01 August 2022
Rishi Sunak and Liz Truss disagree fundamentally about the economic strategy to take the UK economy forward, and this is nothing new. Monetarists and Keynesian have argued for decades over the merits of fiscal and monetary policy. Both have been proven to work, yet both have also ended in periods of economic stagnation. And so it is with anaerobic digestion.
The arguments for the adoption of different equipment and process is seemingly endless. What type of tank you use and what roof you put on your tanks are some of the easiest selections. The choice of mixing philosophy gets more complicated with competing merits found with hydraulic, gas and physical stirring mixing systems. Of course, the size of tank and substrate being mixed should play a significant bearing on the mixing philosophy developed, but as always, manufacturers often complicate the selection over selling their products. We have hardly started in the technology selection process. Feed systems must be procured. If dealing with food waste, there is a long debate about what de-packaging system to deploy and then the old topic of pre or post-pasteurisation.
Once you start operating, the choice continues. Thermophilic versus mesophilic, cold or hot hydrolysis (if you have a separate phase, of course), feed cycles and hydraulic loading, retention times, nutrient addition, and so the list goes on.
On any of the above, the academics have written hundreds of papers. Almost any approach can be supported or rebuffed by conflicting academic studies. Moreover, most of these studies have been conducted in beaker scale studies in the comfort of a laboratory and reflect only some of the reality of operations on a plant.
For those seeking to enter the sector or steer a failing plant to full power, it can be a confusing arena to find yourself in. Employ two consultants, and you will inevitably get two views, three consultants, and you will get three views.
However, there is one area that almost all would agree on. Consistency in the biology is critical. If you can maintain consistency of temperature, feed, Ph, trace nutrients and agitation, you are halfway to success regardless of the other hotly debated choices.
Let's hope our politicians can also find something to agree on.