Wednesday, April 25, 2012

Chicken Barn with Heat from Anaerobic Digestion Plant is More Profitable Than Increasing Dairy Herd

At Bernd Mueller’s farm in Bockhorn, North West Germany, his investment in a new chicken barn would normally set him back with a €15,000 annual heating bill, but thanks to the efficiency of his biogas plant, this expenditure will be zero. What is even better is the fact that his 40,000 chickens will provide him with the manure he’ll mix with maize to produce and sell 725kW per hour of renewable energy produced every day.

This is all a far cry from just five years ago when Bernd was considering whether to expand his dairy cattle herd in order to try and make his farm more profitable.

“Buying more cows just didn’t compare to the potential I could see in biogas,” said Bernd.

“It has taken some time to go through the planning stages and fine-tune everything, but it has all been very worth it”.

Bernd Muller checks that all is well with his biogas process
Initially, Bernd used only maize as his feedstock, but now finds that a combination of 90% maize and 10% chicken manure produces much more gas. This increased biogas production which can be viewed at a glance via the monitoring system on his computer screen.

Now at this point, those that have some knowledge of the AD process will be slightly puzzled, as chicken manure would be unlikely to raise the gas production rate very much, given that it has a fairly low biogas potential compared with maize. Well, you would be right about that, and the reason for the increase is also down to efficient mixing getting the most out of the new manure feed.

Landia’s mixers help boost farmer’s biogas

Look a bit deeper into the biogas production rate and you will find out that at the heart of the biogas operation are three Landia PowerMix side entry mixers, positioned at the bottom, middle and top of the 21m diameter, 9.8m high digester.

Utilizing recirculated liquid from the continuous process with a total of 37 tonnes of maize and three tonnes of chicken manure per day, Bernd produces electricity for use on the farm, with ample left-over to sell to Germany’s national energy grid.  His fully automated system can also pass heat on to neighbours and maintain digester temperatures when necessary in winter, as well as service the new chicken barn, and a further one planned.

“Good mixing is essential to the reliability and productivity of my biogas system,” says Bernd.

“Landia’s mixers do an excellent job and haven’t given me any problems at all”, he added.

Maize for Bernd Muller's biogas plant 
It also hasn’t escaped Bernd’s attention that the Landia mixers minimise energy consumption.  Landia explains that, correctly sized mixing system allows adjustment of mixing operation times to types and quantities of feedstock, dry matter content and gas production. High methane percentage not only depends on the feedstock mix but very much on good mixing. It is the most essential tool for mechanical process optimization in the digester and can be controlled by the biogas plant’s monitoring system.

Trends are duly noted through the monitoring system probes, and should any of the monitored parameters look set to adversely affect the process, an alarm is raised.  It is also important to ensure that the gas the plant produces is at all times cleaned, and then cooled from 41 degrees to 8 degrees, before it enters the big 12 cylinder DEUTZ engine (which is connected to the electrical turbine).

In addition to all the benefits from their biogas plant, the farm also gains a greatly enhanced digestate product for use as a fertilizer – a proportion of which is sold on.

In addition, the entire process is virtually odour-free.

Efficiency is, as reported by Landia, evidently extremely high at Bernd’s farm.  Last year a 97% electricity production time rate was recorded, with just 3% of output lost during engine maintenance.  They are currently receiving a fixed price for electricity, and that regular income clearly helps with budgeting. Bernd’s profits have the potential to rise even further, Landia report, if the farm management reduces the balance of maize which is bought-in, by growing more themselves. Currently, only 40% is produced on the farm against the 60% balance which is bought from other farms.

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