Welded Steel Digester Tanks



Digester tank, also known as an anaerobic digester or a form of anaerobic digestion system, is a type of storage equipment that utilizes the awesome natural process of anaerobic digestion. You might ask: What makes this natural process awesome? In a technical sense, anaerobic digestion is not just comprised of one process; rather, it is a series of biological reactions that break down biodegradable materials, such as peelings, plant remains, or animal excrements, to produce biogas. It might surprise you to know that the “workers” behind this activity are the microorganisms that perform the biological processes of breaking down the organic matter – and this is all done in the absence of oxygen. To top it all off, the utilization of this natural activity is what placed Digester Tanks on the top list of waste management technologies. How? Let’s find out.


The first thing to know about Digester Tanks is that it is not just manufactured as one type. There are differences that set one model apart from another. 

Types Based on Microorganisms Utilized

Generally, there are ranges of temperatures set for Digester Tanks in order to obtain optimal results. This depends on the type of microorganism being used in the digestion process. Different strains of microorganisms require different temperature ranges in order to thrive and function in their immediate environment. Considering these facts, these are three types of Digester Tanks based on the variations of microorganisms employed and their corresponding preferential temperature ranges to yield the best biogas yields:


This type of Digester Tank houses and makes use of microscopic organisms that truly live by its name. Coined from the Greek psychrophile, which means “cold-loving”, these types of microorganisms require temperatures ranging from 5°C to 20°C. Hence, this is the temperature range set for Psychrophilic Digester Tanks for optimal output.


Since mesophilic microorganisms are most active at medium-range temperatures, Digester Tanks, which employ its biological activities, are set to an operating temperature range of between 30°C to 35°C. Among all the types of digester tanks, this one is the most commonly used due to the lesser effort required as compared to other digester tanks.


Thermophilic Digester Tanks are set with a temperature ranging between 50°C to 60°C as this type capitalizes on the digestion activities of heat-loving thermophiles. Compared to the aforementioned Digester Tanks, this is the one that is barely used in the biogas industry, since it requires abundant heat in order to yield positive results.

Types Based on Dry Matter Content

Aside from the different kinds of Digester Tanks based on microorganism type, there are also two types of anaerobic digestion systems differentiated based on dry matter content of the organic materials (also called the feedstock) it processes.

Wet Anaerobic Digestion System

This digestion system uses organic matter comprised of 10% to 20% dry matter, or even less. This results to a higher production of biogas, since this involves optimal mixing process – a requirement that needs to be met in order to attain a stable anaerobic fermentation procedure.

Dry Anaerobic Digestion System

In contrast to wet anaerobic, this digestion system requires a much larger amount of dry organic content in the feedstock. Organic materials, with dry matter content ranging between 20% and 40% or more, are the ideal feedstock to be used in this type of digestion system.

These are the most common types of Digester Tank systems which are mostly in service to industrial settings. With the varying factors by which each type functions, the mechanisms of different tank types also vary depending on its structure. However, to understand more about the concept of Digester Tank, the next section will be discussing the simplest general flow of how this innovation works.


Before we get to the working “spinning gears” within Digester Tanks, it is first necessary to understand that certain measurements of important factors must be considered: temperature, pH, and organic matter – all depend on the type of microorganism and anaerobic digestion system which are being used. Simply put, the effectivity of the digestion process delicately depends on using the right set of procedures with the right factors set in place. Keep that in mind, and let’s move over to the mechanisms of a Digester Tank.


Biomethane plant digester tankThe Process

Feedstocks, such as manure, crop residues, and other biodegradable materials, must be prepared for processing. Preparation includes determining the dry matter content of the material since that would be the basis of choosing whether to go for dry or wet anaerobic digestion system. After preparation, the feedstock is to be loaded to the tank through a duct called the “digester reactor vessel”. This funnels the organic materials down inside the tank where the microorganisms are sealed and the anaerobic digestion takes action. Of course, a Digester Tank must be airtight and well-equipped with both mixing and heating apparatus in order to produce the optimal biogas yields. The digestion process may continue from 2 days up to 60 days, depending on the digestion system utilized and the organic matter concentration of the feedstock.


The Product

The success of the digestion procedure is determined by quantity but ultimately, by the quality of the biogas produced. However, the resulting biogas cannot be used how it is intended to be just yet. Biogas is largely comprised of methane (CH4), but what can be extracted through anaerobic digestion is still raw – meaning, it still has traces of water vapor, carbon dioxide (CO2), and even dangerous impurities such as siloxanes and hydrogen sulfides (H2S). To convert it to its most useful form, the raw biogas must first undergo purification. One example of removing impurities from biogas is through the process of Biogas Cleaning, a series of procedures that lowers water, hydrogen sulfide, and carbon dioxide levels down to specific levels that are dependent on certain applications such as meeting natural gas pipeline requirements or liquified biomethane production. Only after this stage can the biogas products be used for purposes such as its use as sources for natural gas pipelines for homes, or for heating and electricity.


With the fast-paced and constant development of technology, society’s resources, both renewable and non-renewable, must always keep up with the big steps these advancements are making in order to get the best out of it. That is why the innovation of Digester Tank plays a vital role in the steady and efficient production of a renewable resource, which is the ideal type of energy source, in the form of biogas. And its applications? Well, it’s an understatement to say that the list is endless, but it is worth mentioning some of them.

For one, the utilization of Digester Tanks in waste management in Agriculture is surely a notable example. Proper disposal of waste products, such as animal manure and feed spills, is what farm owners face on a regular basis. With Digester Tanks, however, these wastes can be converted to the much more useful biogas. Plus, the remaining digestion residues or “digestates” in the tank can still be put to use as effective and marketable fertilizers and soil amendments.

Another example is the use of Digester Tanks as steady sources of fuel products in the automotive industry. This is utterly a more reliable “spring” of fuels as compared to petroleum products that are yielded via fossils which take years to be located underground and beneath the ocean floor.

So, those are two of the most prominent examples of the application of Digester Tanks. And now, the only lingering question we have in mind is: What is the best Digester Tank? There are many Digester Tanks available in the market, but just like any product, it’s a fact that there are those that function and serve their purpose a lot more effectively and efficiently than the rest.




Here at PTC, we are at the forefront of anaerobic digester tanks development. We construct durable steel storage facilities in a sustainable manner that helps companies which are centered on manufacturing biofuels such as biogas. All of our projects follow general regulations to ensure that they perform and function at their best, especially because each of them deals with highly combustible materials. Our constant pursuit of excellence in the tank manufacturing industry reflects on our dedication to building storage facilities that are beneficial and effectual. Such is also our passion for bringing high-quality Digester Tanks to enrich the community and save the environment.

What Sets PTC Digester Tanks Apart?

Let’s cut to the chase: What truly sets PTC Digester Tanks apart from the competition is that unlike other digester tank manufacturers in the industry who use bolted steel for the construction of their digesters, Pacific Tank utilizes welded steel for all of our tanks. This ensures longer-lasting storage that promises durability and reliability as compared to its bolted steel counterpart. Not only that, but we also construct them with seismic tolerance in mind. This means that in the case of an earthquake, our tanks will be able to endure such events without incurring any catastrophic damages.

There are numerous digester tank designs available to choose from, such as the epoxy-coated tanks which is more cost-efficient. Though epoxy coated tanks are an option to consider, side effects of using such materials for digester tanks is that it may not guarantee full security and durability in the long run. Inspection is crucial for security, but because of the fact that the structural tank walls are already hidden behind an epoxy coating there is no way to fully guarantee if the tank is sound enough to withstand the effects of chemical byproducts of biogas. Welded steel tanks are considered to be the wiser choice because it does not require any epoxy.

With regards to steel tanks, another digester tank construction that may be used is the bolted steel tanks. While they are durable, they aren’t as durable as the welded steel tanks. That’s because welded steel eliminates possible leaks by sealing any gaps found in and out of the tank with the same material that’s been used for the tank itself. Bolted steel cannot provide the same level of sealing effectiveness as compared to Pacific Tank’s welded steel construction.

Among all digester tanks out there, Pacific Tank believes welded steel construction is still the best option for any company venturing into biogas and fuel storage. With welded steel, Pacific Tank can create tanks up to 650,000 cubic feet by 18,400 cubic meters without compromising the integrity of the build and the client’s construction budget.

Pacific Tank is the leader in energy storage engineering, fabrication, and design. If you are in need of engineers and contractors specializing in fuel storage and conversion tanks, there is no other company to go to. Call Pacific Tank today or send an email to discuss your project.

694 Digester Tank 3D Model

694 Mixer Platform

694 Site Plan

Subscribe To Our Newsletter

Join our mailing list to receive the latest news and updates from our team.

You have Successfully Subscribed!