Why use urine as a fertiliser?

Urine is an abundant natural source of nitrogen that we need to grow crops. However, most industrial fertilisers are made using fossil fuels to produce ammonia.

Some studies estimate that the urine produced by one person in a year could provide 50-100% of the fertiliser requirements for growing another person’s food.

Toilets in the UK use between 5-10 litres of drinking water per flush. Given the average person wees 5 times daily, that means in Britain we’re using around 2.5 billion litres of water to flush the toilet – about 100 Olympic-sized swimming pools, every single day! In London alone, that number is 300 million litres.

This water then has to be treated and returned to the environment. Sometimes wastewater isn’t completely treated on leaving the system, resulting in algal blooms or pollution in waterways.

By contrast, using diluted pee as fertiliser uses a fraction of the water and enriches soils, while integrating our bodies into part of the natural ecosystem.

Quick facts

  • Pee is particularly rich in nitrogen, which plants need to grow healthy leaves. It also contains phosphorus and potassium.
  • Applying urine to growing produce can more than double the yield.
  • ‘Nightsoil’ – human waste – has historically been used as fertiliser by all agricultural societies before the invention of fertiliser in the early 20th century and continues today in many countries (both developing and developed).
  • The average person’s pee has an acidity 6 but can vary from 4.5 to 9 depending on diet.
  • Blood meal fertiliser has an NPK ratio of 13:2:1 and costs £30/25kg
  • Urine has an NPK ratio of 11:1:2.5 and costs £0