Compost is decomposed organic matter and provides nutrients for plant growth, similar to what a artificial fertiliser does. But unlike artificial fertiliser, compost also helps to feed soil fauna, like earthworms and microorganisms (bacteria and fungi), which improve soil structure and fertility.

Improved soil structure means roots can better penetrate the soil, improving water drainage and infiltration, as well as soil aeration. In sandy soils, compost provides a substrate to enhance water and nutrient retention. In degraded soils, compost can help mitigate the problems of reduced organic matter and fertility, erosion, or compaction.

Overall, compost helps to increase the quantity and quality of plant yields while regenerating and protecting soils.

Different types of composting

At its simplest, composting can be done by accumulating a pile of wet garden and food waste and allowing the micro-organisms and worms to do their work of breaking it down.

  • Cold - the easiest as material is simply added to the heap as it become available, mixing 'brown' and 'green' matter to create a good carbon: nitrogen ratio.
  • Hot - quickest and best compost, but more exacring as it needs to be a minimum 1m cubed and everything added in one go
  • Vericomposting (worm) - a mini-compost bin filled with brandling worms, who produce solid compost known to gardeners as 'black gold' and concentrated liquid feed
  • Uncomposted mulch - adding green matter to the soils surface is a good alternative to making compost, although care needs to be taken when deciding what materials to use

The 52 Climate Actions website has more on composting and how to Make Compost. 

You can also find out more about how to improve your soil in this GROW PDF.

Europe flagThe GROW Observatory received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 690199.

Three wooden compost bins