Effects of earthworms on nitrification and ammonia oxidizers in vermicomposting systems for recycling of fruit and vegetable wastes

Abstract

Although it is known that earthworms enrich the nitrate content in their final products, the detailed mechanisms behind this are not well understood, and this is important for determining the agricultural value of vermicomposting. Hence, this study aimed to investigate the effects of earthworms on ammonia oxidization and to clarify the functions of ammonia-oxidizing bacteria and archaea (AOB and AOA) during vermicomposting of fruit and vegetable wastes (FVWs). For this, two dry systems using dry FVWs and a fresh system using fresh FVWs were adopted and compared during 60days of vermicomposting. Each system included two treatments, with earthworms and without earthworms. The results revealed that vermicomposting could facilitate the stabilization of FVWs, forming high value-added products. Based on the results of fluorescent excitation-emission matrix analysis, humification indices of the dry and fresh vermicomposts were 4.0 and 4.2, respectively. Moreover, compared to the minus net nitrification rates in groups without worm treatment, the net nitrification rates of 17.5mgN/kg/d and 9.3mgN/g/d, respectively, were found in dry and fresh vermicomposting systems, indicating that earthworms could significantly accelerate the nitrification process. Compost treated with earthworms exhibited elevated numbers of ammonia oxidizers (AOA and AOB) and greater community diversity in final products, compared to the counterparts without earthworms. Final vermicompost products were abundant in the AOB members of Nitrosomonas and Nitrosospira along with AOA groups including Crenarchaeota and Thaumarchaeota. By contrast, AOA were the dominate members completing ammonia oxidization during vermicomposting of dry and fresh FVWs. This study suggests that earthworms facilitate the ammonia oxidization process by promoting both numbers and diversity of AOA and AOB during vermicomposting of FVWs.

Pre-Composting and Vermicomposting of Pineapple (Ananas Comosus) and Vegetable Waste

“…Based on the aforementioned data, percentages of removal for OM were 45.78% (CR); 44.60% (M1); 36.40% (M2) and 40.59% (M3) showing most of the removal in CR and M1. These values are similar to those reported in literature which are within a range of 30 to 56%, with OM removal percentages which are between 30 and 45% [30,49,62,63]. The OM contents at the beginning of the vermicomposting process were significantly different between reactors CR and M1 in comparison to reactors M2 and M3, although the final values of OM in all four reactors did not present significant differences.…”

“…At the end of the vermicomposting process TOC values were 18.21% (CR); 18.60% (M1); 18.98% (M2) and 18.21% (M3) ( Table 3). These values were found within the range reported in the literature which were 15.75 to 38% [33,53,56,61,62,65]. Based on the aforementioned data, TOC removal percentages in the vermicomposting process for the four mixes were 45.78% (CR) 44.60% (M1); 36.40% (M2) and 40.59% (M3), which coincides with consulted studies [32,33].…”

“…Initial values of OM content for all four mixtures were 57.89% (CR) and (M1); 51.46% (M2) and 52.84% (M3) ( Table 2). At the end of the process, final OM values were 31.39% (CR); 32.07%(M1); 32.73% (M2) and 31.39% (M3) ( Table 3) similar to values found for domestic waste within the range of 34.81 and 34.92% [61], whereas for fruits and vegetables the reported value was of 41.9% [62]. Based on the aforementioned data, percentages of removal for OM were 45.78% (CR); 44.60% (M1); 36.40% (M2) and 40.59% (M3) showing most of the removal in CR and M1.…”

“…Initial concentrations for all four mixtures at the beginning of the vermicomposting process were 4.25% (CR) and (M1); 3.5% (M2) and 3.7% (M3) ( Table 2), which coincided with various authors [32,33,59,61,62,65]. At the end, concentrations were 1.5% (CR); 1.9% (M1); 1.2% (M2) and 2.2% (M3) ( Table 3).…”

Resistome metagenomics from plate to farm: the resistome and microbial composition during food waste feeding and composting on a Vermont poultry farm

“…This is driven by the introduction of specific phyla seen only in these samples, including Thaumarchaeota, Verrucomicrobia, and Gemmatimonadetes. These have been prevalent in other vermicomposting studies [39–41]. In particular, Verrucomicrobia was found to correlate with cured composts [39] and be promoted by earthworms [40].…”