Frequently Asked Questions

How much do external carbon sources cost?

The price of any given external carbon source is of little relevance in isolation. It must always be considered in the context of the degree of purity and the active agent (COD-BOD). This means that there are significant differences in the yields of individual products, and only in this light is a comparison with other carbon sources of any relevance.

Please feel free to get in touch with our experts Tina Grosse or Dr. Nils-Oliver Höppner, who will be happy to advise you in this matter and provide further information.

What is the COD/BOD₅ value of individual external carbon sources?
Product Product base Spec. weight Theor. COD g O/g Sub BODg O/g Sub
Methanol Methanol 0.79 1.50 0.96
Ethanol 96% Ethanol 0.79 2.09 1.35
Ethanol 75% Ethanol + acetate 0.83 1.56 1.30
DENiTOL-RG Glycerin 1.25 1.06 0.59
DENiTOL-DG Glycerin 1.21 1.21 0.65
Acetic acid 60% Acetic acid + acetate 1.07 0.64 0.42
MEG Glycol 1.11 1.50 0.75
Is it possible to apply a temporary dose of carbon sources for testing purposes?

If you plan to conduct a test with an external carbon source, we will be happy to design a tailored solution for you. Please get in touch with our expert Dr. Nils-Oliver Höppner, who will be happy to advise you in this matter and provide further information.

Which technical specifications must a tank system comply with?

It is not possible to provide generally applicable information on technical specifications for a variety of reasons. Firstly, structural conditions or local circumstances will usually vary greatly for tank systems. Not only that, but the requirements and regulations imposed by public authorities can also vary from state to state. The size/choice of the external carbon source also affects the technical specifications.

For any further questions, please get in touch with our expert Dr. Nils-Oliver Höppner, who will be happy to advise you and can provide further information.

Which storage options are available for external carbon sources?

There are a number of options for the storage of carbon sources.

Tanks that are permanently installed in the building structure are one option – these are usually installed underground, above ground (horizontal or vertical) or in a covered aboveground structure.

There is also the option of installing ISO containers (usually 30m³) – these are tanks held by a steel frame to enable these containers to be transported. This requires the storage space for the ISO container to be sealed.

Another storage option is the installation of IBCs (1m³) that are filled from a tank truck via a fuel pump nozzle. This option also requires a sealed storage space.

ISO containers and IBCs require the operator to have the storage tanks connected and operated properly and in accordance with the regulations of the competent public authority.

For further questions, please get in touch with Dr. Nils-Oliver Höppner, who will be happy to advise you and can provide you with a wealth of further information.

How quickly can Gelsenchem deliver external carbon sources?

On weekdays (not including public holidays), we can deliver methanol and potassium methylate within 48 hours to any delivery location in Germany. For transportation outside of Germany, we will require prior notice of at least three business days.

For all other products, we deliver within three to four business days after receipt of the written order.

What needs to be considered when storing methanol?

Methanol may only be stored in explosion-proof tanks. The fittings, cabinets and supply lines must also be explosion-proofed.

Are the carbon sources offered continuously available with consistent quality?

Yes, all the products that we offer are continuously available in consistent quality. Customers with whom we have concluded master delivery agreements can rely on their deliveries to be of a continuously high quality standard.

Which external carbon sources can be used all year round?

Almost all the products that we offer can be used all year round.

The sole exception is glycerin, which can exhibit problems in winter; at low temperatures where tanks and pipes are kept in the open, the flow rate of the product may be diminished, which means that additional pressure is then required to pump the product.

Are there different external carbon sources for sewage treatment plants and landfill sites?

Acetic acid, ethanol, monoethylene glycol and glycerin are suitable all-purpose solutions both in leachate installations and in sewage treatment facilities.

For methanol, we recommend our product DENiTOL®-Si, which is especially suitable for the short exposure periods in leachate treatment plants, and our product DENiTOL®-KA, which is used in sewage treatment plants. Both products have been used in the waste water sector for many years without any problems and to the full satisfaction of our customers.

For further questions, please get in touch with our colleague Ingo Rürup, who will be happy to advise you and provide you with more specific information.

Where can I find out about the latest discharge limits?

See keyword Appendix 1 in the glossary
In the glossary, see keyword Appendix 51

I’m looking to put out a call for bids for an external carbon source – what do I need to consider?


Define the tanker volume to be delivered, as this will dictate the freight costs.

The purchase volume should always allow for fluctuations of +/- 10% with larger volumes or 1–2 tanker fillings with smaller volumes.

Alternatively, a fixed time frame with an estimated volume can be quoted.

You should never request bids for a fixed volume with an open delivery period.


Define the quality as precisely as possible to avoid misunderstandings. Express direct prohibitions on problematic substances that may cause blockages.

When calling for bids for technical methanol, stipulate that the provider is required to deliver pure methanol under the same conditions in the event that technical methanol should become unavailable.


Require evidence from each provider that they have continuously delivered the offered quality (for at least two years) to at least three German sewage treatment plants or leachate treatment plants. Alternatively, a list of references may also be provided – showing at least five facilities to which long-term deliveries have been made.


The drawback of fixed pricing over a period of time longer than three months is that any price changes (price increases) will be reflected in the provider’s fixed price in the form of an added risk premium. If the anticipated market price increases do not come to pass, you will have paid too much.

An alternative solution for periods of more than three months is a formula-based price based on the quarterly contract prices for pure methanol, quoted under “Methanol FOB Rotterdam T2” and published on our website.

The advantage over fixed prices here is that, by applying the quarterly contract price for pure methanol, you have already established the standard market price. The provider then only needs to calculate transport and handling costs. It remains possible to compare offers, as your company only needs to compare the respective premiums. The underlying base pricing – the quarterly contract price – is the same for everyone.

Special details

In your orders, specify which technical features the tanker must offer, as well as any relevant information such as the need for the truck to have its own pump, special route instructions, multiple filling stations, limitations on delivery times, etc.

For further questions, please get in touch with our colleague Tina Grosse, who will be happy to advise you.

I have a question about the quality of the external carbon sources on offer. Who can assist me?

For any questions you have, please get in touch with Tina Grosse or Dr. Nils-Oliver Höppner, who will be happy to advise you and provide you with the relevant information at any time.

What do I need to keep in mind as a recipient/unloader of hazardous freight?

See glossary > ADR

How is waste water treated at a public sewage treatment plant?

We have put together an easy-to-understand presentation for you under Waste Water Treatment.


Source: Wikipedia