The importance of organic fertilisers in an ever-changing circular economy | Henning Lyngsø Foged

Organic fertilisers may be produced locally, from local waste whose disposal would otherwise represent costs, environmental pollution and greenhouse gas emissions. Organic fertilisers thus turn a costly and a harmful material into a resource. Furthermore, the use of organic fertilisers can reduce the costs and dependency of imported chemical fertilisers, whose production entails a high use of fossil energy. At present, due to the conflict in Europe, fossil-based energy is 3-4 times more costly than in the recent past due to the use of energy as a political weapon.

Organic fertilisers thus have wider perspectives as they deal with resilience, independence and self-sufficiency of Malta’s economy. The use of fertilisers for crop production may be a small part of the economy in Malta, but a switch from chemical to organic fertilisers is very relevant to start addressing environmental, climatic and economic considerations on a national scale.

Organic fertilisers are made from livestock manure and other organic material, such as plant residues from the processing of vegetables. Malta is characterised by having a high livestock density, compared to the rest of the EU. In Malta, livestock production represents, according to Eurostat, more than 203kg nitrogen per hectare , and is therefore well above the limit of 170kg nitrogen in livestock manure per hectare. The 170kg of nitrogen is given by the EU’s Nitrates Directive as a safeguard for the quality of drinking water, set to maximally 50mg nitrate per litre.

The 203kg of nitrogen per hectare per year is sufficient for economic crop production in many cases, even for growing two crops per year. Malta’s Nitrates Action Programme Regulations (S.L.549.66) is for instance recommending cabbage to be fertilised with 110kg nitrogen per hectare and carrots with 90kg nitrogen per hectare. Despite this, Malta imports about 586 tonnes of nitrogen per year in chemical fertilisers , equal to about 54kg of nitrogen per hectare of cultivated area. In this context, Eurostat has calculated that the annual nutrient balance in Malta is 145kg of nitrogen and 29kg of phosphorus. This balance equates to that part of the fertilisers that is lost in the environment as pollution.

To reduce Malta’s farming polluting potential and to make the situation more sustainable, the solution is to switch to the use of livestock manure as a crop fertiliser rather than dumping valuable livestock manure into the sewer system for treatment. These practices come at a very high cost to the national economy, and which anyway lead to further pollution of air and water. Livestock manure can, according to EU policies alone, be used for one thing, namely as fertiliser for crops.      

The complex problem outlined above is the background for the SYNECO project (https://www.synecomalta.com). SYNECO will promote the process to switch to a more effective use of livestock manure as crop fertiliser and reduce chemical fertiliser imports. Anaerobic digestion will initially recover energy from the manure. One ton of slurry/manure contains the same amount of energy in the form of biogas as about 15-30 litres of oil or diesel. If the biogas is converted to electricity alone, about 40% of the energy is captured as electricity, meaning about 60-120kWh per ton of slurry/manure. Additionally, the heat production in the process can be used for various purposes. One dairy cow represents an annual production of about 25 tonnes of slurry/manure, and one slaughtered pig about half a ton of slurry/manure. A positive side effect of the anaerobic digestion is that the nitrogen and phosphorus nutrients in the digestate is more plant available than that of the raw manure.

After the anaerobic digestion, SYNECO will further process the digestate into fractions that are easily used as crop fertilisers. Despite the short distances in Malta, transport is a challenge and it is important that the manure is treated close to where it is generated. Additionally, the resulting organic fertiliser should be spread on the fields by use of conventional farming machinery without causing odour and other nuisances for people living within close proximity.

SYNECO is a project of the Farmers Central Cooperative Society Ltd (FCCS), the largest fruit and vegetable farmers’ cooperative in Malta. It is a pilot project financed by the European Union (Rural Development Programme for Malta 2014-2020) to recycle manure nutrients for fertilising.

The author is an agronomist with extensive expertise relating to aspects of livestock manure, including policies, fertilising, economy, and processing gained via numerous European research, innovation and development projects. The author developed CropManager (https://www.cropmanager.eu), which is an online software for crop and nutrient management, including manure accounting and nutrient budgeting. The author is involved in the SYNECO project to train farmers to switch from chemical fertilisers to local resources of organic fertilisers to reduce impacts on the climate, environment and the farm economy. The author is the founder of the Organe Institute ApS, Denmark.