A comparative analysis of biogas production from tomato bio-waste in mesophilic batch and continuous anaerobic digestion systems

Árpád Szilágyi,Roland Wirth,Viktória Markó,Attila Bodor,Ágnes Szepesi,Kornél L Kovács,Zoltán Bagi,Norbert Tolvai,Naila Bounedjoum,Gábor Rákhely,László Bodai,Balázs Kakuk,Huan Li

doi:10.1371/journal.pone.0248654

Árpád Szilágyi, Roland Wirth + Show 11 more

Open Access

https://doi.org/10.1371/journal.pone.0248654

Copy DOI

Abstract

Annually, agricultural activity produces an enormous amount of plant biomass by-product. Many studies have reported the biomethane potential of agro-industrial wastes, but only a few studies have investigated applying the substrates in both batch and continuous mode. Tomato is one of the most popular vegetables globally; its processing releases a substantial amount of by-product, such as stems and leaves. This study examined the BMP of tomato plant (Solanum lycopersicum Mill. L. cv. Alfred) waste. A comparative test revealed that the BMPs of corn stover, tomato waste,and their combination were approximately the same, around 280 mL methane/g Volatile Solid. In contrast, the relative biogas production decreased in the presence of tomato waste in a continuous mesophilic anaerobic digestion system; the daily biogas productions were 860 ± 80, 290 ± 50, and 570 ± 70 mL biogas/gVolatile Solid/day in the case of corn stover, tomato waste, and their mixture, respectively. The methane content of biogas was around 46–48%. The fermentation parameters of the continuous AD experiments were optimal in all cases; thus, TW might have an inhibitory effect on the microbial community. Tomato plant materials contain e.g. flavonoids, glycoalkaloids (such as tomatine and tomatidine), etc. known as antimicrobial and antifungal agents. The negative effect of tomatine on the biogas yield was confirmed in batch fermentation experiments. Metagenomic analysis revealed that the tomato plant waste caused significant rearrangements in the microbial communities in the continuously operated reactors. The results demonstrated that tomato waste could be a good mono-substrate in batch fermentations or a co-substrate with corn stover in a proper ratio in continuous anaerobic fermentations for biogas production. These results also point to the importance of running long-term continuous fermentations to test the suitability of a novel biomass substrate for industrial biogas production.

Highlights

There is a growing interest in renewable energy sources due to the depletion of fossil fuels and their negative effects on the environment
The biomethane potential (BMP) of tomato stem and leave residues were determined in batch fermentation experiments
The main fiber components of the corn stover (CS), Tomato waste (TW), and CoS, i.e., solubles, hemicellulose, cellulose, and lignin, were determined (Table 2); CS had a higher content of hemicellulose, cellulose, and lignin than TW

Summary

Introduction

There is a growing interest in renewable energy sources due to the depletion of fossil fuels and their negative effects on the environment. One of the most common non-conventional energy carriers is biogas produced in anaerobic digestion (AD) processes. A wide variety of biomasses, such as maize or grass silage, crop plant and agricultural by-product, wastewater sludge, food processing by-products, domestic organic waste, and manure, have been used as substrates in biogas plants [1,2,3]. The stability and productivity of the biogas plants could be affected by diverse substrates. AD has an increasing role in the agricultural sector for the energetic utilization of organic wastes [4]. 5 billion hectares are used for agricultural production worldwide [5], generating large volumes of plant biomass by-products, such as orange, onion, and potato peels, green plant residues, and tomato pomace [6]

Methods

Results

Conclusion