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Energy Materials

16: Electrical energy from animal dung

Problem:

As all transport transitions to electric propulsion, the increase in the demand for electrical energy will call on a diversity of sources.

Solution:

Anaerobic digesters that convert the dung of horses, cattle, pigs and other livestock to electricity.

Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen and create and capture biogas – a flammable fuel with high methane content which  can be used to run turbines and create electricity.

In the Fall of 1998 two ex-Aachen University students from farming families, Hendrik Becker and Jörg Meyer zu Strohe, built an anaerobic digester at a prototype biogas plant feed facility in Münsterland, north-west Westfalen.

Unlike other biogas technology, their innovative solids injection process can operate using  100 percent manure or manure mixed with difficult to process substrates such as straw and grass.

They started a company, PlanET, to manufacture their green dome-shape digesters for use in rural areas.

During the past two decades, PlanET has sold and implemented nearly 480 biogas plants of between 40 kW and several MW to France, the UK, the USA and Canada.

The total electric power of PlanET installations currently in operation is 142,000 kWel. The plant also processes other waste such as that of cereal farmers (the unusable part of the harvest).

Finland

In 2015, Finland’s state energy company, Fortum, led by Anssi Paalanen, also looked at anaerobic digesters as a fuel source and began trials at Lake Järvenpää, gathering raw materials from four stables from Espoo and Kirkkonummi for their units.

They found that the manure and bedding of three horses could provide heat and light for a single-family Finnish home in a colder climate.

Finland has 70,000 horses, enough to provide heat and electricity for up to 23,000 homes. Fortum began with a small plant, with the manure forming just 10% of the wood-shaving mix used for burning.

By autumn, with more stables taking part, the manure proportion was raised to 20%. The number of horses in society is increasing.

According to Statistics Sweden, there are more than 360,000 horses in Sweden, of which three-quarters are situated in urban or near-urban environments. With a dry matter manure content of 40%, this equates to a quantity of 1,500 tons (1,360 tonnes) of horse manure per annum and corresponds to an annual biogas production of 641 GWh.

In 2016, Finland banned the disposal of manure in landfill sites, along with many other organic, biodegradable materials. This meant that stables risked being stuck with a pile of ordure they could not shift.

The manure can be given to farmers for use as fertilizer, but in the EU this is now permitted only on flat fields because of the risk that exists on sloping fields that the manure will leach into water courses. Flat fields are still fair game for muck-spreaders, but the E.U. bans the strewing of horse manure on any sloping site, as a sensible precaution against equine faeces leaching into the water system.

This means that Finland’s manure does not have many places to go, making the manure biomass plan a double win. The Fortum solution, which they called quite simply “HorsePower”, seemed the most logical.

From August 2017, Fortum set up a pilot project in Bergslagen, southern Sweden, requesting manure from the 400-500 horses in the region, the electricity produced going to households in the town of Hällefors.

Fortum was looking for local suppliers and asked that there are at least 10-20 horses in the stable in order to cover transport costs. By the end of the year 3,000 horses were producing energy.

If Fortum could process the manure mix from 280,000 of Sweden’s horses it would be enough to heat all of the houses in Östergötland and Gotland.

Following the 2017 FEI European Equestrian Championships held in the city of Gothenburg in August, Renova, the municipal waste management, created around 360 000 kWh of district heating and 60 000 kWh of electricity, from the estimated 330 tons (300 tonnes) of horse manure and straw left by the 600 horses participating in the competition.

Two months later, Finland’s Horse Show in Helsinki Ice Hall followed suit. During the event, HorsePower delivered wood-based bedding for the 250 or so horses that stayed in temporary stalls, their dung at Fortum’s Järvenpää power plant anaerobically generating 140 kW to meet all of the electricity needs of the event from lighting to scoreboards to support infrastructure. (fortum.com)

According to a report compiled in 2006 by the Food and Agriculture Organization of the United Nations (FAOSTAT), there are an estimated 58 million horses in the world.

In terms of HorsePower potential, one is therefore talking about gigawatts of electricity. If the manure of the world’s horse population were put to work, this would provide electricity for 19.5 million homes or two New York cities, not to mention electric vehicles.

At the beginning of 2016, the global number of four-wheeled electric vehicles in use came to around 13 million units: 6.18 million electrified power trains will be produced by 2020. This does not take in the hundreds of millions of two- and three-wheeled vehicles, particularly in China.

With such a demand for electrical energy, it is inevitable that horse manure – not to mention manure from cattle, pigs and other livestock – will play its part alongside other sustainable energy sources.

Discover solution 17: the new antibiotics.

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