I’ve been composting for some years now and in 2020 I formalized my learnings by joining the UCCE Master Composter course. Much of the course followed readings from the Rodale Book of Composting and a Master Composter Training Manual Handbook. I learned a bunch, and especially enjoyed the series of guest speakers. Topics spanned soil health, compost and the environment, commercial composting systems, home composting, community scale composting, vermicomposting, applications and use, and community education. I would recommend taking the course if you are in the CA South Bay Area and at all interested. 

Some fun facts I rediscovered looking back at my notes:

  • Top 3 landfill contributors by weight are compostable! – yard waste, food waste, paper & cardboard. 2/3rds of the waste stream!
  • Rhizosphere “liquid carbon pathway” 40% of plant photosynthate goes to soil – plant, fungal, bacteria relationship. Mycorrhizae “fungal root” increases plane root absorption.
  • Grasslands w/ compost is great for carbon sequestration below ground!
    Forests are carbon sequestration above ground
  • Compost is good for water retention, can be used as a bio filter (to catch spills etc), fertilize soil, reduce waste, carbon sequestration.
  • Microbial bodies need more Carbon than Nitrogen (5:1).
    Microbial activity is optimized at 50% moisture

A goal of the course was to train the next Master Composters who can contribute back to the community through education – host workshops, school events, build and manage the community compost site. After graduation I joined an effort to work with Santa Clara University engineering design course students (ENGR 110) to build compost monitoring systems for the community compost site. We had ad-hoc and semi weekly sync up meetings. With the first team we got a raspberry pi, temp and humidity sensors deployed for monitoring the vermicomposting system. The next quarter we worked on better housing for the sensors to survive the harsh compost environment. Last quarter we worked on data availability over the internet. The compost site is off the grid – no internet nor grid power. It does have solar and battery power fortunately. The lack of remote access for the data was a pain point. I got the team to explore using a Blues Notecard which has 10 year cellular connectivity for a one time fee. They got one and made it work. We now get data points and graphs online from this off-the-grid location. 

The community site has a lot of other fun systems – a variety of composting setups, a bike powered leaf shredder, and some windrow static piles aerated by a timer triggered bounce house blower sheltered in a doghouse. 

On a related note, back in 2020 I spent a weekend setting up monitoring for my backyard compost. For the software I used a bespoke github project from someone I had been chatting with at the time, but if I did it over again I would probably stick with Prometheus and Grafana. 

Physical setup

  • Materials: Raspberry Pi, a couple DHT22 temp/humidity sensors, wires, reused plastic container, reused plastic case for the Pi, 5 ft PVC pipe, extension cord. 
  • Construction: cut a hole in the container for the PVC pipe and Pi power cord, drill some air holes in the pipe toward the base and top, thread the DHT sensors into the pipe at various distances.
  • For power, I used a long extension cord to an outdoor outlet.
  • Indoors I have a server and a wifi router. 
  • Outdoors I have a wifi extender as the indoor wifi signal is weaker outside.

Software setup

  • For data collection, management, and dashboard, I used software from this repo:
  • The Pi is installed with the default OS, is configured to connect to wifi (+internet access), and runs the data collection loop after bootup. 
  • UI is available on the local network. 
  • Installed tailscale on the Pi for UI and shell access over the internet. 

Some old screens below. From the graphs you can see the compost wasn’t very active then. 

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