Batch and continuous biogas production arising from feed varying in rice straw volumes following pre-treatment with extrusion

This paper studies the synergistic effects on biogas production obtained when different feedstocks are co- digested with varying proportions of rice straw and explores their behavior at the laboratory scale in continuously stirred digesters. Evaluative measures included methane production, volatile solids degra- dation, ash accumulation, and extrusion effectiveness. The effect of extrusion on the production of energy was also investigated. Results indicated that continuous stirred digesters fed with substrates composed of 10% or 30% of ensiled rice straw (on total FM) produced 146.1 and 140.0 lNCH4 kgDM-1 day-1, respectively. When extrusion was employed, organic matter degradation was promoted and methane production was significantly raised—by as much as 16%. For the feeds containing 10% rice straw, the increase in obtained energy was higher than the energy needed for the extrusion, but the energy balance was close to zero when the percentage of rice straw was the 30% of the feed.