Mellow Compost Lab

 Input Waste Statistics 

Find out about annual, monthly and seasonal variations of waste material used in the compost lab.

In this article, we share some key data and insights for our Input Waste (IW) material; We present these on an annual basis, monthly basis as well as the seasonal variations. We also cover how some IW types are more prevalent in certain periods (seasonal variations)  than others.

Statistical Highlights

In the Mellow Lab, we calculate the (volume) variables below  (established on a long term basis):

  • The IW annual average: ~ 2900L (median ~2700L)
  • The IW monthly average: ~270L
  • Cool season  [Oct-Mar] monthly average: 160L
  • Warm season  [Apr-Sep] monthly average: 375L
  • IW density: 0.466Kg/L
    • We calculate densities of our four key IW elements to get a Weighted average density of the overall IW mix.

Annual Distribution

The  chart below  shows the total IW processed on an annual basis (from 2012). In the first two years, we had three compost bins (A,B,C) and worked on expanding garden space and vegetable (planting) areas. So we had less IW available than subsequent years. By 2014, we more or less reached our cruising speed in IW volumes.


The period between 2017 to 2020 saw a peak of waste material used. The main differentiator  being additional material coming from other sources; for example  friends, family and neighbours. They learnt about our compost project and started to bring in additional material (mainly grass and hedge clippings). The Covid pandemic however has  reduced the contribution from these sources. The long term IW annual median is ~ 2700L (average ~2900L). 

The second chart below shows the annual volume  split by types of IW. We can see that the proportions of the four components are roughly the same year-on-year

Monthly Distribution

Drilling further down, we look at the monthly breakdown of these IW parts. The IW monthly distribution is heavily influenced by seasonality in Yorkshire (Northern England). Grass and hedge trimmings start to dominate the proportions from March. The first hedge cuts of the year  start  in May (consistent over the years) and hence it shows a peak in that month. Other garden waste also starts to pile up as we manage the garden and vegetable plots (in full production). The chart below shows the monthly averages since 2012.

Seasonality matters for garden & compost in Yorkshire (Northern England). It gets very cold in Winter (temperature can drop to -12℃) and Summer does not see very hot temperatures; more on the warm side. We broadly define two seasons for the purpose of composting (and gardening too).

  1. Cool season: October to March
  2. Warm season: April to September. 

Monthly  IW volume averages for warm/cool season are roughly split on a 2:1 ratio (21/3:1 to be precise); that is we get at least twice as much IW material in the warm season when grass, garden waste and boxwood trimmings become available.  The weather also plays its part; whether a particular warm season is wet or hot (extremes); this will impact the volume of grass and garden waste too.

IW Distribution

Broadly speaking, there are  four key components of IW used in our compost lab. The pie chart below shows its breakdown. Kitchen waste makes up a ¼ of the total input; and the garden contributes ¾ roughly equally split between grass, hedge clippings and other garden material. These are the IW proportions measured since 2012.