How can I make sure that trace elements (and macronutrients) are not the limiting growth factor for a biogas plant biology – for an efficient Anaerobic Digestion process?
Why trace elements are so important?
They are essential for AD – they are the most important key element for a stable and performing biological process. They take part of enzymes – without enzymes no biogas production!
How can I find out if my plant is ok?
Please take a sample from the main digester and send it to a certified and experienced laboratory. No cooled transport needed, no problems if the sample takes some days/weeks. It’s not easy to detect trace elements, especially Selenium. Therefore, the choose of the proper laboratory is important.
Someone is telling you is better to analyse every input every … month, just forget it. It’s only a way to sell expensive laboratory services. Inside the digester everything is mixed, hydraulic retention times helps you.
How often I need to analyse them?
2- 4 times per year, with a really stable feeding and perfect process stability and performance also once at year.
But what how I understand the results?
First of all, you need an experienced and well-trained expert which gives you a feedback if the levels are critical, good or also in excess. Please compare the results based on the dry matter results. A historical elaboration would be perfect.
ATTENTION: normally no- one can measure bioavailable trace element levels (someone is offering “magic” methods but they are expensive and not very reliable) – the level is in function of the degradability (digestibility) of the feeding. For example, in straw you will find a certain amount of trace elements, but they have a very low availability.
How to solve?
Simple: Add bioavailable trace elements, or even better add trace elements with components which make present elements bioavailable.
Perfect solution – but it must very expensive!?
No, not at all, chelate based trace elements you need to add once at a while, every week or two. Depending on the input. Few ppm per ton of input. Trace element adding is in function of the biology: During biological start-up you need 4-5 times more product. During temperature induced biological community changes- add twice as normal.
But this are “dangerous” products!!
Yes, and no. Of course, Nickel, Selenium or Cobalt take part as “heavy metals” but we are speaking about few kg per week adding. Without them biology is going down and biogas production can stop completely.
Also chelate based products have a much lower ecological impact then inorganic products dosed at several tons per year.
I heard about tailor made products …
Yes, I few occasions nowadays recommend tailor made products are important. But for cost reduction and for safety rules suggest standard products are the solution. Once you make present trace elements bioavailable the added quantity of elements is limited – all the rest is already present. UFI – Unique Formula Identifier European law must be respected- pay attention that many suppliers don’t put a UFI number on the packaging.
UFI- if something is happening and you go to hospital doctors can connect with this number to the detailed composition and cure you immediately.
How a safe addition is guaranteed?
Liquid products need a dosage system for a safe application. Products packed in biodegradable nylon bags can be safely put into solid or liquid feeding systems.
What will be the proper/best dosage, can I trust the supplier indications?
For sure no-one can tell you the perfect dosage, not knowing bioavailability and biological needs in a certain moment… Every measurement for process stability (FOS TAC, VGA, etc. ) will show you the improvements and best performance level reached. Process efficiency measurements like COD and BOD5 shall improve. After a first starter dosage and a regularly continuous dosage take a sample and compare reached trace element levels.
A lower dosage is not a problem, but once you detect a doubt about biology add an extra dosage.
Normally the cost/benefit calculation is in favour for adding enough trace elements.
Sounds good – I will try!
Best solution is to try onsite, every biogas plant has his own physiological need and times to react after changes. If you don’t use trace elements, or worse if you don’t know if you have limited biological performance then act quick. If you use other products- please be aware of limits and benefits of each single product.
Interferences with other additives?
No, not at all, but vice versa if you use Zeolite, Iron Hydroxides etc. then bioavailable trace elements are essential to maintain existing performance and to assure that negative consequences are avoided.
Can you explain in detail?
Zeolith is not only neutralizing NH3 but also some important trace elements. With continuous dosage a stable trace element source is essential.
With a use of Iron Hydroxides (developed to bind heavy metals in water treatment) the bioavailability of essential trace elements is very limited. Would be better to switch towards Iron Oxide blends.
What’s your favourite trace element.
Macronutrient – phosphor. No-one is aware of the frequency of lack of Phosphorus!
TRACE ELEMENT: Iron. It plays an extraordinary importance in Anaerobic Digestion! Huge potential, enormous improvements reached adding it properly.
