You run a biogas plant and produce electricity and heat. Everyone knows that the electricity goes into the grid. But where does the heat go?
A 500 kW biogas plant has an annual heat surplus of approx. 500,000 l heating oil equivalent or 500,000 m³ natural gas equivalent. In other words, you would need 500,000 l of heating oil to generate the heat that can be extracted from the CHP unit via cooling and the exhaust gas heat exchanger. At a heating oil price of €1.30/l (as of 10 May 2022), that is worth €650,000!!!!
Many biogas plants already have a good outlet for their heat with a local heating network. But:
“I don’t have enough heat in winter. I could sell more.”
A customer on 6 May 2022.
Income from heat sales is becoming more and more important, because feedstock costs are rising while the EEG feed-in tariff stays the same. Many biogas plant operators are caught in the “feedstock cost trap”. The electricity price can hardly be raised. And feedstock costs can hardly be lowered. Only more heat can be used or sold.
Most biogas plants were built without any regard for heat use. The CHP heat was useless anyway. Now that it is used, the situation has changed, and every lost kilowatt hour of heat hurts, because it means losing money directly.
Avoid heat losses and sell more
If just 10% more heat can be used in the example above, that is worth several tens of thousands of euros – plus the CHP bonus for every kilowatt hour used.
Investments in insulation and better heat extraction pay for themselves quickly.
And these investments are even subsidised by BAFA at 40%. CO2 is avoided, and that is the aim of BAFA funding.
Less heat loss through the gas roof
Put a gas roof on the tank. Done. As cheap as possible. That was the philosophy 15 years ago.
Today, you avoid methane losses and heat losses. Losses are always expensive.
Avoiding losses is the most profitable investment.
One manufacturer offers a thermal insulation membrane inside the gas roof. This prevents convection of the biogas. Heat losses drop. An average loss of 10 kW over the year can easily be avoided. That works out at 87,600 kWh/year. In winter, when the heat can be sold well, the higher losses are even easier to avoid.
Extract more heat at the same flow rate
If heat has no value, nobody invests in efficient heat extraction.
Many heat exchangers on the market are old hat. They are simply inefficient.
Today there are graphite heat exchangers that beat any metal heat exchanger in efficiency.
Because graphite does not rust, more heat can be extracted from the exhaust gas flow. The exhaust gas can be cooled to below 60 °C. Condensation in the exhaust gas flow has no negative effect on the new type of heat exchanger.
These highly efficient graphite heat exchangers are also subsidised by BAFA at up to 40%. Instead of blowing heat into the air, it is used. Fossil fuels are replaced and CO2 is avoided.
If that’s still not enough!
Could you sell even more heat in winter?
Then simply produce less heat in summer and more in winter. That won’t work for me! Oh yes, it will.
If you put an SLP biological pre-treatment unit (BVES) in front of your biogas plant, you double or triple the biological capacity of your plant.
We built this BVES in Croatia back in 2014. With the same digester volume, 2.1 MW (instead of 1 MW) are now installed in continuous operation. Feed input is 160% (instead of 210%).
If you install the BVES (with BAFA funding), you can produce and sell three times the amount of heat in winter. And the biology remains stable.
Impossible?
No. It works.
And at the same time you reduce costs, because you need fewer feedstocks. And you can use cheaper feedstocks.
For the last year we have only been feeding grass and solid manure. No more maize.
A customer on 10 May 2022
If one of these three topics – or all three – interests you, just give me a call: +49 151 70115170
