This gives me an idea. We have a very large compost pile from mucking out various horse stalls and pens. It's mainly composed of urine-soaked woodchips and mostly broken-down horse manure. There's also some dirt in there as well. As an experiment this summer, I tried growing potatoes and carrots in it. Potatoes did extremely well, the carrots not so much (but I attribute that to poor watering).

It would be interesting to monitor the temperature to see how active it still is, since I can tell that it's not completely broken down yet. I actually have an ESP8266-based temperature sensor around here that I was using to track ambient temp for another fermentation project.

Now I'm thinking of encapsulating its thermistor and putting the 8266 in an IP67 enclosure along with a solar cell and just planting the whole lot on top of the compost pile. It already serves a web page on a .local domain so there would be minimal work required on my part.

I might actually get to that this weekend!

The soil might have actually been too rich for carrots. In my experience with too much nitrogen grow great tops but the root doesn't form properly.

Was coming here to say that. Agreed. Carrots need poor soil (and love sand for example).

Interesting. That's exactly what happened.

It's the urine. Try sun bleaching it by spreading out the piles to get rid of the ammonia.

Ammonia is produced when there is excess nitrogen. More carbon is needed if there is ammonia. You want to capture as much of the nitrogen as possible. Sun bleaching just bakes the ammonia off and kills the microbiota of the compost.

Compost troubleshooting guide: - smells like sewer = not enough oxygen - smells like ammonia = not enough carbon - smells sweet/fungal = just right

Underline that. As I learnt it, compost mostly benefits from drying, baking it in the sun.

It's a hot manure. Break the rules, gardening gets a lot wrong or is to finicky but for a starting idea -

"Hot manures are high in nitrogen compounds, which decompose quickly in the compost pile and generate a lot of heat in the process. In fact, traditional hothouses harnessed the energy of rotting manure to grow seedlings and cuttings during winter. Hot manures include chicken, duck, and horse.

Cold manures are low in nutrients and release less heat as they break down, posing less risk of burning your plants. Examples are cow, goat, and sheep – ruminant animals that regurgitate and chew cud, extracting most of the nitrogen from their plant-based diet before it comes out the other end. Llama and alpaca aren’t ruminants, but their manure is low enough in nutrients to be considered cold."

Not wanting to minimise your product, it's not something I personally would need. But I'm curious if you looked at what scale of composting would be needed for electronic monitoring to improve the final product enough to pay off the investment? It feels like it would have to be very large scale?

I like the mushroom vibe on your domestic design, it feels like you could have leant into that a bit more even. Cool beans.

No worries at all, I appreciate the curiosity! You’re spot on—electronic monitoring becomes most valuable at larger scales, which is why our upcoming Monty Pro line is tailored for industrial composting facilities and large-scale operations. These setups can really benefit from the efficiency and cost savings that our data-driven insights offer, like optimising aeration cycles or catching inefficiencies before they become costly issues. You can check out the product website here: (https://www.monty-pro.com)

For households, the focus is less on cost savings and more on providing convenient insights to help everyday composters get the most out of their efforts. It’s all about enriching the overall composting experience on a smaller scale :)

Looking at the Hardware requirements of the project:

``` Hardware Requirements

    Raspberry Pi (Zero 2 or another model with BLE support).
    Monty Home BLE Device.
    Additional hardware specific to each project, such as an LED, OLED display, and IFTTT account.

```

You're looking at ~$100 worth of equipment. A very low entry price point

Yes, but it seems like benefit of monitoring compost closely - beyond just looking at it and turning it occasionally - seems like it would be low?

Like: is the compost steaming, then it's probably hot and wet enough. Has it been X days since it was turned, better turn it. My naive intuition is that adding value to the compost is quite hard if you're looking at things like aerating a few days earlier, damping a little more, or whatever.

Like I said, I'm ignorant of the details, which often makes for a good learning experience!

Yes that’s valid. For a lot of setups, this approach works really well.

In terms of the big benefit - faster breakdown, better nutrient retention, and fewer emissions. Without extra monitoring, you might still get to a finished product eventually, but analytics can help speed up the process while ensuring the compost is as nutrient-rich and eco-friendly as possible.

This definitely isn’t a one-size fits all solution but many people do find it to be a helpful tool!

collectd is an open source monitoring system which can record to e.g. RRD flat files or SQLite and can forward collected metrics to SIEM-like monitoring and charting and anomaly detection apps like Grafana or InfluxDB.

Nagios has "state flaping detection" to prevent spurious notifications.

collectd-python-plugins includes Python scripts for monitoring humidity and temp with i2c sensors and Python: https://github.com/dbrgn/collectd-python-plugins

There are LoraWAN soil moisture sensors, but they require batteries or an in-field charging method

"Satellite images of plants' fluorescence can predict crop yields" (2024)

"Sensor-Free Soil Moisture Sensing Using LoRa Signals (2022)" https://dl.acm.org/doi/abs/10.1145/3534608 .. https://news.ycombinator.com/context?id=40234912

/? open source soil moisture sensor: https://www.google.com/search?q=open+source+soil+moisture+se...

Thanks so much for sharing these resources—this is fantastic!

If you’re into LoRaWAN, you might be interested to hear that we’re also developing an industrial composting monitor that incorporates LoRaWAN tech. Here’s the promo video link if you’d like to check it out: https://www.youtube.com/watch?v=TZFiiwLhZh8&feature=youtu.be

Can your sensor product feed data to open source software for hobbyist and professional agriculture?

I set up FarmOS in a container once; the PWA approach to the offline mobile app was cool but I guess I wasn't that committed to manual data collection or hobbyist gardening.

Are there open standards to support architectural sensor data?

Where is the identifier on the sensor? How does the user scan the visually-confirmable sensor barcode or QR code or similar and associate that with a garden bed or a container?

How does it notify of low battery status; is there a voltage reading to predict the out of battery condition?

Is there a configurable polling interval?

How do I find a sensor unit with a dead battery; is there a low-power chirp, or do I need a metal detector or very directional wireless sensors and triangulation or trilateration?

Are there nooks and crannies in the casing?

How to replace the battery?

Can they be made out of compostable materials? E.g. carbon with existing nanofabrication capabilities

After Single Walled Twisted Carbon Nanotube batteries which are unfortunately still only in the lab, and more practically Sodium Ion, which batteries can safely be discarded or recycled in the agricultural field?

LoRaWAN may be more economical than multiple directional long range WiFi antenna like can be found on YouTube. https://youtu.be/GWq6L94ImX8

Notes on LoRa and OpenWRT, which also supports rtl-sdr, BATMAN wifi mesh networking, and (dual) Mini PCIe 4G radios: https://news.ycombinator.com/item?id=22735933

Thank you so much for these questions! For clarity, I’ll copy and paste the question for each response:

Q: Can your sensor product feed data to open-source software for hobbyist and professional agriculture?

A: Yes, our sensors can definitely feed data into open-source platforms, making them a great fit for both hobbyist and professional agriculture setups. The guide offers a helpful starting point for integration. Additionally, data collected by the sensors can be exported as a CSV through our consumer app. This makes it easy to process the information or import it into FarmOS or other open-source tools you might be using.

Q: Where is the identifier on the sensor? How does the user scan the visually-confirmable sensor barcode or QR code or similar and associate that with a garden bed or a container?

A: Each sensor uses its unique MAC address as its name. To make setup even easier, each device features a visually confirmable barcode or QR code. Once connected, the sensor’s indicator lights confirm the connection status, so you’ll know right away when it’s properly associated.

Q: How does it notify of low battery status; is there a voltage reading to predict the out-of-battery condition? Is there a configurable polling interval?

A: For low battery notifications, the device features a red indicator light that activates when the battery is running low. Additionally, you can poll the device over Bluetooth to get the current battery level.

Q: How do I find a sensor unit with a dead battery; is there a low-power chirp, or do I need a metal detector or very directional wireless sensors and triangulation or trilateration?

A: A low battery is signalled by the sensor’s lights turning orange, while a dead battery is indicated by the absence of flashing blue lights. If the sensor still has some power, you can poll it via Bluetooth to check its battery level.

Q: Are there nooks and crannies in the casing?

A: Yes, if you’re thinking of something specific for this — please let me know! I’m happy to chat further :)

Q: How to replace the battery?

A: Currently, the battery in our sensors is not replaceable. However, when the device reaches the end of its life, we’re committed to sustainability. We plan to offer users a significant replacement discount and take back the module and responsibly recycle it into new Montys. Interestingly, the original Monty design included a removable battery pack. Through testing, we discovered that most connectors weren’t durable enough to withstand the tough composting environment, so we shifted to a sealed design to ensure long-term reliability.

Q: Can they be made out of compostable materials? E.g. carbon with existing nanofabrication capabilities

A: We’ve trialed biodegradable plastics in the past, but we found that they degraded in the field. Instead, we’ve opted for a 100% recyclable plastic material to ensure that it is able top withstand harsh compost conditions.

Hopefully, I’ve covered everything here—if you have any further questions, just let me know!

/? crop monitoring wikipedia: https://www.google.com/search?q=crop+monitoring+wikipedia ...

Precision agriculture: https://en.wikipedia.org/wiki/Precision_agriculture

Digital agriculture: https://en.wikipedia.org/wiki/Digital_agriculture

/? crop monitoring system site:github.com https://www.google.com/search?q=crop+monitoring+system+site%...

SIEM: https://en.wikipedia.org/wiki/Security_information_and_event...

Hi!

Which manufacturer/model sensors are you using? I have made some environmental monitoring with very cheap sensors for some hobby projects, but have very bad experience on repeatability of the sensor reading, or for CO2 sensors even noise tolerance (was also dicussed on HN, that discussion made me realize that noise is the cause of the problems, and have managed to verify that).

I have some project ideas beyond my at-home breadboard prototyping but to go beyond I'd rather build on reliable components as the software/infra side is maturing now.

For Monty’s system, we use sensors from Bosch and Sensirion. During our initial prototyping phase, we tested around 20 different types of sensors and found they had the most workable results across a range of composting environments.

Feel free to share more about your project ideas— happy to dive deeper if it helps!

Love this! Hurray for more comprehensive and extensible smaller-scale compost monitoring. You might find some additional interest from our Gathering for Open Ag Tech community (https://forum.goatech.org/).

Oh wow, thanks for sharing! We’ll definitely drop a post in there :)

I love it, but surely just a temp gauge for running a hot compost is nice & simple? If mine is over 45C, I'm fairly sure that means the thermophiles are present and doing their thing

You’re absolutely right— a temperature gauge is a fantastic tool for monitoring for many composters who are focused on the basics of maintaining an active hot composting pile.

Where our system shines is when you want to go a little deeper. For example, adding data on gas, moisture levels, and air pressure allows users to troubleshoot or optimise their process more effectively. Is the activity aerobic or anaerobic? Is your moisture level tipping the pile too far one way or another? These kinds of insights can help when composting setups or inputs get more complex, or when things stall and you’re not sure why.

That said, we totally get that not everyone needs all the bells and whistles—sometimes a reliable temp gauge and your composting instincts are all you need to make amazing, healthy compost!

I can barely get my compost more than 5C above ambient. But I think it is mainly because the compost bin isn't big enough (one of those black plastic daleks), so has too much surface area/volume. Also, it is in a very shady spot.

Shade shouldn't be a problem. In fact, a cover is good because it helps you control the sunlight and rain.

If the pile isn't heating up it's usually either bone dry or there's not enough volume. Aim for at least one cubic meter (or 3x3x3 feet).

If you have fresh grass clippings, add them - they will help a lot. A heap of grass clippings with nothing else will heat up on its own (but don't do it because it will smell).

Your cold compost is going to be fine, it will just take longer and won't cook the weed seeds. If you have more questions there's a composting subreddit: https://www.reddit.com/r/composting/

Thanks, I have done a bit of research of carbon:nitrogen etc. I think it is lack of volume. it still produces good compost, just takes longer.

> But I think it is mainly because the compost bin isn't big enough

Pile size is almost all that matters for how hot it gets, in my experience.

How do you verify the expected metabolic processes are occurring that produce said temperatures?

Great question— thanks for asking!

Verifying the metabolic processes in composting is a bit of a mix between understanding composting fundamentals and interpreting the data we collect. The processes are highly dependent on factors like feedstock type and volume. For example, a sudden spike in temperature might be due to an addition of nitrogen-rich materials or a recent turning of the pile—both of which can accelerate microbial activity.

While our sensors provide 24/7 data on temperature, gas composition, and more, there are always factors we can’t directly see or control for, like the exact distribution of materials within the pile. That’s where a bit of interpretation comes in: matching what the data is telling us with the fundamentals of composting.

By combining real-time monitoring with an understanding of what’s happening in the pile, users can make informed decisions to keep their composting process on track. It’s not an exact science, but the extra data helps a lot!

Thanks for posting!

Out of curiosity, could you talk more about the practical utility of the sensor readings you get while monitoring compost? Temp and moisture seem straightforward, but e.g., does gas composition imply anything about C/N ratio, or does it check if the pile is going anoxic? Is air pressure a general proxy for decomposition rate?

Also, have you changed any of your own composting practices due to what you’ve learned from your experience with monitoring?

To dive into the utility of the sensor readings-- The main gas we monitor is Total Volatile Organic Compounds (TVOCs), which act as a general proxy for decomposition activity. Combined with temperature data, this gives a strong indication of whether the activity is aerobic (a healthy compost pile) or anaerobic (not ideal and potentially smelly!). For example, a spike in TVOCs with decreasing oxygen availability often flags anaerobic conditions.

In terms of air pressure, this is used as part of our pile turn events detection in our companion app Monty Mobile. The app also analyses other data to assess how changes in conditions (e.g., moisture levels, turning frequency) affect decomposition. For most users, though, the general proxy is plenty— by identifying when a pile is “active” or “stalled,” they can tweak their process (e.g., adding browns, adjusting moisture, or aerating).

Compost is incredibly diverse, and the results will vary depending on the setup (tumblers, bins, worm farms) and inputs (manure, food scraps, garden waste). That said, 24/7 data from our system helps streamline the behaviour-change process. Rather than relying on a “try-wait-try-again” approach, users get immediate feedback, which can be a game-changer for both beginners and seasoned composters.

As for me, Monty has been a massive learning tool. Using the Monty Mobile app has personally helped me engage more with my compost pile and remember to add feedstock to adjust the pile when needed. It definitely makes me feel more in tune with what’s going on!

I hope this clarifies things! Happy to chat more :)

Good to see more in the composting space!

Using the oxygen sensor to tell if it's anaerobic or not makes sense, what sensor do you use for oxygen and how accurate is it over time? Does it have to be calibrated often?

And can you talk more about the role of TVOCs in anaerobic conditions? Wouldn't oxygen be enough?

Thanks!

Great questions!

We opted not to use oxygen sensors because they tend to be less reliable, require frequent calibration, and are significantly more expensive. Instead, we focus exclusively on TVOCs, as the technology is more advanced and offers a broader view of compost activity. During our early design stages, we found TVOCs correlate well with microbial activity, much like oxygen, while also capturing changes in the pile that oxygen levels alone might not immediately reveal.

Great summary - tyvm!

I can absolutely see how quick feedback from those metrics could help people dial in their maintenance.

Ohh, interesting. I’ve long wanted to do an adjacent project, that is, creating a monitoring system for plants. Like, a single spike in the pot that measures soil composition, nutrient levels, moisture, wind speed, light exposure, humidity, etc. to give both plant care recommendations and optimise growth. Never got around doing it tho…

Do you have recommendations for buying sensors?

i did a hobby project like this for soil moisture. here's a messy repo that i made when i could barely code. it points to some capacitive sensor guides. https://github.com/smcalilly/sensor

Neat. Thank you for sharing!

We use sensors from Bosch and Sensirion in our systems. They’re reliable and durable, even in tough environments like compost piles, where heat, moisture, and microbial activity can put tech to the test. Finding the right sensors took a lot of trial and error for us, especially since composting conditions are so unforgiving.

Let us know if you decide to pick up the project— we’d love to cheer you on or compare notes!

That’s kind, thank you.

Adding to the main post--

You can check out the Monty Monitor here: https://montycompost.co/products/im-perfect-monty-monitor

I don’t know how you read my mind because completely randomly I was just looking at thermocouples for compost monitoring.

Do you know if anyone is writing a HomeAssistant integration for this?

https://en.wikipedia.org/wiki/Home_Assistant for those like me who have never heard of this software

Not yet, but maybe you? :)

Sadly, it seems to be Bluetooth only, whose range isn't great unless you already have your garden covered. Probably late to ask, but would be cool if future versions also included a Zigbee radio and it will make it 1000 times easier to integrate into Home Assistant :)

Yes— this version is Bluetooth only, which works well for many smaller setups but does have its range limitations. I’ll pass your suggestion for Zigbee radio along to our product team! Expanding connectivity options is something we’re actively exploring for future versions of this Monty.

For larger-scale setups, our upcoming industrial product line, Monty Pro, will feature LoRaWAN connectivity, offering a much wider range. You can learn more about it here (https://www.monty-pro.com). While it’s designed for industrial composting, if there’s interest in hacking it for personal setups— we’d be open to making this available to the community!

Haha, I actually did a project on this last month with arduinos. Cool to see an open-sourced project for this

Why do you need to monitor compost?

I need to monitor my compost to keep it from freezing in the winter. Probably not what OP's system is for, given that they are from Australia.

The biological processes produce enough heat to keep the thermally insulated compost bin from freezing easily down to -15C (~5 F). But this requires that there isn't too much finished compost in the bin that won't produce heat any more, so any turn downwards on the thermometer means I'm probably late in emptying the bin. Which happens every year when it gets cold (below -20C/-5F), but can be remedied by a 40W light bulb for 48 hours to heat up and restart the composting.

Another thing that needs to be monitored is humidity, because too humid and the compost goes anaerobic and starts rotting instead of composting. This I "monitor" by smell but this project has some kind of gas composition sensor which could be useful. I don't have issues with this any more as I have practically unlimited supply of wood chips to keep it dry.

But the wood chips bring another problem which is pH levels that may go too low. Here's where I'd really like to have a monitor so I could estimate if I need to do something to adjust the pH.

> But the wood chips bring another problem which is pH levels that may go too low.

Is this something you've measured? I add a lot of wood chips and conifer needles and it's not a problem; the compost ends up between 6 and 7.5 pH (neutral is 7). I also liberally spread woodchips on the paths between the beds and things are fine.

The effects of wood mulch on plants and composts are well understood:

https://extension.oregonstate.edu/catalog/pub/ec-1629-mulchi...

If want to change the pH of your soil you need something stronger, like sulphur or lime.

I haven't measured because I broke my pH testing kit.

Thanks for the pointers, I will read further.

I don't.

My most-productive compost operation mostly just consisted of just piling stuff up beside my brick shed, which was conveniently near an outside door on my kitchen.

The rest of the process consisted of giving it a bit of a toss with a hoe, a shovel, or a fork if I was outside, bored, and felt like doing that, or giving it a bit of water from the garden hose if it had been very hot and dry. And I did as little of this as possible because taking care of compost, while certainly interesting to me, is just not something I generally enjoy doing.

I really didn't pay much attention to it.

By the time spring came 'round again and I had a use for the stuff, I had plenty of it for the garden.

And this worked very well -- for me, on my scale, in my region, with my needs.

Therefore, I do not need to monitor my compost.

---

But not all composting operations are lazy. Sometimes, they are very active. And some operations are large enough (or the available space small enough) that real estate becomes a seriously-limiting factor.

And in these instances, optimizing the process to get higher-quality compost faster can become a very desirable goal.

Optimization of composting is not dissimilar to optimization of any other process, wherein: Having some good data is better than having no data.

Meeting certain time-temperature requirements decreases pathogens and kills weed seeds in the finished compost. A normal threshold for commercial composting operations is to meet 131 deg F for 15 days with 5 turns (for turned windrow sites).

I agree with everything else that has been said in this thread!

Just to add on, proper composting helps retain more nutrients in the final product, which is great for soil health, and it also reduces harmful emissions like methane that occur when the process turns anaerobic.

To ensure the pile is actually composting effectively.

To monitor the compost