Seaweed’s and macroalgae’s agricultural use could have a role in circularity, particularly in coastal regions or where farming practices increase eutrophication of nearby water sources and this leads to increased waterway macroalgal growth. Rather than allowing this to impact ecosystems, harvesting it for application back onto agricultural soils or feeds could be beneficial. For soil application, consideration of seaweed supply chains needs evaluating to ensure the logistics and cost (economic and environmental) vs value benefits of the application are fully understood. Furthermore, seaweed appears to work better in healthier soils where strategies are in place to reduce the levels of anaerobic microbial activity. This suggests it would work well in combination with sustainable practices such as cover cropping and silvoarable farming. Macroalgae for livestock feed on the other hand have potential as an alternative protein source with some interesting environmental impacts that need further evaluation in large-scale trials. Green seaweed species show promise for soil application whilst red seaweed species show more promise for livestock use avoiding competition between these two products.