Wednesday November 24 2021
Many people think anaerobic digestion is relatively new technology that has come to the fore as an environmentally friendly way to treat organic waste and produce renewable gas and electricity.
But this isn’t the case at all. In fact, anaerobic digestion has a long history possibly stretching back as far as the 10th Century when biogas was used to heat bath water in Assyria.
However, it wasn’t until the 17th Century that Flemish physician, philosopher, mystic and chemist, Jan Baptista Van Helmont, discovered that decaying organic matter gave off flammable gases.
Helmont is even credited with inventing the word gas, which is derived from the word chaos, and was the first scientist to identify the existence of carbon dioxide. His work went on to influence many other scientists working in this field, including British natural philosopher Richard Boyle.
Then, in 1776, Count Alessandro Volta – an Italian chemist and physicist who was a pioneer in the field of power and credited with inventing the first electric battery – concluded that there was a direct correlation between the amount of decaying organic matter and the volume of flammable gas produced.
Volta also discovered methane by recognising anaerobic activity occurs naturally in some soils and in lake and oceanic basin sediments. This was an important step in the history of the development of anaerobic digestion.
The next pioneer in anaerobic science was Cornishman Sir Humphry Davy. Sir Humphry is best known for inventing the Davy lamp, an early form of arc lamp, but he also discovered that methane was present in the gases emitted from cattle manure.
This was just one of Davy’s many achievements in a glittering career that saw him separate elements potassium, sodium, calcium, strontium, barium, magnesium and boron for the first time, and discover the elements chlorine and iodine.
The work of these early pioneers paved the way for the first ever AD plant which was built in Bombay (now Mumbai), in 1859. It was built in a leper colony to deal with the sewage created, but little else is known about the plant.
The technology soon reached England so by 1895, biogas generated by a sewage treatment plant in Exeter was being used to light streetlamps. A similar invention was created by Birmingham engineer Joseph Webb, who designed streetlamps in the 1860s to burn off the excess methane created in London’s new sewage system.
Just one example of the Webb Patient Sewer Gas Lamp remains, in Carting Lane near The Strand.
In the early part of the 20th Century, several incidents occurred in a relatively short space of time that would shape the future of anaerobic digestion.
The first of these was in 1906 when German engineer Karl Imhoff created the Imhoff Tank for the reception and processing of sewage. The tank was separated into two chambers – the upper chamber where sedimentation takes place, and the lower chamber where the biosolid sludge collects and undergoes the digestion process.
The Imhoff Tank was the was essentially an early form of the type of AD plants we see today, and it led to a shift from the use of anaerobic lagoons which had been popular up until that point, to tank-based systems that are still in use today.
The second major shift was the acceptance of microbiology as a recognised scientific discipline in the 1930s. This led to a huge amount of research into anaerobic digestion, looking at the most effective bacteria to use, the best conditions for generating methane and generally making the whole process more efficient.
In World War One, the interest in biogas generation slowed as there was an increase in the use of petroleum-based products and in the inter-war years, petroleum fuels remained the most popular forms of power.
However, petroleum shortages in World War Two led to a resurgence of interest in anaerobic digestion and an increase in the use of biogas. Germany turned to fuelling many of its vehicles and farm machinery on sewage and biogas because obtaining petroleum became so difficult in Germany itself, and its Nazi-held territories.
When the war ended, however, and availability of petroleum returned to normal levels, interest in anaerobic digestion once again waned.
Although the use of anaerobic digestion to create energy lost out to petroleum, around midway through the 20th Century, interest in the process grew as a cost-effective method of removing solids from wastewater and stabilising the settled solids.
This then enabled the process of activated sludge – cleaning wastewater by adding microorganisms such as bacteria, protozoa and fungi, aerating it, and keeping them all in the suspension by stirring the liquid.
Activated sludge is used to remove biological matter, nitrogenous matter, and nutrients from sewage and industrial wastewater, resulting in a liquid that is relatively free from suspended solids and organic material.
The process remains popular today with water utility companies and large commercial businesses employing it to manage their wastewater.
Unsurprisingly, the trend set by World War Two began a pattern; interested in anaerobic digestion increased when the supply of petroleum-based fuels was threatened, or the price increased to unsustainable levels.
Both of these occurred during the 1970s energy crisis when a number of western countries faced substantial petroleum shortages, along with highly elevated prices.
The shortage was a result of wars and revolutions in the Middle East which disrupted supplies. It led to stagnant economic performance in the USA and other developed nations and to an interest in those nations having greater energy security.
This, along with a greater receptivity to innovation, increasing pollution penalties, policy incentives and availability of subsides and funding opportunities all combined to fuel renewed interest in anaerobic digestion.
With the interest in sustainability and renewable energy emerging in the late 1980s, in 1991 Germany became the first country to introduce Feed in Tariffs (FIT) to support investment in AD technology as a form of green energy production. This had the desired effect, with the number of AD plants growing from just 20 in 1991 to 517 in 1998.
However, FIT wouldn’t be available in the UK for another 19 years. They were finally introduced by the Energy Act 2008 but didn’t come into effect until April 2010.
As a result, anaerobic digestion as a process to generate clean energy is more advanced in Europe, and the lack of FIT in the UK until relatively recently perhaps explains why Germany has a total of 9,000 AD plants whereas the UK has just 650.
China adopted anaerobic digestion technology in the 1970s and has employed it in a very different way to western countries. As the vast majority of its 1.2bn people live on farms or in villages with no formal waste management systems in place, individual households have small underground digesters to deal with human and animal waste and agricultural by-products.
The biogas created by the digesters is then used to heat and light their homes.
The USA, by contrast, has just a small number of AD plants for a country of its size, with around 2,200 in operation. 250 of these are on farms and another 1,269 are on wastewater treatment plants.
The remainder are food waste digesters and landfill gas projects.
So, now you know all about the history of anaerobic digestion, make sure your plant doesn’t become a thing of the past by keeping it in tip-top working condition.
For all service, maintenance, and operational needs, contact Birch Solutions now.