Mellow Compost Lab

Concepts, Aims & Background

The Mellow lab is a multi-purpose home composting project. Here we outline the motivations and key concepts and objectives.

The Mellow compost lab (MCL) is located in north Leeds (Yorkshire county, United Kingdom). The term “Mellow” in the naming of the compost lab reflects  well its combined goals;  enjoying the activities, taking it easy, undertaking controlled experiments whilst getting some (good) compost at the end.  Here we discuss the key motivations behind the creation of the Mellow Lab; from the benefit of outdoor activities to deriving compost input/output trends & ratios etc.. 


  • Home composting with a difference - Data analysis, charts, trends & insights 

  • Physical exercise, workouts and mental health benefits

  • Self-sufficient in compost requirements for our garden and house plants  

  • Learn & understand the compost basics and also the science & engineering 

  • Help & share with others to learn & take on composting

  • Reduce waste to local authorities recycling centres

  • Fun in combining outdoor activities with computing & data analysis

One of the main concepts behind the Mellow Lab is

“home composting” with a difference 

  • Showing data analysis, insights, charts, trends, ratios and more ...

  • Live  and continuing operations

  • Sharing lessons learnt, what worked for us and not; theory, practice and experience

  • An experimental focus with some scientific rigour in a practical and pragmatic way whilst keeping the fun into the hobby

  • Replication of experiments: Provide enough information here for anyone wishing to repeat these experiments

  • Using data sets from  12 years in operations and over 56 completed bin cycles  and going ....

MCL (multiple snapshots) dashboard


Around 2010/11, I started to be interested in gardening and composting as potentially  good outdoor hobbies. Our children just passed their teenage periods and the large trampoline and other artefacts in the garden were just rusting. This was an opportunity to reclaim plenty of space.

So I started to experiment in our back garden with various containers and large plastic bags to understand how composting works and whether this is something I wanted to pursue. I got interested in  the nature of organic material/waste, the chemistry and engineering of composting and also tested some aerobic versus anaerobic decomposition. 

After a few experiments and witnessing the conversion from green & brown material taking place into some black compost, I was sold on the idea. The Internet is full of how-tos and  do’s-and-don'ts and tutorials. This was a great help.

I am passionate about STEM (Science Technology, Engineering & Mathematics). I really enjoy working on  data analysis, inferring & explaining patterns, modelling & developing/programming dynamic systems. By education & profession, I am a computer scientist and applied mathematician. 

So combining  composting, data analysis and  computing had a great attraction for me.


In April 2012, I got my first compost bin (220L) to learn and experiment with a proper container. I grew in  confidence and felt this is something I want to do and enjoy doing. Coupled with the fact that we have a good size garden (~100 m2), one 220L compost bin would not be sufficient, so I bought two further bins (330Lx2)  in December 2012. I also acquired compost instruments for various measurements

I looked into best practices from various Internet sites, University reports and other labs (including local and regional authorities Worldwide, specialised companies etc..). From there, I started to formulate  simple schemes for measurements including volume, weight, temperature, density & ratios as well as other attributes such as precision, accuracy and error control. This ought to get as close as possible to a controlled environment for experimenting with compost making. 

Very early on, I made the decision that whatever I was going to start & build would take the shape of a “small-scale” home compost lab with some form of a controlled environment. I also decided to measure, document and analyse whenever possible & relevant. The idea was to have an experimental focus with some scientific rigour in a practical and pragmatic way whilst keeping the fun into the hobby

Long Term waste decay

Image above shows a long term trend of waste volume decaying to a 1/3rd of its original volume to give mature compost. For example here, ~61% of the decay occurs in the Active phase and ~6% in the cooling & maturing phase, leaving 33% of resulting mature (finished) compost. 

Principles & Benefits

Home composting with a difference: There are plenty of very useful online documents, videos and websites explaining the basics of home composting.  The aim of the Mellow lab is to complement these by sharing experimental findings of home composting over periods of time.

It is my gym: The physical and mental benefits of composting (and gardening) are well documented. I plan my time outdoors for composting activities by time-slicing the various physical activities; so as not to spend too much time in one posture or repeating the same exercises continuously. So for example, I would shred some waste material for a period, then stir compost bins, weeding, seed planting, walk about to move compost material from one area to another and/or sieve finished compost to various grades.  Then I would go and repeat these activities in a kind of round robin fashion. These are examples where I consciously divide the time in various activities working on different parts of the body. This would also mean walking from one part of the garden to another. Time-wise, it is not the most efficient way to complete these activities; but if the aim is to also combine a sequence of balanced and varied physical activities (and potentially reduce impact of RSI), it worked for me.

self-sufficient in compost requirements: In the early years, we bought quite a few bags of compost to fill-up some of the newly-built raised beds (RBs), pots etc.. We have heavy clay soil in our garden; so raised beds were a good option to give a better chance to growing vegetables and plants. However, the aim has been to be self-sufficient in compost as soon as reasonably possible and whenever possible. By 2015, we became self-sufficient in compost for garden and home needs.  The annual volume of compost was complemented by leaf mould (when we learnt how to make it).