Bio-gas is produced during the biological breakdown of organic solids through anaerobic digestion. The gas resulting from this process is an energy source that can be collected and utilized or safely burned.

Recovered Bio-gas can be used in many ways :

  • Run generators to produce electricity
  • Run boilers to heat the anaerobic digester or the treatment facility
  • Eliminate natural gas and propane usage for cost savings and profit

Anaerobic digestion is a very safe and effective way of treating bio-solids from municipal and industrial waste-water. It is ideal for meeting strict environmental regulations, especially with emission standards becoming more stringent in urban areas.

The anaerobic process takes place in the digester (closed tank), covered ponds or lagoons by the use of a thermophilic or mesophilic process. Landfills also generate Bio-gas naturally as buried organic refuse biodegrades.



Bio-gas collection and utilization are important to the anaerobic digestion process. The gas is saturated and contains elements harmful to people as well as corrosive to piping and equipment. It is important for the Bio-gas handling equipment to be of high quality and operate as a system.

  • Moisture and Sediment : 

Bio-gas is saturated when it leaves the digester, covered pond or lagoon. In order to avoid damage to downstream equipment, moisture and sediment should be removed. A Condensate and Sediment Trap with drip trap should be located immediately downstream of the digester, covered pond or lagoon. A condensate accumulator should be considered when an accumulation of condensate is expected. This will help lower operating and maintenance costs.

  • Foam :

Pressure and vacuum relief valves with flame arresters are installed on digester covers. When foam clogs the flame arresters, it may prevent the pressure and vacuum relief valves from properly relieving pressure or vacuum accumulation which could cause damage to the digester and the digester roof. Emergency pressure or vacuum relief can be accomplished by installing emergency relief valves. Installing a foam separator immediately downstream of the digester will prevent foam from entering downstream of the digester.

Flame arresters should be installed between ignition sources and vital equipment. In addition, thermal shut-off valves should be used along with all in-line arresters. Flame arresters should be installed along with all pressure and vacuum relief valves on the digester roof to prevent external flames from igniting gas inside the tank.

Blanket Gas Regulators will direct the gas to utilization equipment such as boilers and engine generators and may be located upstream or downstream depending on specifications.

Check valves should be located where a reversal of flow would damage rotating equipment or disrupt the system’s pressure balance. Bio-gas can become explosive within flammable concentrations of gas and air.


This schematic is for general presentation purposes only and is not intended to represent a specific design. Please contact us for complete product information.

Related pressure and vacuum safety-relief products


If you or your team want to know more about Tank Venting or get up to speed with the latest changes to API2000 we will be happy to run a technical seminar or lunch and learn session for you. We make no charge for the sessions for end users or groups of 5 or more people.


Some of our customers testimonials

Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech- pilot operated pressure relief valves service and calibration

After conducting a Third Party Witness Inspection, I was most impressed with Ewart and his team, their professionalism, and product knowledge I found to be excellent.

Ian Johnston

Director, RAK Inspection

Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech- Geodesic Dome Installation

Assentech were subcontracted to assemble and install a 25m geodesic dome for Shaft G on the Lee Tunnel project. My experience with Assentech from pre-contract through to assembly has been very positive. Unlike other subcontractors I have experienced on this project, Assentech had a very positive attitude to producing the level of documentation required for a project of this scale. Leading to a high quality pre construction packaged approved in a timely manner. The communication regarding the manufacturing process was first class allowing us to easily plan our works and prepare the site. Dome assembly was carried out very efficiently and completed to programme. The task was correctly resourced and well supervised. The work force had a positive attitude and carried out the task safely. In summary from my perspective it has been a very easy subcontract to manage with a high quality finished product.

Robert Colthorpe

Site Agent – Lee Tunnel Project, Morgan Sindall

Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech wins supplier excellence award from Eastman Chemicals

We were extremely pleased with the level of service and professionalism demonstrated by Assentech, right from our initial enquiry, through delivery and post installation. As a recipient of only two of these awards made by Eastman Chemical Company in the UK, based on performance in 2014, Assentech are rightly proud of their achievements.

Robert Dodgson

TH3 Project Procurement Lead, Eastman Chemical Company

Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech-IFR Installations at Vopak, Teesside

As you said “you delivered what it said on the tin”. On time and on budget.  Your up front engineering to determine the suitability of your product for our application was second to none, i have not seen anyone else in the industry pay as much attention to detail before you get the purchase order number as Assentech.

Garry Lee

Project Manager, Navigator (formerly Vopak Limited)

Emergency-Relief-Valve-Pilot-Operated-2500a  Assentech-IFR Installations at Navigator Terminals

Assentech have supported our Navigator Terminal (formerly known as Vopak Teesside) on two important projects by providing technical assistance and supplying and fitting a total of 11 Internal floating roofs. Both projects have been completed on schedule and on budget. Assentech have provided an excellent level of experience and front end engineering support with high quality drawings and documentation. Their specialist on site labour have worked collaboratively with us and Assentech have proven to be open, honest and flexible partners.
We have experience of both their Heavy Duty Pontoon type and Full Contact IFR’s and we continually monitor operation and performance of all lFR units Installed on site and consider the Assentech supplied Matrix brandto be the best in the market with exceptional build quality and rigidity. Our clients have inspected the installations and have always remarked upon the build quality and have been impressed with their strength in fully supporting up to four people without noticeable deformation. The design and construction of their stainless steel shoe seals continue to prove to operate excellently with no noticeable reduction in performance or flotation ability over the time since Installation.
Assentsch have proven to be extremely competitive on price and their installation and inspection activities have always been thorough. Navigator therefore have no hesitation in recommending Assentech to other companies considering their services.

Brian Beddow

Project Manager, Navigator Terminals Seal Sands