Digesteinä

Digesteinä, or digestates, are the nutrient-rich residues that remain after the anaerobic digestion of organic matter in biogas plants. They accompany biogas production and represent the main fertilizer-like product of the process. Digestates can come from a range of feedstocks, including farm manure and slurry, agricultural and food waste, and sewage sludge.

Production and composition. Digestates are typically slurry or liquid, and many facilities separate them into liquid and solid fractions. The liquid fraction is often used for fertigation, while the solids can be further processed into compost or used as soil conditioner. Their composition includes plant-available nutrients such as nitrogen (ammonium), phosphorus (as phosphate), and potassium, along with organic matter, moisture, and a microbial community. Nutrient content and stability depend on the input material and digestion conditions; pathogen reduction is common but not guaranteed without additional hygienisation steps.

Uses and management. Digestates are applied to agricultural land or used in horticulture as a source of nutrients and soil amendment. Application rates and timing are guided by nutrient management plans and agronomic needs, with care taken to avoid over-application, runoff, or leaching. Solid fractions may be further treated or used as a soil conditioner or component of compost.

Environmental and regulatory aspects. Using digestates supports nutrient recycling and can reduce reliance on synthetic fertilizers, while capturing methane during digestion lowers greenhouse gas emissions. Potential concerns include contaminants such as heavy metals or pharmaceutical residues, and the risk of odour, odor, or groundwater impact if mismanaged. Regulation typically addresses storage, handling, labeling, contaminant limits, and land-application standards within national or regional fertilizer and waste frameworks.