digestaatti

Digestaatti, or digestate, is the material left after anaerobic digestion of organic matter in biogas plants. It is a nutrient-rich slurry consisting of both liquid and solid fractions that remains after the production of biogas from feedstock such as livestock manure, agricultural residues, food waste, and energy crops. Digestate is typically produced continuously in biogas systems and may be stored, treated, or separated to create distinct liquid and solid streams.

Two common forms are liquid digestate, which is high in dissolved nutrients such as ammonium, and solid digestate, which contains more organic matter and particulate nutrients. Mechanical separation, centrifugation, or filtration is often used to obtain these fractions. Depending on the process and feedstock, digestate can be stabilized to reduce odors and pathogens; some plants also dry or pelletize the material for easier handling and transport.

Digestate can be used as a fertilizer or soil conditioner in agriculture and land restoration. It supplies nitrogen, phosphorus, potassium, and other micronutrients, while contributing organic matter that can improve soil structure and water retention. The specific agronomic value depends on the feedstock and the digestion conditions, as well as on post-treatment.

Regulatory and environmental considerations include limits on nutrient content and contaminants, requirements for storage and land application, and measures to minimize odors and nutrient losses. Pathogen reduction is influenced by digestion temperatures and residence time. When properly produced and managed, digestate supports nutrient recycling and the circular economy as an alternative to conventional fertilisers.