Other Sources of Waste

Here we  discuss the different waste sources (and statistics); home generated and external (friends, family, neighbours etc.)

Once we get the compost "bug" and get passionate about it, one of the raw material that is "hard" to come by is "additional" green waste material (at least in our experience). We can get plenty of brown material (Autumn leaves, shredded cardboards, wood sticks, charcoals etc..) but the green stuff is limited to what the garden and kitchen can supply. So when other sources became an option; that opened the scope for producing more compost. Of course other limiting factors are time and effort available for home composting.

Highlights

• Other sources of green waste contributes ~ ⅓  of the total waste

• The annual total volume (long term averaged) is ~2900L; with ~1930L (⅔) generated from home and ~970L (⅓) other 

• Grass and hedge clippings make the bulk of all external material we get

• The  waste we receive tend to arrive in large volumes and varies widely from one year to another, mainly in the Spring/Summer. 

Note we use "Other" and "External" interchangeably in the context of waste sources at MCL

Where do we get it from

We split the sources of our waste material  in two categories: Home and Other. The Home waste is generated from our home only, that is kitchen & garden and on a recurring (annual) basis. 

The Other material is the additional waste obtained via “other or external sources” typically friends, families & neighbours. This waste is grouped separately. This distinction would also enable the study of home composting for a  type of household (such as the house we live in) and allow comparisons on a like for like basis. 

The Other category also includes special projects. For example, if we undertake a one-off large garden project, we class the resulting refuse as special projects and fall under Other. The Home material is generated by our home (kitchen/garden) on a seasonal or repeated basis. The one-off large projects do not fall in the Home category. For example we had a set of wide and tall hedges in our back garden that grew too tall and started to be a threat of breaking or snapping (we live at the top of a hilly area and are subject to strong winds). So between 2019-2022, we started a special project to cut these. This in turn generated a significant amount of hedge trimming material (classed as Other).

On a long term basis, the Home category contributes ⅔  of the total waste used and the Other provides the remaining ⅓.

Annual Insights

The chart below shows the split of home and other waste material on an annual basis in the Mellow lab. Between 2012 and 2016, all waste material was home (recurring) generated. By 2016 and up to 2019, external waste  started to increase significantly. The Covid’19 pandemic however has  reduced the contributions from these sources.

The annual total volume (long term averaged) is ~2900L (with ~1930L (⅔) brought by Home and ~970L (⅓) by Other. Note however that  the spread (variance) is much greater for the Other category. The Home category has an annual volume of 1930L with a standard deviation of 538; whereas Other has 970L with a standard deviation of 528. It is not surprising that the Home group has a lower spread. Year-on-year, the waste generated is expected to be within range whereas the Other/external depends on external and often independent events such as friends, family bringing large bulk material and special projects.

Capacity Planning

Up to 2016, the three compost bins (A,B,C) with a total capacity of 880L would have been (in theory) sufficient to process all the waste generated from our kitchen and garden. We started to share our passion for home composting with our neighbours, friends, families and colleagues at work..

Some of these people gave composting a try. Others started to bring their own garden refuse (mainly grass and shrub/hedge clippings) to our place.  It was quickly clear that our compost bins capacity would not be sufficient. That is when we got additional bins (D and E) to get to the current 1520L total capacity .

Example (Cycle #30)

To illustrate the Home and Other category of waste; here is an example for cycle #30 (bin B) in 2018. The first chart shows the top-ups volume (L) split Home/Other in a time series fashion (here Other is called External). Note that in this cycle, the Other class dominates the waste volume (65%). The pie chart shows the overall proportion of Home/External.