Compost Calculator

The calculator allows you to see the financial values of the key nutrients N, P and K present in compost and digestate (biofertiliser), when compared with inorganic fertilisers.

The values are based on current market prices for fertilisers and the typical readily available nutrient content of composts and digestates.  Data on readily available nutrient content is taken from RB209, for compost, and the DC-Agri project for digestate.  It is worth remembering that, in addition to the readily available nutrients, organic materials contain nutrients in more complex forms which will become available for crop uptake in future seasons.  For example, composts have a low readily available nitrogen content (5%), but a high total nitrogen content (11kg/tonne of green/food compost) which will contribute to soil nitrogen supply.

The difference between readily available and total nutrient contents could make fertiliser planning complicated, but the free to use MANNER-NPK tool can help you integrate digestate and compost use into your fertiliser planning.

Don’t forget that compost is also an excellent source of organic matter, which can offer significant improvements to soil quality in the medium and long term – providing further financial savings.

To find your local supplier, who will be able to provide you with the specific nutrient content of their product, please use the Find a compost supplier near you search tool.  You should also consult your agronomist to ensure that fertiliser advice is tailored to your individual requirements.

Source: fertiliser prices are based on current market prices provided by FARM BRIEF.






Market price of fertilisers (£/kg)0.740.590.44 
Green Compost    
Readily available nutrient content (kg/tonne compost)0.00


Financial value of readily available nutrient content (£/tonne compost)0.000.881.952.83
Green/Food Compost    
Readily available nutrient content (kg/tonne compost)0.551.906.40 
Financial value of readily available nutrient content (£/tonne compost)0.401.122.844.36
Digestate (Biofertiliser)    
Readily available nutrient content (kg/tonne digestate) 
Financial value of readily available nutrients (£/tonne digestate)2.940.150.713.80