Evaluating the agronomic value of mussel shell waste

Aglime 

Just over 1 million tonnes of lime are used annually in New Zealand (Statistics New Zealand). A highly productive legume/grass pasture may need 400-500 kg/ha/y to maintain soil pH (Morton 2019). It is important to maintain soil pH within optimal levels (e.g. pH 5.8-6.0 for pasture) to ensure the availability of nutrients to plants and soil health. 

Mussel shell 

Just over 100,000 tonnes of mussels are harvested annually in New Zealand, and the government wants to grow the aquaculture industry to $3 billion by 2035. Mussels are filter feeders and actively clean the water and perform an important ecosystem service. However, an unavoidable waste stream from this industry are the shells (ca 40,000 tonnes/year). There are some niche uses for mussel shells, for example landscaping and chicken feed, but there are still more waste shells than uses. Mussel shells are 85-90% calcium carbonate and could be used in the same way as lime. Regions with mussel production are all close to agricultural regions, meaning that transport distances are minimised, or at least similar to lime fertiliser. Waste mussels also contain other marine waste that could be beneficial to soil microorganisms and plants.

NZBIDA