Possibilities and Limitations of Anaerobic Co-Digestion of Animal Manure—A Critical Review

Abstract

Anaerobic digestion is a well-known and long-used biological method for stabilizing organic materials. Among the benefits of this process in waste management are the reduction of greenhouse gases, the production of alternative energy, and the acquisition of valuable digestate that can be used in the form of biogas, thereby closing the cycle of elements in nature. For some materials, such as manure, which is heterogeneous in terms of morphology and chemical composition, digestion of a single substrate may not be very efficient. Therefore, more and more studies on the co-digestion process are appearing in the literature. This solution allows higher biogas production and the possibility of processing several wastes simultaneously. The prospect of the future effective application of anaerobic co-digestion depends on regulations, work regime, and access to raw materials. Therefore, there is a need to systematize the available knowledge and results, as well as to identify the possibilities and limitations of the discussed process, which is undertaken in this paper.

The potential of Nordic microalgae in nutrient removal from anaerobic digestion effluents

“…The higher initial ammonium concentration in CKM might inhibit algal cell growth. One of the major problems in animal manure digestion, particularly poultry manure, is the high nitrogen content (Jasińska et al 2023). The main nitrogen sources in chicken manure are uric acid (around 70%) and undigested proteins (around 30%), resulting from chickens' diet.…”

A Review on the Anaerobic Co-Digestion of Livestock Manures in the Context of Sustainable Waste Management

“…The rapid expansion of livestock production has led to a substantial increase in the volume of livestock manure, estimated at approximately 13 billion tons annually on a global scale. This poses potential environmental hazards if left untreated [2,3]. Comprising a blend of feces, urine, and flush water, livestock manure is inherently biodegradable.…”

Methane Recovery from Cattle Manure: Role of Granular Activated Carbon Amendment into Anaerobic Digestion-Microbial Electrolysis Cells (AD-MECs) Integrated Systems

“…1 The former aims to provide a more balanced feed to AD reactors in terms of the C/N ratio by mixing CM with a carbon-rich feedstock such as agricultural biomass. 3 However, this option may not be feasible due to different constraints such as the price, composition, and accessibility. 3 On the other hand, feed pretreatment, such as microwave and steam explosion, is typically applied to target the lignocellulosic portion of the CM to enhance the hydrolysis step of AD.…”

“…Despite the benefits of AD, biogas generation from CM may end up in low CH 4 yields and slow conversion rates due to the intrinsic characteristics of this highly heterogeneous material, such as low C/N ratio and high lignocellulosic content. , Therefore, researchers work on strategies to boost AD performance of CM, and the two most commonly applied traditional methods for increasing the performance of CM-fed AD systems are co-digestion and feed pretreatment . The former aims to provide a more balanced feed to AD reactors in terms of the C/N ratio by mixing CM with a carbon-rich feedstock such as agricultural biomass . However, this option may not be feasible due to different constraints such as the price, composition, and accessibility .…”

“…3 However, this option may not be feasible due to different constraints such as the price, composition, and accessibility. 3 On the other hand, feed pretreatment, such as microwave and steam explosion, is typically applied to target the lignocellulosic portion of the CM to enhance the hydrolysis step of AD. 1 However, most pretreatment methods are energy-intensive, and some release inhibitory compounds, which may adversely impact CH 4 production.…”