Safe use of organic fertilizer from animal by-products: occurrence of glyceroltriheptanoate (GTH) in different matrices

The Farm to Fork strategy promotes the development of organic farming and discourages the use of artificial fertilizers. The sustainable agricultural system increases the reduction of waste, allows the reuse of by-products and prefers renewable resources for the production of fertilizers. The European Union (EU) Regulation 2019/1009, called the Regulation on Fertilizer Products (FPR), enhances biomass conversion in organic fertilizers through the exploitation of certain animal by-products. High- and medium-risk animal by-products (Category 1 and 2 materials) must not be recycled in the food chain and therefore must be traceable and permanently marked with glyceroltriheptanoate (GTH) to discriminate them from low-risk materials [processed animal proteins (PAPs) and category 3 fat]. The EU regulates the use of category 2 meat and bone meal (MBM) and PAPs for fertilizers’ production which can ensure a proper supply of macro, micronutrients and organic matter. This study aimed to improve fat extraction and to quantify with gas chromatography mass spectrometry (GC–MS) the detectable amount of GTH in organic fertilizer containing MBM, PAPs, and dry manure in different percentages. The following performance parameters were evaluated: fat recovery (%), GTH recovery (%), matrix effect (ME%), linearity range, coefficient of variation (CV%), and repeatability limit (r). This research represents a first evaluation of organic fertilizers produced from MBM, PAPs, and dry manure and its willing to be a starting point for a deeper investigation of a higher number of organic fertilizers produced from different kind of animal by-products’ raw materials according to FPR regulation.