What Are Common Biogas System Problems?

“Hey there, I’m just starting my biogas journey and have been running a small system at home in Brisbane, Australia, for a couple of months. Lately, the gas production seems to be dropping off a bit, and I occasionally get a bad smell from the digester. Is there something I might be doing wrong, or is this normal for a small setup? Also, are there any other common problems I should keep an eye out for to prevent things from getting worse?” Thanks, Megan, Brisbane, Australia.

What Are Common Biogas System Problems?

Running a biogas system at home, like Megan is doing, is gratifying but requires some maintenance and troubleshooting along the way. Biogas systems can encounter a variety of issues, especially when you’re still fine-tuning your setup. The good news is, most of these problems have straightforward fixes once you understand what’s going on. Below, we’re going to walk through some of the most frequent issues, why they happen, and how to address them, so Megan – and others – can get their setups running smoothly again.

Poor Gas Production

One of the most common concerns for people new to biogas systems is the frustrating issue of low gas production. In Megan’s case, gas levels have started to drop, which can happen for various reasons. Biogas systems rely on bacterial activity breaking down organic waste in an oxygen-free environment, so if something in that process is off, the gas output won’t be where you want it.

Reasons Behind Low Gas Production

Gas production can falter for numerous reasons, but here are a few common ones:

• Inconsistent Feedstock – If the organic matter you’re feeding into the digester changes drastically or you’re feeding it irregularly, this can impact production. Biogas digesters thrive on consistency, so it’s important to feed them the right amount of food waste (or other organic material) on a regular schedule.
• Temperature Drops – The microbes that produce biogas prefer to digest material at temperatures between 35-40°C (95-104°F). If it gets too cold, like during a chilly Brisbane winter, Megan’s gas production will slow down significantly.
• pH Imbalance – Anaerobic bacteria, responsible for biogas generation, like a near-neutral pH of 6.5 to 7.5. If the pH is too low (acidic) or too high (alkaline), production will drop off. Sometimes, feeding too much acidic material, like citrus or vinegar, can throw off the balance.

How to Boost Gas Production

There are a few tips to get that output back up to where you want it:

• Maintain Temperature – Since temperature is so important, try insulating your digester. If the climate is cooler, consider using darker materials to absorb more heat from the sun or even setting up a small greenhouse around it. If needed, heating elements can be used to keep the temperature consistent.
• Check Your Feedstock – Make sure you’re feeding your digester consistently and offering it a variety of substrates. You want to avoid dumping in loads of acidic material all at once. Use a mix of food scraps, yard waste, and if possible, some manure to balance out what goes in.
• Adjust pH – If pH is the issue, you’ll need to check it regularly. If you find that the system is too acidic, you can add some lime or wood ash to neutralize things.

Smells Coming from the Digester

Megan mentioned she occasionally detects a foul smell coming from her digester, and she’s not alone – this can happen with poorly performing systems. A well-run biogas digester should produce very little smell, but certain problems can cause it to stink up the place.

Why Does the Digester Smell?

• Leakage – If the system isn’t airtight, gas can escape in the form of hydrogen sulfide, which smells like rotten eggs. Checking for leaks is a critical first step if you start noticing smells.
• Overloading the System – In Megan’s situation, adding too much feedstock at once could be overwhelming the system, causing incomplete digestion, which can lead to smelly byproducts. You want to keep a balance of carbon-rich and nitrogen-rich material, with an overall moderate feeding strategy.
• Clogged Piping – If the biogas isn’t flowing freely through pipes, it can slow down production and potentially make the system smell. Debris or organic build-up in your piping could be trapping smelly gases.

How to Fix Digester Smells

• Check for Airtightness – Carefully check the system for cracks or leaks, especially around the fittings and outlets. If you find any, reseal those areas, and the smell should start to decrease within a few days.
• Feed Slowly and Steadily – To avoid overloading, start feeding smaller quantities of waste and see if that helps stabilize the system. You can gradually ramp back up once things settle down.
• Clean or Replace Pipes – If you suspect clogged pipes, try flushing the system to clear out any blockages, or if the pipes are particularly bad, it might be time to replace them.

System Freezing or Overheating

One challenge you might face depending on your climate is overcooling or overheating. While Megan’s situation in Australia might lean more towards overheating in the summer months, colder climates often battle freezing, which can crash gas production entirely.

Tips for Handling Temperature Variations

• Insulate Your System – In colder conditions, adding insulation or using a greenhouse method can help trap heat. In warmer areas, you’ll still want some insulation to keep a stable temperature, but ensure there are steps in place to minimize overheating.
• Use Water in Hot Climates – If the temperature skyrockets during the summer, you can pour water over the digester (so long as your materials can take it) or shade it with a tarp to keep temperatures from getting too high.
• Build Your System Correctly – If you haven’t already, place your digester in an area that maximizes climate control. Ideally, pick a spot that gets ample warmth in winter but is shaded a bit in hot summer months.

Foaming Inside the Digester

Another issue that could crop up – especially if you’re new like Megan – is discovering foam inside the digester. Foam can reduce the volume available for gas production, and untreated, it will limit your system’s overall efficiency.

Common Causes of Foaming

• Overfeeding with Protein-Rich Material – If you’re adding too much manure or food wastes that are heavy in nitrogen, it could lead to proteins breaking down and creating foam.
• Surfactants or Detergent Contamination – Household cleaners accidentally added to a digester can cause foaming too. Be cautious about adding anything that may come into contact with soaps or surfactants.

How to Avoid or Fix Foam

• Balance Feedstocks – Take a close look at what you’re feeding the system. Reducing protein levels and adding more fibrous plant waste can often balance things out.
• Create an Overflow Fix – In some cases, adding an overflow or vent system could help reduce the accumulation of foam inside the chamber.

Blockages in the System

Blockages can happen at almost any point in a biogas system, from feed pipes in the digester itself all the way to the outlet where the gas comes out. These can significantly disrupt gas production.

Where Do Blockages Happen?

• Feed Pipes – If you’re using large food scraps or fibrous materials, you may find blockages in the feed pipe. Overloading the pipe can make this more likely.
• Gas Pipes – Gas pipes can become clogged with liquid, foam, or bits of organic matter that have escaped the digester.

How to Address Blockages

• Pre-process Feed – Before adding material, make sure it’s chopped into small, manageable pieces. This helps avoid blockages in the feed pipe.
• Install Sediment Traps – When possible, include sediment traps in the system. These will help keep organic matter or foam from clogging your gas pipes.

Final Thoughts…

Megan, thanks again for sending in your question—that’s what these discussions are all about: picking up small tips here and there to keep your biogas system humming along. Remember, a well-fed and well-maintained system will give you good gas production, and by fixing little issues like temperatures, leaks, or blockages, you’ll be back on track in no time. Keep an eye on these common problems, and you’ll find your groove with it soon enough!