Anaerobic digestion of horse dung mixed with different bedding materials in an upflow solid-state (UASS) reactor at mesophilic conditions.

This study investigated the treatment of horse manure through a process known as upflow anaerobic solid-state (UASS) digestion. The results showed that a single-stage UASS reactor could effectively enhance methane production when using straw mixed with hay horse dung.

Explanation of Research

The research was dedicated to finding an effective method for treating horse waste by means of an anaerobic digestion process. The specific process used was termed upflow anaerobic solid-state (UASS) digestion – a method used to break down organic materials without the presence of oxygen.

• To perform the study, a series of Biochemical Methane Potential (BMP) tests were undertaken. These tests varied the mixtures of two types of dung (hay and silage feed) and four types of bedding material (wheat straw, flax, hemp, wood chips).
• From the BMP tests, it was found that straw mixed with hay horse dung had the highest potential for producing methane.
• Then, continuous mesophilic digestion was performed for 238 days using two types of reactors: a single-stage UASS reactor with a 27 L capacity and a two-stage UASS system with an anaerobic filter (AF), with a capacity of 21 L.
• Different Organic Loading Rates (OLR), ranging from 2.5 to 4.5 g vs L(-1)d(-1), were used to see how they affected methane production in the single-stage reactor. The results showed that as the OLR increased, the rate of methane production also increased. However, the yield of methane decreased.
• Similar results were observed with the two-stage system, as methane yields were about the same as with the single-stage reactor.
• Taking these results into account, the researchers concluded that for solid-state digestion of horse manure, a single-stage UASS reactor is sufficient.

Significance of the Research

This research contributes to our understanding of how to efficiently treat and manage waste from horse stables. Since horse manure is a significant source of methane – a potent greenhouse gas – figuring out how to best utilize it for energy recovery while reducing its environmental footprint is beneficial. Moreover, this study also provides useful information about the potential of different types of dung and bedding materials in methane production, offering groundwork for future studies or practical applications in the field of waste management and renewable energy.