Assessment of a full-scale solid-state anaerobic co-digestion: A multi-component substrate analysis by using ORWARE.

The researchers investigated the application of horse manure in producing biogas via anaerobic digestion, using the ORganic WAste REsearch model. They found that horse manure combined with wood chips as substrate yielded optimum energy and nutrient concentrations in the resulting digestate.

Objective of the Study

• The main purpose of this research study was to explore alternatives for sustainable biogas production by reducing the dependence on food waste, a predominant organic substrate used in biogas generation.
• Specifically in Sweden, the availability of large quantities of horse manure (HM) prompted the researchers to assess its viability and possible challenges as a raw material for biogas production through anaerobic digestion (AD).

Use of the ORWARE Model

• The study employed a modified ORganic WAste REsearch (ORWARE) anaerobic digestion model to simulate the process and assess the results of the HM digestion.
• The model enabled the researchers to analyze the digestion process of different substrates and their combinations at the elemental level, during a full-scale solid-state (SS)-AD process.

Findings of the Study

• According to the simulation results from the ORWARE model, the replacement of green waste (GW) with horse manure (HM) paired with wood chips as bedding material yielded the best energy turnover.
• The liquid fraction of the digestate (residue left after digestion process) from the mixture of these substrates showed the highest concentration of all analyzed nutrients. Total carbon-biological and phosphorus were significantly present in the digestate.
• The nutrient concentrations in the digestate from the aforementioned scenario comply with the SPCR120 certification, a Swedish standard for biofertilizers from anaerobic digestion.

Implication of the Results

• The results of this research provide an impetus for wider use of horse manure as a raw material for biogas production, especially in regions with an ample supply of this waste.
• Aside from sustainable biogas production, the use of horse manure with wood chips also leads to an advantageous by-product, a nutrient-rich digestate that can be utilized as a biofertilizer.