ANALYSIS OF THE IMPACT OF CEREAL STRAW PRETREATMENT ON BIOGAS YIELD POTENTIAL

Abstract

The study investigates the effect of different pretreatment methods of cereal straw on the biogas yield potential under mesophilic anaerobic digestion conditions. The aim of the research was to evaluate how mechanical, hydration-based, biochemical, and extrusion pretreatments influence the biodegradability of cereal straw and its cumulative biogas production.

The objectives included comparative assessment of untreated chopped straw, pelleted and briquetted straw, hydration-mechanical pretreatment, biochemical treatment using an enzymatic-microbial additive, and extrusion pretreatment, with particular attention to changes in biogas yield per unit of volatile solids.

The methods involved biochemical methane potential (BMP) tests conducted in batch reactors under mesophilic conditions (37.5 ± 0.5 °C) in accordance with standardized procedures. Biogas production was monitored over a 40-day digestion period, and results were normalized to volatile solids content.

The results demonstrate that untreated cereal straw exhibits the lowest biogas yield (460 m³ t⁻¹ VS) due to the resistance of its lignocellulosic structure. Simple pretreatment methods significantly enhanced biogas potential: hydration combined with mechanical size reduction increased the yield to 507 m³ t⁻¹ VS, while biochemical treatment provided a moderate improvement (490 m³ t⁻¹ VS). Among physical forms, pelleted straw showed the highest increase (+19.3%), whereas hydrated briquettes achieved the maximum yield (561 m³ t⁻¹ VS). Extrusion pretreatment also improved substrate accessibility, resulting in stable biogas production (500 m³ t⁻¹ VS).

Overall, the findings confirm that pretreatment is a critical factor for intensifying hydrolysis and improving biogas production from cereal straw, with practical implications for optimizing substrate selection and processing strategies at existing biogas plants.