Biogas: Prospects despite diffi­cult times

Biogas and its uses account for around 10% of all agri­cul­tural sales in Germany. This energy revo­lu­tion has economic heft and offers an impor­tant oppor­tu­nity for agri­cul­tural busi­nesses and rural areas. But with exper­tise and produc­tion methods varying – how is it working in prac­tice?

When the maize harvest gets under way, things get busy at Gut Ruten­stein farm, with large machines in constant oper­a­tion, oper­ating along­side the farm’s biogas plant. The estate harvests the maize kernels and crushes them before storing in silos. “We’ve had great success in doing this for a number of years,” explains Mr von der Decken. “Using this method, we get a concen­trated feed that can replace conven­tional purchased concen­trates, which are often imported from over­seas, and need to be dried else­where using an energy-inten­sive process.”

This corn­meal is fed to the farm’s 500 dairy cows – an enter­prise taken on a few years ago. And the company’s biogas plant, with 500 kW elec­tric power and double flex power output, is fed with its self-produced concen­trated feed, in addi­tion to corn and grass silage, dried chicken drop­pings, pig and cattle manure.

Since the biogas plant began oper­ating in 2012, the elec­tricity gener­ated has been fed into the northern Lower Saxony grid. The plant also produces suffi­cient heat to supply the neigh­bouring educa­tional centre, retire­ment home, country store, and 17 indi­vidual houses, including the brick build Ruten­stein Castle. The biogas plant is only around 5km away from the decom­mis­sioned Brokdorf Nuclear Power Plant, which is located on the other side of the Elbe, on the north side of Schleswig-Holstein.

At the Gut Ruten­stein farm, the maize kernels are crushed before being poured into silos in order to increase the energy yield.

The crop gets processed.

The busy activity of the biogas plant against the inac­tivity of the nuclear power plant embodies the energy course taken by the Federal Republic of Germany in the past two decades – away from nuclear power, away from fossil fuels, and towards renew­able ener­gies.

To a large extent, Mr von der Decken is well estab­lished in the renew­able ener­gies sector, not only having built the biogas plant, but also with the construc­tion of wind turbines on his own premises, and solar photo­voltaics on top of court­yard build­ings. “Of course, every successful farm must constantly deal with energy issues,” he empha­sises. On his farm he grows wheat, barley, oats, oilseed rape, maize, field beans, sugar beet, and grass on 500ha.

Every successful farm must constantly deal with energy issues.

Herwart von der Decken

Despite the energy price crisis, the busi­nessman, now in his mid-forties, says he doesn’t worry about the scare­mon­gering going on at the moment. “The price hikes are a factor, no ques­tion. However, they are some­what over­rated. “If the price of diesel per litre rises from €1.20 to €1.70, that will end up being only €50/ha. Ulti­mately, that is not a deci­sive cost, it is much more impor­tant that I get good harvests and do the agri­cul­tural work that I have to do,” he says.

Biogas industry

By far, the majority of the esti­mated 10,000 biogas plants in Germany are oper­ated by agri­cul­tural busi­nesses like to one in Freiburg an der Elbe. Overall, agri­cul­tural biogas oper­a­tions in German gener­ates gross sales of €5bn to €6bn, with energy crop inputs of around 2m ha comprising mainly maize, but also grass, sugar beet, clover grass, hybrid silphium, flow­ering mixtures, and fruit. According to industry experts’ esti­mates, the propor­tion of manure and slurry being fermented in biogas plants is currently around 25-30%.

And so, with regard to the pending require­ments for reducing emis­sions in agri­cul­ture, there is still great poten­tial to achieve ambi­tious climate protec­tion goals, with a further increase in use of liquid and dry manure. Further devel­op­ment in the biogas process is also possible, with options to sepa­rate the carbon dioxide contained in the biogas – biolog­i­cally or tech­ni­cally – and convert it to methane, in combi­na­tion with hydrogen. How quickly this option will be put into prac­tice on farm is not yet clear.

Stadtwerke Greves­mühlen GmbH, in co-oper­a­tion with neigh­bouring farmers, oper­ates two biogas plants, which provide elec­tricity and heat for the resi­dents of the small town in North-Western Meck­len­burg, Photo: Andreas Birres­born

It is also diffi­cult to esti­mate whether the direct injec­tion of biomethane into the gas grid, or for supply at filling stations, will increase signif­i­cantly in times of gas short­ages. So far, biomethane has accounted for only around 1% of Germany’s gas require­ments. Theo­ret­i­cally, this propor­tion could increase signif­i­cantly if the vast majority of biogas plants oper­ating today were to produce gas instead of elec­tricity and heat. However, such a change cannot be made overnight. Currently, biogas elec­tricity is extremely impor­tant for a stable elec­tricity grid because it can close the gener­a­tion gaps, even in the so-called dark times when the sun is not shining, and the wind is not blowing.

In order to cover this demand, which skyrockets during peak loads, many biogas plants have been equipped with addi­tional capacity, so that, depending on market require­ments, they could increase the power output two, three or even four-fold. For compa­nies that have invested in this so-called flex­i­bility in recent years, a sudden switch to methane feed-in is, under­stand­ably, not possible.

Biogas plant on the West coast of Schleswig-Holstein

Impor­tant contri­bu­tion to Germany’s energy supply

In late autumn, a note from the Federal Network Agency showed the impor­tance of biogas, and bioen­ergy as a whole, for Germany’s power supply in the energy tran­si­tion period. It reported that, on the grey and almost wind­less 29th of November, elec­tricity gener­a­tion from biomass was even higher than that from wind, and far ahead of that of solar photo­voltaics. In fact, according to industry insiders, there is now a defi­nite demand for biogas on the energy market. Espe­cially for the sort of biogas which is consid­ered to be partic­u­larly sustain­able within the Euro­pean biomass strategy – those coming from waste, liquid and solid manure, or organic farming, and offers great economic oppor­tu­ni­ties.

Someone like Lothar Braun-Keller, one of the few in the Bioland Asso­ci­a­tion who relies on biogas produc­tion, is of course happy to hear this. He esti­mates that there are around 180 plants in Germany that do not produce “agro-biogas”, as he puts it, but rather “eco-biogas”. But whichever gas is used, in the end “no one likes us grubby urchins, the ones that have anything to do with biogas,” says Mr Braun-Keller with a smile. And he remarks that he is not worried about this bad image, he can live with it.

In oper­a­tion since 1996, when his first biogas plant was installed with a capacity of 45kW on his farm in Leib­ertingen on the Swabian Jura, the system has grown. Today, with a flex­ible oper­a­tion, his plant produces 860kW. In addi­tion, there are also large solar photo­voltaics on farm build­ings, which help cover a large part of the farm’s own needs.

Lothar Braun-Keller produces biogas on his farm using flex­ible oper­a­tions, and gener­ates elec­tricity using photo­voltaic systems.

At the same time, the biogas plant on the farm supplies two local heating networks, oper­ated by the munic­i­pality of Leib­ertingen, with a satel­lite co-gener­a­tion unit. During the summer, Mr Braun-Keller also offers contract drying for neigh­bouring farmers. The fermenters are fed a total of 13,000t/year, with 64% of total input coming from grass and clover, 35% from cattle manure, and the rest made up of mixed silphium – about 2.5ha, comprising 0.6% of the total substrate.

I consider the posi­tive effect of biogas on agri­cul­ture as a whole.

Lothar Braun-Keller

Mr Braun-Keller is defi­nitely not complaining, because the inte­grated biogas plant on his farm, which he runs with five full-time employees and 10 other employees on a €450 per month basis, has proven its worth. Despite green energy produc­tion, he is, first and fore­most a farmer. “I consider the posi­tive effect of biogas on agri­cul­ture as a whole,” he adds. He believes that biogas produc­tion should serve agri­cul­ture without any compro­mises – which clearly is being done at the Leiper­tingen site.

“Our humus-poor, calcareous soils in the Swabian Jura benefit from the nitrogen-rich fermen­ta­tion residues. Without being able to precisely define the humus content at present, we simply find that our yields, in a diverse crop rota­tion, are higher than before – despite the drought that we have expe­ri­enced here in recent years,” Mr Keller-Braun states with satis­fac­tion. He believes that 9,000mW of elec­trical output from sustain­ably produced biogas to be achiev­able; the methane equiv­a­lent of this could help cover a large part of the previous gas imports. That’s a good outlook.

Biogas in Germany

There are around 10,000 biogas plants in Germany. The vast majority of these are run by farms. The installed capacity ranges from less than 100kW (slurry) small systems to multi-megawatt (MW) satel­lite co-gener­a­tion units. All in all, the German biogas industry has an output of almost 4,000mW, and almost 2,000mW of flex­ible capacity. The waste heat produced during power gener­a­tion can supply the equiv­a­lent of 1.1m house­holds with suffi­cient heat, and many villages throughout Germany are already bene­fiting from this. In addi­tion, a small propor­tion of the biogas plants, around 250, feed methane directly into the gas grid; the carbon dioxide contained in the biogas is sepa­rated using so-called metha­na­tion. This sepa­rated CO2 is not yet being used, but that will soon change because more methane can be produced from it by using hydrogen. The beverage industry is also inter­ested in this valu­able raw mate­rial.

The first bio-LNG plants are currently being built in Germany, like in Darchau in the east­ern­most tip of Lower Saxony, where biomethane is used to produce sustain­able fuel.