METHOGAS is a specialised crust control additive for anaerobic digesters. It targets the formation of floating crusts and sediment build-ups, ensuring that the digestate remains fluid and well-mixed.
METHOGAS is a combined-action product formulated with electrically charged polymers (polyamines) that both enhance the biological breakdown of fibrous material and physically disrupt crusts. By boosting the activity of naturally occurring hydrolytic enzymes, METHOGAS helps increase the digestibility of fibrous feedstocks and promotes methanogenic bacteria activity.
The result is a more homogeneous, less viscous digestate that is easier to pump and handle. Crust control is vital for maintaining optimal efficiency, safety, and cost-effectiveness in AD plants, and METHOGAS provides a proactive solution to keep your digester free of crusts and performing at its best.
Eliminates Floating Crusts and Sediments: METHOGAS breaks down superficial crust layers on the digester surface and also helps disintegrate fibrous build-ups at the bottom. This keeps the digester contents fully mixed and prevents dead zones or gas entrapment.
Reduces Viscosity for Easier Pumping: By making the digestate more homogeneous, METHOGAS significantly lowers its viscosity. A less viscous digestate means pumps and mixers operate with less effort, reducing parasitic energy use and wear-and-tear.
Enhances Fiber Digestibility: METHOGAS boosts the activity of hydrolytic enzymes already in the system, leading to better breakdown of tough fibers that would normally require long retention times. This not only helps prevent crust formation (since undigested fiber often contributes to crusts) but also can increase biogas yield from fibrous material.
Improves Methanogenesis: By promoting conditions that favor methanogenic bacteria (breaking crusts improves contact between bacteria and substrate, and the polyamines directly or indirectly stimulate microbes), METHOGAS enhances methanogenic reactions and the proliferation of methane-producing archaea. This translates to more efficient biogas conversion.
Operational Convenience: A digester treated with METHOGAS is easier to manage – issues like scum removal, manual mixing, or unplanned downtime to break crusts are avoided. Also, because it’s a targeted additive, you can often address crust issues without mechanical intervention, saving labor and time.
METHOGAS works through a combination of chemical and biological facilitation:
Polymer Action: The core of METHOGAS is polyamines, which are positively charged polymers. When added to the digester, these polymers interact with negatively charged particles (like fibers, cells, and colloids). They cause small particles to aggregate or break the surface tension that holds crusts together. Essentially, polyamines can penetrate and destabilise the fibrous matrix of a crust, causing it to break apart and sink. They also help release any biogas trapped within the crust by popping bubbles or preventing foam formation on the crust.
Enzyme Stimulation: METHOGAS doesn’t contain enzymes per se, but it increases the activity of the hydrolytic enzymes naturally present in the digester. It does this by fostering better contact between enzymes and substrate. Normally, enzymes might be diffused in liquid while substrate is locked in a crust or sludge. By breaking up those physical barriers, enzymes can more readily attack fibers. Additionally, the polyamines might help draw enzymes to the substrate surfaces (since many enzymes are negatively charged, they can adsorb onto the positively charged polyamines that are attached to fibers). This catalyzes the bond between enzymes and their fibrous substrates, accelerating the hydrolysis of fibers.
Enhanced Methanogenesis: With fibers broken down into simpler compounds more quickly, methanogens get a steadier supply of substrates (like acetic acid, hydrogen, etc.). METHOGAS promotes methanogenic bacteria proliferation and metabolism as a secondary effect of having a more mixed and nutrient-available environment. It can also help buffer localised inhibitions; for instance, crusts can create pockets of high pH or poor mixing – breaking them evens out conditions so methanogens thrive.
Homogenisation: All these actions lead to the digestate becoming uniform. Solids that would float or sink are dispersed, so the digester essentially “self-cleans” its stratified layers. This homogeneous state ensures that solids and liquids separate more easily when intended (e.g., in post-digestion separation units) because there isn’t a stubborn fraction that refuses to mix.
In summary, METHOGAS chemically attacks the physical structure of crusts while simultaneously empowering the biological process to degrade the material that forms crusts, tackling the issue from two sides.
METHOGAS is typically used in a two-phase approach: an initial dose to break existing crusts (or as a strong preventative boost), and a maintenance dose to continually suppress crust formation.
Initial Dose: If a crust is present or you anticipate one (like starting up on fibrous feeds), an initial high dose of about 45 kg per week per 1 MW of plant capacity is recommended. This might be split into daily doses; roughly, 45 kg/week is ~6.4 kg/day for a 1 MW plant. For example, a 500 kW plant might start with ~3.2 kg/day initially.
Maintenance Dose: Once things are under control, a maintenance dose of around 15 kg per week per 1 MW keeps the digester crust-free. That’s about 2.1 kg/day for a 1 MW system. Adjust proportionally for other sizes (e.g., ~1 kg/day for 500 kW).
Consultation: The daily/weekly dose should be agreed with a Realistic Agri advisor as it depends on specific factors like feeding rate, mixing system, and extent of problem. So, while the above are guidelines, some fine-tuning is needed. Some digesters might get by with even less in maintenance if feed is seasonal or if the initial dose cleared a one-time issue.
Method of Addition: METHOGAS comes in 15 kg bags. You can add the product directly into the digester:
If you have a solid feeding system, empty the contents into the feeder.
If adding manually, try to distribute it across the surface or different feeding ports to cover the whole digester.
It might also be possible to mix METHOGAS with some water and spray it on a crust via a top manhole for faster interaction, especially for the initial dose.
Frequency: During the initial phase, you might add daily or several times a week. For maintenance, you could add a smaller amount daily or the full weekly dose in one go, depending on convenience and what your advisor suggests. Smaller regular doses often keep a steadier state.
Important: Ensure your mixers are running after adding, to help spread the additive. If a crust is very thick, consider breaking it up a bit (mechanically or by recirculation) so METHOGAS can penetrate. But often the chemical action will handle it.
Also, measure the crust thickness or mixing torque over time – you should see improvement within a few weeks. If not, dosage might need to be adjusted.
METHOGAS is provided in 15 kg bags for easy handling.
A 15 kg bag can be handled by one person, but it's on the heavier side, so be careful lifting properly or use a trolley for longer distances.
Storage: Store METHOGAS bags in a dry, cool area. The polyaminesc can be hygroscopic (absorb moisture) so keep them sealed. They have good shelf life as long as kept dry. Stack bags on pallets or shelves off the floor to avoid moisture wicking.
Handling:
Wear gloves when handling, as polyamines can be irritant or at least dry out your skin. If it's a powder, a dust mask and eye protection are also advised to avoid irritation from dust. Always follow the instructions on the label.
Polyamines can have a strong odor (sometimes a fishy or amine smell) – good ventilation in the storage and handling area is helpful.
When adding to the digester, avoid breathing dust directly and avoid skin contact; wash hands after.
If spilled, sweep or vacuum the dry product. It’s not toxic waste, but you wouldn’t want a lot of it in a puddle as it could make a gel or be slippery.
Mixing with other feed: It’s compatible with feeding equipment; just ensure it doesn’t linger on metal surfaces too long (polyamines can be mildly corrosive in concentrated form). But once diluted in the digester, no issues. Usually, it’s fine to add with other feedstocks.
Environmental: The product is meant to stay in the digester and will exit with the digestate, where it likely binds to solids. Polyamines in soil can act as soil conditioners and are not hazardous in the small quantities dosed, but always follow local regulations for digestate spreading.
METHOGAS yields ROI by preventing the inefficiencies and costs that crusts cause:
Maximised Biogas Production: A digester without crusts is fully utilising its volume for biogas production. Crusts can trap biogas or reduce active volume, causing lower output. By eliminating crusts, METHOGAS can lead to a noticeable increase in biogas yield (operators have seen more gas once a crust is dealt with). More biogas means more energy to sell – direct revenue gain.
Energy Savings: Crusts make mixing harder – mixers may run longer or at higher power. Pumps pushing thick sludge consume more energy. Removing crusts reduces the parasitic energy consumption, saving on electricity costs. This also frees up mixer capacity to perhaps allow higher loading rates if desired.
Maintenance and Downtime Reduction: Crusts and sediments can cause major headaches: clogged outlets, stalled mixers, even require periodic tank cleaning if severe. METHOGAS prevents these issues, meaning you avoid the downtime and labour of manual cleaning or emergency fixes. Not having to open a digester to clean out a crust (which could mean a full stop of operations) is a huge cost avoidance, potentially tens of thousands saved in labour and lost production.
Equipment Longevity: A homogeneous digestate is gentler on equipment. Mixers not fighting a crust experience less mechanical stress and can last longer between overhauls. Pumps that aren’t pumping half-solid sludge won’t break as often. Therefore, equipment replacement and repair costs go down. For example, you might extend a mixer’s life by years, saving the cost of a new unit.
Feeding Flexibility: With crust control in place, you can use fibrous or high-solids feedstocks more confidently, knowing they won’t create an unmanageable crust. This means you can take advantage of cheaper feeds (like crop residues, grasses, straw) which you might have limited before. Cheaper feedstock or higher solids feeding can improve the plant economics, and METHOGAS makes that feasible without negative side effects.
Safety and Compliance: Large crusts can hide issues like gas pockets that might lead to surges, or can suddenly break apart and cause foam-over or overflows. By preventing crusts, METHOGAS indirectly helps avoid such safety incidents or environmental non-compliances (spills). Avoiding any incident that could result in regulatory fines or work stoppages is a financial safeguard.
Consider this scenario: a plant was losing 5% efficiency due to a crust (some gas not captured, some volume lost). After METHOGAS, that 5% is recovered – for a 1 MW plant that’s like adding 50 kW of constant power, worth many thousands per year. The cost of METHOGAS is much smaller in comparison. Plus, factor in not needing to hire a vacuum truck to remove crust annually, etc. The ROI often comes in the form of trouble avoided is money saved, and in improved performance metrics.
METHOGAS essentially ensures you get the full value out of your digester capacity and feedstock, which, for an asset-intensive operation like a biogas plant, is critical to profitability. Operators who have implemented it typically find that the smooth operation and enhanced gas output quickly justify the additive cost, often with a comfortable margin.