How to Utilize the Biogas from an IC Anaerobic Tank?

Hi there, I’m Jake, and for the past seven years, I’ve been working as an anaerobic wastewater treatment equipment supplier—specifically, IC anaerobic tanks, those workhorse systems that turn industrial and organic wastewater into something far more useful than just treated water. When I first got into this business, I’ll admit I thought the main value of an IC tank was just meeting discharge standards. But over hundreds of client projects across food processing, pharmaceuticals, and even municipal organic waste facilities, I’ve learned that the real magic happens with the biogas that comes out of that tank’s gas hood. It’s not just a byproduct—it’s a revenue stream, a sustainability win, and often a game-changer for businesses looking to cut energy costs and shrink their carbon footprint. Today, I want to walk you through exactly how to utilize that biogas from your IC anaerobic tank properly, drawing on real projects I’ve supported, scientific best practices, and common pitfalls I see business owners make every day. IC Anaerobic Tank

First, let’s ground this in a quick, plain-language recap of where that biogas comes from, because understanding the source makes the utilization choices make sense. Inside an IC (Internal Circulation) anaerobic tank, you have three main zones: the bottom reaction zone where high-rate anaerobic bacteria break down complex organic matter, the middle gas-liquid separation zone, and top clarification zone. As those bacteria do their work—digesting things like sugar from sugarcane processing wastewater, fats from meat packing plants, or volatile solids from brewery spent grain—they produce biogas: roughly 50-70% methane (CH4, the combustible part), 30-50% carbon dioxide (CO2), plus trace amounts of hydrogen sulfide (H2S), moisture, and small particulates. The composition can shift depending on your feedwater: for example, high-protein wastewater will produce more ammonia in the gas, while high-sulfate feedstocks lead to more H2S. That’s important because the impurities in biogas are what make pre-treatment non-negotiable, not optional. I’ve had a client come to me two years ago with a broken gas boiler—they skipped pre-treatment, so H2S corroded their heat exchanger in six months. That’s a $12,000 repair bill they didn’t plan for, all because they tried to use raw biogas.

So step one before any utilization: properly treat the raw biogas to remove corrosive or clogging impurities. This is non-negotiable for every end use, no matter how simple. The key contaminants here are H2S and water vapor, with others like siloxanes (from cleaning products in wastewater, common in pharmaceutical or textile plants) needing removal if you’re upgrading biogas to pipeline quality. Let’s break down common, field-proven pre-treatment methods I’ve seen work across dozens of sites. For H2S, the most low-cost, low-maintenance method for small to mid-sized IC tanks is iron oxide filtration. You fill a canister with activated iron oxide media—when biogas passes through, the H2S reacts with the iron to form iron sulfide, which is safe to dispose of as non-hazardous waste once spent. For larger volumes, or sites with very high H2S (over 500 ppm), a simpler chemical scrubber using a weak caustic solution (like sodium hydroxide) works; we’ve installed these with our IC tanks for meat processing clients and they cut H2S to under 10 ppm consistently. Water vapor is easy: a simple condenser, usually set at 2-5°C, cools the gas so moisture condenses out before it can cause corrosion in pipes or equipment. If your wastewater has siloxanes (look for your treatment lab results to confirm), activated carbon filtration will strip those out—critical if you’re going for biogas upgrade, as siloxanes turn to glass when burned and damage engines.

Once your biogas is properly treated, the next step is matching its volume and quality to your end use, because not all applications need the same purity or pressure. Here’s where I’ve seen clients pick the best fit for their operation, based on what their energy needs are.

The most common, and often most cost-effective, utilization for biogas is on-site heat and power generation via combined heat and power (CHP) units. Let’s be clear: this is not a niche technology. CHP systems run on treated biogas, using an internal combustion engine or a microturbine to turn the methane’s energy into electricity, and they capture the waste heat from the engine’s exhaust and cooling system to use for process heat in your facility. For an average IC anaerobic tank treating 100 cubic meters of wastewater per day, you’ll get around 20-30 cubic meters of biogas per day, which is enough to power a 5-10 kW CHP unit—more than enough to offset the power needed for your IC tank’s recirculation pumps, aeration (if you have aerobic polishing), and even part of your facility’s general lighting. A brewery client I worked with last year in the Midwest: their IC tank processes 800 m³ of spent grain and yeast wastewater daily, producing ~200 m³ of biogas. They installed a 50 kW CHP unit, which now powers their entire brewhouse and office, and uses the waste heat to warm their process water for mashing. Their monthly utility bill for power and heat dropped by 65%—$14,000 a month in savings. That’s money they put back into expanding their taproom and sourcing local hops. The key here is sizing the CHP correctly: I always work with clients to size the unit to 70-80% of their maximum biogas production, because IC tank output can fluctuate with feedstock load (like a brewery’s production peaks on weekends, so biogas goes up on Monday). Over-sizing leads to wasted gas, which is a costly mistake.

Another underrated use for smaller IC tank sites is direct heat application, no CHP needed. If your facility has a steady demand for low-to-medium temperature heat—like drying food products, heating wastewater for your treatment process, or space heating for a warehouse or greenhouse—you don’t need the complexity of an engine. You can run the treated biogas directly into a gas boiler or a radiant heater. For a small organic fertilizer plant I installed an IC tank for last year, their main need was heat to dry their composted manure waste. Instead of installing a CHP (which would have needed extra maintenance), we piped the treated biogas to two 200,000 BTU boilers that supply all their drying heat. Their biogas production covered 100% of their drying heat needs, and they only buy propane for backup on low-gas days. That’s a $7,000 annual savings on fuel costs, with zero added complexity. The only catch here is you need a steady, consistent demand for heat; if your peak heat use is only seasonal (like a fruit drying plant that only works in harvest season), direct heat is still a good fit, but you’ll need to store excess biogas for off-peak times.

Speaking of storing biogas, that’s a critical part of utilization I rarely see business owners plan for upfront. IC tanks produce biogas in batches, often—peak production happens when the tank’s loading is highest, so you need storage to cover gaps when demand is lower, or when the IC tank is down for maintenance. The most common and cost-effective storage for biogas for IC tank sites is a flexible membrane biogas holder, usually installed on top of the IC tank’s gas hood or adjacent to it. These are low-pressure, fabric holders that can store 1-2 days of biogas production, which is enough to smooth out fluctuations. For example, a dairy farm client I worked with: their IC tank processes milk wastewater, and biogas production peaks right after milking (6 a.m. and 6 p.m.). Their CHP runs all day, but their heat demand is highest during daytime feeding times, so the membrane holder stores the excess biogas produced at milking to use when demand is lower. Without storage, they would have had to flare the excess gas (which is a waste of energy and a small emission source) or buy extra fuel during peaks. I always recommend a membrane holder for any IC tank over 50 m³ biogas production per day—it’s a small upfront cost that pays for itself in 12-18 months.

If your operation is bigger, or you have access to a nearby pipeline or heat demand (like a municipal wastewater treatment plant or a food park with multiple businesses), upgrading biogas to pipeline quality (called “biomethane”) is the highest-value utilization option. Biomethane is chemically identical to natural gas, so you can inject it into the local natural gas grid or use it as vehicle fuel for your fleet. Upgrading removes nearly all CO2, H2S, and other trace contaminants, bringing methane content up to 95% or higher. For a large sugar mill client I supported, they upgraded their IC tank biogas to biomethane, which they inject into the national natural gas pipeline. They now sell the biomethane to the local utility, generating $22,000 a month in revenue, while still using 10% of the gas for on-site operations. That’s a massive shift from treating biogas as a waste product. The upgrading process uses methods like pressure swing adsorption (PSA), membrane separation, or water scrubbing, and while upfront costs are higher (usually 2-3 times the cost of a CHP), the long-term revenue stream makes it ideal for sites with consistent, high biogas output (over 500 m³ per day).

Now, let’s talk about the mistakes I see that derail even the best biogas utilization plans. First, not monitoring biogas quality and volume. I can’t tell you how many clients don’t have basic sensors on their IC tank’s gas line—they just assume the gas is good, until their CHP breaks down or their boiler starts corroding. Installing simple, low-cost sensors for H2S, methane content, and gas flow takes 2 hours of labor, and prevents costly repairs. Second, skipping pre-treatment for end uses that need it. A client in the textile industry tried to run raw biogas through their CHP and the H2S ruined the engine’s piston rings in three months—costing $18,000 in parts and labor, plus 2 weeks of downtime. Pre-treatment media isn’t cheap, but it’s a fraction of that cost. Third, not integrating biogas utilization into your IC tank design upfront. I work with clients during the planning phase, not after they’ve already installed their IC tank and realized they have no way to use the gas. For example, if I know a client has a nearby greenhouse that needs heat, I’ll size the IC tank’s gas handling system to accommodate a direct gas boiler, instead of a CHP, saving them 30% on upfront equipment costs.

Let’s wrap this up with a quick, real-world example that ties all this together, to make it tangible. Last year, we installed a 500 m³ IC anaerobic tank for a craft brewery in Ohio. Their wastewater is spent grain, yeast, and residual wort, with an average organic load that produces ~180 m³ of biogas per day. We paired the IC tank with an iron oxide H2S filter, a water condenser, and a 400 m³ flexible membrane biogas holder. They had two main needs: power for their brewery equipment, and heat for their brewhouse and packaging line. We sized a 45 kW CHP unit, which meets 100% of their power needs (powering recirculation pumps, fermenters, bottling lines) and provides waste heat that covers 80% of their process heat. The remaining heat demand is covered by a backup gas boiler that uses excess stored biogas. Their numbers, after 12 months: $16,800/month in utility savings, payback on the IC tank and gas system in 21 months, and a 42% reduction in their operational carbon footprint. That’s not just a “good idea”—that’s a concrete business case, built on proper biogas utilization.

At the end of the day, biogas from an IC anaerobic tank isn’t a secondary byproduct—it’s a flexible, valuable resource that can save you thousands in energy costs, create new revenue streams, and help your business meet sustainability goals. Whether you’re a small food processing facility looking to cut propane bills, a large plant with enough biogas to sell into the grid, or anything in between, the key is matching your pre-treatment, storage, and end use to your specific operation—not using a one-size-fits-all approach.

If you’re in the planning phase of an IC anaerobic tank project, or you have an existing IC tank and are looking to unlock the value of your biogas, I’m here to help. We design, manufacture, and install IC tanks tailored to your wastewater profile, with integrated gas handling systems that make utilization straightforward from day one. I’ve worked with hundreds of operations across food, pharma, agriculture, and more, so I can help you avoid the common mistakes and build a biogas system that works for your business’s unique needs. Reach out to start the conversation.

Aerobic Aeration Products References

1. Metcalf & Eddy, Wastewater Engineering: Treatment and Resource Recovery, 5th Edition, McGraw-Hill, 2014
2. International Water Association (IWA), Anaerobic Biotechnology for Industrial Wastewaters, 2019
3. American Society of Mechanical Engineers (ASME), Biogas Utilization Guidelines for CHP and Grid Injection, 2021
4. European Biogas Association (EBA), Biogas Upgrading and Storage Best Practices, 2020

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