The poultry industry is one of the largest and fastest-growing agro-based industries in the world. At the same time, the growth brings along a number of environmental problems. One of the major environmental problems is the accumulation of large amounts of wastes, e.g. manure. In order to mitigate these problems new economically sustainable technologies are needed.
Manure has often been referred to as a waste or an undesirable by-product of poultry and livestock production. In reality, manure is a valuable source of nutrients, soil amendment, and can be a desirable renewable energy source. Due to an increasing poultry production, the industry generates approximately 2.1 billion tonnes of manure annually worldwide (based FAO statictics). This amount of manure creates a huge and almost untapped feedstock source for biogas.
Poultry manure has a very high biogas potential, which nearly equals to the biogas yield of energy crops (example corn silage). However, currently biogas is only produced in limited quantities from poultry manure. This is mainly caused by a high concentration of nitrogen in the substrate. Nitrogen in the manure is converted into ammonia which inhibits the formation of biogas already in low concentrations. An effective biogas production from poultry manure requires a fermentation technology that can use high portions, up to 100%, of poultry manure.
Ductor® fermentation technology
Ductor Corporation in Finland has been investigating the ammonification of high nitrogen substrates since 2009. First, the aim was to efficiently recycle nitrogen, but it soon became clear that the process would benefit biogas fermentation. The core technology for the ammonification of nitrogen was developed and proved in laboratory in 2011. The pilot plant was built in 2014, and now the company is selling its patented biological nitrogen removal process (NRP) worldwide. The first plants will be built in Germany by the end of summer 2016.
While investigating different options for the ammonification of organic nitrogen, a natural microbial population was detected. The powerful microbial population, which develops under selection pressure, has been patented. This natural, not genetically modified population has been tested with a variety of substrates. Even feathers can be ammonified and liquefied in 14 days. More easily convertible materials require less time, for example poultry manure needs five days. The fermentation step where organic nitrogen is transformed from solid phase into liquid phase ammonia is followed by a stripping step where the ammonia is recovered as ammonium salt, e.g., ammonium sulfate. The NRP process is capable of removing over 60% of the nitrogen from organic waste materials. Because the NRP takes place before biogas production. It enables the utilisation of high-nitrogen containing organic wastes as feedstock. The NRP is good news to the biogas industry that has long suffered from remarkable operational costs. Advantages for existing and new biogas producers include improvements in the economic efficiency, operational stability as well as social and environmental benefits.
If biogas producers in the EU would replace expensive maize silage with inexpensive poultry manure the producers could achieve a 1 billion euros improvement in their profitability and simultaneously cut CO2 emissions by 1.5 million tonnes (own calculation with data from JRC Report EUR 26696, 2014) while releasing more than 811,000 hectares (source: EC IP 10/27 August 2004) of cultivated land for a socially and environmentally sustainable use, such as food production.
Nutrient recycling potential
The ammonium sulfate from the NRP is N-fertilizer as such. For every ton of poultry manure about 80 kg of ammonium sulfate can be produced. This corresponds to 20 kg of ammonium-nitrogen. If the 2.1 billion tonnes of poultry manure were treated by NRP, over 30 million barrels of oil could be saved annually as the Haber-Bosch process uses 3,600 kJ for every kg of ammonia produced. In fact, Haber-Bosch is responsible for about 2% of world’s energy consumption. Additionally, as the digestate from biogas production from poultry manure has a reduced nitrogen phosphorus ratio, its use as fertiliser will become easier as now nitrogen and phosphorus can be applied separately according to the need of the crop. This way, NRP closes the nutrient cycle: nitrogen and phosphorus from field to field. Another advantage of the biogas process is the hygienisation of manure, and the prevention of nutrient leakage into ground or flowing waters.
The role of biogas in a battle against climate change
On 12 December 2015, a climate change agreement was approved in Paris. The international community finally succeeded to agree on binding targets to limit global warming to 2oC (ideally even 1.5oC) by the end of the century. Greenhouse gas (GHG) emissions are one reason for the increase in the atmospheric temperature. Agriculture and livestock are significant sources of greenhouse gas emissions. Biogas production can use agricultural side steams and wastes for the production of renewable, sustainable energy and substitute fossil fuels. By capturing the methane from manure storage, biogas production can protect the atmosphere from substantial emissions of a gas strongly associated with climate change (the GHG effect of methane is about 25 times higher than that of carbon dioxide). The use of biogas will also decrease the use of fossil fuels in an environmentally benign way.