Did you know tank storage breather vents leak? Mitigate the risks and protect your facility by knowing the facts, advises Debbie Pearce
Assentech was recently approached by the senior engineer from an anaerobic digestion waste to energy facility. He was investigating ways to defend pending enforcement by the Environment Agency for emissions violation.
Tank breather vents are used as the last line of defence against biogas digester over pressurisation. Digesters are an easily recognised landmark on many farms as the large green domes that are inflated by biogas, which is 60% methane and 40% carbon dioxide. Both gases are greenhouse gases (GHGs).
The methane is used to produce electricity and so is a highly valuable renewable energy resource. Escalating gas prices make this resource more valuable by the day and leaks to the atmosphere both highly damaging to our environment and a costly loss to the business.
The Environment Agency is now issuing Regulation 61 notices to any company leaking methane to the atmosphere. Leaks are easily detected using optical gas imaging cameras but, more significantly, traces of highly dangerous hydrogen sulphide can be detected by the smell of rotten eggs.
Assentech’s customer was in this situation when it approached the firm for advice. The customer’s site had four large breather vents installed, all of which were leaking significant volumes of biogas into the atmosphere and the company needed advice on how to reduce emissions to keep its licence to operate.
Assentech engineers visited the site and replaced the breather vents with quality units. To assist the customer, the team measured the leak rate of the vents they removed and the vents they replaced.
The reduction in vent leak rate dropped from an astounding 90cfh per hour to 0.08m3 per hour at 90% of set point. The saving to the environment was a reduction of the equivalent of 119 double decker buses to 0.1 bus. This represented a cost saving to the business of over £8,037 per annum.
According to the Government Environmental Impact Cost this represents a reduction from over £35,000 to just £7 per valve per annum. This was a relatively small site with only four vents but the savings were huge.
The Environment Agency thanked Assentech for providing the expertise, technology and solution to support this customer, safeguard the neighbouring communities and protect our environment. The return on investment for the customer was less than 12 months and underpins the value in purchasing quality breather vents that are individually tested to the International Standards (API2000 section 5.4) at initial start-up.
When quality breather vents are installed and maintained according to the International Standards, a site can evidence its duty of care, best practice and demonstrate its compliance. This is vital for defending criminal prosecution, litigation claims or environmental enforcement notices.
Assentech has now launched an environmental leakage calculator on its website, which is free for anyone to use. One of the conversion metrics is in CO2, which is commonly used in carbon offsetting terminology and calculating a company’s carbon footprint. Understanding leakage rates before and after vent servicing, set time intervals or at unit replacement stages, can give tank storage facilities a new metric for ESG reporting. Until now, there has not been the technology that can measure, monitor and record leakage from tank storage vent or a convenient calculator to convert biogas to a CO2 measurable.
Assentech has also produced what it believes to be the world’s first automatic tank breather vent mobile testbench that can measure the volume of leakage using highly accurate calibrated measurement and control devices. It incorporates artificial intelligence and QR code technology. The Vent-Less testbench performs a comprehensive two-minute test aligned to the test protocol of API2000. An instantaneous leak test and functionality report is generated within two minutes.
Debbie Pearce is with Assentech