Characterisation of sludge produced by the agri-food industry and recycling options for its agricultural uses in a typical Mediterranean area, the Segura River basin (Spain).

Agri-food sludge is both an environmental and economic problem, since companies must bear the costs of proper management as required by current disposal regulations. The aim of this work was to quantify the sludges in a typical Mediterranean area like the Segura River basin in Spain, which has a high concentration of agri-food businesses and intensive farming operations. Ultimately, we wanted to offer options for converting this "waste" into a "resource." The agri-food companies studied were classified according to their final product: juices, frozen vegetables or canned products. The total volume of sludge ranged between 12,895 and 22,520 tonnes per year, with an average cost of around 350,000 euros. In characterising the agri-food sludges, we identified a high organic load and nutrient content. Besides, the heavy metal levels were well below those legally permitted in sewage sludge, fertilisers or similar products for agricultural use. Furthermore, we only detected pesticide residues occasionally, and we did not detect Salmonella spp. or Listeria monocytogenes in the samples analysed. E. coli was only found in about 20% of the samples. This paper identifies the most suitable technologies for the specific agri-food industries in the area, which are surrounded by intensive agriculture operations. We have analysed direct soil application, sludge drying, composting and the use of anaerobic digestion to produce energy and have shown the main advantages and disadvantages of each. We found that composting and its advanced modifications for making tailored composts are among the most adequate strategies for obtaining organic amendments.

Agroindustrial composts to reduce the use of peat and fungicides in the cultivation of muskmelon seedlings.

BACKGROUND: Environmental concerns about peat extraction in wetland ecosystems have increased. Therefore, there is an international effort to evaluate alternative organic substrates for the partial substitution of peat. The aim of this work was to use different composts (C1-C10) obtained from the fruit and vegetable processing industry (pepper, carrot, broccoli, orange, artichoke residues, sewage sludge (citric and pepper) and vineyard pruning wastes) to produce added-value composts as growing media with suppressive effect against Fusarium oxysporum f.sp. melonis (FOM) in muskmelon. RESULTS: Composts showed values of water-soluble carbon fractions and dehydrogenase activity that allowed them to be considered mature and stabilized. All compost treatments produced significantly (F = 7.382; P < 0.05) higher fresh shoot weight than peat, treatment T-C2 showing the highest values. Treatments T-C5, T-C7 and T-C8 showed percentages of disease incidence that were significantly (F = 16.052; P < 0.05) the lowest, relative to peat, followed by T-C6, T-C10, T-C1 and T-C9 with values below 50%. CONCLUSION: Composts produced are suitable components of mixed compost-peat growing media, providing a 50% substitution of peat. Furthermore, some of these composts also showed an added value as a suppressive organic medium against Fusarium wilt in muskmelon seedling, a fact probably related to high pH and pepper wastes and high content of pruning waste as initial raw materials. © 2016 Society of Chemical Industry.