Agricultural residues, such as lignocellulosic materials (LM), are the most attractive renewable bioenergy sources and are abundantly found in nature. Anaerobic digestion has been extensively studied for the effective utilization of LM for biogas production. Experimental investigation of physiochemical changes that occur during pretreatment is needed for developing mechanistic and effective models that can be employed for the rational design of pretreatment processes. Various-cutting edge pretreatment technologies (physical, chemical and biological) are being tested on the pilot scale. These different pretreatment methods are widely described in this paper, among them, microaerobic pretreatment (MP) has gained attention as a potential pretreatment method for the degradation of LM, which just requires a limited amount of oxygen (or air) supplied directly during the pretreatment step. MP involves microbial communities under mild conditions (temperature and pressure), uses fewer enzymes and less energy for methane production, and is probably the most promising and environmentally friendly technique in the long run. Moreover, it is technically and economically feasible to use microorganisms instead of expensive chemicals, biological enzymes or mechanical equipment. The information provided in this paper, will endow readers with the background knowledge necessary for finding a promising solution to methane production.

This study investigated the effects of applying anaerobically digested food waste and dairy manure-derived biofertilizers to processing tomatoes. The biofertilizers were produced from a pilot scale system consisting of coarse solid separation and ultrafiltration (5,000 Da) with a capacity of approximately 3.8 m³·d⁻¹. The coarse solids had particle size >53 μm and were not used for drip fertigation. The liquid concentrate and permeate from the system were both delivered to tomato plants through a subsurface drip fertigation system in a farm-scale cultivation experiment. The results showed that liquid digestate biofertilizers could be effectively delivered to the tomato plants given that steps to ensure suitable particle sizes were maintained prior to delivery. The ultrafiltered dairy manure digestate biofertilizer (DMP) had the highest yield of red tomatoes (7.13 ton·ha⁻¹) followed by the concentrated food waste digestate biofertilizer (FWC) and mineral N fertilizer treatments with 6.26 and 5.98 ton·ha⁻¹, respectively. The FWC biofertilizer produced tomatoes with significantly higher total and soluble solids contents compared to the synthetically fertilized tomatoes. Few significant differences between the treatments were observed among the pH, color, or size of the red tomatoes. These results indicate promise for the prospect of applying digestate biofertilizer products to tomatoes using the industry standard subsurface drip fertigation method. Additionally, digestate-derived biofertilizers may have potential to increase crop yields as well as certain quality characteristics of the harvested tomato fruit. No changes in soil quality were found among treatments but more study is required to understand long-term effects of biofertilizer applications with regards to soil quality and environmental risks.

Ke Wang and Ruihong Zhang. J. Microbiol. Biotechnol. 2021;31:338-47. https://doi.org/10.4014/jmb.2008.08057