28. Apr, 2020

Composting Coffee Grounds & Chaff

The Carry on Composting page on the composting coffee grounds and Chaff at http://www.carryoncomposting.com/443725798 has been updated. A summary is given below but does not include the section on wormeries or Bokashi. 

In composting terms coffee grounds are a “green”  providing  nitrogen to the  compost with a C:N ratio of about 20:1.  Coffee also provides up to 2% potassium as well as phosphoric acid  and potash. On the negative side,  a search of the internet will show that coffee is acidic and some suggest that it should only be added to acid loving plants but then very few people would make coffee only to pour it on their plants. In fact, the acid is water soluble, so little remains in the used grounds which tend to have a pH of 6.5 to 6.8 . It is advised that grounds should be restricted to not  more than 20% of the  total compost volume. 

 Domestic quantities of used coffee grounds can be added directly to compost caddy, bin or   wormery.  If coffee filters are used there is no need to separate the grounds from the filter both can be added. Some suggest tearing the filter into strips, but this is quite messy if they contain  coffee grounds and I just put the wet filter and grounds straight into the kitchen caddy. 


Coffee Chaff

Coffee Chaff is the dried husk (skin)  of the coffee bean and is a waste product of the roasting process. This waste product  decomposes quickly when composted.

Chaff is lightweight and tends to blow over the garden  if used as a mulch,  but it mixes well with other organic material in the bin. The nitrogen content is slightly higher than that of coffee grounds. As they have a high C/N ratio during layered composting, small amounts  have been layered or mixed with or immediately above another  layer of greens such as manure or food waste which are rich in easily compostable nitrogen  into which they can be incorporated, followed by a layer of browns. If there are larger quantities, they could form their own green layers.   When the bin contents are turned to mix and aerate the material, the chaff will be distributed throughout the organic material.