Production of biogas from co-digestion of livestock and agricultural residues: A case study

ABSTRACT

This study was undertaken to determine the possible changes in the digester yield and performance for the anaerobic co-digestion under mesophilic conditions of strawberry residues (SRs) together with pig manure (PM). The first part of this paper deals with the digestion of SR as a single substrate. For organic loading rates (OLRs) of 4.4 (g L⁻¹ d⁻¹) or less, the experimental specific biogas and methane productions are 0.588 and 0.231 L g⁻¹, respectively. When higher OLRs (5.5 g L⁻¹ d⁻¹) are used the digester fails due to acidification. In the second part, the co-digestion of both residues is explored using a wide variety of SR:PM ratios and OLRs of 5.5 g L⁻¹ d⁻¹ with good stability. Therefore, it is demonstrated that co-digestion allows the improvement of the treatment capacity as compared with SR as a single residue. The methane and biogas productions increase as the SR:PM ratio increases. It may be concluded that, when a digester works with a certain OLR, the performance for co-digestion is always better than for single substrates because the presence of PM provides a better stability and the presence of SR improves the biogas and methane production.

KEYWORDS:

• Farm wastes
• organic loading rate
• pig manure
• resource recovery
• strawberry residue
• waste valorization

Funding

This work was supported by the Junta de Andalucía [Project of Excellence RNM-09-5095 BIOPURIN].