Digestate increasingly recognized officially as a fertilizing residual material

While we talk more often about biogas when it comes to anaerobic digestion considering the obvious lure that emanates from its energy potential, the other output generated by the process, namely digestate, must not be overlooked. To allow a quick comparison, digestate obtained from the anaerobic digestion process is the equivalent of the compost obtained from the composting process. In the anaerobic digestion process, digestate stays at the bottom of the digester tank while biogas, because of its much lower density, accumulates from the top. It is very encouraging to note that on both sides of the Atlantic, the biogas industry can rejoice to see the digestate increasingly recognized officially as a fertilizing residual material (FRM).

Digestate, obtained in relatively liquid or solid form, is an excellent fertilizing product as it is a substance rich in nutrients for plants. Indeed, nitrogen (N), phosphorus (P) and potassium (K) contained in the digester inputs are all elements that are not present in biogas and thus remain in the digestate. Whereas biogas is extracted from the organic material in the absence of oxygen in the digester, the remaining digestate, which represents between 90% and 95% of the inputs volume, consists of a mixture of these fertilizing elements as well as non-digestible residues and dead microorganisms.

On both sides of the Atlantic

Quebec has recognized the fertilizing virtues of digestate and confirms that there is a market potential for this product as a fertilizer for agriculture. The 2015 Guide of FRMs clarifies the status of digestate as an FRM and has therefore put in place measures to reduce the previously required administrative burden for producers to obtain the acceptance of their digestate to market it for spreading in agriculture. This measure was taken considering the announced construction of several plants according to the Program of treatment of organic matter by anaerobic digestion and composting. While mineral fertilizers accounted for nearly two-thirds of the spreading on agricultural land in Quebec, the use of FRMs is thus expected to grow significantly by 2020 due to the favorable political environment.

The same pattern is happening in Europe where was filed on March 17, 2016, at the European Parliament in Brussels, Belgium, a proposal to amend the European regulation for fertilizing products and make FRMs more freely accessible to the market. Indeed, about half of fertilizers marketed on the European territory are excluded from the current legislative framework, including virtually all fertilizing products from organic materials and processes. This measure will thus greatly facilitate the activities of public and private operators that collect organic residual waste (ORW). They could indeed more easily value their outputs, which would at the same time stimulate investments in infrastructures for the treatment of ORW, including by anaerobic digestion, while promoting the development of new fertilizing products based on ORW.

While climate change will lead to global financial losses of USD 2.5 trillion, amount that could even climb to USD 24 trillion (17% of total financial assets) in the worst case scenario projected according to a study from the London School of Economics, it is important to quickly implement processes, practices and solutions that are more ecologic among the energy and agriculture industries. Thanks to its digestate, anaerobic digestion allows saving energy and reducing fossil resources necessary for the production of synthetic mineral fertilizers based on natural gas. It must also not be forgotten that biogas is an obvious substitute for fossil fuels. It is therefore for these reasons, among others, that anaerobic digestion greatly helps to optimize the global circular economy and to reduce significantly the human carbon footprint in order to achieve the objectives of limitations of global warming.

By Simon Lefebvre | 2016-04-05

Sources:  Biogas-Info.co.uk, Ministry DDELCC of Quebec – Guide FRMs, European Commission (Circular Economy Package: COM(2016) 157 – Proposal for a Regulation), The Guardian, Farmers Weekly (image)