Why Has My Biogas System Stopped Producing Gas?

“Hey there, I’ve been running my biogas system for a couple of months, and it’s been working great. Recently though, I’ve noticed gas production has significantly slowed down, and now it seems the system has completely stopped producing gas. I haven’t changed anything major, still feeding it similar food scraps and manure as before. It’s been colder lately, but I’m not sure if that’s a factor. What could be happening, and how can I get it back on track?” Thanks, Amanda, Ashford, UK.

Why Has My Biogas System Stopped Producing Gas?

Hey Amanda! I hear you – it’s frustrating when all seems fine, yet your trusty biogas system decides to take a prolonged “break.” Don’t worry, you’re not alone. This issue can pop up every now and then for all sorts of reasons, especially with changing weather conditions. Let’s unpack what might be going on with your system and how to troubleshoot effectively.

Common Reasons for Gas Production Halts

When your biogas digester suddenly stops producing gas, it could be due to one or more of these common factors:

1. Temperature Fluctuations

Amanda, since you’re in the UK and are noticing a change in weather, this is likely one of the main reasons your system is lagging. Biogas production thrives in warm environments, ideally between 30°C and 40°C (86°F to 104°F). Below 20°C (68°F), methane-producing bacteria slow down significantly, which may be what’s happening in your case.

If temperatures have dropped around your setup, the bacteria responsible for breaking down the organic matter in your digester might be operating at a sluggish pace or could even be going dormant. When these little guys slow down, gas production falls off.

2. Overloading or Underfeeding the Digester

Another possibility could be that the balance of your feedstock has slightly shifted, even if it feels like you haven’t changed much. When you add too much organic material too quickly, it overwhelms the bacteria, leading to slower gas production as the system tries to catch up. On the flip side, if you’re not feeding it enough or consistently, the bacteria will run out of material to process, halting gas output.

In your case, Amanda, if you feel like your inputs are roughly the same, it could be that colder weather is causing bacteria to break down material slower, and thus they might feel “overloaded” with what they’re getting. Scaling back during winter or colder seasons might be helpful.

3. pH Imbalance

The bacteria that produce biogas are quite picky about their environment, and the optimal pH for them to work their magic is between 6.8 and 7.5. If the pH swings too far out of this range, it can completely stop gas production. Things like acidic food scraps (citrus peels, vinegars) or an overload of fats can disrupt the pH balance.

While you might not notice this right away, over time, the accumulation of these materials could have tipped the balance. It might be a good idea to test your digester’s pH if you suspect this could be an issue.

How to Troubleshoot Your Biogas System

So with these potential culprits in mind, here’s a step-by-step breakdown of ways you can get your system back up to speed:

1. Check the Temperature

Since weather seems to be a possible factor in your situation, the first thing to do is check the temperature inside your digester. Thermometer strips or probes can help here, and will give you a sense of whether it’s dropped below that ideal range of 30-40°C. If it’s cooler, you might want to consider:

• Insulating your digester: Simple steps like wrapping the digester in insulating materials can make a big difference. You could use straw, blankets, or thermal sheeting to prevent heat from escaping.
• Relocating the digester: If possible, find a sunnier spot or shield it from cold winds.
• Introducing a heat source: Using solar heaters or other passive heat methods can help boost the temperature enough to keep gas production going through colder months.

2. Reduce Load if Necessary

During cold weather or slower digestion periods, it might be helpful to reduce the amount of daily feed material. This will take the pressure off the system and allow the bacteria to catch up with processing. Since you’re in the UK, where winters are quite chilly, plan to decrease feed during the cooler months unless you’ve managed to keep your digester warm.

On the opposite end, if you’re underfeeding, slightly increase the amount and see whether the bacteria kick back into gear. It’s all about finding your digester’s sweet spot when it comes to feeding rates!

3. Test and Adjust pH Levels

Get yourself a pH testing kit to see how close your system is to the ideal range. If the pH is too low (acidic), you can bring it up by adding buffering agents like wood ash or calcium carbonate in small doses. Keep testing periodically after adding these to maintain the ideal pH range.

4. Clean or Unclog the Pipes

Amanda, one sneaky issue that’s easy to miss is a blockage in the gas outlet pipe. Sometimes residue or over-condensed water can clog the pipes, preventing any gas from escaping from the digester. It’s good to inspect the gas collection pipes and clear any blockages that might have developed over time.

Also, consider installing or checking a water trap if you haven’t already – this simple device clears out water that condenses as biogas cools, preventing any backflow that could affect production.

Signs That Your Biogas System Is Recovering

After you’ve tried the troubleshooting methods above, how do you know if things are moving in the right direction? A couple of signs to watch out for:

• The digester temperature is slowly warming up to more favorable conditions.
• There’s a steady increase in the amount of gas being produced daily.
• The slurry becomes less acidic (if pH was the issue), showing that the balance is being restored.
• No unusual gurgling, bubbling, or strange smells coming from the system (a great sign that it’s working smoothly).

What if None of This Works?

Fear not, it’s not the end of the road. Sometimes it takes a bit of fine-tuning. If these adjustments don’t produce improvements, it could be something more subtle in your system inputs, perhaps contamination from non-organic materials or an unnoticed drop in microbial activity. You could try:

• Add a starter culture: These are designed to revitalize digestion by reinoculating your system with a fresh batch of the necessary bacteria.
• Test for contaminants: Common toxins such as bleach or strong chemicals can stop bacteria in their tracks. Ensuring your inputs are clean is key.

Other Factors that Can Impact Biogas Production

For a bit more context, Amanda, beyond temperature, pH, and feeding balance, several other factors can influence how much gas your system produces, and at what speed. Here are a few that might be helpful to consider:

• Retention time: This refers to how long the material stays in the digester from entry to exit. A healthy retention time of roughly 30 to 60 days helps maintain biogas output. If material moves too quickly through the system, it won’t produce gas effectively.
• Types of materials used: Some plastics, large amounts of oils, or high-fiber food scraps (like corn stalks) can be harder to break down. Be mindful of these or limit how much of them you’re adding to the mix.
• Carbon to nitrogen ratio (C/N Ratio): Keeping the right balance of materials rich in nitrogen (like vegetable scraps or manure) and rich in carbon (like leaves or paper) helps optimize gas production. An ideal ratio is 25-30 parts carbon to 1 part nitrogen.

Final Thoughts…

Amanda, thanks for your question! Hopefully, after troubleshooting using some of these tips, your biogas system will soon be up and running again. It’s often just a case of tweaking a few variables to get the bacteria back to their optimal working conditions. Patience is key here, but once the system stabilizes, I’m sure you’ll see the results you’re hoping for. Keep at it, and don’t hesitate to reach out if you have any more questions in the future!