Nutrients and Plant Hormones in Anaerobic Digestates

Anaerobic digestion (AD) provides a versatile technology platform for reducing organic agricultural waste and energy utilization. Digestate, which is typically a mixture of liquid and solid material, remains a by-product of the AD process. The benefits of soil application of digestates include improvement in seedling growth, crop yield, and fruit and vegetable quality, as well as an increase in insect and disease resistance. This chapter presents studies assessing changes in nutrient and plant hormone availability in digestate. It discusses the use of digestate for stimulating seedling germination and interactions with soil. After solid-liquid separation, digestate can be found in two forms, differing in nutrient compositions and in physical and chemical properties. Digestates contain high levels of nitrogen, phosphorus, and potassium in the bioavailable form; hence, they have the potential to replace mineral fertilizers. Though digestates provide nutrients and organic matter to the soil, their application may potentially affect soil microbial activity.