For German dairy farmer Andreas Berling, starting a co-operation with his neighbour in a biogas plant was an alternative to expanding cow numbers. Nevertheless, like several German colleagues last year, he increased the dairy herd but the biogas plant is still a main pillar of the farm.

Andreas (44) operates a family farm, near Frenswegen, on the German-Dutch border with 65 dairy cows, rearing 350 beef bulls on 90ha. Andreas works on the farm every day, while every morning Andreas’s father feeds the cattle and steps in when necessary, as both of their wives do.

The small village of Frenswegen consists of surrounding farms and a monastery more than six centuries old, all owned by a Count.

The nearest farms are situated about 50m from the monastery; the farms themselves are even closer together.

When farmer Jörg Pikkemaat (44), the closest neighbour of the monastery, had plans to expand his farm with a pig barn, his interests and those of the monastery threatened to clash.

Consultation between the farmers, the monastery and the Count resulted in Jörg discontinuing his pig expansion plans. He stopped keeping pigs altogether and, alternatively, decided to build a biogas plant with neighbouring farmer Andreas. Since 2007, they feed the electricity generated from the biogas plant to the grid and release heat to the monastery.

Half of public price

Together, the two farmers invested €1m but the monastery also had oil to biogas conversion costs. A total of €100,000 was paid for the adjustment of the heating system.

The hot water supply from the biogas plant is separated from the central heating system circuit by a heat exchanger. The monastery financed the 600m underground pipeline to and from the biogas plant.

Until this was paid for, the monastery did not have to pay Jörg and Andreas for the heat it consumed.

Two heat meters in the monastery, one on the supply pipe and one on the return pipe, record how much heat has been consumed. In less than five years, the pipeline was paid off. Since then, the monastery pays half of the public consumer gas price. The heating costs of the monastery have dropped closer to €20,000 from an average of around €40,000 previously. The biogas heating project is part of the endeavours of the monastery to work together with the surrounding farms, as it had been doing for centuries, since the monastery was founded in 1394.

Quota too expensive

The biogas plant combines well with the two family farms, according to Andreas. His neighbour, Jörg, has stopped farming livestock altogether. Jörg now farms about 90ha of arable land.

Andreas had a family farm with 40 dairy cows, 350 beef bulls and 90ha of land but, in September 2013, the dairy herd increased to 65 cows, which are now milked by a robot.

The rolling average milk production of the herd is almost 9,500kg milk with 4.1% fat and 3.3% protein. In 2012, Andreas increased the milk quota from 390,000kg to the current rate of 470,000kg. At that time, the price was 3c/kg milk, but the current quota price is 8c/kg.

Andreas says 8c is ‘‘too expensive’’, and at that price he would prefer to pay the quota fine for the production surplus.

After the abolishment of the milk quota in 2015, he hopes to optimise the robotic milk production but has no plans for a second robot yet.

Andreas and Jörg take turns weekly in looking after the biogas plant. “Feeding and controlling the plant takes approximately one hour per day, not counting harvesting the crops, accounting and maintenance.

Andreas said: “Annually, the accounting and maintenance also average one hour per day. However, if a pump fails, you are unable to do anything else that day,” he adds. They keep a log of their work on the plant. If the plant malfunctions, the person on call receives a message on his mobile phone.

Fermentation

From October to March, the plant is fed with maize silage (12t/day), sugar beet (6t/day) and cattle slurry (9.5m3/day). For the rest of the year, sugar beet is substituted with extra maize silage and/or a corn cob mix.

They put the maize silage and sugar beet into a stationary mixer using a telescopic loader. From there, it is fed into the first digester silo by a computer-driven auger. Slurry goes directly into the silo.

Both the primary and secondary fermentation silos have a diameter of 18m, a height of 6m and a capacity of 1,250m3. The fermentation of the silo contents produces methane gas. For maximum efficiency, the substrate from the first silo is transferred to the second silo, or the secondary fermentation silo, explains Andreas.

In both fermentation silos, the temperature is 40oC and the overpressure is one millibar. Both silos are covered by a plastic cover.

The first fermentation produces most of the gas and, also, the highest quality of gas.

V12 cylinder engine

The gas contained in the space above the substrate is extracted from both the silos via the same pipeline and mixed. It is cooled down in an 80m long underground pipe. Then it serves as fuel for a V12-cylinder engine, which drives a power generator. Last year, after 60.000 running hours, the engine was overhauled, at costs of €50.000 (excluding VAT). The cost of a new engine would have been €130,000. The electricity generated is fed to the grid at 10,000 volts. The engine and generator are housed in a separate small building.

Bonuses

The German government is stimulating the use of renewable energy, which includes biogas. There is no direct subsidy on the capital investment, but the price of energy produced is subsidised. Before building the biogas plant, the investor signs a contract with a regional energy supplier, in this case RWE, for a fixed price for part of the electricity delivered to the grid, spanning a term of 20 years.

The regional energy supplier pays the possible price difference between the electricity purchased from biogas plants and sold to other consumers out of a surcharge on the electricity supplied to all users.

Andreas explains that the biogas plant has a capacity of 350kW of electric and 400kW of thermal power. The basic price of the electricity fed to the grid is a little more than 8c/kWh. Because they only use unprocessed vegetable feedstock, they receive an additional amount of 7c/kWh.

Utilising the heat for a building, in this case for two houses and the monastery, gives them an extra bonus of 2c/kWh. In addition, they receive a bonus of about 2c/kWh as more than 30% of the raw material in the biogas plant consists of manure. This brings the total fixed yield of the electricity to 19.9c/kWh.

Had the capacity of the plant been less than 150kWh, the amount would even have been 4c/kWh higher.

In addition to the fixed yield, part of the heat produced by the biogas installation is sold to the monastery; last year, this was 40% of the produced heat. For this, the monastery paid €21,600.

The total investment in the plant, including the two bunker silos for silage maize, amounts to €1m. Both bunker silos are 70m long, 17m wide, with sides of 2.5m and, last year, were filled to a height of 6m.

Maize price & return

The economic efficiency of the biogas plant depends on the price received for the power supplied which has, in part, been guaranteed for 20 years, although some of the bonuses have not, and particularly on the price of raw material, according to Andreas.

Annually, about 6,000t of silage maize (product) is required for 120ha. Depending on the yield and the amount required for his animals, Andreas is able to supply about 30ha to 40ha of silage maize annually. His partner Jörg supplies 70ha annually. Both also grow 10ha of sugar beet.

The harvesting of maize and sugar beet is in the hands of a contractor. Harvesting maize is done at 30% dry matter. “The maize in the bunker silos must be so dry that it produces no silage effluent, as this would cause energy loss.”

Annually, the partnership purchases 20ha to 30ha of maize from farmers in the area.

Last year, the price of silage maize was €30/t, with 30% dry matter. In 2012, this was €34, in 2011 €32, exclusive of VAT and harvest costs. In the last 10 years, the average hectare supplied 50t to 55t, which would make the price for a hectare of maize at €1,700/ha.

Five years ago, this was about €800/ha. Maize price, as well as the price of land, has increased because of the number of biogas plants in the area.

The average lease price is €1,000 to €1,200 per hectare but for bigger pieces of land, €1,400 is paid.

Andreas said: “When we invested in the plant, biogas was much more profitable than dairy or beef cattle. Now, it is obvious that biogas is only one pillar of the farm. Some people say that we are milking biogas. We will continue to milk cows also.”

Feeding a biogas plant is similar to feeding cows, according to Andreas. “The norm for a plant like this is that the engine runs 8,300 hours per annum, 8,000 hours at full capacity. In the third year, our engine ran only 7,800 hours.

‘‘We had overfed the bacteria causing the contents of the silos to get too acidic, which resulted in the bacteria producing less gas. “The idea is for the substrate to have a pH of 7.5 to 8.0. The run time of the continuous process is 110 days. After the second fermentation, the substrate is pumped to a covered silo with a capacity of 3,000m3. Most is used on Andreas and Jörg’s land; the surplus is spread on the land of neighbouring farmers.