Table 1 Diameter mean using DLS to particles SiO2 synthesized with bioprocess and without bioprocess With bioprocess Diameter mean (nm) 81.1 81.1 81.8 – Variance relative 0.018 0.041 0.014 – Without bioprocess Diameter mean (nm) 233.4 185.1 152.6 75.8 Table 1 shows variations in mean diameter in nm and variance relative to particles SiO2 synthesized since precursors: rice husk, sugarcane bagasse and coffee husk with bioprocess and without bioprocess. A comparative with Aerosil 130 too is presented Table 2 EDS to particles SiO2 synthesized with bioprocess and without bioprocess % weight % Atomic Element % weight % Atomic % weight % Atomic 1414 Sample Rice husk Sugarcane bagasse Coffee husk Aerosil 130 Rice husk Element O K Na K Mg K Al K Si K K K Ca K Ti K Fe K Total 52.90 0.350 0.790 1.030 41.62 1.390 0.450 0.350 1.120 100.0 66.82 0.310 0.650 0.770 29.95 0.720 0.250 0.150 0.410 Nanoscale Res Lett (2010) 5:1408–1417 Coffee husk Element O K Na K Al K Si K K K Ca K Mo L Total 55.39 0.540 0.510 41.68 0.900 0.330 0.650 100.0 Variance relative 0.025 0.000 0.036 0.000 68.88 0.470 0.380 29.52 0.460 0.160 0.130 Sugarcane bagasse C K O K Na K Al K Si K K K Ca K Fe K Total 31.35 42.37 0.410 1.140 23.37 0.680 0.610 0.280 100.0 42.02 42.91 0.290 0.690 13.48 0.280 0.250 0.080 Table 2 shows EDS analysis in percent weight and percent atomic to nanoparticles SiO2 employing bioprocess in rice husk, sugarcane bagasse and coffee husk Table 3 shows the crystallization percent, considering precursor type and calcination temperature employed. Crystallization degree is obtained for both: particles obtained via bioprocess and particles synthesized without using bioprocess. These values are calculated by consid- ering mean low curve area in the peaks from XRD. It is observed that, for rice husk, the effect in the temperature is not enough as to transform the amorphous phase. However, the metabolic effect in earthworms increases the crystalline phase up to 28.47% (500 C) and 16.69%(700 C). In sug- arcane bagasse, the effect is the opposite, the crystalline phase is low for the samples obtained via bioprocess and crystallinity percent increases for particles obtained with- out bioprocess. In addition, diffractrograms obtained from sugarcane bagasse show that some crystalline phases do not correspond to SiO2, such as zinc phosphate and aluminim phosphate; however, when the bioprocess is not used, particles show a considerable number of SiO2 polymorphs. This suggests that most of the oxygen needed to form SiO2 may be consumed by the earthworms during their meta- bolic process. This assumption is in agreement with EDS analysis, inasmuch as EDS results for particles obtained from sugar baggasse show lower percent of oxygen than 123 particles synthesized from rice husk and coffee husk. With respect to the crystallization percent in the particles obtained from coffee husk, there is not a clear tendency. For the samples obtained using bioprocess at 500 C, the crystallization percent is lower than that of samples syn- thesized without bioprocess. Probably, bioprocessing con- tributes to provide certain array in the nanoparticles, depending on organic matter, oxygen and other inorganic compounds present in the precursors. This would conﬁrm that temperature is not the most important factor for the crystallinity in these kinds of nanoparticles. Conclusion The microbial population in annelids is very important to achieve the biotransformation of the amorphous silica naturally present in the analyzed agro-industrial wastes. Characteristics of the organic matter exposed to a broad variety of microorganisms, as well as the method employed for the fragmentation and minerals release, represent key factors to understand the biocrystallization. Our results reveal a novel synthesis method to obtain SiO2 crystalline