Biogas is the circular economy's first great opportunity
- Published: Wednesday, 13 April 2016 08:36
No plant can grow without phosphorus, and the world's phosphorus mines will be emptied within the foreseeable future. It is thus nothing short of essential that we work on achieving a circular economy, where nutrients are maintained in the cycle. The EU commission has come up with an action plan that is aimed at making it easier for biogas plants to undertake this important task.
When cows are fed, and when industry manufactures food and other products based on organic material, the nutrients come from the ground where the plants have grown.
So once we have drunk the milk, eaten the beef and used the organic products, it is therefore important to maintain the nutrients in this cycle. That is, to get them recirculated into the ground as nutrients for new plants, which can then also become cattle feed, cheese, hamburgers and popcorn.
"Not least, this applies to the nutrient phosphorus, which is not a renewable resource. Today, phosphorus is excavated in large quantities by mines in Morocco and China, as well as other countries. A number of international research groups have warned that these mines will be exhausted during this century. It is therefore important that we work on recycling phosphorus as much as possible," explains sales manager Michael Kjølner Hansen from Xergi.
Large amounts of phosphorus and nitrogen are currently discharged into the sea all over the world. This makes it very difficult to reuse the phosphorus, which also causes problems for the marine environment. So there are many benefits to retaining the nutrients in a cycle, and this is something that biogas plants are very good at doing.
Recirculates more than 2,000 tonnes of nutrients
Each time a biogas plant is built, the circular economy breaks new ground. For example at Bogense in North Funen in Denmark, where NGF Nature Energy inaugurated a new biogas plant on 29 January 2016, which was supplied by Xergi.
Each year some 250,000 tonnes of liquid manure, 34,000 tonnes of food waste and 42,000 tonnes of deep litter and energy crops will be transformed into a fertiliser, which will kick start agricultural growth on Funen's fields.
When the plant is up at full rotation, it will recirculate approx. 1,300 tonnes of nitrogen, 250 tonnes of phosphorus and 950 tonnes of potassium each year. This according to figures calculated by Xergi as the basis for approving the plant. During the process, the plant produces 10 million cubic metres of biomethane, which is pumped directly into the natural gas grid, thereby making Danish gas consumption greener.
Exploiting local resources
The biogas plant's treatment of both slurry and solid mass means that the nutrients in the livestock manure are easier for the crops to receive, so the region's livestock manure becomes more optimally exploited. It also gives the plant the opportunity to exploit the nutrients in food waste, which would otherwise be burned away.
Overall this means that farmers in the region can reduce their use of imported artificial fertiliser and instead make better use of local resources.
This is the case for farmer Lau Hvid Hansen, who primarily grows crops on his property. As a crop farmer, he needs more fertiliser than his herd of pigs can produce, which is why he has grown accustomed to importing artificial fertiliser each year.
Now part of the artificial fertiliser can be replaced by biofertiliser from the biogas plant, which helps redistribute the fertiliser from the livestock production, where there is too much manure, to crop growers, who do not have enough.
"The quality of the fertiliser is crucial for me as a crop grower. The fertiliser must be uniform each time, and it must be easy for the plants to receive the nutrients in the fertiliser. The biogas plant supplies a fertiliser with all the right qualities," says Lau Hvid Hansen.
When it is easy for the plants to receive the nutrients, then this also means a reduction in the leaching of nutrients into the aquatic environment, he emphasises.
It is good for the aquatic environment, and also means that we avoid any of the valuable phosphorus disappearing out to sea. It will be very hard to retrieve from the oceans, once phosphorus reserves become scarce.
The EU will promote the recirculation of nutrients
When a biogas plant like the one in Northern Funen is taken into use, some of the need to extract more phosphorus from mining is removed. It also reduces the demand for chemically produced nitrogen, which requires a large consumption of natural gas.
This is the background for the decision by the EU Commission in its action plan for a circular economy to get started on a proposal for a revision of the Fertilisers Regulation from the start of 2016 with the aim of promoting the recirculation of nutrients from waste.
Many European biogas plants have been attempting to recirculate an ever-growing amount of nutrients for over 30 years. The biogas plants are thus the circular economy's first great opportunity.
"It has been a long, tough process, and the European politicians can learn a lot from the development that the biogas industry has undergone. It offers plenty of inspiration for how one can promote an economy that optimises the environment. Politicians continue to have a large task ahead of them in removing barriers and strengthening the development. We naturally hope that the action plan for a circular economy will be an important step in the right direction," says Xergi's CEO Jørgen Ballermann.
Read more about the EU's strategy for a circular economy:
European phosphorus platform:
International expertise on phosphorus: