20 \\ \multicolumn{1}{c}{_S. latissima_} & 120 & 10 & 70 & 0 & 0 & 39,460 & 1670 & 0 & 8670 & 0 & 30 \\ \multicolumn{1}{c}{_P. latifolia_} & 260 & 20 & 10 & 510 & 7420 & 123,530 & 1270 & 420 & 12,340 & 0 & 30 \\ \multicolumn{1}{c}{_C. peregrina_} & 9310 & 50 & 230 & 19,610 & 252,290 & 46,930 & 670 & 3350 & 55,640 & 20 & 50 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mineral composition of seaweeds from South West England (ppm). One ppm is equivalent to 0.0001% of total dry biomass. The phosphorus content in the seaweeds analysed ranged from 0.1 to 0.3% of dry biomass--ideal for fertilizer products.